SPONSORED BY THE

OFFICE OF NAVAL RESEARCH
a and the
NRC COMMITTEE ON GEOGRAPHY

Stoel OFFICE OF NAVAL RESEARCH
DEPARTMENT OF THE NAVY

0 0301 0040733 4

NULLA

Coastal Geography
Conference

18 FEBRUARY 1954

OFFICE OF NAVAL RESEARCH
DEPARTMENT OF THE NAVY

PREFACE

The principal objectives of the Coastal Geography research program of the Office of
Naval Research are to provide new scientific information on the coastal zones of the world,
and to enable a better understanding of coastal processes and changes. The complexity of
coasts, their diversity and seemingly unsystematic alterations, have long intrigued scientists.
However, until recently, comparatively few scientists devoted their efforts to the solution of
the many apparent and innumerable obscure problems associated with this land and water Zone.
Too little was, or in fact, is known of the processes and mechanisms of change. Although a
considerable body of theoretical knowledge slowly accumulated, it was not accompanied by a
commensurate amassing of precise measurements and observations. World War II brought
into clear focus not only the need for specific information on individual coasts, but also, and
more important from the research view, the lack of fundamental knowledge concerning coasts
in general. The increased and urgent demand for information brought many new scholars to
this field. Wartime studies, which frequently took on the aspects of expediency, did much to
pinpoint and clarify the basic scientific problems. Today, partly under the sponsorship of the
Office of Naval Research, appreciable, yet insufficient, effort is being directed toward the solu-
tion of these problems which cut across the various disciplines of science and involve aspects
of essentially all the sciences.

Included in the program of coastal research as conducted by the Geography Branch of
ONR are studies ranging from detailed examinations of individual coasts to classification and
description of coastal zones on a world basis. A wide variety of scientific and engineering
skills, techniques, and procedures are employed. New methods are being developed and new
applications are being made of standard techniques. It is to be expected that such a broad and
varied program will provide the Navy with many of the answers itseeks. There is also promise
of substantial contribution to fundamental scientific knowledge.

To assure success of this program, it is felt desirable from time to time to bring to-
gether some of the scientists participating in the ONR project to present their research find-
ings even though these may be preliminary and tentative. This allows the scientists and the
potential users among the military services to become acquainted with the progress that is
being made, the trends and developments, and to make suggestions for strengthening and im-
proving the program.

The papers published here were presented at the Conference on Coastal Geography. It is
earnestly hoped that comments concerning individual tasks or the research program as a whole
will be directed to the Geography Branch.

The Office of Naval Research appreciates the fine spirit of cooperation, service, and
interest of the Earth Science Division of the National Academy of Sciences—National Research
Council whose untiring effort made this conference possible.

Z spe ie: PRUITT

Geography Branch
Office of Naval Research

os

CONTENTS

COASTAL GEOGRAPHY CONFERENCE

Sponsored by the
Geography Branch, Office of Naval Research
and the
NRC Committee on Geography, Advisory to ONR

February 18, 1954

NAS-NRC Building
Lecture Room

Chairman: Richard J. Russell
Louisiana State University

Morning Session

OBJECTIVES AND METHODS OF PHOTO INTERPRETATION RESEARCH
ON-TEHESMEDITERRANBAWN BIASING] (2 5 c:c. 6 oo obs oe wleciice 0) e1e.s) elise els © sissies es 1
Charles V. Crittenden

PHOTO INTERPRETATION OF COASTAL ZONES OF DALMATIA..............-. 7
Geza Teleki

CORRELATION OF SHORELINE TYPE WITH OFFSHORE CONDITIONS
IN THE GULF OF MEXICO .............. SoOOCKDDODD ODDO OOOO DODD DODS 11
W. Armstrong Price

SOUTHEASTERN LOUISIANA MARSHLANDS.........2cccccccsccccvecscccece 31
Robert C. Treadwell

CORRELATION OF CULTURAL REMAINS WITH THE PHYSICAL SETTING........ 36
William G. McIntire

COASTAL MARSHES OF LOUISIANA .........cccsccvvcvsccvesces ate otete 40
Richard J. Russell

Afternoon Session

THE MANGROVE SWAMP OF THE PACIFIC LITTORAL OF COLOMBIA.......... 44
Robert C. West

COASTAL PDUNESE marcy crcicccuensi oh otenerenconene arewenenoie eitentire eo retiste feu Silclfeuie\'s te clereilnisieler ers 51
H. T. U. Smith

— A PRELIMINARY INVESTIGATION OF SHIFTING BEACH PROFILES ........ Aicsorohee aU

Henry C. Stetson

CLASSIFICATION AND IDENTIFICATION OF COASTAL ZONES OF THE WORLD.... 63
William C. Putnam

ie

ry

hain

OBJECTIVES AND METHODS OF PHOTO INTERPRETATION RESEARCH
ON THE MEDITERRANEAN BASIN

Charles V. Crittenden
Virginia Geographical Institute

Contract N7onr- 37203
Task NR 089-031

Since the early nineteen forties, more than twelve years of the middle portion—the most
mature—of the careers of numerous American scientists have been associated more or less
directly with problems of the United States Government under emergency and near emergency
conditions. This experience has led, irregularly and during less hectic moments, to some com-
parisons of notes and ideas on such matters. Some of these scientists on both the Governmental
and scientific sides have wondered if worthwhile basic parts of such work could not be planned
and developed, with mutual advantages, in advance of more acute emergencies. Each of us here
today probably finds numerous persons present with whom we have had such exchange of ideas;
and this appears to be one of the reasons for the present symposium.

Problems involving the character of areas repeatedly trouble the minds of men, especially
during emergencies. Plans have to be formulated and decisions made on policy activities and
operations ranging from individual to major strategy, and including diplomatic and military as-
pects. Intelligence has to be expanded and new hands quickly trained in its work which com-
monly involves questions of places and area relationships. Our war-time and post-war expe-
rience, as geographers and related scientists drawn in to aid with such problems, led us to
depend upon or develop new materials like maps, map intelligence, and written area reports
when beset by requests for aid in matters of policy and action of men in areas.

During and after the war, I became more and more struck with the idea that the growing
files of aerial photographs offered a little-used but potentially valuable source of basic area
knowledge for those who could develop an understanding of the patterns. Techniques for use
of such photographs were advancing rapidly in several specialized fields, but little of this was
done in area studies. The Navy, the Air Force, and civilian agencies began to experiment with
“photo-geographics” and interpretation keys of one or two elements (i.e., “Pacific Landforms
and Vegetation”) or of striking pattern portrayals within large areas (“Photo Interpretations of
Arctic Territories”). Neither of these types of outstanding work or manual went very far in
telling where the considered patterns or features were distributed or how they were inter-
mingled with other features of such large areas.

Scientific and technical experiment with aerial photographs developed rapidly but irregu-
larly on both sides of the Atlantic. We found that German scientists had gone farther in the
direction of area studies in their “Forschungstaffel”—particularly in their analogous area
studies, some of which were focused upon coastal margins. Many agencies in this and other
countries became interested in keys for the interpretation of aerial photographs. Few of these
keys, however, were pointed toward being area keys; and yet, aerial photographs portray, better
than maps or written accounts, the contextual character of things together which is the reality
of areas in which men must live and operate.

Several experimental aspects of area study and the transmittal of such knowledge are
combined in our investigative project.

First—We are experimenting with methods for the use by scientific personnel of files of
air photographs as a main source, along with documents and maps, of contextual information

2 CRITTENDEN

about areas, such as the Mediterranean coastal zones. This technique might well apply for
future use on areas which are becoming less peadily, studied through field observation and
normal research methods.

Second—Experiments are being conducted with what we have sometimes called “photo-
geographical” techniques for analyzing and transmitting our understanding of coastal zone pat-
terns and problems. It is planned that the achievements of this research be measured, ina
considerable degree, by summarizing graphic manuscripts for ready conversion by publication
into manual form for use by the Navy. Thus we will today give you a representative sampling
of the graphic portrayals of Mediterranean coastal zone patterns which we are now completing
while initiating work on coastal zones of a second sea area—the Black Sea. These keys are
intended to be of worth to photo interpreters, from trainee to professional, and also of more
general value in two ways: (a) to transmit a sound understanding of coastal zone areas to
other personnel as background for judgements at various levels of responsibility, (b) to take a
sound place, if desired, in developing programs of basic intelligence centered on important sea
areas.

Third—We are consciously attempting to find a way around one of the oldest difficulties
in the field of area studies. Some 40 years ago, William Morris Davis said, “There can be
little question that the least satisfactory feature of regional description lies in the necessity
of presenting in separate, successive paragraphs or pages the many kinds of things that occur
together in natural but unsystematic groupings.” We wish that we could report as completed
a brilliant, new, briefer, and more forceful technique for transmitting an understanding of
areas. We still have to consider or present many of the different things in separate successive
paragraphs. However, we do feel that our present results with combined photo and graphic
portrayals with a minimum of written words warrant continuing hard work and support from
the varied scientific, institutional, and Governmental quarters which make such project re-
search possible. We feel that our present results are far more than the negative which would
be proper to report after fruitless research. Perhaps the best summary can be made by the
hope that our developing technique will become even a fraction as forceful and attractive a
graphic medium as the ubiquitous and, in some cases, rather sinister “comic books” have be-
come for the youth of our land.

A consideration of other and interesting experimental aspects of the work is thought less
essential at the present meeting. Let us turn to samples of graphics, especially some from the
Mediterranean research.

Patterns of aerial photography are becoming less strange to many people. Slide 1 (an
aerial view of Washington, D. C.)* shows that obliques, even near-vertical obliques, now appear .
in the newspaper because of their beauty in pattern and designs shown. The vertical view re-
mains, however, technically most valuable and most difficult to interpret.

From the outline and end-plate diagram at hand you can observe that we are forcing our-
selves to organize and present in graphic report the result of a large amount of research. In
doing this we have found it necessary to adopt, modify, and use in tentative form, several
methods and organizational plans which some of you, rightly, may consider subjects of your
current research and investigation. In some cases, we have done this inadvertently; in others,
we choose and use the plan in advance of your developing conclusions. Much better results
should ensue from our closer exchange of ideas in the future.

*This slide was presented at the conference but is not reproduced here.

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4 CRITTENDEN

Virginia Geographical Institute
February 1954

WORKING OUTLINE—SUBJECT TO REVISION
(End Plates—Generalized Diagram)

COASTAL ZONES OF THE MEDITERRANEAN BASIN
Photo Keys of Salient Surface Patterns

PART I: INTRODUCTION—AIDS & TECHNIQUES
(Pages 1-99 allocated; about 40 to 50 two-page presentations.)

Acknowledgements
Foreword
Aim and Purpose
Map of Mediterranean Coastal- Zone Types faced by Table of Contents
Definitions, Aids, and Points of View: Presentation, Graphic, and other Aids to Photo Interpre-
tation in Mediterranean Coastal- Zone Regions.
1. Coastal Zones as distinctive regions.
2. Terminology and Definitions:
a. General and Generalized Diagram of Land Form and Surface Configuration in
Land-Sea Zones.
b. Glossary and Index of Technical Terms.
3. Explanation of cross-reference methods in these manuals.
a. Table of contents on page facing the map of Coastal-Zone Types and Distribution.
b. Place-name index at end of Part I.
c. Combined glossary of technical terms and topical index.
d. Patterns and topics on particular photo keys are commonly cross-referenced to
related keys.
Types of presentation and their orientation practices in regional photo representations.
Distributions and map graphics as aids to Mediterranean photo keys:
a. Map of Coastal-Zone Types and Distributions.
b. Hypsometric Relief Map.
c. Regional Map of Predominant Land Form, Land Structure, and Sea~Bottom
Configuration.
d. Climatic Types.
e. Generalized Terrain Types, 1:15,000,000.
f. Terrain Types, 50 sheet map at 1:1,000,000, Legend and Index.
g. Block Diagrams as interpretive aid in understanding Mediterranean surface
patterns.
Survey and Elemental Analysis of Mediterranean Region as a whole.
1. General Statement: of major or salient elements, their distributions and regional
combinations.
2. Mediterranean surface configurations considered as coastal-zone character.
3. Climate and related patterns of Vegetation and Drainage as coastal-zone character.
4. Salient Cultural Patterns.
General Statement of the Three Major Divisions of Mediterranean Coastal Zones Selected for
Use in these Manuals. Characteristics and subdivisions exemplified for:
1. Low to Moderately Sloping Coastal Zones (Green areas on map)
a. “Coastal Plain” Coastal Zones.
b. “Low Platform” Coastal Zones.
c. “Alluvial Plain” Coastal Zones.
2. Abruptly Rising Coastal Zones (Red patterns on map)
a. Hilly Upland Coastal Zones.
b. Plateau Coastal Zones.
c. Mountain Coastal Zones.
3. Complex Coastal Zones (Brown or orange on map)
a. Compactly Variable Combinations of Low and Abrupt Types.

oO

CRITTENDEN 5

b. Volcanic Coastal Zones.
c. “Ria Shore” Coastal Zones.
(End Plates—Generalized Diagram)

PART II: LOW TO MODERATELY SLOPING COASTAL ZONES

(of Mainland and Larger Islands—Pages 100 thru 203 or about 50 two-page presenta-
tions)

General—General Introductory Statement and Graphic Illustration of the Three Kinds of Low
Coastal Zones of the Mediterranean. Areas appear in green on map.

1.

2.

“Coastal Plain” Coastal Zones.
102-115 Tunisia—largely Eastern Basin and Semiarid Climate.
116-129 Levant—Eastern Basin and Subhumid, Semiarid, Arid.
“Low Platform” Coastal Zones.
130-133 Italy—Eastern Basin and Subhumid
134-143 East Tunisia, GabesShottes-Eastern Basin and Arid.
144-149 Libya—Eastern Basin and Arid.
150-153 West Egypt—Eastern Basin and Arid.
“Alluvial Plain” Coastal Zones.
154-159 Egypt, Nile Delta—Eastern Basin and Arid.
160-163 Northeastern Greece—Eastern Basin and Subhumid.
164-167 Greece, Peloponnesos—Eastern Basin and Subhumid, Highland.
168-173 Albania—Eastern Basin and Humid, Subhumid.
174-178 Italy, Po Delta—Eastern Basin and Subhumid.
179 Albania, Soni Strip—Eastern Basin and Subhumid.
180-181 Italy, Agri River—Eastern Basin and Subhumid.
182-183 Italy, Latinum—Western Basin and Subhumid.
184-185 France—Western Basin and Subhumid.
186-189 Spain—Western Basin and Semiarid, Subhumid.
190-203 Algeria—Western Basin and Subhumid.

(End Plates—Generalized Diagram)

PART II: ABRUPTLY RISING COASTAL ZONES

(of Mainland and Larger Islands—Pages 204 thru 323 are allocated for about 60
two-page layouts)

General—Introductory Statement and Graphic Illustration of the Three Kinds of Abruptly Rising
Coastal Zones of the Mediterranean. Areas appear in red on map.

it,

Hilly Upland Coastal Zones.

206-209 Italy, Ancona-Vasto—Eastern Basin and Subhumid.
210-219 Western Greece—Eastern Basin and Subhumid, Highland.
220-221 Cyrenaica—Eastern Basin and Semiarid.

222-223 Sardinia—Western Basin and Subhumid.

Plateau Coastal Zones.

224-227 Eastern Spain—no photography available.

Mountain Coastal Zones.

228-231 Morocco, Rif-Atlas—Western Basin and Subhumid, Highland.
232-240 Algeria—Western Basin and Subhumid, Highland.

241 Spain, Pyrenees—Western Basin and Subhumid, Highland.
242-245 Southeast Spain—Western Basin and Subhumid, Highland.
246-247 France, Nice—Western Basin and Subhumid, Highland.
248-251 France-Italy—Western Basin and Subhumid, Highland.
252-253 Italy, Spezia—Western Basin and Humid, Highland.

254 Sicily—Western Basin and Subhumid, Highland.

255 Sicily, Southeast—Eastern Basin and Subhumid.

256-271 Yugoslavia, Karst—Eastern Basin and Humid, Subhumid, Highland.
272-281 Yugoslavia—Eastern Basin and Humid, Highland.

282-287 Albania—Eastern Basin and Humid, Highland.

288-289 West Greece—Eastern Basin and Humid, Highland.
290-295 Gulf of Korinth—Eastern Basin and Subhumid, Highland.
296-305 SW Peloponnesos—Eastern Basin and Subhumid, Highland.

306-309

CRITTENDEN

East Greece—Eastern Basin and Subhumid, Highland.

310-313 Aegean Islands—Eastern Basin and Subhumid, Highland.

314-321
322-323

Crete, Rhodes, Fournoi—Eastern Basin and Subhumid, Highland.
Levant—Eastern Basin and Subhumid, Highland.
(End Plates—Generalized Diagram)

PART IV: COMPLEX COASTAL ZONES
(of Mainland and Larger Islands—Pages 324 thru 481 are allocated for about 75 two-
page layouts)

General—Introductory Statement and Graphic Illustration of the Three Kinds of Complex Coastal
Zones of the Mediterranean. Areas appear in brown or orange on map.
1. Compactly Variable Combinations of A and B Types.

2.

326-349
350-357
358-359
360-361
362-365
374-375
376-389
390-397
398-401
402-405
406-409
410-419
420-425
426-441
442-443
444-449
450-453
454-455
456-457
458-459
460-461

West Greece—Eastern Basin and Humid, Highland.

W. Peloponnesos—Eastern Basin and Humid, Subhumid, Highland.
Greece, Marathon—Eastern Basin and Subhumid.

Greece, Maliaic Gulf—Eastern Basin and Subhumid, Highland.
Aegean Island, Lemnos—Eastern Basin and Subhumid, Highland.
Italy, Gargano—Eastern Basin and Subhumid, Highland.

Italy-E and S Sicily—Eastern Basin and Subhumid, Highland.
Tunisia, S of Cape Bon—Eastern Basin and Semiarid.

Morocco, Ceuta—Western Basin and Subhumid, Highland.
Morocco, Alhucemas—Western Basin and Subhumid, Highland.
Morocco & Algeria—Western Basin and Subhumid, Semiarid.
Algeria thru Oran—Western Basin and Subhumid, Semiarid.
Algeria, Area 3—Western Basin and Subhumid, Highland.
Tunisia, Area 3—Western Basin and Subhumid, Highland.
Islands of Egadi Group— Western Basin and Subhumid.
Sicily—Western Basin and Subhumid, Highland.

Italy, Orbetello—Western Basin and Subhumid.

France, Martigues—Western Basin and Subhumid.

Spain- France—Western Basin and Subhumid, Highland.

Spain, Malaga—Western Basin and Semiarid, Subhumid, Highland.
Spain, Gibraltar—Western Basin and Subhumid.

Volcanic Coastal Zones.

462-463
464-473

Spain—Western Basin and Semiariad..
Italy, Sicily, Aegean Islands—Subhumid, Highland.

“Ria Shore” Coastal Zones.

474-481

Istria—Eastern Basin and Subhumid.
(End Plates—Generalized Diagram)

PHOTO INTERPRETATION OF COASTAL ZONES OF DALMATIA

Geza Teleki
Virginia Geographical Institute

Contract N7onr- 37203
Task NR 089-031

Mr. Crittenden has discussed the aims, methods, and systems of our project in general.
Now I will try to present the application to a specific case. I have selected for this purpose the
coastal zones of Dalmatia, also called the Dinaric Karst. This region is an ABRUPT type,
MOUNTAIN sub-type coastal zone.

About one-quarter of the Mediterranean coastal zone areas has a limestone rockbase.
More or less conspicuous karstland topography can be detected in about one-half of these lime-
stone regions. A typical region with karstland topography is that of the Adriatic and Ionian ~-
Seas. This region presents different coastal zone types, for example:

1. Low to moderately sloping coastal zones—sub-type: Low Platform which can be seen
on Slide No. 1* (layout page No. 131),* the heel of the Italian peninsula, the region of
Puglia;

2. Abrupt coastal zones—sub-type: Mountain, to be seen on Slides Nos. 2 & 3 (layout
pages Nos. 296-297) and representing the SW Peloponnesos;

3. Complex coastal zones—
a. Sub-type: Combination low and abrupt, as shown on Slides 4 & 5 (layout pages Nos.
336-337), a region of Central Western Greece;
b. Sub-type: Ria, represented by Slides 6 & 7 (layout pages Nos. 478-479) showing
coastal zones of Istria.

The slides shown so far illustrate the fact that karst topography is not limited to one specific
coastal zone type.

While investigating a great number of air photos of the Mediterranean, we were convinced
that regional treatment based on interpretation of air photographs could be used successfully by
the Navy. Topical treatment based on types of climate, structure, vegetation, etc. alone, al-
though it improves the analytical study of regions, tends to suppress somewhat the contextual
understanding. The interpretation of air photos involves the necessity of dealing with inter-
mingling factors on one or a few photos. The understanding of the intermingling of these fac-
tors, as seen through aerial photographs, is essential to a grasp of regions. Therefore, our
aim was based on an approach to comparative study of landscape elements and landscape types.

Yet topical treatment forms a valuable aid within the frame of our work. This holds true
mainly for areas with unknown or generally unfamiliar features to U.S. citizens. In such cases
we have introduced the regional interpretation of a characteristic area by a series of photos
presenting the characteristic surface features. But even in such cases the topical treatment
is that of a single region of the Mediterranean. The treatment of the Dalmatian Karst there-
fore contains expressly the karst topography of Dalmatian coastal zones.

*These slides were presented at the conference but are not reproduced here. These layout
page numbers refer to the pages listed in the outline presented in the preceding paper [Ed. | 5

7

8 TELEKI

The topical treatment of Dalmatia’s karstlands contains two sections, each with two sub-
sections:

1. Specific physiographic patterns:
a. Karst features and terrain forms.
b. Karst shoreline types.

2. Characteristic cultural patterns:
a. Cultivation patterns.
b. Settlement types.

Slide 8 (layout page No. 256) shows the Dalmatian karst features and their local termi-
nology. It also reveals that there is no true relation between precipitation and rock type or
between structure and karst landforms.

Slide 9 (layout page No. 257) shows a typical karstland with those karst features marked
which generally can be seen on smaller scale air photos. Such features include dolines, uvalas,
karst canyons, dry valleys, and poljes.

Slide 10 (layout page No. 258) is a detail of the previous slide. Larger scale naturally
shows features like dolines better. One of these dolines is represented by a groundshot. An-
other groundshot shows the lapies, which cannot be detected on air photos. Yet these are of
great importance because they may act as a barrier to cross-country movement and traffic-
ability.

Slide 11 (layout page No. 259) is a forested karst region of the backland of northern
Dalmatia. The presence of karst topography is discernible solely by the “doline pattern.” The
groundshots show an uvala easy to detect on air photos, whereas the bogaz shown on the other
groundshot does not show up on air photos or is much too often undiscernible.

Slide 12 (layout page No. 261) shows a polje of the northern forested karstlands of
Dalmatia. Its presence can be seen mainly by the checking of drainage which disappears in the
center of the polje and shows thus subsoil karst structure, rather than by the groundshot taken
at early spring time and showing the flooded stage. Seasonal flooding again is of military im-
portance but can be detected on air photographs only if air photos taken at different seasons
are available.

Slide 13 (layout page No. 262) shows a karst canyon as a detail of slide 9. These karst
canyons commonly contain routes or trails important to communication. The other photo of
this layout shows a section with submerged canyons which are generally good navigation chan-
nels to larger sheltered bays. The ground shot shows a number of huge springs, which indicate
indirectly the existence of a huge underground cavern system. Oblique shots taken from the
right angle could show this kind of karst feature.

Slide 14 (layout page No. 265) shows karst plateaus and their escarpments. The ground
shots show the rough and dissected surface. This surface and the escarpments with their
steep walls facing the sea are considerable barriers to cross-country movement and traffic-
ability. The broken surface cannot be seen on air photos, but generally appears as wide grey
patches.

Slide 15 (layout page No. 267) shows karst shoreline types. The four upper stereos are
of limestone coasts; the two lower ones are coasts composed of clay. Among the four upper
views, the two top stereos show shoreline patterns of the northern Dalmatian karst. The two
lower are of the southern area. In the northern area, islands lie off the mainland shore. In the
southern area no islands shadow the shores. Wave erosion is therefore different and produces
the highly intricate “lacy” shoreline of southern Dalmatia. These factors may be of importance
to landing operations.

Slide 16 (layout page No. 270) presents cultivation patterns of the Dalmatian coastal zone
area. Cultivation pattern of a barren and a forested karst region is shown on the two lower
stereos. The upper left stereo represents a pre-war Italian, the upper right stereo a pre-war

TELEKI 9

Croatian cultivation type. Note difference between the two—the intensity of cultivation of the
Italian area as against the desolate character of the Croatian area. This may be of importance
to the military since it reflects the differing skill and standards of the population as well as
population density factors.

Slide 17 (layout page No. 271) shows a cultural barrier to cross-country movement;
“stone hedges” built by the population to preserve the little top-soil against heavy runoff, but
also to get rid of the tremendous amount of rock which certainly does not facilitate plowing.

Slide 18 (layout page No. 272) presents a settlement of the Stolbuanea Dalmatian coastal
zone, the town and port of Omis.

Slide 19 (layout page No. 273) presents a similar, although bigger settlement of the north-
ern Dalmatian coastal zone, Rijeka (Fiume). Note on both slides the difficulty to harbor build-
ing, the abruptness of the coasts and the backland, and the exposure to winds and waves. Rail-
ways and other routes wind considerably, and viaducts have to be built over karst canyons.

Slides 20 and 21 (layout pages Nos. 274-275) show the northern Dalmatian coastal zone
type by means of block diagrams and vertical stereo pictures.

Slides 22 and 23 (layout pages Nos. 276-277) show the same for the southern Dalmatian
coastal zones. These last four slides may give an impression of the general character of an
abrupt coastal zone type, mountain sub-type, of the Mediterranean area. Because mountain
ranges run parallel to the shoreline and plateau escarpments have the same direction, land-
ward operations become somewhat difficult. Sometimes better circumstances prevail in areas
where the structural strike of mountains is oblique or vertical to the shoreline, as in western
Turkey or Spain.

In general, abrupt mountain coastal zones with karst topography present real barriers to
cross-country movement, especially where the access is by rocky and steep coasts exposed to
the wave and current action.

10
SUMMARY OF DISCUSSION OF PAPERS BY CRITTENDEN AND TELEKI

The discussion of the two papers indicated it was not considered important in this study
of the Mediterranean Basin to make a systematic classification of shoreline types. No classi-
fication system had been developed specifically for this area. However, where the shoreline
type was regarded as important to the regional description, it was taken into consideration.
Although some of the coastlines, such as in parts of Dalmatia and Istria, were apparently
drowned coasts, no attempt had been made to determine whether coasts were submerging or
emerging. This would have involved much more time in research than was warranted to fulfill
the objectives of the project. The coastal descriptions are intended to define the pattern and
characteristics essential in operational planning, rather than trace the development of the
coasts.

CORRELATION OF SHORELINE TYPE WITH OFFSHORE
CONDITIONS IN THE GULF OF MEXICO

W. Armstrong Price
Agricultural and Mechanical College of Texas

Contract N7onr-48706
Task NR 388-009

The project on which I have been working is an attempt to correlate shoreline type with
offshore conditions. It has been limited to the Gulf of Mexico where there is a broad or fairly
broad continental shelf. So far I have been working necessarily on the basic science phase of
the problem. Next will come the applied phase which has special interest for the Navy. The
objective of that phase is to find some of the index conditions in the offshore area, which would
indicate the type of shoreline that you would expect if you landed on a little-known coast, and
vice-versa: knowing something about the shoreline, you could predict what you would encounter
off shore. This applied phase can be started now because much of the basic information which
I needed has just arrived.

The shoreline is the place where land and ocean meet. Under peacetime conditions, the
geography and physiography of the land are easily determinable. For our project we should
find out what the ocean has done in modifying the land surface, or in controlling any extensions
of the land which are taking place contemporaneously, such as deltaic growth. That is a tradi-
tional, well-known situation with geologists and geomorphologists.

My previous experience was in the study of the deltaic Pleistocene coastal plains of the
Gulf of Mexico, trying to learn their nature—that is, what were the characteristics easily de-
terminable from the surface so as to find out the normal, and then discover the abnormal on a
small scale, for example, surface anomalies of the oil-field structure type and size. For in-
stance, the deltaic plains have characteristic slopes depending on such factors as the energy of
the streams that deposited them, the coarseness of grain and volume of the sediment, and the
slope of the land. We have found that each of the five successive deltaic plains of the Gulf
coast has its own slope and own topographic characteristics. After determining the normal
characteristics of the plains, the objective was to find the abnormalities caused by structural
uplift. These appear as domes, up-warped ridges, and scarps.

In coming to this project of the offshore area, I thought that we might find some such
basic control. Adopting the viewpoint of the oceanographer, a strictly geophysical one, my ap-
proach was to determine the wave-energy relationships on the continental shelf, get actual
figures on the energy, and determine spectra of wave energy across the shelf; that is: (a) the
total energy of the deep water wave as it approaches the edge of the continental shelf, and (b)
the degree to which that energy is dissipated as it crosses the shelf. With this done, we might
find out what the residual energy does to the shoreline. In other words, would it be possible
some day to set up a classification of shorelines and shelf zones based on the amount of energy
used in developing them? Of course there would be many other factors to consider besides
those mentioned, and we would find many varieties and sub-varieties of coasts, but might there
not be a basic relationship between the amount of energy and the type of shoreline?

At first I used relative energy values, as it took considerable time to find the right peo-
ple to make the numerical energy computation on a regional basis. The usual approach of the
oceanographer is extremely time-consuming and expensive—to determine in detail the amounts
of energy that are going to be thrown against a single structure built at the shoreline. There-
fore, we had to find a method of determining the energy from a regional standpoint.

11

12 PRICE

We approached the problem from the viewpoint that if we could take the meteorological
data on the region, the duration and velocity of winds, and determine the wave energy from all
the winds which would develop waves at different parts of the coast and the variations from one
part of the coast to the next, we would have quantitative energy figures which would apply to
the shoreline study.

The first consignment of the quantitative energy figures came in as I was writing this re-
port. I apologize for not having the report coordinated better, and not having the final correla-
tion table for the Navy’s purposes, which I will be able to write now. The energy calculations
were made, as the reports show, by Dr. Warren C. Thompson and Charles L. Bretschneider.

The figures will show you the characteristics of the continental shelf and the shoreline of
the Gulf of Mexico, and some of the methods by which this study is being made.

Figure 1: Large-unit classification of the coasts of the Gulf of Mexico, which I made a
couple of years ago.

The deltaic coastal plains [1]* extend from the Apalachicola Delta in Florida around the
coast to the west and south to the steep young mountain-making coast of Tampico-Vera Cruz
[3] with a narrow continental shelf and coastal plain, where the influence of the Sierra Madre
Oriental is felt.

= or
ac egemaecasen,

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Figure 1.

*Bracketed numbers indicate zones marked on Figure l.

PRICE 13

I had to do some field work this summer to find out whether I should classify the section
of the coast between the Mississippi and Apalachicola deltas as deltaic [1.2], but I believe I
should.

There is a 200-mile delta [1.11] on the Isthmus of Tehuantepac in the rain forest area.
The two limestone peninsulas [2] of Florida and Yucatan are shown,and imposed on their
shelves is what has been called a biogenous type of coast. I do not consider this a basic coastal

type as far as the land is concerned, but it is a marine overlay on other basic geological units
such as the drowned limestone peninsulas. We could consider the limestone itself as a product

DGCos0"

We

z
3

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c=,

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dg

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2

Sf ve
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Figure 2.

14 PRICE

of former biogenous conditions. In the tropical regions where corals and mangroves are con-
spicuous, the biogenous coastal condition is widespread.

The western or Gulf coast of Cuba[3], which was studied in part, is another steep young
mountain-making coast, but one without a continental shelf or coastal plain. The Cuban section
[3] and the Mexican sections [1 and 3] have not been included in the energy study because of
lack of detailed data. I have investigated the geomorphology of these coasts and classified some
of the shoreline types.

Figure 2: Map from the Coast and Geodetic Survey Journal. G. C. Mattison has given us
this nice contouring of the continental shelf off Texas. You will notice the shelf comes out
evenly and smoothly, and then (with a change of contour interval) curves down more Steeply to
the very rough continental shelf slope.

Notice the Rio Grande Delta. While it is only a small extension of the coastline of about
15 or 20 miles, there is a similar bending out of the depth lines all the way down to the con-
siderable depth of 100 fathoms. The profiles will show that this shelf seems to be broadly
down-warped.

At the north, on the Brazos-Colorado Delta, there is a widening of the shelf which con-
tinues out to 10 fathoms.

Figure 3: Profile off Corpus Christi Pass. This is a typical profile of the northwestern
section of the continental shelf between deltas. At the shoreline is the short but very steep
offshore slope of the barrier islands which continues out through a zone which is slightly con-
cave, and then begins to be convex, the convexity extending down the slope of the continental
shelf.

Figure 4: Profile of the Rio Grande Delta. The preceding profile between deltas is shown
by the broken line. The comparison of the two profiles shows an extension of the shelf which
seems to be a filled terrace. It passes landward into what seems to be a cut terrace with large

po) ee fol.) Se igo) |g GO|

Figure 3.

PRICE 15

bars on it. It may seem incautious to compare two particular profiles without a large number
of others to check them, but I have drawn a number of others and these two are characteristic.
This figure shows the typical textbook cut-terrace and filled-terrace. There is more material
in the filled area than has been lost in the cut area. Deltaic deposits should account for the
excess.

Figure 5:* Indicates erosionat the shoreline of the cut terrace of Fig. 4. This body of
clay on a sandy beach is rare here, but I have two or three photographs of the occurrence taken
by other people, although I have not seen it myself. This seems to be deltaic clay from a sub-
delta of the Rio Grande which protruded into what is now the Gulf. The shoreline in this par-
ticular area has retreated. This figure shows that erosion of the delta is going on, and our
deduction of a cut-terrace is warranted in actual fact.

Figure 6: Typical profile off the northwest coast of the Gulf of Mexico (Big Constance
Bayou), showing again for comparison the Corpus Christi profile and a somewhat similar pro-
file off Panama City, Florida, east of the active Mississippi Delta. The comparison shows the
outbuilding that takes place where the Mississippi, Red, and subsidiary rivers enter the Gulf.
The outbuilding extends eighty miles to the steep continental slope.

Figure 7: Profile off Panama City in the Panhandle of Florida, shown as the second
broken line in Fig. 6. This is more or less the Corpus Christi type, with some built-up mate-
rial on the shelf, but not as smooth as the Corpus Christi profile. This figure exhibits the
typical sudden short descent off the sandy barrier island, and some bars or old deltaic de-
posits. The concave portion of the profile is about 18 miles long.

Figure 8: G. F. Jordan’s published map of the new, very accurate contouring of the con-
tinental shelf slope off Florida. Note the De Soto Canyon and some lesser drains on the slope
and the great scarp at the base of the slope. The shelf has no sharp edge but is broadly and
smoothly bowed down. At the other side of the Gulf the contouring off the Corpus Christi and

Figure 4.

*This figure was not available for publication.

PRICE

16

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PRICE 17

Rio Grande delta areas shows a similar type of profile, smoothly bowed down with scarps at
the base. The similarity is striking: one profile is on the hard limestone shelf and the other
on a deltaic shelf. This similarity has some implication as to the history of the building of the
continental shelf.

It was seen that the profile from the north Gulf coast at Panama City, east of the Missis-
sippi Delta, is also steep and abrupt like the profiles at Corpus Christi and here. These pro-
files show a similar characteristic of the continental shelf from west to east, regardless of the
type of sediment forming it.

Figure 9: Profile off Crystal River Mouth, Florida (going south on the Gulf coast of the
peninsula of Florida). This one, off Crystal River, is from the northern third of the peninsula
where there is what I call a drowned karst coast and shoreline. You notice again the inshore
concave section of the profile. Neither a sandy beach nor a barrier island exists here. The
concavity is very low and flat, and there is not a steep jump-off just offshore as seen earlier,
only a slightly modified karst plain with some elevations (bars) in the sand zone.

The land portion of the limestone plain slopes about one and one-half feet per mile. Off
shore this slope is one foot to one and one-half feet per mile with the same karst pattern seen
through the water as seen on land. Some fathograms show the rolling karst depressions and
ridges as expected. Others to the south off the central beach-bordered sector of Florida are
nearly smooth showing the karst depressions partly filled.

The sailing directions say there is not enough sediment in the karst depressions to make
good anchoring. Therefore we know that the sedimentation is quite slight, as indicated also by
Howard Gould’s studies, but there is still much to learn about the character of this shelf and
the limestone composing it.

Figure 10: Profile off Las Bocas on the western (Campeche) mangrove coast of the
Yucatan Peninsula. This profile is similar to that shown for the drowned karst coast of Florida,
but it has a coral platform. The small scale of the generalized chart from which the profile is

Figure 7.

NAUTICAL MILES

R.F.A. STUDS, Director

2

U.S. COAST AND GEODETIC SURVEY
\—FIG 11

GULF OF MEXICO

CONTINENTAL SLOPE

tee
Zh

f Ss Yi
\ (ANS ZY
——s \

VE
\\

4

PRICE 19

(STATUTE MILES)
20 40 60 80 100_ 120 140 160

100

200

PROFILE OFF CRYSTAL
i RIVER MOUTH, FLORIDA 100

FROM C&CS CHART 1003

(FEET)
(NETERS)

400)

500

600

50 100 150 200 250
(KILOMETERS)

Figure 9.

made does not show the details. The coral platform has its base between 20 and 30 fathoms
along the Campeche banks off the north and west shores of the peninsula. There is a build-up
of 8 fathoms of material standing above the normal profile of the continental shelf, in addition
to the reefs.

Figure 10.

1000'S OF FEET

20 PRICE

Figure 11. The Three Hydrologic Regimes. We have seen a series of characteristic
profiles of the continental shelf of the northern half, and a portion of the southern half of the
Gulf of Mexico. We found that the profiles are concave near the shore, and that there are var-
ious obstacles farther off which stand above the projected line of that concavity. Seaward from
these obstacles the profiles show a general convexity at the edge of the continental shelf. This
convexity merges quickly with the steep continental slope.

Comparing the shelf profile with that of the river, which is well-known, and that. of the
submarine canyon, which is beginning to be known through the work of Maurice Ewing and
others, I find we can make a generalization that sedimentary particles moving from the moun-
tain top or slope to the oceanic abyss, must pass through three—possibly in some cases only
two—hydrologic regimes. :

First the particle comes down the river, descending the steeply concave slope of the
upper river profile, very much exaggerated here; then the middle and lower courses through
the plain; then the delta.

The delta extends into the Gulf and overlaps the profile of the next regime, that of the
continental shelf. This drawing is approximately to scale so that the shelf is shown very short.
(The shelf profile is shown enlarged on thenext figure.) At the outer margin of the shelf is a
convexity which usually occurs except in badly deformed shelves. Clay is found here. It is in
this convex portion that you find the heads of the average type of submarine canyon.

Last month Kuenen presented a classification of submarine canyons. He calls his com-
mon type the New England type. Study of the New England type of canyon shows the head to lie
commonly just at the inner side of the outer shelf convexity, where it joins the nearly horizontal
section or its built-up portions.

RIVER SHELF SUBMARINE CANYON ___ ABYSSAL
REGIME REGIME REGIME PLAIN

MOUNTAIN PLAIN

TURBIDITY CURRENT TROUGH
DELTA

sea level

FILL

BEACH DELTA
& SHOREFACE “
5
[ SUBMARINE
CANYON
Y ; NATURAL LEVEES
SHELF_ “V7 er CHANNEL
Ly \ Pie TURBIDITY
YY é, CURRENT
<

OF BEACH, aA
BETWEEN
DELTAS ABYSSAL PLAIN

20
Dd

a
100 200 300 400 500 600 700 800 900
MILES

Figure 1l. The three hydrologic regimes of sediment transport and
erosion, true proportions diagrammatically shown.

PRICE 21

If one were to analyze the few contour maps we have of the submarine canyons, one would
find their upper parts cut into the shelf and then emerge as channels in deltas. The shaded
portion of the figure indicates the built-up section of the delta that becomes an apron, apparently
a very widely dispersed, widely extended, thin layer of depositional material extending beyond
the definite delta. The delta is at the foot of the submarine canyon, and the apron is where the
turbidity currents flow out on the abyssal plain. Maurice Ewing’s work of last year in the At-
lantic shows that the turbidity flows which come down from the northeastern coast of North
America enter the great western Atlantic Canyon from Greenland and flow down a tremendous
distance to the abyssal plain and into the deep off Puerto Rico. Figure 11 shows, diagrammati-
cally, the same situation with the apron reaching a trough which might be receiving some of the
turbidity-current material.

Ewing showed that along the great Atlantic canyon the landward side of the abyssal plain
was higher than the other side. Justification of similar conditions shown here is found in the
contouring of the bottom of the Gulf of Mexico.

Computations by C. L. Bretschneider, V. J. Henry, my son William, and myself indicate
the astonishing volume of 19,000 cubic miles for the deep delta at the foot of the Mississippi
canyon. In computing the volume of the delta, I assumed that the continental shelf originally
had the steep slope which is shown at the north (Fig. 7) and at the west (Fig. 3) and that the
delta was built on such a shelf and with a nearly flat Gulf floor. If we assume major irregu-
larities of the floor and projections of the slope, we may subtract a third of the volume and
still have approximately 12,000 to 13,000 cubic miles of material.

I did not know that this shoreline study was going to involve consideration of the bottom
of the Gulf, but from the shoreline to the abyss there is a continuity of events and processes.
This is itself a major scientific result of this research project.

You will notice on Fig. 11 that the three different regimes each have a concave profile.
At the lower ends of the upper two profiles where the energy is about spent, the curves become
convex in the terminal dumps. This low-energy convexity is an overlap and an interfingering
with the next lower regime.

A basic similarity in these three profiles is the drop in elevation (with the resulting
gravitational difference) between the ends of each profile to provide energy in a moving body
of water. Material is transported down the river. There must be transport of material across
the shelf, although the exact method is not known to me. Water coming in from the land must
get off the shelf. Water transported landward with the waves must also get off the shelf. There-
fore, there must be a movement of water across the continental shelf to the oceanic basin, and
this movement must effect the transportation of material. You find the finest material, clay,
commonly building up the terminal dump of the shelf in a zone of spent energy. The energy is
mostly confined to a thin zone at the surface. This fine land-derived clay has been transported
across the shelf in suspension in the water which we have deduced must somehow flow outward
off the shelf. Whatever movement there may be at the surface of the shelf in deep water re-
mains to be discovered.

Figure 12: Diagrammatic bottom profile of continental shelf illustrating some of my
terminology. I extend the shoreface out somewhat farther than some writers, and place the
seaward edge at the point of rapid change in rate of concavity, not merely at the edge of the
beach or intertidal zone. Where I have data,the shoreface of a sandy barrier island seems to
extend to the bottom of the sand structure.

The ramp is a gently sloping surface, slightly concave, and asymptotic to the horizontal.
In this figure a broad irregular submerged deltaic mass is shown rising from the plane of the
ramp. It is being smoothed in its Gulfward parts and eroded and graded into the shoreface-
ramp profile near shore. Where the submerged deltaic deposits and other obstructions have
been removed, as they have in a few places, the ramp continues to join the terminal convexity,
shown by the extrapolated broken line. I have applied the word camber meaning convexity, to
the terminal convexity of the shelf. Some people call the zone where the curvature reverses
from concave to convex the “shelf break,” others pick any point where the curvature is chang-
ing rapidly near the shelf edge; some consider a terrace or some kind of slope irregularity as
the “break.” If we are to use such a term, it should be defined.

22 PRICE

I use the terms “camber,” “ramp,” and “shoreface” for the three parts of the profile and
do not attempt to fix a “shelf break.” Neither do I analyze the topography of the shelf slope.

You will notice there is an overlap of the concave river profile on the continental shelf,
and overlap of the camber on the submarine canyon profile. Each high-energy zone begins in
the low-energy section of the preceding profile.

Figure 13: Map of wave energy and shelf conditions showing energy data computed from
wind data for six coastal stations. The energy of wave motion in the wind-wave is computed in
terms of horsepower-days per foot of crest advance and per foot of wave crest length for on-
shore winds on a deep-water basis. The figures were developed by Dr. Warren C. Thompson,
now of the Navy Post Graduate School of Monterey, California. He used regional wind data
taken at the coastal Weather Bureau Stations to compute the energy from each onshore wind
direction using a series of formulas and curves he developed. These values are shown in his
report in an energy wind-rose for each station. These shore data are considered to be appli-
cable to the adjacent edge of the continental shelf. The energy for the deep-water wave applies
at that point.

At first we worked on the idea that it was mainly the onshore wind-wave movement which
was Significant. When we thought about it more, we saw that offshore winds must also do ap-
preciable work on the continental shelf. As the fetch increases, the wind strength and wave de-
velopment increase gradually, and there is significant wave attack on the bottom.

Charles L. Bretschneider, who has developed formulas and curves for computing bottom-
friction losses in wave motion, helped on this problem. He computed the total wave energy for
winds from all directions for one of the stations used by Thompson. His computation for Gal-
veston show 654 horsepower-days as a deep-water gross-energy figure as compared with 346
for onshore waves.

Figure 14: Spectrum of Bretschneider’s wave-energy values along a profile of the shelf
off the Brazos delta and river mouth near Galveston. Energy along the bottom slowly decreases
landward up the steep shelf slope. Only 5% is “lost” in motion across the remote, deep camber
section of the continental shelf. A total of 20% is “lost” on reaching a depth of 100 feet. Ap-
proximately 75% of the energy reaches the outer edge of the ramp after crossing the broad but
low deltaic elevation which has absorbed some of the energy. However, in speaking of “lost”
energy, we are considering also changes in energy due to reduction in fetch of offshore winds.
On this nearly horizontal ramp, eight or ten miles long, only 10% of the energy is “lost.” Thus,
in this example, 64% of the energy is left to be expended on the shoreface, the surface of the
steep, sandy barrier island with its offshore bar zone. As we will see, this flat ramp is a low-

energy zone.
RIVER
REGIME |
BARRIER
a
LAGOON
SHORE FUTURE pore CAMBER
FACE
| CONTEMPORARY
RAMP SHELF sea_level

MAY BE

REPLACED f if
BYE CT UNGRADED_ EXTRAPOLATED
DEPOSITS

TURBIDITY CURRENT
DELTA

wy
SUBMARINE) \
CANYON

DIAGRAMMATIC BOTTOM PROFILE OF CONTINENTAL
SHELF

Figure 12.

PRICE 23

‘We would like eventually to develop such energy spectra for all the characteristic pro-
files of the continental shelf. We would like to do this on a more detailed basis, because all
these profiles have been drawn from the navigation charts. We realize that the details will be
much more interesting when we are able to contour the smooth-sheets. However, it will take a
great many man-hours to contour many smooth-sheets, and the project, as set up, does not
provide for that much work.

If, somehow, we can get that type of work done, the study will be very much improved.
We think there will possibly be a correlation between the sediments, the minor bathymetry of
the submerged deltaic plain, and groups of the bottom living organisms. This is a fertile field
for investigation from the scientific standpoint, with the hope that something will result in the
applied phase.* We have a project planned for which we are going to try to get support, to
enable a biologist to study those details in an area where we are now getting samples, fatho-
grams, and other information in another Navy project.

With the data on energy that we now have and our knowledge of the shorelines, we made
this diagram map (Fig. 13) of the Gulf. Starting in 1951, I made a typical geomorphic study of
the shorelines of the Gulf of Mexico and also a series of maps showing the different types.
Fifty-eight types were found; nine of these were new. It was necessary to enlarge the genetic-
geomorphic classification tables to accommodate the new types and listings.

eg
K
Z 0) ex

xO

OBSTACLES
ABOVE RAMP sHaLLOW WATER

: I WAVE ENERGY AND SHELF CONDITIONS
i en a GULF OF MEXICO
22 ~—— ~
re : ENERGY
\ alles i [mm] smooTHED (HP-DAYS)
EN / PARTLY
ae : )” | Pew] Moor, OEEP-WATER BASIS
L a g rae —346 FROM ONSHORE
\ aa Wn WINDS ONLY
a LP © st war WY] sqooTH (654) USING ALL WINDS
veRA\ ay ee W/

easy VERY BROAD BASI
es] SHOAL BOTTOM (4/6) ALL WINDS

= 5 A RELATIVE ENERGY(DEEP-WATERHIGH,
‘ t 1p |_MEDIUM, LOW ,SHALLOW-WATERHM LO)

Figure 13.

*Correlation between minor bathymetry, sediments and bottom organisms are good in the first
NW gulf area surveyed in detail by an oil company.

24 PRICE

Most of the shoreline types of the Gulf belong to the inner lagoons and bays. However,
we are Studying at present only the marine shoreline. I find that the significant factor for the

outer coast is the degree of smoothing.

Smoothing is significant from the geological as well as the energy relations standpoint.
It is very significant with respect to landings and all kinds of shore operations. Smoothing is
primarily accomplished by wave energy, which grades the shoreline and shelf bottoms. It is
well known that progressive modification of the shoreline by the ocean brings about simplifica-
tion and smoothing. A smooth coast should be considered in a mature condition.

The heavy black lines in Fig. 13 indicate the coasts which are well smoothed. Ona
drowned river-valley coast, numerous in this area, shorelines may be smoothed by sandy bar-
rier islands built across the river mouths. Thus a smooth coast is found wherever such bar-
rier islands are formed.

The barrier islands are built of sand. Proved sources of this sand are dominantly river
and bay sediment in Texas, southwestern Louisiana and central Florida, bottom sands in the
Chandeleur Islands of Louisiana, and shell sand on the north shore of the Yucatan peninsula.
Pocket beaches on the west coast of this peninsula have limestone cobble eroded from up-
faulted limestone hills. The limestone coast of the Champoton-Campeche fault-block is
smoothed by erosion of the rock and building of pocket beaches.

In the Gulf all the smoothed coasts show high to medium energy inshore. The completely
unmodified, unsmoothed shorelines are where the energy is very low. Along the northern third
of the Florida peninsula there are numerous areas, each several miles long, having almost
completely unsmoothed shorelines. These unsmoothed shores are found on the drowned karst
with practically zero energy. There we find innumerable small peninsulas and islets with
small bays and channels. The low elevations are occupied by palms and other trees. There
are archipelagoes of islets extending four or five miles from the shoreline. I described this
type of coast in a manuscript which will be published in about a year (Communications of IV
Congress, INQUA, Rome and Pisa, Italy).

TTA sieyteasestastand apapafasteatast ESETEEESI OM
EEEEEEEHEE H : GEE
THEE H : EEE
1, :BOUSHSESESUSEEG#GES#BESHGESESTEEE® Baie
t Teer Balle a5
oon Ht ig
fae
a t eengneee ale
H H EEE EEE peeeat SS :
q a is Sena a5 od ¢ a
aa ry i ali pood [)
4 # HA alee | HH Be
: tt iaiais He tHE t 4 ttt a a :
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a ada HE HH Het EEE i. HEE :
i ap HH i B Bali
t seeercey 5 } Hitt Act
PFE PERE | } Zo)
(NING F i }
it t

Figure 14.

PRICE 25

At the southern end of Florida there is a mangrove barrier ridge with an irregular lagoon
behind it. The mangrove growth is a completely unsmoothed archipelago, partially protected by
Cape Romano, a barrier peninsula which is partly smoothed by hurricane erosion where the
coast is entirely open. This is a low- to zero-energy coast.

On the northwestern part of the Yucatan peninsula the mangrove Swamp fills the karst
re-entrants ona slightly steeper karst plain, making a somewhat smoother coast. All the marine
mangrove swamp shoreline is cross-channeled by tidal scour.

Another example of a completely unsmoothed coastal feature is the crow-foot delta of the
Mississippi, which the wave energy has not been able to reduce. Although the sides of the “leg”
may have somewhat smooth shorelines, the “feet” (passes) are strongly protuberant features.

On the drowned karst coast of Florida there are areas where a low-lying coastal strip
was filled in by sand during a previous high sea level. This produced a low sandy plain that
probably originally had a smoother shoreline than it has today. The coast has been abundantly
cross-channeled by tidal scour in the sand, presumably between buried karst elevations. This
is considered a zero energy coast and the longshore currents, longshore sediment drift, and
wave attack have been too weak to smooth the coast. It has been made irregular by tidal scour.

A moderately smoothed coast is found in Louisiana west of the delta. The coast is lobate.
Bay barriers of sand or oyster reefs smooth the shoreline but are not well aligned. In places
they are retreating rapidly due to decreasing sand supply in the longshore drift accompanying a
shift of run-off volume from the Mississippi to the Atchafalaya River. Atchafalaya Bay has no
longshore sand drift, and, in consequence, an irregular barrier oyster reef replaces the usual
smooth bay barrier of sand.

FLA. STRAITS

DEEP WATER WAVE ENERGY,
(+ shows unmeasured hurricane excess)

GRADIENT IN FT. PER STATUTE MILE

RAMP |\\\\|_—s SHELF SLOPE

SUBMERGED original gradients on slightly

KARST ~~ graded deltaic and limestone
plains

SUBMERGED DELTAS & HILLS (H)

standing ungraded above ramp and

Plain gradients.

Figure 15. Relation of energy, obstacles, original gradients, and lithology of bottom to
gradients of ramp and submerged land surfaces on continental shelf.

26 PRICE

The north shore of Yucatan is smoothed by beaches of shell sand and barrier islands
which, however, are not well aligned, probably due to irregularities of the limestone. The
mapping is poor and only a few aerial photographs have been examined.

Before I had any numerical figures for energy, I considered first, the two wind systems
of the Gulf, the southeast trades and the cold fronts of winter; and second, the slopes of the
ramps or hard-rock shelf surfaces (Fig. 15). The trades (a) blow at right angles against the
west coast of the Gulf, delivering their full energy, (b) blow alongshore or diagonally at the
north coast, giving less energy there—I call it medium energy, and (c) blow offshore at the
east, which I call a low-energy coast with zero energy where the hard-rock shelf is both broad
and very shoal.

The cold fronts come from the north. Their winds, and the induced wave fronts, blow
alongshore at the east and west, and do not do much work. The northern Yucatan shoreline lies
across their path, and these “northers” produce high energy at the edge of the shelf and medium
energy at the shore. The very high energy figure for Vera Cruz shown on Fig. 13 (736 horse-
power-days) is due to the long fetch of the northers and the work done by cold air on a warm
ocean. Apparently the north Yucatan coast must have some similar figure, perhaps three-
fourths at least of the Vera Cruz value. This would account for that fairly high energy north-
facing coast. The appreciable slope of the bottom and the considerable distance off shore and
depth (20 fathoms) of the coral platform allow a fairly large percent of the energy (“medium
net energy”) to reach the shore.

On the low-energy coast, wave activity is low and breakers absent. Along this type of
coast on the northwest Florida peninsula the U. S. Army Engineers, much to their surprise,
could work far out on the shelf in small 2-spud coring boats even in winds up to 25 or 30 miles
per hour. The same thing is true behind the barrier reef along the Florida Keys. There is
only choppy water, even with high winds.

These relative energy concepts were applied before we had any numerical energy values.
Now we have the Thompson figures for the wind-wave energy of onshore winds on a deep water
basis. You will see that in the north half of the Gulf the values range from about 400 at the
west to 200 at the extreme east where the broad shallow shelf absorbs nearly all the energy of
the onshore wave systems.

In the energy study there are two situations: the gross-energy values at the shelf edge
determined either by a relative scale, or numerically from the regional winds on the deep
water basis; and the net-energy values of waves that reach the shallow water zones near the
shoreline. The inshore net energy largely determines the individual type of modification of
the shoreline, but the total or gross values are involved in shaping the continental shelf. Ac-
tually there is a continuous energy spectrum and a connected series of bottom conditions across
the shelf.

I have drawn on the maps of Figs. 13 and 15 the obstacles which stard above the ideal
continuous smooth profile of the ramp and camber. These obstacles absorb more energy than
would be absorbed by a smoothly graded shelf. On relatively flat ramp slopes there is a large
energy loss by bottom friction, while on steeper slopes there is only a small frictional loss.

Off the Mississippi-Red-Brazos deltaic zone there is a great submerged deltaic plain
which is quite rough, rising above the ramp-camber curve. Off Yucatan a coral platform
standing above the drowned land surface has gross features which probably have not been very
much modified by the waves. The two shelf regions are basically similar, although of different
origin, lithology, and energy relations. Each has a ramp-camber plain encumbered by an un-
reduced elevation extending to the camber.

Along the north Gulf coast (Fig. 15) the energy is low and the ramp is relatively flat be-
hind an obstacle. Where there is no obstacle, the energy is greater and the ramp is steeper.

We are now ready to understand and interpret the maps of the continental shelf. Figures
16, 17, and 18 show the first mapping of the physical environments of the continental shelf of
the Gulf of Mexico that I know, other than sediment maps. The environments mapped are

PRICE 27

properly dynamic environments defined by topographic (bathymetric), physical, and geological
data. Using the slopes of the continental shelf taken from profile studies, the outlines of the
submerged deltaic plains, reef platforms, and other obstacles, I have drawn major longitudinal
zones. The transverse energy zones are not shown on these maps but have been inditated
(without boundary lines) on Fig. 13.

The shoreface is the narrow belt between the ramp and the shoreline. I have determined
the height of the shoreface roughly at different points. The ramp zone passes almost entirely
across the front of the deltaic plains. In places there is an inner and outer ramp. New ramps
are being cut at the shoreline on very recently submerged deltaic masses, with the older, more
prominent ramp on the offshore slope. Apparently there must be breakers along the outer sub-
merged edges of deltaic shoals with a shoreface where the edge of the shoal is less than about
12 feet deep. I am sure that in storms there would be a line of breakers in such places, and
we have indicated the outer ramp to show that this is the case, as on shoals off Atchafalaya
Bay. The camber zone is shown along the shoulder of the deltaic north shelf but not on the
west and east shelves in the broad, supposedly down-warped areas off Florida and Texas.

In regard to the “down-warp” of the western shelf, zones of strong folding buckle the
Cretaceous and early Tertiary strata only 60 miles inland. Off shore from the Rio Grande
delta there are submerged mountains shown by the war-time soundings. One mountain top
stands about 3,800 feet above the adjacent bottom. Its flanks slope several hundred feet per
mile. Thus, this western shelf lies between areas of considerable diastrophism and is
apparently a down-warped shelf as its broadly bowed profile suggests.

Se NA 6 oo

SHORE FACE SHORE FACE

| DYNAMIC ENVIRONMENTS
OF CONTINENTAL

f SHELF

| GULF of MEXICO

ie W.Armstrong Price

tw “SHEET =

MANY BASINS AND GANYONS ON SLOPE
A oy ‘i

see

Figure 16.

28 PRICE

Figure 17: Companion chart for the eastern half of the Gulf. The same longitudinal zones
are present. We have discussed them in connection with the diagram maps of the Gulf (Figs.
13 and 15). The submerged karst plain of Florida is slightly modified by recent deposition in
the karst depression and by erosion which is partly organic.

As discovered by Howard Gould in his dredging, the shelf of the beach-bordered central
Florida coast is covered by a crust or spongy zone, perhaps a foot or two thick in places,
formed by the calcareous tests of all kinds of organisms. Gould hoped to obtain samples of
the rock but could get only tiny chips of black limestone which were dredged up with large
amounts of the spongy crust.

The Florida Keys stand on a reef platform like that on the Campeche Banks off Yucatan.

Off western Florida, in the low-energy zones, are a range of limestone hills, low ridges,
and dome-shaped mounds. Gould concludes from samples that the mounds and low south-
pointing ridges along the 30-40 fathom contours are probably algal reefs. Rock ledges are re-
ported by divers. The ledges overhand slightly at the east.

Much narrower and much steeper submerged deltaic bodies than those in the west are
found east of the Mississippi delta. These eastern bodies are less effective as energy reduc-
ing obstacles than those to the west. The navigation charts are not detailed enough for a satis-
factory study of the surfaces of these obstacles. They seem to be consistently cross-gullied

DYNAMIC ENVIRONMENTS {L)
OF CONTINENTAL
SHELF
GULF of MEXICO
W.Armstrong Price February 1954 f-

"NE SHEET

a HET

oe
5 t r

yh
Sat

i
|

|

{

i

)

Figure 17.

PRICE 29

as if transversely entrenched stream valleys were cut during the last lowering of sea level.
The gullies have not been filled by sedimentation, nor have their divides been removed by
erosion. Some of these gullies are definitely shown by the soundings, and others inferred from
insufficient data.

The floor at the upper end of the Mississippi submarine canyon is about 450 feet below
sea-level, which Fisk estimates to be the amount of the last great lowering of the sea. The
contours on Fig. 17 from U.S.C. &G.S. Chart 1003 show the deep delta of the Mississippi canyon
better than the older charts. The top seems to be about at 600 fathoms and the base at 2,000
fathoms. The fan extends out and down to meet the Yucatan shelf and the mouth of the straits
of Florida. Its front is some 300 miles wide.

Figure 18: The Yucatan area. The shoreface is 18 feet high, which is fairly low in com-
parison with those of 45 to 50 feet high common on most sandy coasts. The mangrove coast is
merely sketched in with only the entrances to the numerous tidal channels shown in a rough way.

The submerged karst plain at the north slopes about two feet per mile. On the low-energy
coast at the west it slopes 1.3 to 1.9 feet per mile. The few elevations available on land on the
north coast indicate a slope of three feet per mile to the north, suggesting that the offshore
slope may be a partly built-up slope, rather than an erosion slope.

DYNAMIC ENVIRONMENTS
OF CONTINENTAL
SHELF

GULF oF MEXICO
W.Armstrong Price February 1954

SE SHEET

CTSUeMERGED:~ #7 S-- Y
ee ws SEARO. REA ah ce

CAMPECHE BANKS
OF

YUCATAN PENINSULA

Se SES "= 14.3 Statute Miles

1°*15.9 Stotute Miles

Figure 18.

30 PRICE

By use of the concepts and data described in this talk Iam able now to make some gen-
eralizations as to the energy distribution in the Gulf of Mexico, its effects on the shoreline and
on the shallow part of the continental shelf. I hope in the next few months to produce a correla-
tion table showing all these features, and to add a number of other items of practical value.
Perhaps additional maps will be used. By such means we hope to correlate a great many
specific offshore conditions with shoreline types.

SOUTHEASTERN LOUISIANA MARSHLANDS

Robert C. Treadwell
Coastal Studies Institute
Louisiana State University

Contract N7onr -35608
Task NR 388-002

The area under consideration, the easternmost Louisiana marshlands, is outlined on
Fig. 1. It is one of five areas into which the Louisiana coastal marshlands project has been
divided. The western part is low marsh, broken by many lakes, bayous, and a few natural
levee ridges. To the east are ten to fifteen miles of open water of Chandeleur and Breton
Sounds bounded on their seaward side by the low, discontinuous, sandy Chandeleur Islands.

The area is a former subdelta of the Mississippi River and is now abandoned. Aided by
subsidence and eastward tilt, land is retreating before the attack of the sea.

4

Figure 1.

31

32 TREADWELL
TRAFFICABLE UNITS

Natural levees are the dominant topographic feature of the marshland and form the only
continuous high ground. The levees radiate in a branching pattern from a focal point at New
Orleans. Levee heights near New Orleans are about ten feet, but gradually diminish seaward
as the levees dip beneath marsh level. Levee widths reach one and one-quarter miles on upper
parts of the distributaries and gradual!y narrow toward downstream regions. Under natural
conditions vegetation is very dense, mainly live oak and various kinds of underbrush. Natural
levees are composed of silty clay and silt, and ordinarily have = high moisture content because
the water table is close to the surface. The upper portion is usually oxidized, and reducing
conditions prevail below. Dry levees are excellent trafficable units; however, after rain they
become sticky, and ordinary vehicles are easily bogged. The effective trafficable limits of
levees are always outlined either by trees or agricultural areas, which allow easy determina-
tion of this boundary on aerial photographs.

An ideal cross section of the sedimentary sequency associated with natural levees is
presented in Fig. 2. The basal layer is marine sand antedating delta encroachment onto the
area. Overlying this are pro-delta clays which are fine, stream-carried sediments deposited
in advance of distributary mouths. River bar material rests on the pro-delta clays. Bar sedi-
ment is deposited around distributary mouths, as the stream velocity is checked by waters of
the Gulf of Mexico. Fine, silty clays and clays are deposited concomitantly with bar sediment
in interdistributary areas and lense into bar material. Above this are the natural levees.
Levee silts and clays take the shape of a double wedge, thickest near the stream channel and
thinning into the flanking marsh or lake deposits. Channels of abandoned distributaries are
located between the natural levees. The basal portion of channels typically contains sands and
silts, and the upper portion is filled with fine clays and vegetation. A tidal channel frequently
occupies the remnant distributary channel.

Stranded beach ridges, or cheniers, are secondary trafficable units in this area. In the
western part of the State they are better developed, and owing to the lack of natural levees, they
are the only means of land travel in the marsh.

Cheniers of this eastern area are largely buried under marsh, but are continuous under
marsh between outcrop areas. These features nearly always form a linear pattern. Their

1
, y
‘a : t (ty
[SILTY CLAY SLTY CLAY AND”
AND SILT uk VEGETATION _
_ = SILT AND CLay

BARES SAND Soe

MARINE —~ [Gee

Figure 2. Ideal cross section of natural levee.

TREADWELL 33

maximum height is about 15 feet, and their bases extend twenty or thirty feet below sea level.
Width of the largest cheniers, most of which are buried under marsh, is about two miles. Veg-
etation is chiefly slash pine, live oak, and palmetto, and underbrush is thick, but does not
approach the density found on natural levees.

The cross-sectional appearance of a chenier is shown in Fig. 3. It is a sand wedge partly
buried under marsh and mudflat deposits, here shown resting on lake and bay deposits underlain
by compact Pleistocene material.

Being thick lenses of sand, cheniers are excellent trafficable units. They support weight
better than levees, and because they are porous, are as easily traversed during wet weather as
during dry weather.

Present sand beaches are confined to Breton and Chandeleur Islands, a chain of islands
about fifty miles long and one mile wide. The average height of the islands is about five feet,
although some sand dunes rise to fifteen feet. Beaches are found only on the seaward side of
the islands. The Sound side is black mangrove swamp. Beaches rest on buried swamp which
they override as they move inland, and beach thickness approximates elevation. The trafficable
value of beaches is similar to that of cheniers except that, because the beaches are not as thick,
they will not support as much weight. Along the inner margin of Chandeleur and Breton Sounds
are many small shell beaches, but they are too discontinuous to have any appreciable traffic-
ability value.

One other marshland feature needs to be considered—the marsh itself. Marsh composes
over 95% of all land south of the Pleistocene terrace. Its elevation varies from about sea level
to one or two feet. Marsh vegetation consists of various grasses, rushes, and sedges, which
are normally higher and thicker in fresh water than in salt water marsh. Fresh water marsh
is confined to more inland areas, and is composed of highly organic clay, silt, and vegetation.
Silt is deposited on the outer marshes when storm tides sweep over them.

The section in marsh areas is identified on the left margin of Fig. 2. Typically, there
are 20 to 25 feet of soft organic clay resting on river bar material. In many places this or-
ganic material is so soft that a pipe can be pushed into it by hand until the hard bar materials
are encountered. This is in sharp contrast to levee materials which are very compact and
“tough.”

CHENIERE

MARSH,
\

\\N TET B=
~\
A ___OLDER MARSH _DEPOSITS—

<i LAKE AND BAY DEPOSITS

i
| OXIDIZED PLEISTOCENE DEPOSITS
'
i

Figure 3. Cross section of a chenier.

34 TREADWELL
NAVIGABILITY OF WATERWAYS

In order to travel in most of the area, one must rely on boats; therefore, an understand-
ing of water-depth distribution is very important.

Water deep enough for an ocean-going vessel is present to within one to five miles of the
Chandeleur Islands on the Gulf side. Chandeleur and Breton Sounds and Lakes Borgne and
Pontchartrain are between five and twenty feet deep. The more shallow parts lie close to
shore. Except for the large water bodies just mentioned, marshland lakes are nearly always
less than six feet deep. Deeper water is confined to “passes” between lakes. Depths of lakes
can generally be correlated with size—the larger, the deeper.

Tidal streams of this area vary in depth from less than a foot to a hundred feet in some
cases, such as the channel between Lake Pontchartrain and Mississippi Sound. The width of a
stream is a reflection of its depth; however, allowances must be made for its origin. Although
origins are diverse, only two types need be considered: tidal streams originating between
levees of former distributaries and tidal streams forming in “open” or unobstructed marsh.

Tidal streams develop between natural levees by adopting the remnant distributary course,
producing rather straight, frequently long, channels. This pattern is evidenced even after five
or ten feet of levee subsidence. However, streams that develop in marsh with no obstructions
meander considerably and rarely have the straight pattern associated with tidal streams
confined by levees.

The width and greatest depth of ninety tidal streams are plotted on Fig. 4. The chart is
divided into three bands. The uppermost represents the depth-width relationships of tidal
streams originating between levees; the central band represents the depth-width relationships
of tidal streams forming in open marsh; the lower band shows that bends of tidal streams, like
bends of gravity-motivated streams, are deeper than reaches. By measuring the width of a
stream on an aerial photograph or map, it is possible to predict the approximate depth of that
stream. Furthermore, the chart shows that streams originating in open marsh are deeper for
a given width than those formed between natural levees. Although a few exceptions to the limits
presented are known, the chart may be used with success at face value. However, consideration
of the size and shape of a stream’s drainage basins allows even closer depth prediction. The
chart was constructed from data collected in easternmost Louisiana, but it has been found appli-
cable throughout the marshlands of the State. This is an area of fine sediment and extremely
low tidal range (1.5 feet). The effect of greater tides and coarser sediment on the depth-width
relationship of tidal streams will be studied this summer in the New England coastal marshes.
Necessarily, a new Set of values will have to be compiled for this region.

SEDIMENTATION

In addition to work on trafficability and naviga-
bility, a hundred and twenty sediment samples were
taken and analyzed for grain size, sorting, organic
content, percent shell, and glauconite and pyrite
content.

It was found that “clean” sands are present near
the Chandeleur Islands. Muddy sands or silts bottom
the sounds, and the lake beds are composed of silty
clay and clayey silt.

ECOLOGY

From the sediment samples about sixty species
of Foraminifera and a similar number of species of
Figure 4. Depth-width relationship Mollusca have been identified and their ecologic rela-
of tidal streams. tionships determined.

TREADWELL 35
HISTORY OF DELTAIC DEVELOPMENT

The sequence of deltaic development in this area is rather complicated, and only a
condensed version can be presented.

The oldest features now present at the surface are the stranded beach ridges, or cheniers.
Their age is on the order of 3000 to 5000 years (see Area 1, Fig. 5).

A very early subdelta was present, but very little is known about it. A second subdelta
entered and spread over most of the area. Evidence of it has been found on the Chandeleur
Islands, and an isolated remnant occurs within the area 2. Following the second subdelta, river
flow began to shift into area 3. During this time much of area 2 was subject to marine erosion.
As area 3 continued to enlarge, activity also was extended into area 4, and the delta was again
extended an unknown distance seaward of the Chandeleur Islands. Deltaic sedimentation con-
tinued to about 1500 A.D. Since that time, the river has shifted to the south, and the older sub-
deltas have been subject to marine erosion.

Combined with physical evidence, refuse of Indian people, such as pottery, has aided in
solving the developmental sequence just outlined and has been used throughout the State to help
affix the chronological sequence of deltas.

Figure 5.

CORRELATION OF CULTURAL REMAINS
WITH THE PHYSICAL SETTING

William G. McIntire
Coastal Studies Institute
Louisiana State University

Contract N7onr- 35608
Task NR 388-002

The deltaic area in south Louisiana is a very complex region from the standpoint of se-
quential development of the various trafficable units within the area. Threaded throughout the
area is a network of natural levees; and in limited areas, salt domes, active and stranded
beaches are present. These are the dominant characteristics in an area otherwise devoid of
natural relief and are the only overland routes or passes available in the near-sea-level
marsh. These trafficable units, in various degrees of decay, are directly related to the devel-
opment of coastal Louisiana that has taken place over many thousands of years.

The master stream built its deltas for thousands of years before man entered the scene.
It is estimated that the process of delta building has been going on for twenty to thirty thousands
of years whereas man is believed to have lived in coastal Louisiana only during the last two
thousand years. Since that time, however, many changes have taken place in the deltaic plain.
As one of the district investigators on this project, I approached the problem of working out
relative ages of trafficable streams by correlating the cultural remains of man with the physical
remains of the river.

The area covered in the study extends from the Texas border in the west to the Missis-
sippi border in the east. Approximately 15,000 square miles of near-sea-level lakes, marshes,
Swamps, bayous, and tidal channels were covered. The region is very rich in natural flora and
fauna. Profuse vegetation and abundant sea and animal life offered many inducements to early
man to settle in coastal Louisiana. He made his home on the most secure ground and took ad-
vantage of the many natural food resources abounding in the area. Mollusks were probably the
most important of all marine life in the regions where they were abundant and numerous, and
extensive shell heaps testify to their role in the economy of the early inhabitants.

The history of man in the deltaic plain
follows the phases of the changing stream. As
the river changed its course, it built in one
area and buried its past in another. A new
system of levees was built and since the old
had lost their fresh water and continual sedi-
ment supply, they began to decay. Eventually,
the requirements for human habitation were
no longer available on these natural eminences
and man was forced to move.

During a particular and limited time
span, man usually performs his daily tasks
in a certain manner. His various utensils
are designed and made in ways that reflect
his styles, those of his neighbors, and also
those used by his predecessors. In coastal
Louisiana, pottery fragments, or potsherds,
Figure 1. Shell midden. are the only universal cultural remains that

36

McINTIRE 37

have withstood both time and the elements. Although limited, these artifacts provide a relative
scale when classified, whereby the sequence of time is measured by culture change. In order
to ferret out the culture changes and consequently apply them to the changing river, archaeo-
logical methods have been used to order, collect, and classify the material.

Fortunately a competent group of archaeologists has worked out a chronological time
scale for the Lower Mississippi Valley. This chronological scale was used as the basis for
sorting and classifying the ceramic remains recovered during the project. At the present time,
the following periods are recognized for the Lower Mississippi Valley:

Youngest ... Natchez Period
Plaquemine Period
Coles Creek Period
Troyville Period
Marksville Period

Oldest ..... Tchefuncte Period

The periods were usually named after the localities where the pottery complex was first recog-
nized. For the purposes of this discussion these cultural divisions will be used to designate
time periods.

It was in the shell middens that much of the cultural remains left by the aborigines was
recovered. After the collections were made, the potsherds were classified according to type
of design and means of manufacture and then segregated into a particular time period.

Figure 1, a cross section of an ancient submerged shell heap deposited by the Indians, is
a good example of the sites visited. The shell heap is based on an old natural levee that has
subsided beneath the marsh level to a depth of eight feet. The only feature that remains to in-
dicate the presence of a natural levee is the top of the shell heap deposited there by early man.

This remnant feature is a frequent one throughout the deltaic area and is often the only
clue to the location of former streams. Hence it was necessary to scrutinize the aerial photos
of the area to locate trees and vegetation variations which almost inevitably indicate old Indian
sites. After the site was located, bore holes were drilled to determine whether the site was
resting on an old natural levee or an abandoned beach.

In addition to the identification of physical features, the Indian mounds and middens also
suggest ecological environments of the surrounding water bodies. The cross section of the
mound (Fig. 1) shows a layer of fresh-water clam shells (Unio) directly above the levee; cap-
ping this is a deposit of brackish-water clam shells (Rangia). This general stratification pic-
ture is found in many of the shell heaps in the area and indicates that a change in water condi-
tions must have taken place. Salinity change is caused either by encroachment of Gulf waters
due to subsidence or to the influx of fresh water due to active deposition of streams.

The sites investigated are indicated on Fig. 2 and show the widespread distribution
throughout the area. Various ages of the pottery are indicated by different. patterns on the map.
Clusters of sites suggest areas or streams which were active during a phase of the cultural
continuum and thereby indicate different shifts of the master stream. A very brief summary
of the cultural periods from oldest to youngest is all that is possible in this limited discussion.

Tchefuncte is the oldest culture isolated in coastal Louisiana and pottery of this complex
is found in both eastern and western Louisiana. The sites are usually associated with stranded
beaches or Pleistocene terrace material. Subsidence and burial of Tchefuncte sites by more
recent movements of the major streams has likely obliterated the record in the flood plain and
it is doubtful that much information about this early period will be recovered from the central
area.

Cultural remains of the Tchefuncte period give little definite information about the loca-
tion of the master stream, but Marksville sites in the flood plain show more definite correla-
tions. It has been established by competent geomorphologists that the Mississippi River
occupied the Teche- Mississippi channel prior to its diversion to the eastern side of the alluvial

McINTIRE

38

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McINTIRE 39

valley. After the master stream abandoned the Teche-Mississippi course, the Boeuf-Red occu-
pied the old entrenchment and therein built its levees. The presence of both the master stream
and the Boeuf-Red in the Teche- Mississippi course is without question. The major problem is
one of dating. The Gibson site (Fig. 3) located on the Teche-Mississippi course seems to fur-
nish evidence as to the approximate time that the Boeuf-Red was occupying the channel. As is
the case with many sites investigated during this survey, the Gibson site appears to be a mound
complex of a late period. However, borings show that the mounds were built upon an older shell
midden base, and pottery recovered from the midden is classified as Marksville. The midden
material extends to approximately twenty feet below the ground level and is intermixed with
red sediments. This indicates that the master stream was no longer flowing within the Teche-
Mississippi entrenchment during Marksville times but rather that the Boeuf-Red was occupying
the channel.

After the master stream left the Teche- Mississippi channel it diverted to the eastern
side of the flood plain and extended its deltaic mass in the area presently known as the St.
Bernard subdelta. Marksville sites as far out as the Chandeleur Islands indicate that the island
arcs were land-connected during Marksville time and that they were probably part of an ancient
subdelta extending at least to the island limits. The ceramics recovered during this study give
the first hint that there may have been an earlier subdelta in this region than the one presently
recognized.

The examples of cultural correlations with the natural setting given for Tchefuncte and
Marksville periods are generally found throughout the remaining culture periods. During Troy-
ville, Coles Creek, and Plaquemine periods the picture becomes clearer but the entire record
is not always possible to interpret because of subsidence and aggradation. However recent
streams leave the most distinct records and correlations are more easily determined.

The map indicates areas of site clusters and suggests the regions of deposition for each
period. The relationship of the aboriginal population of coastal Louisiana and the physiographic
features they inhabited is indicated from the numerous and widespread occupation sites through-
out the region. Many sites in one area and the paucity of sites in others indicate the areas in
coastal Louisiana where habitation was possible for any one period. These sites were located
on the most stable ground in the unconsolidated deltaic mass and indicate the trafficable passes
during a particular time period. Cultural remains have provided many clues regarding the
natural setting during aboriginal time.

FEET

VERTICAL EXAGGERATION = 5 TIMES

° 60 120 180 240 300 360
FEET
Figure 3. Cross section of Gibson site.

COASTAL MARSHES OF LOUISIANA

Richard J. Russell
Director, Coastal Studies Institute
Louisiana State University

Contract N7onr -35608
Task NR 388-002

Dr. Morgan, who was to present this paper as the concluding portion of the Louisiana
section of this conference, was unable to be present, and I will attempt to fill in for him from
some of his notes.

Dr. Morgan served as the Field Supervisor in the project, and Mr. Treadwell was one of
five district investigators. We budgeted nine months for training time and fifteen months in the
field for the district investigators. If our group had a full day at this conference instead of an
hour or so to review the Louisiana project, we would have included the other investigators.
They all have interesting stories.

Apart from the five district investigators, Mr. McIntire acted in the capacity of tying the
whole thing together. He ranged throughout the various districts working on the problems of
chronology and relative dating.

As we divided the Louisiana region, three of the investigators had areas of quite recent
delta growth. Mr. Treadwell’s talk concerned an area of recent growth in several deltaic suc-
cessions, but all quite recent as far as the whole history is concerned. Two of the investigators
covered roughly the western half of the Louisiana coast, and Dr. Morgan had intended to speak
particularly about their region.

There is a little story that Iam just going to sketch in a few minutes, which is somewhat
dramatic as to what has happened on the western coast. In general, the eastern portion of
Louisiana is the region of growth whose history does not go back too many centuries. The
western coast, ina sense, is much older and smoother. Wave erosion in general has taken off
the irregularities of the coast, so that there is quite continuous beach. In driving cattle west-
ward, it is only necessary to swim them three times across this whole area. A great many
cattle are grazed down here in the salt marshes, and actually the beach, as a cattle drive,
has some consequence.

This region is one in which there has been a history of alternation between periods of the
growth of marshes outward into the Gulf of Mexico, advancing the shoreline to the south, and
periods when the beaches formed by the waves are driven northward across the marshes.
Within recent centuries, most of this western half of Louisiana has been a region in which the
beach has been driven back across the marshes.

Comparing the old Land Office Survey maps and whatever data we could get, some over
20 years old, we published to the effect that this coast on the whole was receding at the rate of
about 600 feet per century. As a matter of fact, now that we have aerial photographs of this
entire region taken in 1952, in addition to those of 1932, we know the average recession of this
coast was 800 feet within this twenty-year period. The beach has been encroaching on the
marsh much more rapidly. It also has grown in size. Anything coarse which can be picked up
by the waves has been accumulated back on the beach.

The “coarse” material in this region is, for the most part, very fine sand or coarse silt,
so that while the beaches are quite firm and appear white, still they are composed of materials
among the smallest sand sizes. Other coarse materials are shells, bottles, pieces of steel

40

RUSSELL 41

from old ships, and the like, all of which get incorporated in the beach deposit. One of the in-
teresting things is the amount of Indian pottery which also gets incorporated because it is
coarse. I think it is not possible to walk very far along the beach, the way McIntire walked
around the beach, before a pottery fragment will be picked up. The beach has been straightened
since Indians, who had used the pottery, had been living south of the current beach.

In general, this land has grown southward when the Mississippi River and Red River have
discharged considerable amounts of sediment toward western Louisiana. At other times, as
under recent conditions when the river has been much further east, the deposition of the delta
has been concentrated away from this area. Those times are, in general, periods when the
beach encroaches northward over the marshes. There have been alternations in the past, which
are shown by the presence of old beach ridges, old cheniers, that lie back in the marshes. They
each represent a time when sediments were deficient in quantity and the beach had a chance to
be driven some distance inland.

There is ample mechanism-for making a beach move inland and no mechanism for pulling
a beach out. Once the accumulation, the sand, shells, etc., is driven back, there it stays. If
sediments come in quantities, the marsh grows off the beach and the coast grows outward.
Thus there is the alternation of the shoreline back and forth.

It is very interesting that the Indian story ties in nicely with this. As Mr. McIntire has
shown, the oldest Indian settlements are predominantly inland, and the most recent ones are
close to the coast.

The dramatic part of the recent history is this: starting a little over five years ago, the
pattern changed. This coast, after that retreat of 800 feet in the twenty-year period prior to
1952, is starting to grow out again. This is another cycle that has set in.

There are several elements involved in the reason for this. In the first place, the
Atchafalaya River, which comes down through a low basin, in the year 1900 was carrying 13
percent of the combined flow of the Lower Atchafalaya and the Mississippi. By 1950 this quan-
tity had climbed to 31 percent. Every single decade since 1860, when artificial accumulations.
were cleared out on a stretch of this river, has seen more water coming down the Atchafalaya
River than came in the decade preceding. The amount of alluviation in the Atchafalaya Basin
has so overwhelmed the old water bodies that most of the lakes have been obliterated. Most of
the lakes on the maps are very shallow. The basins are essentially full. People throughout the
Atchafalaya Basin can recall old landmarks and points that in earlier times they used as guides
in steering their boats, and now these landmarks are entirely inland. In one place, a prominent
citizen of Louisiana had a hunting lodge out in the basin, and he built a levee around his place
to protect it. Today the house is in a depression, with an alluvial plain surrounding it.

Since these lakes have filled up, they are no longer trapping the sediment. About six
years ago the first of the sediment reached the Gulf of Mexico. With increasing discharges
down the Atchafalaya River, not only is more sediment being brought down, but it is no longer
being held in the basin; so the sediment is now coming to the Gulf.

In the Gulf, the present dominant set of the current is westward. Atchafalaya sediment
has now formed an ooze or mud flat across this western coast, which has advanced westward
about 125 miles during the last five years. We have probed this. You can drag a skiff over it
and probe to determine the depth of this accumulation. You could run right through this ooze
with any sort of a landing boat but it is up to six feet deep. We have mapped it in three dimen-
sions for a report which we have submitted on this project. In many places the exposed flat is
100 yards in width at sea level. Pioneer salt water plants are now starting to get a good hold
on it, and this soon will become a brackish salt marsh area. The old beach is now becoming a
chenier.

These older cheniers were formed in the same way. In general, the chenier cross sec-
tion, exhibited by Mr. Treadwell, indicates a deposit 8 to 10 feet deep of beach material, over-
lying marsh and various other things, and up to a mile or so in width. Of course, any such
diagram is greatly exaggerated in its vertical and horizontal scales, but these are the general
dimensions.

42 RUSSELL

As far as land trafficability is concerned, the chenier units are excellent, and the stretch
along Grand Chenier, which was a beach not too many centuries ago, is actually trafficable by
trucks for over ninety miles.

The cheniers are also sources of potable ground water and are populated. There is quite
a little settlement in remote Pecan Island. Chenier au Tigre has been ruined recently because
of the mudflat that now isolates the beach. This old resort area has disappeared because of
mudflat development starting five years ago. On cheniers people dig only a few feet to finda
source of water. Troops could be brought in and landed in such places. and could stay there
for some time on perfectly firm surroundings.

The chenier belt shows a pattern narrowing to the west. It affords excellent trafficability
in directions parallel to the coast. Transversely, however, the marshes between the cheniers
are generally too soft, and waterways must be used to get from one ridge to another.

One of the tedious things to map is the inner extent of the marshes. This boundary has
been shown on the maps exhibited. North of the boundary is all good substantial dry land. Thus,
any route followed in crossing the marshes of Louisiana would end in the inner part on the good
firm dry land.

Well, those are the things that Dr. Morgan would have said. He would have said a good
deal more, too, but from his notes, and from the time I have available, I have tried to boil down

some of the points. I might say that these are all generalizations. We have completed the detailed

mapping of seventy-four quadrangles. Our field parties have done the soundings for depths indi-
cated on the maps. They show controlling water depths, and show them quite accurately, and also
define areas of firm land.

43

SUMMARY OF DISCUSSION ON PAPERS BY THE GROUP FROM
LOUISIANA STATE UNIVERSITY

A question was raised as to the effect the increasing flow down the Atchafalaya was having
on the lower Mississippi. In answering, Dr. Russell made it clear that he expressed only his
own views because he felt the problem had some political aspects. He pointed out that the city
of New Orleans needs a water supply and that this need could be easily fulfilled. There is an
abundance of water a few miles to the north that could be piped into the city instead of using
Mississippi River water. As far as the port is concerned, Dr. Russell felt the diversion of the
Mississippi into the Atchafalaya would be an excellent thing. If a dam should be built in connec-
tion with the diversion, he would prefer a dam across the Mississippi because a dam across
the Atchafalaya or Old River, would concentrate the flood flow down the channel and New Orleans
would begin to suffer from floods. This would be extremely dangerous. The hydraulic gradient
at extreme flood down the Mississippi is almost the same as at the lowest stage down the
Atchafalaya. The Atchafalaya has the ability to accomplish the drop to sea level in half the
distance needed by the Mississippi.

In addition, Dr. Russell suggested that a dam across the Mississippi would reduce the
number of days of fog in the passes. Fog, the chief fear of pilots, is caused by the cold river
water coming into the warm Gulf water.

However, the river towns’ water supply is the really critical thing, and that could become
a catastrophy unless steps are taken to bring decent water into the region.

In discussing the problems of deposition at the mouths of the Mississippi it was noted
that the two commercial outlets of the river are artificially maintained. The other outlets
barely maintain a depth of four feet over their bars. During time of flood, even with only a foot
of water, it is possible for a small boat to cross the bars because there is only a soft ooze to
plow through. However, at time of prolonged low water, the bottoms have hardened and a boat
drawing four feet has a difficult time coming in a pass not maintained by the U. S. Army
Engineers. Each pass tends to build a barrier, and therefore the natural depth of any pass
is less than one fathom.

a

THE MANGROVE SWAMP OF THE PACIFIC
LITTORAL OF COLOMBIA

Robert C. West
Louisiana State University

Contract Nonr -454(00)
Task NR 388-059

A study has been made of the physical characteristics of the Pacific coast of Colombia
and of certain relationships between these characteristics and problems of travel and living
along the coast. Data for these observations were obtained through field work done under an
ONR contract, which calls for a reconnaissance survey of the geography of the Pacific lowlands
of Colombia.

The Pacific littoral of Colombia is characterized by two distinct coastal types: (1) A low,
alluvial coast, fringed by a dense mangrove swamp forest, stretches from the Ecuadorean border
northward for more than 400 miles to Cabo Corrientes. (2) From Cabo Corrientes to Panama
and beyond, the coast is mountainous; cliffed headlands alternate with short sand beaches formed
in small coves.

Only the low, swampy mangrove coast is considered here, for it presents special prob-
lems for travel and subsistence; such problems may be characteristic of most mangrove coasts
of the humid tropics. Moreover, low alluvial coasts are the least understood of all coastal types
in terms of physical processes and development.

The mangrove swamp of the Pacific littoral of Colombia occupies the tidal fringe of a
narrow alluvial coastal plain. This plain, 5 to 30 miles wide, is being formed by material de-
posited by streams flowing from the western versant of the Andes. These streams carry an
enormous volume of water, and probably a large load, for they drain areas having an annual
rainfall of 200 to 400 inches. A large tidal range—an average of 10 to 12 feet—occurs along
this coast.

Two types of mangrove swamp coast exist along the Colombian littoral: (1) One is char-
acterized by dense mangrove forest growing to the edge of the sea and fronted by extensive mud
flats at low tide. Such a coast occurs in areas protected from strong wave action, as in bays or
behind shoals. (2) The other type of mangrove coast is characterized by the development of
extensive sand beaches along the seaward edge of the forest. Such beaches occur in sections
of strong wave action and longshore currents. Sand for building of beaches comes mainly from
stream load, which is effectively sorted by wave action. Minor amounts of sand probably de-
rive from erosion of occasional small headlands that occur south of Cabo Corrientes, such as
that near Buenaventura. Approximately 45 percent of the mangrove coast of Colombia is
fringed by sandy beaches.

VEGETATION ZONES ALONG THE COAST

Along most of the mangrove coast there exists a definite zonation of vegetation associa-
tions inland from the shore. Each of these zones is related to given physiographic conditions,
and each presents peculiar problems for living and travel. These zones are as follows: (1)

The beach zone, with its low shrubs, creeping vines, and stands of coarse grass. (2) The
mangrove zone, which consists of dense tidal forest of various species of mangrove. These

line the lagoons immediately back of the beach, and continue inland for a distance of one-half

to two miles. This zone penetrates much farther inland along the lower parts of streams, where

44

WEST 45

salt or brackish water occurs at high tide. (3) The fresh-water swamp, which is flooded by
fresh to slightly brackish water from rivers during high tide. One-half to two miles wide, the
vegetation of this zone is comprised of the giant nato tree (Mora megistoperma) and clumps of
the naidi palm (Euterpe, sp.), highly reminiscent of the nipa palm association of Southeast Asia.
(4) On slightly higher ground immediately inland from the alluvial areas affected by tide, begins
the fourth zone—the vast equatorial rainforest that covers the rest of the coastal and western
slopes of the Andes to an elevation of four to five thousand feet.

This peculiar zonation of vegetation appears to be typical of most mangrove coasts of the
world. It is described for the Malaya Peninsula by Watson! and by Dobby, for the west coast
of Africa by Grewe,> and for the Guiana coasts of northern South America by Martyn.4 Further
field work is necessary to ascertain the actual distribution of this zonation along other man-
grove coasts.

With the gradual extension of the coast seaward through deposition, there seems to be a
slow successional change within the vegetation zones. As the floor of the fresh-water swamp
becomes higher and better drained, equatorial rainforest plants invade; eventually fresh-water
Swamp plants encroach upon the landward margin of the mangrove. In turn, mangrove succeeds
the beach associations as the beaches become remnants cut off from the ocean front by forma-
tion of new strands and buried by tidal muds. Finally, the beach plants colonize newly deposited
stretches of sand along the ocean front.

THE BEACH ZONE

The beaches are made up of fine, compact sand, sorted from the river load by wave ac-
tion and distributed up and down the coast by longshore currents. Many beaches are five to
six miles long. Their width varies from 100 to 400 yards at low tide to zero to 25 yards at high
tide. They are smooth and firm and could support heavy motor vehicles. Some beaches, how-
ever, are crossed by rivulets, whose beds are often composed of quicksand. Fresh to slightly
brackish water can usually be found on the beaches by digging a few feet below the surface.
Moreover, tidal ponds, called pozos, form in slight depressions and shallow lagoons on the
landward side of beaches. At low tide these ponds afford an abundant supply of fish which na-
tives catch by spearing or by poisoning. Small fishing villages often occur at the end of beaches
near the mouths of estuaries or rivers. Groves of coconuts, small patches of maize and manioc.
are often cultivated in the sandy soil of beach ridges near the villages. In terms of travel and
living, the beach zone appears to be the most favorable of those along the mangrove coast.

Beach formation has been one of the major factors in the seaward extension of the low
coastal plain. Remnants of beach ridges separated by mangrove-enclosed lagoons occur in
abundance back of the present beaches. Due probably to slight sinking and alluviation, the beach
ridge zone is invaded by mangrove and eventually becomes part of the swamp.

THE MANGROVE SWAMP

This zone presents the most difficult problems in terms of travel and subsistence. The
most conspicuous tree of the swamp is the giant red mangrove (Rhizophora brevistyla) which

1Watson, J. D., “Mangrove Forests of the Malay Peninsula,” Malayan Forest Records, No. 6,
pp. 1-275, 1928.
2Dobby, E.H.G.; “Southeast Asia,” p. 67, London, 1950.

3Grewe, F., “Africanische Mangrovelandschaften. Verbreitung und wirtschaftsgeographische
Bedeutung,” Wiss. Verdéff. d. Deut. Mus. f. Landerkunde zu Leipzig, N.F. 9, pp. 103-177, 1941.

4Martyn, E. B., “A Note on the Foreshore Vegetation in the Neighborhood of Georgetown, Brit-
ish Guiana,” Journal of Ecology, Vol. 22, p. 293, 1934.

46 WEST

grows in solid stands; individual plants often reach heights of 80 to 100 feet. At low tide the
gnarled prop roots of this tree, four to ten feet high, are completely exposed, rising from a
surface of soft, brackish ooze, into which a heavy man would sink to his knees. At high tide,
however, the Rhizophora swamp can be penetrated along a maze of tidal estuaries and creeks
in small boats or canoes.

Although the Rhizophora is the dominant mangrove component, it is best developed along
the edge of tidal channels where there is complete flooding by the tide twice each 24-hour pe-
riod. Inland, there exist round patches of low growth, four to six feet high, composed of
dwarfed Rhizophora with stunted prop roots, mixed with black mangrove (Avicennia nitida) and
other brackish water swamp plants. These patches of low growth occupy ground that is higher
and drier than the channel banks. They are flooded usually by semimonthly spring tides only.
The soil is peat-like, soggy, and quaking underfoot; a heavy man sinks to his ankles in the top
muck. Often in the center of these patches are found hammocks of the naidi palm, a plant
characteristic of the fresh-water swamp, or in some instances even clumps of equatorial rain-
forest. The centers of these patches are the highest, driest, and firmest parts of the mangrove
swamp, but they are extremely difficult to reach.

The curious occurrence of such patches of low growth on higher, drier ground is typical
of other mangrove areas. For example, along the coast of Malaya such areas are called
“byiaks” and are readily noticed on aerial photographs.> The formation of such features is
probably due to the slow rise of land through the decay of mangrove vegetation. The underlying
peat contains remains of large Rhizophora roots and trunks.

Another curious feature characterizes the mangrove swamps of the Pacific coast of
Colombia. Within the swamp back from the seacoast for a distance of one-half to one mile,
one frequently encounters along tidal channels small areas of sandy material which rise slightly
above the general level of the swamp muck. These sandy “islands” are locally called “firmes.”
They are sites of human habitation within the mangrove swamp, fresh water is usually found at
a depth of three to four feet below the surface, and coconut palms, patches of maize and other
crops are grown. These peculiar sandy “islands” appear to be remnants of old beach ridges
that have been largely destroyed with the general seaward advance of the coast.

THE FRESH-WATER SWAMP

The fresh-water swamp affords greater ease of travel and better possibilities for food
supply than the mangrove. The prop roots of red mangrove and the soft brackish muck are
absent. Yet the daily flooding by river overflow makes most of the swamp penetrable only by
canoe, during high tide. During the past 25 years natives from up-river have been utilizing the
flooded banks of the rivers within this zone for growing rice. This development has lessened
the problem of obtaining food within the coastal area.

Although malaria occurs throughout the Pacific coast, the Anopheles mosquito prevails in
the fresh-water swamp zone. Pools of standing fresh water, left by the retreating tide, form
excellent breeding places for these insects. At dusk and at dawn swarms of mosquitos and other
biting insects (mainly black flies and gnats) occur around every hut and canoe to pester unpro-
tected occupants to distraction. Smaller numbers of mosquitoes breed in the mangrove zone
(chiefly in small bodies of rainwater that collect in epiphytic plants on the trunks of large trees)
and in the beach area (principally in the shallow wells dug into the sand). Curiously, few mos-
quitos are encountered along the middle and upper courses of the streams that flow across the
narrow coastal plain.

MANGROVE AS A GEOLOGIC AGENT

It is commonly stated that red mangrove (Rhizophora) is an important agent in the sea-
ward advance of coastlines. It is supposed that Rhizophora is the pioneer colonizer of

5Stamp, L. D., “The Aerial Survey of the Irrawaddy Delta Forests,” Journal of Ecology, Vol. 13,
pp. 262-276, 1925.

WEST 47

partially submerged mud banks and shoals, that the growth of young plants fixes the shoal, and
that the later development of prop roots of the plant is instrumental in building the shoal into
an island, which eventually is attached to the mainland by alluviation. It is true that the prop
roots of mature mangrove probably serve to catch fine particles in water and thus aid in deposi-
tion. However, along the Colombian coast and elsewhere,° it is observed that land must be
entirely emerged before it is colonized by plants, that the first colonizers are not Rhizophora,
but black mangrove (Avicennia), and that Rhizophora will not establish or even maintain itself
except in quiet saline to brackish water in protected bays or along coastlines protected from
wave action by offshore bars or shoals. Strong wave action appears to preclude the develop-
ment of mangrove and destroys existing stands. Constant shifting or destruction of mud shoals
and of offshore mud or sand bars causes continual change of locale of strong wave action along
mangrove-bordered bays. At such points wave action immediately begins to erode the muck
and underlying peat-like material which supports the mangrove, eventually killing extensive
areas of Rhizophora and Avicennia forest.

The Pacific coast of Colombia contains but a small fraction of the world’s mangrove
swamp; nevertheless, it affords an excellent exampie of the physical and related travel and
subsistence conditions to be expected within such a type of littoral. Detailed comparisons with
other mangrove areas of the tropics would doubtless reveal interesting and valuable facts. Un-
fortunately, however, although numerous botanical and ecological studies of mangrove swamps
have been made for small areas, the world distribution of that feature has never been adequately
mapped, and the world cultural and physical geography of mangrove swamps remains to be
studied.

SUMMARY OF DISCUSSION

Some comments were made on the ability of mangroves to pioneer in areas protected
from strong wave action. The black mangrove (Avicennia) appears to be much more tolerant
of high temperatures than the red mangrove (Rhizophora) and may be more tolerant of salt.
Consequently it is found nearer the sea. In some areas, as along the Gulf Coast of Florida
where there is little sediment in the water, the prop roots of the mangrove are not too effective
in building shoals.

6See, for example, Freyberg, G. von, “Zerst6rung und Sedimentation an der Mangrovekiste
Brasiliens,” Leopoldina, Vol. 6, pp. 69-117, 1930.

WEST

48

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WEST 49

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WEST

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COASTAL DUNES

H. T. U. Smith
University of Kansas

Contract Nonr-583(06)
Task NR 387-012

INTRODUCTION

Most of the papers presented at this symposium are concerned with projects which are
well along toward completion. Iam perhaps at somewhat of a disadvantage in discussing a
project which is only beginning, and therefore have little in the way of results or conclusions
to offer. I will endeavor, however, to outline some of the main points of interest in my project
and provide some degree of orientation in (a) the study of coastal sand dunes, (b) the practical
implications of such studies with particular reference to terrain intelligence through air photo
interpretation, and (c) engineering problems encountered in dune terrain.

OCCURRENCE OF COASTAL DUNES

Sand dunes of various sizes and shapes are widespread along the low-lying coasts of the
world, and in many regions occupy up to 10 percent of the total length of the shoreline. In some
places, of course, they occupy much more of the shoreline. They are found along the coasts of
both arid and humid regions, in all latitudes, bordering a wide range of types of inland terrain,
and occur both on the mainland and on barrier islands. In all areas where coastal dunes occur,
effective planning of engineering and military operations requires that due consideration be
given to the special characteristics of dune terrain.

In addition to coastal areas proper, the shores of inland seas and lakes, ancient abandoned
shorelines now well above water level, and the beds of dry lakes in arid regions all provide
sites for dune topography.

The scale of the dune topography ranges widely from place to place. In height, the dunes
range from less than 10 feet to more than 200 feet. In some places, as along the southern and
eastern shores of Lake Michigan, dunes constitute the highest hills, if not the only hills, of the
coastal region. In considering width, it is the width of the dune belt rather than the individual
dunes which is significant, and this also ranges widely, from less than 100 feet to many miles.
Height and width do not necessarily vary together.

The terrain on the inland side of the coastal dune belt may be of many varieties. In some
places it is essentially flat, in other places it is hilly. In many localities, swampy ground or
actual ponds and lakes are found on the inland border, and in fewer areas there are continuous
bodies of water.

In the United States, examples of coastal dunes are numerous. Along the Atlantic coast,
narrow zones of low dunes are common from Florida to North Carolina, and limited areas of
higher dunes are found near Kittyhawk, North Carolina; Cape Henry, Virginia; Cape Henlopen,
Delaware; and Cape Cod, Massachusetts. Along the Gulf Coast, dunes occur at many places in
Florida and Texas, the largest area being in southern Texas. On the Pacific Coast, important
dune areas are located near Los Angeles, San Luis Obispo, Monterey, San Francisco, and
Eureka, in California; along roughly one third of the Oregon coast; and at many points along the
coast of Washington. In the Great Lakes area, dunes of unusual size border the southern and
eastern shores of Lake Michigan. In Europe, coastal dunes are widespread along the coasts of
north Germany, Denmark, Belgium, northern France, and the Bay of Biscay, and more sparsely

51

92 SMITH

distributed around the British Isles and the Mediterranean. In north Africa, there are numerous
areas of coastal dunes, and in some places the great areas of interior dunes come so close to
the coast as to enter into consideration of coastal problems. In South America, dunes are ex-
ceptionally well developed at many places in the desert coastal strip of Peru.

GENERAL DESCRIPTION OF COASTAL DUNES

The appearance of dune areas ranges from that of comparatively simple and well-defined
unit dune forms to complex mazes of ridges, mounds, and hollows with seemingly extreme de-
grees of disorder. The simpler forms comprise the following:

(1) Foredune ridges, or elongate mounds of sand up to a few tens of feet in height, ad-
jacent and parallel to beaches.

(2) U-shaped dunes, arcuate to hairpin-shaped sand ridges with the open end toward the
beach.

(3) Barchans, or crescentic dunes, with a steep lee slope on the concave side, which
faces away from the beach.

(4) Transverse dune ridges, trending parallel or oblique to the shore, and elongated in a
direction essentially perpendicular to the dominant winds. These dunes are asymmetric in
cross profile, with a gentle slope to the windward and a steep slope on the leeward side.

(5) Longitudinal dunes, elongated parallel to wind direction, and extending perpendicular
or oblique to the shoreline; cross profile is typically symmetric.

(6) Blowouts, comprising a wide variety of pits, troughs, channels, and chute-shaped
forms cutting into or across other types of dunes or sand hills. The larger ones are marked
by conspicuous heaps of sand on the landward side, assuming the form of a fan, mound, or
ridge, commonly with a slope as steep as 32 degrees facing away from the shore.

(7) Attached dunes, comprising accumulations of sand trapped by various types of topo-
graphic obstacles.

The above types of dunes may exist in either an active or a stabilized condition. The
active dunes have loose, bare sand on all or part of the surface, and undergo continuous change
in size, shape, and/or position under the impact of strong winds capable of drifting the sand.
Stabilized dunes are those so well covered by vegetation as to inhibit further drifting of the
sand. Different degrees or stages of stabilization may be distinguished, and in advanced stages
a well-developed soil is present. Any dune may become stabilized if conditions permit the
spreading of vegetation over its surface. Also, any stable dune may become active again if the
cover of vegetation is weakened or destroyed, either locally or generally, as by fire, deforesta-
tion, excavations, climatic changes, etc. Large-scale reactivation of dunes by the work of man
has been known to do great damage by overwhelming arable lands and settlements and remov-
ing the dune areas themselves from profitable uses.

The simpler types of dunes, whether active or stabilized, exhibit a wide range of modifi-
cations and variations, and the over-all characteristics of dune assemblages are subject to
innumerable complications by the crowding or merging of individual dune forms, by alterna-
tions between activity and stabilization, by the juxtaposition or superposition of one type or
scale of dune form on others of different type or scale, by shifts in wind direction during dune
building, by wave erosion, and by other factors. Much remains to be learned both about the
general principles governing these complications and about the detailed features of specific
areas of coastal dunes.

SMITH 53
RECOGNITION AND INTERPRETATION OF DUNE TERRAIN

Identification of dune terrain is generally possible from analysis of landforms as shown
on air photos. For the simpler types of dunes, this may be done in an empirical way by per-
sonnel of limited scientific training. For the more complex types, however, and for dune areas
which have undergone modification during long intervals of stabilization, the experience and
training of the specialist are required.

Interpretation follows after identification and may be concerned with one or more of the
following factors:

(1) Direction of the effective sand-moving winds. For areas in which no meteorological
records are available, dune forms may provide the best available data on wind direction. Some
caution is necessary in making interpretations, however, for such a factor as unequal exposure
to winds from different directions may introduce qualifications, particularly in the case of
partially stabilized dunes.

(2) Offshore conditions. Analysis of the source of sand supply for dune building may
lead to significant conclusions as to nature of the bottom on the seaward side. In some places
it has been determined that the sand now incorporated in stabilized dunes could have been de-
rived only from sandy flats some distance from the present shoreline and exposed at a time
when sea level was much lower.

(3) Present trend in coastal development. Tendencies toward erosion or fill along the
shore, important in the planning of permanent installations, may be recorded in the form and
pattern of dunes.

(4) Ground and underground conditions. The range in size of sand grains that are readily
moved by the wind is comparatively small, thus dune sand is characteristically well sorted and
generally is composed mainly of grains between 1/2 and 1/8 mm in diameter. Identification of
dune topography, therefore, leads at once to the conclusion that incoherent, fine sand lies at or
near the surface. Some implications of this fact are outlined in a following section. Although
the characteristics of the subsoil, as noted above, are relatively constant, the nature of the
soil on stabilized dunes ranges widely, particularly with respect to thickness and degree of
stability. Correlation of these characteristics with the details of dune morphology is a matter
for continued research, and it is hoped that this project will contribute useful data.

(5) Other terrain conditions affecting military operations, as discussed in the next sec-
tion of this paper.

The general directions in which interpretation, particularly photo interpretation, of dune
terrain for practical purposes may proceed are thus marked out. Progress in these various
directions, however, will be conditioned to a large extent by continued basic research on the
geology and geomorphology of the widest possible variety of coastal dune areas and types.

ENGINEERING AND MILITARY ASPECTS OF DUNE TERRAIN

Dune sand in general has the following characteristics which are important from the
engineering standpoint:

(1) It is easily excavated, but sides of excavations require support.
(2) Drainage is excellent, except in low-lying hollows or depressions.
(3) It provides good foundations for roads and other structures, if properly confined.

(4) It provides excellent fill material, and has been used extensively for this purpose
near Chicago.

54 SMITH

(5) Unless blended with coarser sand, it is unsuitable for concrete aggregate, but is
suitable for bituminous surfacing.

(6) Special protective measures against sand drifting are necessary where the surface
is bare.

(7) Stabilized surfaces readily revert to drifting if improperly handled.

Dune topography also has the following surface characteristics which are significant for
military operations:

(1) Dune ridges and blowout hollows offer good cover from ground fire, and the nature of
the sand tends to muffle and restrict the effects of bombs and shell fire.

(2) Dunes commonly provide excellent concealment from the ground view.
(3) In many coastal areas high dunes provide the best available observation points.

(4) Special camouflage methods, such as simulated blowouts, might be adapted to dune
areas.

(5) Tracks of men and vehicles on bare sand are quickly obliterated if the wind is blow-
ing strongly, and the same effect probably could be obtained by airplane propellers or helicopter
rotors.

(6) Actively blowing sand introduces special maintenance problems for equipment.

(7) The readiness with which stabilized dune sand reverts to the actively blowing condi-
tion introduces an additional factor in planning operations or installations, and offers a possible
means of harassing enemy-held coastal territory.

(8) Bare dune sand provides poor footing for men and for wheeled vehicles with ordinary
equipment, but offers fair to good trafficability for tracked vehicles or for wheeled vehicles
with 4-wheel drive and oversize, low-pressure tires, within certain limitations of slope.

(9) Stabilized sand surfaces under certain conditions offer good trafficability initially but
tend to deteriorate rapidly if traffic continues.

(10) In swampy areas, dune ridges may provide the best available trafficability.

(11) Various types of dune topography provide innumerable combinations and patterns of
channels and obstacles for movement. Where the dunes are strongly asymmetric, movement
may be a one-way proposition. Movement toward inland points is facilitated by some types of
dunes and greatly retarded by others. Knowledge of the general types of dunes present permits
rapid appraisal of the possibilities for movement.

CONC LUSIONS

Dune topography constitutes one important type of coastal terrain, and has certain special
characteristics that play an important part in the planning and execution of operations in the
areas concerned. Some of these characteristics are essentially the same for nearly all types
of dunes, whereas others are more individualized and more specifically g-verned by local
conditions. Proper appraisal of the latter must be based on continued research on the geogra-
phy and geology of a wide range of representative areas, in as many different types of environ-
ment as possible. Such studies may be expected to make for more rapid and efficient procure-
ment of terrain intelligence for those coastal areas where dunes occur, by air-photo interpre-
tation or by other procedures. It is hoped that the project here represented will contribute to
that general objective.

SMITH

Figure 1 - Complex dune topography along the southern shore of
Lake Michigan. The light-colored areas are active blowouts, and
the contorted ridges are stabilized dunes. Maximum height of the
dunes is slightly less than 200 ft. The complexity of this dune area
is due to the superposition of different types of dunes of different
ages. (U. S. Department of Agriculture photo)

be pg 2 MILE
se ;
a :

Figure 2 - Broad belt of active dunes along
the southern Oregon coast. (U. S. Depart-
ment of Agriculture photo)

55

56 SMITH

SUMMARY OF DISCUSSION

Much of the discussion concerned sand dunes as indicators of wind direction.

It was pointed out that if there were very strong, persistent offshore winds, there would
be few dunes. Dunes are built only where the onshore winds are more vigorous than offshore
winds, unless there is enough vegetation to prevent the offshore winds from contacting the sand.
Wherever blowouts rise high enough to top the vegetation, they are exposed to winds from both
directions. If blowouts are extended in a landward direction, there cannot be very effective
winds from that side. Some types of dunes are much better recorders of wind directions than
others, some give only a very rough indication or net resultant.

Mainly, the dunes indicate the direction of winds strong enough to move the sand. It
might be possible that a wind from one direction would be considered the prevailing wind in
terms of time, but might not be strong enough actually to move the sand, while an occasional
wind from another direction might be above the critical velocity necessary to move sand. In
such a case, the direction indicated by the dunes would be that of the occasional winds. The
only winds of significance in dune building are those strong enough to move the sands.

In less arid regions some consideration must be given to the time of year when the strong
winds blow in reference to the amount of evaporation and rain. Although it has been reported
that even moist dune sands can be blown by winds of sufficient velocity, ordinarily sand is
moved by winds free from a great amount of precipitation.

A PRELIMINARY INVESTIGATION OF SHIFTING BEACH PROFILES

Henry C. Stetson
Woods Hole Oceanographic Institution

Contract Nonr-1254(00)
Task NR 388-018

The purpose of this investigation is to map the changes in the beach profile throughout a
twelve month’s period, choosing portions of the Massachusetts coast where a variety of beach
environments could be found. The exposure, that is intensity of wind and sea conditions, the
abundance of supply of sand and the proximity to the source, the slope of the offshore bottom and
the depth of water are all factors that exercise a control over the resultant form. Furthermore,
the rapidity with which a beach changes shape, and the shape which it assumes are likewise
controlled by them.

For this investigation the terminology adopted by the Beach Erosion Board is used and
the term beach profile includes the backshore, the foreshore, and the offshore portions. They
must be considered as a unit. The entire beach profile is mobile and varies constantly. Strictly
speaking, observations are only good for the time when they are taken. It is becoming apparent,
however, that certain broad patterns are repetitive, that these patterns may be seasonal, and
that by continuous observations on selected traverses, certain principles can be established
concerning the responses of different types of beaches to the various forces which control their
form. On most beaches at any given time there will be features which are hold-overs from a
previous set of conditions and which are in the course of being modified. Spot observations of
any given beach are, therefore, of limited value and only by a continuous series can the
evolutionary sequence be unraveled.

PLYMOUTH BAY

WAUSED
ACH CG

BARNSTABLE

Figure 1. Locations of the traverses.

57

58 STETSON

The following locations were chosen for this study. On the Atlantic side of Cape Cod
traverses have been maintained at the following places; Nauset Coast Guard Station, the aban-
doned Highland Light Coast Guard Station, and about three-quarters of a mile west of the Race
Point Coast Guard Station. The first site is a traverse off the southward growing spit which
protects the Eastham-Orleans shore, the second is off a cliff section which is shedding debris
of all types, and the third is off the north side of the Provincelands section where the shore is
being prograded by a succession of beach ridges and offshore bars. The exposure to onshore
gales is severe and is about the same on all three, although the tidal currents run stronger off
the Race Point traverse. Wave action is as violent as you can find anywhere on the Atlantic
coast. On the Cape Cod Bay side, two traverses have been maintained: one at Sandy Neck,
Barnstable, and the other at Duxbury Beach. On neither of these beaches is wave action as

_violent as on the outer Cape, although wind velocities are probably as high and dunes have been
extensively developed, especially at Barnstable. Geologically, both are wave-built spits. In the
case of Sandy Neck, the source of the sand is the cliffs north of the Cape Cod Canal, but at Dux-
bury the source is not apparent, possibly coming from the bottom off shore. Both seem rela-
tively stable and have exhibited little topographic change from year to year. They present a
marked contrast to the outer Cape where every storm brings marked alterations in width of
the backshore and in the position and height of the berms, as well as shifts in the offshore bars
of the seaward portion (Fig. 2).

For any given set of environmental controls, looked at in the large, there is a correspond-
ing form which any given beach tends to
assume, although it may change tempo-
rarily and in response to seasonal altera-
tions in the environment. The profile will
not be permanently altered unless the
controls, such as supply, also change per-
manently. The more rigorous conditions
of winter cause the most rapid fluctuations,
and it was for the purpose of charting these
shifts and the return to equilibrium condi-
tions that a twelve-months’ period was de-
cided upon for the observations. There is
a strong possibility that any given beach
will tend to develop what might be termed
seasonal characteristics, which may be
repeated in response to changing weather
conditions as the seasons succeed each
other. It may well be that conditions ob-
served in one winter may be used as pre-
dictions for what may be expected in
subsequent winters.

Field work has been carried out in
the following manner. The form of the
emerged portions of the beach, that is the
backshore and the foreshore, is surveyed
with a transit and the offshore portion is
sounded from a dory with a hand lead and
a marked bamboo pole. A permanent base-
line of 600 to 1000 feet has been staked out
depending on the curve of the shoreline.
The seaward portion of the traverse is
about 1500 to 2000 feet long, and the boat’s
‘ : : position upon it is cut in with the transit up

See é to 609. Every time a sounding is taken
TE flag signals are made by the boat’s crew
and acknowledged by the instrumentman.

Figure 2. The outer beach of Cape Cod looking F 4
north. Note the marked variations in width and On the Race Point and Highland traverses,

the position of the offshore bars as marked by parallel profiles 400 feet away are being
the line of breakers. run this winter [Feb. 1954], as the position

‘

STETSON 59

and shape of the bars are thought to vary considerably in a short distance horizontally. The
boat’s course off shore is maintained by permanent range markers set up on the beach, dunes,
or cliff. Occasional echo sounding profiles have been run into deeper water from the outer ends
of the traverses with one of the Oceanographic’s smaller power boats to supplement the above
data. It is not expected that any changes in bottom topography will be recorded in water deeper
than is found over the outer ends of the traverses, which is about 40 to 50 feet. Bottom samples
are also taken on the emerged and submerged portions of each beach not only to get an over-all
picture of the texture but also to determine, if possible, the relationship of texture to slope and
to other changes in the topography.

As was expected to be the case, summer conditions were very stable. The easterly
storms of that season were neither heavy enough nor of long enough duration to produce sig-
nificant changes in profile. In fact, it seems probable that the profile of early summer can be
counted upon to last with very little change at least until the heavy gales of late fall and early
winter begin.

The profiles figured here were chosen as examples of the type of surveys made and on
which some change has been observed, rather than as illustrative of any fundamental trends.
A delineation of the cyclical change which these beaches go through, if it is a cycle, can be
made only after the twelve months of observations have been carried out. It is expected that
these beaches will return to the profile observed during the summer months after having gone
through many variations; but this has never been established for any beach regime (Figs. 3, 4,
5, & 6).

HIGHLAND

aE TIOE LEVEL

6 HRS. 4 MINS. AFTER HIGH WATER AUGUST I8

i NOVEMBER I7----—

25 ITIOE LEVEL
3 HRS. 49MINSAFTER HIGH WATER

RACE POINT
SS AUGUST 4

I5= TIDE LEVEL
= 1HR.18 MINS. AFTER LOW WATER

OCTOBER 15 ---——

FEET

45 — x10 ~

Figure 3. Highland traverse showing cut and fill on the emerged and submerged por-
tions. Note cutting of berms for the dotted traverse but no significant trends in the
offshore portion. Race Point Traverse shows smoothing of berms and also a very
marked excavation and seaward fill of the offshore section.

FEET 9 400 eno woo 1600 zooo)

TIDE LEVEL NAUSET,
N S 6 MINS. AFTER HIGH WATER AUGUST 20

SEPTEMBER 10 -———

a

a
wo —sITIDE LEVEL =
4 25_ 2HRS.33 MINS. AFTER HIGH WATER

ae x10
35_

Figure 4. Nauset traverse showing removal of an offshore bar.

60 STETSON

a0 oP WP 80 92 ae te ne ‘go Geo er

Th HIGHLAND

= S.

ial SSN OCTOBER 14

Es SS. ---—OCTOBER 27

SO; in pee ay 17

5_ NSe ee NOVEMBER

ee \ we i

N\ \
XN
a N
SS
— Co
“N
N

aT XN
lo_

= : WATER LINE

~ _ SX—3 HRS. 21 MINS. AFTER LOW WATER
Sa

ey WATER LINE
UJ . IHR. 54 MINS.

ly x 10 \. ‘—AFTER LOW WATER

\,_LOW WATER LINE
Figure 5. Highland traverse showing changes in the foreshore and

backshore. Note the marked cutting between Octobe 14 and 27, with
partial restoration by November 17.

4 ee sp 6° ae we Ee 170 se Ge ee =

SF HIGHLAND
> SS
vies NNN OCTOBER 14
hi SS ——--——OCTOBER 27
5_ NSN oN} cso NOVEMBER 17
Nas ee SS
\ N.
XN
— N
N
= SS 225
SS
N
— XN
10_ :
reo : WATER LINE
mi Null SX —3 HRS. 21 MINS. AFTER LOW WATER
e are WATER LINE
—- 1HR. 54 MINS.
ee x 10 \ —AFTER LOW WATER

= \\_LOW WATER LINE

Figure 6. Duxbury traverse showing slight fill on the backshore and
cutting on the foreshore. This is a relatively stable beach.

The emerged portion of the profile also shows considerable change of form. One of the
most striking features which may appear very suddenly is a steepening of the beach profile with
the cutting of a vertical scarp at the seaward edge of a berm. This scarp is usually of small
dimensions but may, on a steep beach, be several feet high and, because the sand is loose, dif-
ficult for a man to scale. It cannot be stated at present with any degree of certainty just what
wave conditions are responsible for this cutting on the beach face but they are thought to be
correlated with short, steep seas (Figs. 7 & 8).

A series of aerial photographs have been taken on four flights from a PBY which is at-
tached to the Oceanographic Institution. The flights covered the entire length of the outer Cape

STETSON 61

Figure 7. High water at the Race Point Traverse showing the berm
beginning to be cliffed by a thirty-mile northwest wind, January 1, 1954.

Figure 8. Low water at Race Point Coast GuardStation, showing a more
extensive cliffing in the berm caused by some previous blow. Note the

light snow cover which has been removed to the last high water mark,
January 1, 1954.

and all of Sandy Neck and Duxbury Beach. Although these photographs are not entirely satis-
factory as they were taken with a hand-operated Graflex, they do give some idea of the chang-
ing configuration of the beach outline and of the offshore bars. One of the difficulties of using
aerial photographs for beach work in this region is the steepness of the offshore portion bring-
ing relatively deep water close inshore which obscures the bars unless marked by breakers.
Furthermore, the water in the Gulf of Maine often contains considerable amounts of plankton
resulting in low visibility.

62 STETSON

The equipment for the field work has proved entirely satisfactory. The jeep with over-
sized tires can tow the trailer with the dory to any necessary location, sometimes over dune
country. The dory has proved entirely practical for taking soundings, and rowing has the ad-
vantage over a power boat for sounding on a range because it can be better controlled. It can
be launched from the beach except when the bars are breaking heavily which would preclude
sounding even from a DUKW. Sounding with a pole and a hand lead is probably more satisfac-
tory in these waters than a portable fathometer would be. In smooth water the fathometer would
be superior but such is rarely the case on the outer Cape. With a rough or lumpy sea it would
be very difficult to sort out wave heights on the fathometer tape from bottom irregularities.

The sites for the present traverses were chosen because they represent what might be
called “simple” or average sections of the shoreline. Serial observations of the regimen at
such places are necessary for a basic understanding of the full beach cycle before more com-
plicated cases are considered. The continuation of this study in addition to the present trav-
erses will include the following areas where the beach is prograding rapidly and shoals and
spits are forming. From Wood End to Long Point, the section of beach which encloses Province-
town Harbor, growth is taking place by the extension of large, steepsided beach ridges, overlap-
ping at their distal ends. At Race Point Light the beach is prograding by the addition of ridges
and swales in a seaward direction. Nauset Inlet is an illustration of two complex spits which
are attempting to grow across an inlet where there are strong tidal currents. The amount of
sand supplied by beach drifting and longshore currents is large. The result is a complicated
series of recurving spits with their attendant shoals which are constantly shifting. The situa-
tion provides a good example of a balance between erosion, transportation, and deposition.
Beaches constitute one of the most mobile of landforms and one which may change radically in
a matter of a few hours. They are never static.

SUMMARY OF DISCUSSION

Matters relating to grain size and sorting were discussed. It was suggested that along a
stretch of coast there would be marked changes in size of materials. To determine this,
samples are being taken both off shore and on the emérged portions each time the beach pro-
files are surveyed. The samples are being studied to discover any correlation between slope
and grain size and shape. In general it is recognized that the flatter the beach, the smaller the
grain size.

Figure 9. Field equipment.

CLASSIFICATION AND IDENTIFICATION OF
COASTAL ZONES OF THE WORLD

William C. Putnam
University of California, Los Angeles

Contract Nonr-233(06)
Task NR 388-013

Throughout the day we have listened to descriptions and studies of detailed areas of spe-
cific regions, of things that one might say are concerned more, I hope, with fact than with fancy.
I find myself now in the predicament of attempting to describe and classify all the coasts of the
world. This is indeed a problem of great complexity because we are dealing not only with an
aspect of the entire earth but with all the variation of climates and processes that operate upon
it, as well as with one of the most dynamic interfaces on its surface—the boundary between land
and sea.

This study was taken on as an applied project, one which would be of direct and pertinent
significance to the military. As I envisage the project and the goal we are attempting to
achieve, it has become one of primarily establishing communication: the development of a
common language between groups of people of diverse backgrounds and interests.

Communications have always been one of the more difficult problems in military affairs.
The anecdote I treasure in this regard is one that appeared in a recent issue of the “American
Scientist,” which dealt with the life of Lord Rumford, a leading British scientist of the period
of the American Revolution. I had not known that he was of American birth, and had quite a
career and variety of interests in the United States. As a Loyalist, he refused to take up arms
against his king, went to England, and was quickly depressed by the deplorable state of commu-
nications then existing in the Royal Navy. One of the less publicized episodes, I am sure, had to
do with a time when the British Fleet sighted the French on the horizon. The-admiral hoisted a
signal, probably some spirited remark, such as “Engage the enemy and they are ours,” where-
upon to his dismay the fleet lowered its sails, broke out the small boats in a hurry and these
rowed furiously toward the flagship, under the impression that the signal read, “Today is payday.”

Difficult as communications may be within the military frame of reference, the problem
becomes even more acute when we attempt to communicate from one field to another. In science,
it seems to me, the basis of communication is classification—and from this the development of
a working nomenclature. If there was any hallmark of 19th Century science, perhaps as con-
trasted to what we think of science today, it was its overwhelming concern with setting up clas-
sifications of birds, rocks, insects, people, etc., etc. The prevailing belief then was that if you
had classified something, you had answered all the basic problems in considerable measure.

Today I think we have gone on in many fields to attempt to find the answer to the more
fundamental question of “why,” rather than simply “what.” Although coasts have been classified
in one fashion or another for quite some period of time, perhaps as much as a century, most
geologic classifications are based on the geologist’s primary concern with genesis. The chief
question he seeks to answer is how did this thing happen, a concern of little interest to the
practical person, who instead wants to know what is going to happen when he makes changes in
the natural environment. He is not concerned whether the rocks on which he is building, for
example, are 2,000,000 years or 2 years old.

The classification of shorelines now used in almost all textbooks is the one promulgated
by the late Professor Douglas Johnson, who placed major emphasis on emergence and

63

64 PUTNAM

submergence. His classification becomes extremely difficult to apply in a military sense, be-
cause it forces the user to make a decision—namely, did this coast rise or sink or remain
static with respect to sea level—that has little relevance to the problem at hand, which is the
determination of those characteristics of a given coast that are of strategic significance.
Secondly, the classification itself encounters difficulty because sea level is such an inconstant
datum—the last significant change has been a world-wide rise following the melting of the con-
tinental ice caps at the end of the Pleistocene. This has had the practical effect of making
almost all the shorelines of the world ones of submergence.

An outgrowth, in part, of Johnson’s classification, but a much broader extension of it, is
a recent book by Valentin, “Die Kusten der Erde.” Valentin set up a four-fold approach to
coastal morphology, recognizing that there are dynamic processes operating within the earth
itself. Some forces tend to elevate parts of the earth’s crust, others to depress it. Operating
in conjunction with these forces are processes of erosion and deposition which also may cause
a shoreline either to advance or to recede. The result is a four-component system that treats
land loss or land gain as the resultant of emergence, submergence, construction, and destruc-
tion. Unfortunately, the complex interplay of those self-same components is difficult if not im
possible to determine in relation to the appearance of most of the world’s coasts. In applica-
tion, then, Valentin’s scheme has difficulties similar to Johnson’s classification.

In contrast, we have attempted to set up a classification in which the matter of problem-
solving might be cut to a minimum, and in which we could arrive at a common means of com-
munication so that people of widely ranging backgrounds end up speaking a common language.
This means we should avoid loaded terms, terms that mean different things to different people,
or terms that have lost all meaning because they have been bandied around so much they no
longer have any special significance.

We are confronted by the fact that we live on a globe, that it has different climates, and
that the effects of these climates are expressed in different ways in a pattern often recognizable
on the surface of the earth. Of all these secondary effects, the most visible is the carpet of
vegetation. If, for example, we take the simplest of all landforms, a plain, then I think all of us
know how different that plain will look on aerial photographs depending upon its environmental
situation. An arctic plain has an entirely different appearance and complex of operating prob-
lems than a tropical plain.

The accompanying tables are the outgrowth of an as yet uncompleted attempt to recognize
these environmental factors and arrive at a workable coastal classification that will include all
the elements of our scheme. The first table (Fig. 1) is a classification of those coastal types
that are determined by the major landforms present in the coastal strip extending some 5 to 10
miles inland. For that reason the character of the gross structure involved is indicated in the
names of the coastal types, which stand out in bold letters. The agents shaping these structures
are listed across the top of the table, where they are grouped according to broad zones of cli-
matic influence. The two dominant agents, ice and running water, are given the leading positions.

Obviously some of the processes and landforms do not conform ideally to such a simplifi-
cation as this, and examples of these are the work of the wind, of organisms, and lastly the re-
sults of processes originating within the earth, such as volcanism. But at least I believe that
we can resolve most of the coastal landforms of the world into a relatively small number of
structural types that can be placed in climatically controlled environments.

It is now our hope—and this is only a progress report—that we have evolved a system
that appears to be working and which fits the facts. If this is the case, our next move will be
to reduce the classification to a symbolic code that can be used to represent the leading coastal
landforms of the world on a map at a scale of approximately 1:25,000,000.

For example, a pattern of closely-spaced horizontal green lines within the dotted outline
of a coast will tell the user that this is a plain, very nearly at sea level, underlain by layered

Since this talk was given, an excellent summary and review of the entire problem of coastal
classification has been written by C. A. Cotton, “Deductive Morphology and Genetic Classifica-
tion of Coasts,” Scientific Monthly, Vol. 78, pp. 153-181, 1954.

PUTNAM 65

sedimentary rocks, that these rocks are flat-lying, and that the surface of the plain was shaped
by ice scour. Therefore, one can expect a wholly different set of operational consequences here
than would be encountered on a geometrically similar plain shaped by streams and located ina

tropical region.

These coastal types determined by the major landforms present in a 5- or 10-mile wide
strip do not convey the whole picture, however, in spite of a rich variety stemming from various
combinations of structures and climates. Shore features, though much more limited in areal
extent, are often of equal or greater military importance. They are, in effect, obstacles form-
ing a narrow fringe between the open sea and the particular major coastal landform with which
they are associated locally. We therefore recognize a second category of coastal types—those
determined by shore features (Fig. 2). Properly included in this category are such things as
kelp beds. Dense kelp fouls propellors, makes maneuvering of small craft extremely difficult,
and otherwise causes serious problems in amphibious operations. Coral reefs belong here too,
as a lot of hard-won experience gained in the last war will testify. Tidal woodland in Fig. 2
refers not to mangrove swamps exclusively, because there are other kinds of coastal vegetation

that also extend into the sea.

Beaches other than barrier beaches are being excluded from our classification and map
because they are the subject of highly detailed operational intelligence studies conducted by the
military. Furthermore, a great many beaches are of extremely limited linear extent.

Shore feature coastal types can be shown on the world map by the use of suitable carto-
graphic techniques, though they will necessarily have to be exaggerated for such small-scale

CLIMATICALLY-CONTROLLED COASTAL ZONES a

ZONE OF ZONE OF econ pep| ZONE OF |TROPICAL ZONE
gE ch Sore ae Se at bo
HUMID REGIONS
PRINCIPAL
LITHOLOGY

RELATIVELY ICE ae ALLUVIAL PLAIN | EOLIAN [CORAL
FLAT-LAYERED | PLAIN |MEDEPOSITION PLAIN) “ DeTTA PLAIN PLAIN rein
REL, og SEDIMENTARY PLAIN |
PLAINS FLAT- | Siaiaeeaananniinaianeee
Bestar rec] LCA | SCOURED ¢ VOLCANIC PLAIN} ERODED
PLAINS |————————— PLAINS
COMPLEX

LANDFORM
CLASS

CONSTRUCTIONAL
PLAINS

COMPLEX PLAIN

LOW SEORENTARY

PLATEAU” REMNANTS

2 | eae SINE
LOW “VOLCANIC ERODED

SCOURED *
WILLS |-PLATEAU'REMNANTS( OL <

COMPLEX HILLS

HIGH “SEDIMENTARY
PLATEAU” REMNANTS | 5p 44
GLACIATED) HIGH "VOLCANIC Fone)
MOUNTAINS) PLATEAU"REMMANTS (10

COMPLEX MOUNTAINS | |
4

MAJOR

COMPLEX

COASTAL DESTRUC- ge, PEDIMENTAR
TIONAL - | ROCKS

FLAT:
VOLCANIC |
aaa AYERED ROCKS |

COMPLEX

| UPLANDS} UPLANDS
DFORMS

aaa SEDIMENTARY PLATEAU |
FLAT: aunenc) ——_——_———_| Skea
PLATEAUS LAYERED| VOLCANIC | VOLCANIC PLATEAU } ERODED

PLATEAUS

| =EaRn eo sees | RCATIEAUS,
COMPLEX PLATEAU |

|

CONSTRUCTIONAL] RELATIVELY | ICE way cee CORAL LAA PLATA
UPLANDS | FLAT-LAYERED | PLATEAU HILLS |PLATEAU! vor cano

Figure 1. Classification of Coastal Types Determined by Major Landforms (By J. T. McGill)

66 PUTNAM

representation. They can be indicated, for example, by narrow color bands in contrast with
broad color bands denoting the associated major landform coastal types.

We are now in the process of adding a third element to our coastal classification, and
this will be essentially a climatic pattern as exemplified by the characteristic type of vegeta-
tion. This, I believe, we shall represent by numbers or by some kind of symbol or color scheme
overriding the symbols for coastal types. These environmental categories will be selected on
the basis of type areas, such as the Visayan Type or tropic grassland, Malayan Type or ever-
green rain forest, etc., in order to give them geographic relevance. They will be chosen as
nearly as possible to be representative of really distinctive and readily recognizable climati-
cally similar areas. In other words they can be used as analogs for predicting operational
problems in inaccessible areas.

In summary, the proposed world map will show, in a landward sequence, the nearshore
and shoreline conditions, the character or major landforms and vegetation in the coastal strip,
and then the extent of climatically similar regions over the continents. This will provide a pic-
ture, we hope, that when interpreted will bring much-needed information into the strategic plan-
ning of landing operations. To restate our goal, it is to build a workable classification using
simple, meaningful terms that will convey some understanding of operating conditions to people .
not necessarily trained in the military evaluation of terrain. Finally we want a classification
of coastal forms that is based almost entirely on their representation as seen from the air.

The aerial photograph is unquestionably the most powerful tool in our possession today, and
this classification is intended to aid photo interpreters.

The oblique air photographs that follow are all from one region, the coast of southern
California, much of which is reasonably representative, we believe, of what might be described
in the first step of our scheme as complex hills. This is in considerable part a dry region,
which means that most streams are intermittent and do not supply a large volume of sediment
to the sea. As a consequence, beaches are relatively thin. Long stretches of the coast are
bordered by bare rock whose ledges can be traced into the sea (Fig. 3). The strike of the rocks
on land commonly is reflected in their seaward continuation by kelp, a plant which introduces a
second operational problem on a coast such as this because it is commonly quite difficult to get
small landing craft ashore through this marine growth. Bedrock crops out practically every-
where on the surface of the ground inland. Some rocks are stable and hold up well, as in the

IN CLIMATICALLY-CONTROLLED COASTAL ZONES
AS LOCALLY APPLICABLE

Ca Pera Nreraarion
VHD | corat | VEGETATION |

BACKSHORE Se ys e
CONSTRUCTIONAL |e Ope suoRE TIDAL FRINGING OR
FEATURES MUD FLAT PAI BARRIER REEF) WOODLAND
SHORE / BARRIER ISLAND, ISOLATED
CORRS | BEACH OR SPIT reer | KELP BEDS
NOTE: “SHORE FEATURE COASTAL TYPES
| ARE ASSOCIATED WITH MAJOR
DESTRUGTIONAS eae estoReit| aoe LANOFORM COASTAL TYPES.
FEATURES COMBINATIONS OF BACKSHORE,
FORESHORE AND OFFSHORE
ee MARINE TYPES OCCUR LOCALLY.
OFF SHORE BENCH
oe ee

Figure 2. Classification of Coastal Types Determined by Shore
Features (By J. T. McGill)

PUTNAM 67

terraces adjacent to the shore. Shales, on the other hand, and especially those with a high con-
tent of volcanic ash, often fail through landsliding, as in the area near the center of the photo-
graph. Such ground is quite unstable for military operations.

Figure 4 shows a mountainous coast in the same region. Here again are a set of operating
problems that we hope can be set forth in tabular form and that can be recognized by a relatively

Figure 3. Stream-eroded complex hills, dry region. Coastal
terraces on Palos Verdes Hills, Southern California. (Spence
Air Photo)

Figure 4. Stream—eroded complex mountains, dry region. Seaward
slope of Santa Ynez Mountains, Southern California. (Spence Air Photo)

68 PUTNAM

inexperienced interpreter. If he can locate himself on the proposed coastal map of the world
and can relate his picture to our tables and illustrations, he can set up a pattern of more or

less predictable events that he will encounter, such as the following, which are typical of this
particular region: offshore kelp, rocks, narrow beach, small intermittent streams, rock rather
than soil, sparse vegetation, and vegetation whose distribution is controlled to a marked degree
by the kind of rock. The terrain in the foreground is underlain by shale, a rock that is relatively

Figure 5. Alluvial plain margin,dry region. Coastal swamp
and lagoon near Point Mugu, Southern California. (Fair—
child Aerial Surveys, Inc.)

Figure 6. Coastal dunes, dry region. Coastal dunes near
Casmalia, California. (Spence Air Photo)

PUTNAM 69

impermeable, which means that water does not sink into it very far. The result is that seasonal
vegetation with short roots, such as grass, dominates. Back in the mountains where the rocks
are more permeable, slopes are mantled by a permanent vegetative cover of thick, thorny
shrubs and bushes that are virtually impenetrable. The fire hazard is very high during the
summer dry season, and fire in this country introduces all sorts of operational difficulties that
will not be encountered in a more humid region.

Figure 5 is a good example of the complexities that must be faced in setting up a classi-
fication. An excellent beach fronts the shore, but its value is reduced by the coastal lagoon and
tidal marsh that constitute a formidable barrier denying access from it to the land, as well as
by the fact that it can be taken under observation and fire from the nearby mountains. The
mountains have about the same structure and vegetative pattern as those in the preceding photo-
graph and like them are characterized by a high correlation between rock type and the distribu-
tion of the plant cover.

The coast shown in Fig. 6 is for the most part an extension of Professor Smith’s talk. In
fact he showed a slide of essentially the same region as this, not far from Santa Maria, Califor-
nia. This is a very exposed coast. Landings are difficult, but are possible. Once ashore the
problem of dispersal is paramount, and getting rid of the mountains of gear that any amphibious
operation requires must be a first order of business. All men and supplies are in an exposed
position with almost no cover. Troops will encounter very marked differences in trafficability
in crossing the fresh beach sand, then rather active dune sand, then vegetation-stabilized older
dune sand, until finally solid ground is reached some distance inland.

Figure 7 is an extension of the same problem, but with a further complexity introduced.
If a landing is made here and troops cross the shore dunes, they may find access to the interior
barred where stream drainage has been blocked by the dunes and water is ponded. Between the
coastal dune belt and dry ground inland there is a moat of marshy, low-lying ground. A photo
interpreter without too extensive a background of experience should be able to read these major
terrain characteristics from the photograph if he has the proper guidance. We hope to provide
him with that guidance by means of a classification which has a rational, scientific, and genetic
basis, but one that is cast in empirical rather than theoretical terms so that there will not be
a breakdown in communications.

Frankly, I should have been much happier if we could have turned this problem around
the other way and made a number of regional studies from which we could have built a body of

Figure 7. Coastal dunes, dry region. Dune lakes near
Oceano, California. (Spence Air Photo)

70 PUTNAM

theory. In a sense we could have piled up a lot of bricks and ultimately made a structure out
of them, instead of possibly constructing a pyramid resting on its point. At the moment we are
in the unfortunate position of having to build an intellectual edifice with almost no foundation of
actual field studies. But since time is of the essence, I believe we are justified in attempting a
first approximation at a classification, inadequate as it may be, than to strive for perfection
through several decades of field work. Then with the benefit of constructive criticism from the
users of our system we may achieve something of really practical value.

SUMMARY OF DISCUSSION

The scientific basis and the purposes of this coastal classification were further defined
during the discussion. It was generally agreed that in devising a classification of coasts, con-
sideration should be given to the matter of genesis. In fact, several participants stated that
they felt any classification which would be valid in scientific terms would be basically a genetic
classification. It was pointed out, however, that the classification need not make explicit the
bases used in its development nor require the user to repeat all the thought processes used in
developing the classification. The prime objective of this research is to devise a coastal clas-
sification of use to photo interpreters, who may not be trained in geology or geography. This
classification must provide a means of enabling interpreters to obtain valid answers to military
problems without getting involved in problems of landform origins.

The classification has to be workable and easily understood. In setting up the classifica-
tion every effort has been made to avoid problems of semantics, the use of too highly special-
istic terminology and complex definitions, although all the technical scientific bases were
thoroughly considered. For example, in considering climate it was felt best to avoid the com-
plexities of standard classifications. A person operating out in the field will not be interested
in having to decide whether or not it is a Cw climate. He wants to know whether it’s dry? Or
is it wet? Or is it very wet? The use of the word “dry” in the coastal classification means
what the average person means by dry. There is not much rain. The ground is dry. There is
not very extensive plant cover.

The new classification is being applied to the coasts of the world and the results plotted
on a Single map. The scale requires considerable generalization. However, the map is ex-
pected to enable the strategic planner or other user to gain an idea of what would be encountered
on a five to ten mile strip inland from any coast. If, for instance, he is concerned with the coast
of Kamchatka, the map will give him an idea, graphically, of the offshore conditions he will en-
counter as he approaches the coast, of the dominant landing conditions, and of the principal
coastal landforms with their vegetation cover. Will he encounter a high tidal range? Is ita
coast where it does or does not rain a lot? Is it beset by strong winds, or do calms prevail?
Is it a foggy coast? Is it icebound? The user should be able to answer all these questions
from the information symbolically represented on the map.

Bedrock problems have been minimized as much as possible in this classification. In-
cluded are three categories of rock-structure: flat-layered sedimentary rocks, flat-layered
volcanic rocks, and the complex. The last category, probably by far the largest, includes com-
plexes of structure and/or lithology, many of which appear to be essentially massive on aerial
photographs. This is about as far as the users would want to get involved. They do not want to
add research in geology to their other tasks.

A studious effort has been made to avoid producing a classification similar to the kind
rather widely used in photo interpretation, sometimes referred to as the “postage stamp clas-
sification” with its reference book full of pictures. You have a photograph to identify. You do
not know what it is. It has a round shape in it. You go through your book trying to find some-
thing with a similar round shape. It is about like matching a Guatemalan issue of stamps. You
cannot read Spanish, you do not know who El Presidente is, but you have a picture of him and
look through your Scott catalog until you find a similar face. Ergo, this must be it.

The final product of this research will include numerous elements. First is the ancient
genetic framework of the coastal strip, the kind of rock, the grass structure, and the major
landform. These are physical combinations that have world-wide applicability. On the

PUTNAM 71

framework are superimposed the regional or local effects of climatic control; the shaping of the
landforms, formation of shore features, and other things that add up to a specific pattern or
complex. Included here is the cover of vegetation, often the dominant effect visible on aerial
photographs. Then there can be set up an environmental type or regional pattern which will be
identifiable in people’s minds, because there will be analogies between similar climates on
similar terrain. In essence, this will be a physical geography of coasts, so organized that from
it can be read the conditions that probably will be encountered, thus alerting and guiding the
users of aerial photographs. This is a tool that will be used for terrain interpretation and by
people not necessarily trained in this field.

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