The Bulletin of the Beach Erosion Board

Vol: Sy Wes

DEPARTMENT OF THE ARMY
CORPS OF ENGINEERS

7

- WOODS HOLE i
OCEANOGRAPHIC INSTITUTION +
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JUL 12.1949
WOODS HOLE, MASS. |

THE

BULLETIN

OF THE

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BEACH EROSION BOARD

OFFICE, CHIEF OF ENGINEERS
WASHINGTON, D.C.

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VOL. 3 JULY 1, 1949 NO. 3.

DEPARTMENT OF THE ARMY

CORPS OF ENGINEERS

THE BULLETIN

OF THE

BEACH EROSION BOARD

TABLE OF CONTENTS

Page
Beach Erosion Board Research ce ccoccccecccccccccccccece all
New Jersey Creates Beach Erosion Committee ...2.ccececcce 5
The Causes of Plunging and Spilling Breakers .ccccoec. i
Discussion - A Formula for the Calculation of
Rock Fill Dikes ...ccceccccos SOODD0OD000000000000006 11

Comite Central d'Qceanographie et d'Etude des Cotes ... 13
Measurement of Heights by Resistance Elements 2.0... 16

Beach Erosion Studies ..0.0c.c0c00000000e000000000027000e0 23

PUBLICATION OF
THE BEACH EROSION BOARD
CORPS OF ENGINEERS
WASHINGTON 16, D. C.

JULY 1, 1949

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BEACH EROSION BOARD RESEARCH

Extracts from a speech by Lt. Col. Wm. B. Stelzen—
muller, Assistant Resident Member, Beach Erosion

Board, at the Great Lakes Conference on Lake Shore
Erosion Control Problems held May 13-14 at Toledo,

Ohio, under auspices of the Council of State Cov-
| ernments.

The Beach Erosion Board was established by Act of Congress in 1930
to investigate, study, and report on effective means of controlling or
preventing erosion of the ocean, gulf, and major lake shores of the United
States. The Board has seven members -- The President and three members
are engineer officers of the Army, and three members are civilians
selected from engineers of State agencies cooperating with the Federal
Government in the study of shore problems. The Board reports directly
to the Chief of Engineers, Department of the Army.

,

Our mission is fourfold:

lst, we assist the Division and District Engineers of the
Corps of Engineers in setting up cooperative study programs that
result in a report to the local interests and to the Congress on
the most practical means of correcting specific erosion problems;

2nd, we review these reports, just as the Board of Engineers
for Rivers and Harbors reviews navigation and flood control reports,
and transmit our findings to the Chief of Ingineers;

3rd, we review navigation reports on proposed improvements
that may affect the shore line and inform the Chief of Engineers of
any effects to be expected on the shore line for ten miles on either
side of the improvement; and

4th, we conduct research or general investigations of the
various factors involved in coastal erosion with a view to increas-
ing our knowledge of the complex relationships between the factors,
and to improving the design of protective works.

Cooperative beach erosion studies have been frequently discussed,

» and I will merely recall to you that the Beach Erosion Board provides
consultative services and exercises the function of review of these
reports. The reports are prepared by the field officers, the District _
and Division Engineers of the Corps of Engineers.

In order to carry out our research responsibility, the Board main-
tains a small laboratory in Washington, D. C., and two field research
groups equipped for accurate hydrographic surveys, sampling of beach and
offshore materials, current and wave measurement, and numerous other
field research operations. In the laboratory we have one large wave
tank, 4 feet deep, 14 feet wide, and 85 feet long, and two small wave
flumes. Scheduled for early construction are a large outdoor tank about

600 feet long, 15 feet wide, and 20 feet deep, anda coast model test
basin 3 feet deep, 300 feet long and 150 feet wide. In the large tank,
we hope to study at full scale the action of waves up to six-feet in
height. It is expected that these two new Esau tee will eviee the
means to answer many troublesome problems.

Our work in the laboratory at the present time is principally con-
cerned with studying beach slopes of maximum stability under particular
wave conditions, with special attention being given to the effects of
sand grain size, initial beach shape, and wave character. Several other
related studies are being carried on at the same time, and our objective
is to develop criteria for modifying natural beaches so as to obtain
slopes that will be more stable within the range of wave conditions which
exist in each section of the shore line.

Another important activity in the laboratory is the development of
new or improved instruments for taking essential measurements in the
field. Some of the instruments which have been developed are wave height
and wave direction recording gauges, devices for sampling the suspended
sand load in the sea, and for sampling the bed load (or sand in move-
ment on the sea bottom), and an apparatus for measuring the settling
velocity of beach sands. It might be mentioned that our current feeling
is that the settling velocity of sand in water is a more reliable in-
dication of its probable behavior on a beach than is the grain size alone,

It will be obvious that we must know a great deal about the height,
frequency, and direction of waves reaching the shore if we are to es-
tablish dependable quantitative information about rates of littoral
drift. For this reason, one of the key objectives in our entire general
investigative program is to obtain accurate statistics on waves for long
periods of time at selected points along each of the principal shore
lines of the United States, and particularly at locations where we are
gathering data on sand movement. Wave stations are now located at
Huntington Beach and El Segundo, Califomia; at Long Branch, New Jersey;
and on an oil drilling platform seven miles or so offshore from the
coast of Louisiana. These stations have been in operation for approx-
imately one year, and already a tremendous mass of wave data is on hand
and is being analyzed by our Engineering and Research Branch.

A project that is closely tied in to the program of recording wave
conditions is that of developing and testing methods of forecasting
waves from weather reports and synoptic charts. If a satisfactory
method can be devised and perfected, it would be of untold benefit to
everyone whose occupation or avocation is connected with the sea and
its changeable moods. We are carrying on this study partly by means
of a contract with the New York University.

might be of interest. One party is now on the West Coast and on® on
the East. The West Coast group has three projects, two of which\wll

An account of the current activities of our field ae
°
be described briefly to illustrate the type of work being done.

In 1947 and 1948, approximately 14 million cubic yards of sand was
deposited on central beaches of Santa Monica Bay. (See figure) The
beach was widened some 600 feet from Hyperion northward a distance of
seven miles to the Ocean Park Pier. This wide section of beach is to
be developed with access roads, parking areas, and playgrounds, and it
will be of immeasurable value to the people of Los Angeles County, as
well as to the beach cities of Ocean Park, Venice, Playa del Rey, and
Manhattan Beach.

The field research group is conducting a sand movement study in
this area. As mentioned before, a wave recording station was establish-
ed on the end of the El Segundo pier, near the center of the Santa
Monica Bay shore line, and seasonal volumetric surveys are being made.
Daily littoral current readings are taken in cooperation with Los
Angeles County authorities, and beach and offshore sand samples are
taken.

Littoral drift is quite variable in this large bay, and the study
of sand movement is further complicated by a deep submarine canyon off
Redondo Beach that approaches within a few hundred feet of the shore.

The fill was not completed until October 1948 and its slopes
have not yet reached equilibrium. Preliminary studies indicate a net
downcoast movement of sand over the fill area at a rate of about 1,300
cubic yards per day. This rate will lessen considerably as the fill
stabilizes. This study will naturally be of value in determining the
rate at which this filled beach will need replenishment, but it will
also provide us with basic knowledge which will be very helpful in
studying similar situations elsewhere.

The second project is in the vicinity of Anaheim Bay, California.
From October 1947 to January 1948, approximately 1,100,000 cubic
yards of sand was deposited on the beach fronting the Surfside Beach
Colony and the Anaheim Bay Naval Ammunition Depot. The beach had been
denuded due largely to interruption of the downcoast littoral movement
of sand by the jetties protecting the Anaheim Bay entrance.

The field research group has been studying the movement of this
fill since March 1948. A wave station has been established at the
seaward end of the Huntington Beach Pier, and volumetric surveys and
littoral drift studies are being made from Anaheim Bay south to the
mouth of the Santa Ana River, a distance of eleven miles.

The littoral drift in this area is predominantly upcoast in the
summer, due to waves from storms generated in the Southern Hemisphere,
and downcoast during the rest of the year. As a result, the rate of
littoral sand movement has varied during the seasons from about 200
cubic yards a day upcoast to about 2,500 cubic yards a day downcoast.
The net movement in the vicinity of the fill from April 1948 to
February 1949 was about 600 cubic yards a day to the south.

The other field research group, on the Hast Coast, is studying a
somewhat different kind of problem -- the movement of a spoil bank of
dredged sand containing 600,000 cubic yards in 38 feet of water. This
project was an experimental one to determine whether dredged material
from harbor channels dumped by hopper dredges, as close to the shore
as they could safely navigate, would eventually move in to the beach.

The dump area is about 3,700 feet long by 750 feet wide and is
located about one-half mile trom shore, just north of the pier at
Tong Branch, New Jersey. The material was dumped during the spring
and summer of 1948, and surveys were made by the field research group
before, during, and after the dumping operations. The surveys extend-
ed for four miles along the beach and for a distance of a little more
than a mile out to sea. Surveys of the entire area were made in April,
July, and October, with weekly surveys of the immediate dumping area,
weather permitting.

On this section of the New Jersey Coast, the predominant littoral
drift is northward toward Sandy Hook. OQnshore winds prevail about 60
per cent of the time. It was found that bottom velocities existed in
the dump area high enough to move the sand in the pile, but on com-
pletion of the fall surveys no appreciable movement of the pile shore-
ward could be detected. About 21 per cent of the dredge bin measure
appeared to have moved outside the dump area, but the beach showed
little evidence of receiving enough sand to measure. The change was
in the nature of a flattening of the pile and some scattering of sand
in a thin layer away from its boundaries.

The spring surveys completed in April are being studied now.
Detailed computations have just begun, and the general indication
is that a rather appreciable portion of the pile has been moved. The
beaches nearby appear wider in places to the casual observer, but we
cannot attribute any apparent improvement to the offshore sand bank
until we have made an exhaustive analysis of the data from the spring
surveys.

In conclusion, it can be stated that the Board feels strongly
that the general investigative program will be of great benefit in
providing more economical, yet sound, solutions to individual coastal
erosion problems. The results of the research are made available
in publications of the Poard and are applied to specific beach erosion
studies by means of consultation between personnel of the field
offices and the staff of the Board.

NEW JERSEY GREATES BEACH EROSION COMMITTEE

The State of New Jersey has by action of its legislature on April
9, provided for the creation of a commission to consider and provide
ways and means to protect and preserve the beaches and shore front of
the state by the erection and construction of protective works, dredg-
ing, and other suitable methods.

The enabling act follows:

Senate Bill 120
State Beach Erosion Commission

TITLE

AN ACT creating 4 commission to investigate and study the subject of
the protection and preservation of the beaches and shore front of the
state from erosion and other damage from the elements, to effectuate
such protection and preservation of the said beaches and shore front
and other purposes incidental thereto and making an appropriation

to the said commission. (Herbert and Farley)

Commission created. There is hereby created a permanent commission
to investigate and study the subject of the protection and preservation
of beaches and shore front of the state from erosion and other damage
from the elements, to effectuate such protection and preservation of
tke said beaches and shore front, and other purposes incidental thereto.

Name ; members; terms. The name of the said commission shall be
the state beach erosion commission, and the said commission shall be
composed of four members of the senate,.to be appointed by the
president of the senate, four members of the general assembly to be
appointed by the speaker thereof, and four members, at large, to be
appointed by the governor.

The terms of the members appointed by the president of the
senate and the speaker of the general assembly shall continue from
the date of their respective appointments until the second Tuesday
in January following. The term of each commissioner appointed by
the governor shall be four years. Vacancies occuring otherwise than
by expiration of term shall be filled in the same manner as though
occurring by expiration of term but for the unexpired terms only.
The members of the commission shall serve without renumeration but
shall be reimbursed for all expenses incurred in connection with the
work of the commission.

Duties. In connection with the effectuation of its purposes, the
commission shall consider and provide ways and means to protect and
preserve the beaches and shore front of the state by the erection and
construction of seawalls, bulkheads, jetties, basine, and other
devices, and shall take into consideration dredging and other methods
suitable for said purposes. The said commission shall also take into

2

consideration the advisability of repairing existing seawalls, bulk-
heads, jetties, basins, and other similar devices.

Chairman: by-laws. The members of the commission shall choose
one of their number to be chairman and may adopt by—laws for the
regulation of its meetings and to carry out its purposes. The several
state departments and agencies shall render assistance to the commission
in making its studies when called upon to do so by the commission.

Meetings: annual report. The commission may hold meetings in any
part of the state and shall annually report to the legislature and to
the governor and any such report may embody the findings and recomm-—
endations, including planning and other proposals of the commission.

Appropriation. There is hereby appropriated to the commission
from the general funds of the state the sum of thirty-five thousand
dollars ($35,000.00), when included in any annual appropriation act;
for payment of expenses incurred and services required in preparing
a state program for coast protection based upon the regional planning
concept. —

Material to commission. The commission created by joint
resolution number nine of the laws of one thousand nine hundred and
forty-eight, shall turn over to the commission, created by this act
(chapter), any and all material which it may have relating to its
studies, hearings, and report to the governor and the legislature.

The members of the commission had not been named at the time of
preparation of this note.

THE CAUSES OF PLUNGING AND SPILLING BREAKERS

The following notes first appeared in limited
issue as Technical Report HE-116-192, Fluid
Mechanics Laboratory, University of California.
They are reproduced here to bring the concepts
therein to the attention of research workers
and other persons having an interest in ocean
waves. The notes were prepared by Dean M. P.
O'Brien, University of California in January
1946.

Plunging breakers are more hazardous for landing craft than spill-
ing breakers. As yet there has been no method developed to forecast
the type of breaker. The following notes discuss this problem quali-
tatively. It is hoped that quantitative data will follow.

Plunging breakers are characterized by uniformity of breaker
height and by long-crestedness but there are other factors involved
in this phenomenon. Field observations and examinations of photo-
graphs have led to the following general conception of the conditions
causing plunging or spilling breakers:

Plunging

a. Long crests and uniform wave height.

b. Small curvature of crests. (small angle of breaker with
shore line.)

Co Steep bottom slope.

d. Regularity of bottom.

e. Absence of other swells or wind waves and absence of
irregular current.

f. Size; large waves tending to plunge.

Spilling
a. Short crest length or variations in height.

bo. Large curvature of crests at the break.
(Abrupt change of crest angle by refraction.)

co Flat bottom slope.

d. Irregularity of bottom.

e. Superimposed waves, such as wind waves making an angle
with the main swell in the breaker zone.

f. Irregular current, particularly "tide rip" and tidal
current.

go Obstacles such as boats, piers, etc.

h. Variation in strength of proceeding backrush current due
to variations in height and period.

SPILLING BREAKER

PERCENT

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PLUNGING BREAKER

PERCENT

The principle underlying these statements is that the plunging
breaker is the "ideal" breaker in the sense that it will occur only under
conditions approximating the idealized conditions assumed in theoretical
investigations and approximated in the laboratory, namely, infinite crest
length and uniform period and height. Any disturbance which causes the
wave to peak up more at one point than at adjacent points tends to pro-
duce a spilling breaker.

The role of slope seems clear. On a steep bottom the wave must
complete its break quickly, leading to plunging and there is the added
factor that the distance over which the wave is peaked up approaching
the point of breaking is short and the wave is thus exposed during only
a short interval to the disturbing influence of superimposed waves,
currents, and irregular bottom. On flat slopes, a wave is exposed longer
to the possibility of disturbance by the factors causing spilling.

The role of wave steepness, or Hua Eas is complex. It appears that
smaller values of this ratio lead to more pronounced plunging if the
general conditions for plunging are met. For example, if the bottom is
smooth, the wave length uniform and the crest long, swells of small
Hie will plunge even on a flat slope. However, waves of small H',/lo
which exhibit a greater increase in height before breaking are more
easily affected by the factors causing spilling.

If this conception of the causes of spilling and plunging is
correct, it has a bearing on the relationship between depth and wave
height at the point of break. The more nearly ideal the conditions, the
more the wave peaks up before it breaks and the smaller the ratio,
dp/Hp- (Water depth at point of break/wave height at point of break).
Spilling is the result of an incomplete transformation before break—
ing starts and the ratio d>p/Hy is larger. The two dimensional labora—
tory experiment probably approaches the limiting ratio of depth to height
at breaking as closely as ocean waves ever do. It is believed that the
ratio dp/Hp does not have a single value but may have any value greater
than that for the "ideal" breaker of the same eo ie moving over the
same bottom slope. As the distrubing influences previously enumerated
increase in importance, the wave crest breaks earlier in its transforma-
tion and the ratio d)/H;, increases.

Determination of breaker heights from aerial photographs may be
obtained from either wave velocity or depth but wave velocity itself
depends upon depth in shallow water. The value of dp/Hp to be used
must therefore be a matter of judgment based on an appraisal of the
effect of all types of irregularities, most of which will be evident
in the photographs. Neither d,/H; or dp/Hy (Hp is wave height in
deep water) has a definite value for all waves and the breaker index
values or the relationships between d/o and Ho/lo at the point of
breaking is a zone and not a line.

The point at which the quantity dp, is measured must be accurately

defined for breakers on steep beaches because an appreciable change
in depth occurs in the zone in which the wave breaks. In certain

9

laboratory experiments, the depth d, was taken at the point at which
the crest reached its maximum elevation, and this condition occurred
before the wave plunged. Consequently, this depth is probably greater
than would be observed with less precise methods of measurement in a
dynamically similar prototype.

It is likely that not all of the factors which lead to spilling
change the relationship between dp/Hp: For example, short crestedness™
leads to spilling but each point of the crest may break at the same
depth as would a long crested wave of the same height.

Observations of breakers made in conjunction with studies of
landing craft included an estimate of the percentage of breakers which
were spilling or plunging. These observations were made for another
purpose before the causes of spilling and plunging had become clear.
The local wind velocity was measured and it was noticed that the per-
centage of spilling breakers increased with wind velocity. This effect
was the result of superposition of wind waves, usually at an angle, on
the main swell. It was also noted that the larger the breaker, the
less the tendency towards spilling at any wind velocity. Figure l
shows the observed percentages of spilling and plunging breakers. The
breaker heights are shown near points in the range 5 to 10 m.p.h. wind
velocity to indicate the effect of breaker height.

In the lee of headlands such as at San Simeon and Halfmoon Bay,
California, the filtering effects of refraction results in long
crested breakers of small effective steepness. The breakers at these
points are almost always of the plunging type, even though small. A
relatively slight disturbance, such as the superposition of waves from
small boats, changes those waves to the spilling type. At the earliest
opportunity, a controlled experiment of this type will be performed
using Dukw's to generate waves.

Observers of landing craft performance agree that plunging breakers
are more hazardous for landing craft than are the spilling type. Jd. De
Isaacs estimates that a plunging breaker presents about the same hazard
as a spilling breaker 50 per cent higher. The differential may be even
greater for LCVT's. Two important consequences follow, namely:

1. In the critical range of breaker heights, where casualties
increase rapidly with height, weather forecasters should
forecast breaker type.

2. Artificial means of changing plunging to spilling breakers
may be feasible.

*
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10

DISCUSSION- A FORMULA FOR THE CALCULATION OF
ROCK FILL DIKES

Discussion by Mr. R. M. McCrone, Lower Mississippi Valley
Division, Corps of Engineers

Formulae set forth by Mr. Iribarren, or appropriate modification
thereof, will be quite useful to shore and harbor engineers concerned
with sizes of stone and slopes of riprap structures for resisting wave
action. Presumably, the Beach Erosion Board will correlate these data
with those presented in the report on “Slope Protection" presented in
Proceedings ASCE, June 1948, with discussions in later months. It
seems pertinent to suggest that serious consideration be given to
developments in the use of sand asphalt mixtures for structures which
are to provide protection against wave action or erosion due to river
currents since it has been demonstrated to practicable and economical
to place suitably proportioned masses of hot mix by gravity under
water as well as in air to congeal as dense, insoluble, homogeneous,
concreted masses with adequate stability and toughness, highly resist-
ant to water and hence to attack by wave action or stream flow.
(Reference discussion pages 1653 and 1654, Proceedings, ASCE, December
1948).

It seems pertinent to emphasize that structures for protection
against wave action or scour due to stream flow preferably should
be homogeneous non-erosible monoliths rather than heterogeneous
masses of riprap consisting of discrete aggregates even if rock sizes
are adequate. Where such structures are sited on sand, it is ob-
viously desirable that the sand, the nearest and cheapest material,
be used for construction. Developments in the use of hot sand as-
phalt mixtures in large mass demonstrate the feasibility of combining
sand and asphalt suitably proportioned at appropriate temperatures
for gravity placement under water or in air to congeal substantially
as a homogeneous monolith. One such monolith , about 1,800 tons, is
pictured on page 1654 of the December proceedings. Another, upward
of 6,000 tons, placed (Fall 1948) as a wing dam in the Mississippi
River (Mile 468 AHP), provides protection at the lower end of the
Filter Bend revetment.

*¥ FF * EF

11

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ST NICOLAS
REVETMENT,

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ROCKS i fi

POINT OF GRAVE

VERDON
_OUTER PORT

LE VERDON

vA Se
*% VERDON MARSH BARBE GRISE
ora GROIN ;

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VICINITY MAP

SCALE

7 y 2 MILES

FIGURE |

COMITE CENTRAL D'OCEANOGRAPHIE ET D'ETUDE DES COTES

The Central Committee for Oceanography and Coastal Studies is a
French Governmental agency associated with the Naval Hydrographic
Service of*the French Ministry of National Defense. The president of
the committee is Vice Admiral Missoffe and the permanent secretariat
is under the direction of Chief Engineer A. Gougenheim.

The Naval Hydrographic Service have conducted studies of the
regime of various coasts over a long period. The results of these
studies are published in "Recherches hydrographiques sur le regime
des cotes",

In January 1949 the Central Committee for Oceanography and
Coastal Studies initiated the periodic issuance of an information
bulletin. This bulletin contains articles of general information on
committee activities and interests, technical communications in con-
densed form, and bibliographic notes. Distribution of the bulletin is
limited to members of the Central Committee and associated local
committies, and a few French and foreign persons or agencies whose
principal interest is research in oceanography and coastal phenomena.

Four issues of the Bulletin have appeared (January-April) and
have been received at the Beach Erosion Board. This opportunity is
taken to brief some of the information thus received in order to
acquaint American students with the extent and character of the coast—
al problems in France.

NOTES ON POINTE de GRAVE, FRANCE

The coast between Soulac and Pointe de Grave, (see Figure 1) at
the mouth of the Gironde River, is retreating rapidly to an extent
endangering the port installations at Verdon and the existence of the
point itself. The eroded material, which is chiefly fine dune sand,
is shoaling the Gironde River channel.

The shore is constituted by dunes formed since the 17th century
of fine sand derived from the larger size beach sand, the dunes being
covered by pine forests. At Pointe de Grave the shore is advancing
by accretion, whereas to the south, toward Soulac, erosion has been
very rapid, destroying the dunes and the forest.

The eroding areas have been protected by concrete revetments and
groins but have nevertheless receded as much as 200 feet since 1914.
Several German pill boxes, built during the last war, have contributed
to dune: erosion. The revetments are of massive construction, it having
been found that light construction is easily destroyed by wave action.

x x # *#

THE CENTER FOR RESEARCH AND OCEANOGRAPHIC STUDIES

The objectives of the Center are to unite research personnel and
means for solution of problems in geology of the oceans and its applica-
tions to economic and technical problems (exploration and prospecting
of the continental shelf, shore protection, improvement and maintenance
of navigable channels and estuaries, land reclamation, utilization of
marine sediments, etc). The center provides facilities for practical
training, specialized marine laboratory studies, planning and execution
of oceanic research, etc. as well as collaboration with various marine
services.

Required financing is furnished from public funds and private sub-
scription.

Recruitment of young research workers is one of the most important
problems facing the Center and will be the immediate major field of
activity of the administration.

RECORDING MANOMETER FOR SUBMARINE PRESSURE

Note: This manometer was developed at the National
Hydraulic Laboratory at Chatou, and is the first
such instrument developed in France. It will be in-
stalled at Mont St. Michel in connection with a pro-
ject for the development of electric power from the
tides, and at Tamatave.

The device (see Figure 2) consists of dual chambers connected by
a capillary, and an electric differential manometer composed of a metal
diaphragm to which strain gauges are attached. Variations in resistance
of the strain gauges are measured by a Wheatstone bridge circuit. The
system is sensitive to pressure differences of the order of 1/1000 of
the maximum pressure differential of the manometer. An armored cable
of the submarine telegraph type connects the pressure element to a shore-
based recorder; maximum cable length is of the order of 7,000 feet.

RESISTANCE MANOMETER

IAPHRAM TYPE

SUBMARINE
CABLE

NATIONAL HYDRAULIC LABORATORY

WAVE GAUGE
SCALE
as

FIGURE 2

MEASUREMENT OF HEIGHTS BY RESISTANCE ELEMENTS

The following article was first published in
limited issue as Technical Report HE-116-270,
Fluid Mechanics Laboratory, University of Calif-
ornia. It is reproduced here to acquaint re-

search workers and others who would not other-
wise know of the work with the valuable results
of the study. The paper was prepared by Mr. J.
R. Morison, University of California.

Introduction

In measuring wave heights for model studies, it has been found
that wire elements or electrodes placed in the water act as a varia-
ble resistance for a recording system. Through many experiments, a
definite method has been established for this type of-wave height re-
cording. It is the purpose of this paper to summarize the method of
measuring wave heights with wire elements recorded by an oscillograph.
Further, some of the difficulties and limitations of the method will
be presented for the experimenter. The essential difficulty of the
method is in obtaining a stable, correct, and characteristic calibra-
tion of the system used.

General Measurement of Wave Height

The measurement of one wave height at just one point by electrodes

may be accomplished in several ways. A two wire element fed by a
transformer and powerstat and connected in series to the galvanometer
of an oscillograph is a very satisfactory method. The calibration
curve in this case is practically linear depending, of course, on the
actual experimental conditions and instruments used. It is also
possible to use the side of a metal tank as one of the wires of the
electrode. The calibration curve in this instance is not linear.

The immediate questions arising from the above statement are:
(1) What is the effect of the distance between the electrodes?; and
(2) What type and size of electrodes are being discussed? The
distance between the electrodes when small (less than one-half inch)
is a factor in determining the resistance that is in the circuit.
When the electrodes are farther apart, the resistance is determined
by the water to wire relationship. A small diameter (0.033 inches)
wire in water gives a higher resistance than does a larger diameter
wire (1/16 inches). It has been found that a distance of approximately
one-half inch (range 3 to 1) is very satisfactory for two wire
elements and distances up to 6 inches have been used for the case
where the metal tank is one electrode. Further consideration of the
resistance of the water between the wires and how the circuit actually
operates indicates that the wire and water act together in taking
resistance out of the circuit. This resistance starts near infinite
(electrodes in air) and is immediately reduced to several thousand
ohms when the wires touch water (the magnitude of this resistance
depends on the distance between the electrodes, the solution, and the

16

wire size). The resistance is further reduced by lowering the elements
into the water until they are completely submerged, at which point only
the resistance of the recording circuit remains. Hence, it is seen
that the galvanometer (a current measuring instrument in this case)
will record from a zero current to some constant current of the circuit
with respect to the variance of the resistance as described.

The type of electrodes used have been (1) silver plated constantine
wire, (2) silver plated music wire, and (3) iron welding rod. Sample
construction of elements are shown in Figures 3-A, B, C. For conven-
lence of measurement the wire elements are attached to point gages which
’ have a least count of 0.001 foot. Types (1) and (2) were 0.033-inch
diameter wire and 6 inches in length. Type (3) was 1/16-inch diameter
wire and 15 inches in length. The 0.033-inch diameter wires and 6 inches
long were used to measure waves of 0.45 feet maximum height and a
magnification of the actual wave was obtained when desired. This type
of element requires a smaller power supply (1 to 13 volts) than does
the larger elements. It is more sensitive to amplitude changes and
less sensitive to power changes than the larger elements.

The 1/16—inch diameter wires and 15 inches long were used to
measure waves of 1.3 foot maximum height and a reduction of the actual
wave was obtained. This type of element requires a larger power supply
(1% - 2 volts) and is more sensitive to power changes than is the smaller
element. The 1/16 inch diameter elements with a high power input
(2.5 volts) were used satisfactorily for measurement of small model
Waves ©

The power supply to the elements, of course, depends on the
resistance and the magnification desired. Thus, it will be different
for each experimental set up.

The effect of the meniscus or surface tension on the wire element
compared to another type of wave measurement was found to be about
5 per cent when compared with a point gage. The experiments showed
that there was 3 per cent variation in the wave heights as measured by
the point gage due to its meniscus effect and the variation of waves
generated. The corresponding measurements made with the wire elements
were found to differ from the point gage measurements by a maximum
of 7 per cent in all cases. Thus, it is seen that the actual meniscus
effect is about 4 or 5 per cent. Furthermore, the difference was on
the high side part of the time and on the low side at other times.
The meniscus effect will be neglected in the future.

Two or More Circuit Method

The measurement of wave height at several stations simultaneously
is often desired so that not only the wave height can be determined
from the record but also the wave period, wave velocity and wave length.
The method proposed is best described by Figure 1-A. It is seen that
for any one power supply or transformer that one and only one circuit
can be traced out and, hence, the water path connecting pairs of

: 17

elements has no effect and can be ignored.

The calibration of the individual elements is independent of the
position of any of the other elements. Hence, each calibration curve
measures only what takes place at the corresponding element. Further-
more, the calibration of each element is essentially linear. A typical
calibration curve is shown in Figure 2-A. The calibration and op-
eration of the elements are independent of the solution's electrolytic
properties other than its influence on the resistance of each element.
The non-linearity of the calibration is slight and contributed to the
water to wire resistance relationship. The calibration may be effected
also by progressive corrosion. Best results will be obtained in water
of constant temperature.

It may be possible to eliminate the first set of transformers
and supply power to the set of powerstats with one transformer. It is
also possible to supply the power to the set of transformers with one
or more powerstat by connecting the 155-V line to the powerstat and
thence to the transformers. In both cases different powerstats or
transformers would be needed. The disadvantage to any such saving of
equipment is that the resulting maximum current available to the
galvanometer and elements is limited and the reading of any one element
cannot be made prominent. It is considered that the flexibility of
this system outweighs any saving of equipment. From an electrical
standpoint, it is better to feed the transformers through the power-
stats but no difference in the two methods has been noticed.

Sources of Errors in Using Single Power Supplies for Multi-Hlements

and Common heads

The possibilities of connecting a series of elements to galvano-
meters and installing switching circuits for ease in handling in many
cases leads to erroneous results between calibration curves and actual
measurements. The three common and elementary circuits found to be
subject to errors are presented in Figures 1-B, C, D. The same equip-
ment is used in these figures as was used in Figure 1 unless otherwise
noted. In each of the cases presented it is seen that there is more
than one method of completing the electrical circuit when using the
water as a path. This immediately induces the electrolytic character-
istics of the water into the problem. When the electrolytic properties
of the water solution are such that the resistance of the solution
is low and of the order of magnitude of the recording circuit, then
errors are observed and the relative sulmergence of the elements
effects their mutual recording circuits. Figure 2-C is an example
of a calibration showing this effect. The error is due partly to
the polarization effects when the solution is a concentrated one.
However, when the electrolytic properties of the water solution are
such that the resistance of the solution is high, (reference is made
to tap water as compared to laboratory storage water which contains
a solution to prevent fungus growth) and, hence, is very large com—
pared to the recording circuit; then the errors disappear and the

18

elements are independent of each others position when recording.
Figure 2-B is an example of a calibration showing this effect. The
full explanation of the phenomena discussed requires a knowledge of
the theory of interionic attraction, the disassociation theory of
solutions, and the tank effect on the interionic force fields. Itis
plainly seen that the change of the electrolytic properties of the
water during an experiment or even from day to day would give undesir-
able results.

Conclusion

The above method of measuring wave heights at simultaneous positions
will give accurate measurements of wave height, wave length, wave
velocity, wave period, and in special cases, wave profiles. The ex-
pected error can be less than 5 per cent if the proper type of elements
and magnitude of power supplies are used when recording. This, of
course, requires a beforehand knowledge of the maximum wave height to
be expected so that the range of calibration necessary can be made.
Calibrations should be made before and after each experiment or at
least twice a day if elements are used continuously.

Acknowledgments

The author wishes to take this opportunity to thank Dr. H. A.
Einstein for his helpful advice and Professor J. W. Johnson for his
suggestions and cooperation. The confirmation of the information
assembled and helpful reference suggested by Mr. F. F. Davis was
deeply appreciated. Since this report is an extension of previous
work, the author feels that Mr. R. L. Wiegel was instrumental in lay-
ing the ground work.

Bibliography

DAVIES, Cecil W. - The Conductivity of Solutions, J. Wiley &
Sons, New York, 1930.

WIEGEL, R. L. - Measurement of Surface Waves by Electrodes,
Report No. HE-116-269, University of California Wave
Project, Department of Engineering, September 30, 1947,
unpublished.

WIEGEL, R. L. — Some Studies of Surface Waves in Shoaling

Water, M.S. Thesis in Engineering, University of Calif-
ornia, Berkeley, 1949.

19

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BEACH EROSION STUDIES

The erinetpall types of beach erosion reports of studies at specific
localities are the following:

a. Cooperative studies (authorization by the Chief of
Engineers in accordance with Section 2, River and
Harbor Act approved on 3 July 1930).

b. Preliminary examinations and surveys (Congressional
authorization by reference to locality by name).

c. Reports on shore line changes which may result from
improvements of the entrances at the mouths of rivers
and inlets (Section 5, Public Law No. 409, 74th Con-

gress).

d. Reports on shore protection of Federal property
(authorization by the Chief of Engineers).

Of these types of studies, cooperative beach erosion studies
are the type most frequently made when a community desires investiga-—
tion of its particular problem. As these studies have, consequently
greater general interest, information concerning studies of specific
localities contained in these quarterly bulletins will be confined to
cooperative studies. Information about other types of studies can be
obtained upon inquiry to this office.

Cooperative studies of beach erosion are studies made by the
Corps of Engineers in cooperation with appropriate agencies of the
various States by authority of Section 2, of the River and Harbor
Act approved on 3 July 1930. By executive ruling the cost of these
studies is divided equally between the United States and the coopera-
tive agency. Information concerning the initiation of a cooperative
study may be obtained from any District Engineer of the Corps of
Engineers. After a report on a cooperative study has been transmitted
to Congress, a summary thereof is included in the next issue of this
bulletin. A list of completed cooperative studies and of those now
in progress follows.

COMPLETED COOPERATIVE BEACH EROSION STUDIES

Published in

Location Completed House Doc. Congress
MAINE
Qld Orchard Reach 20 Sep 35 ae Brie

NEW HAMPSHIRE

Hampton Beach 15 Jul 32 =o ere

23

Published in

Location Completed House Doc. Congress
MASSACHUSETTS
South Shore of Cape Cod
(Pt. Gammon to Chatham) 26 Aug 41
Winthrop Beach 12 Sep 47 7164, 80

RHODE ISLAND

South Shore
(Towns of Narragansett, South
Kingstown, Charlestown & .

Westerly) 4 Dec 48
. CONNECTICUT
Compo Beach, Westport | »\ 18 Apr 35 239 7h
Hawk's Nest Beach, Old Lyme oy gun 39
Ash Creek to Saugatuck River. ~ 29 Apr 49

Hammonasset River to East River 29 Apr 49

NEW YORK
Jacob Riis Park, Long Island 16 Decwssian 397 74
Qrchard Beach, Pelham Bay,

Bronx 30 Aug 37 450 ES)
Niagara County | 27 Jun 42 271 78
South Shore of Long Island 6 Aug 46

NEW JERSEY
Manasquan Inlet & Adjacent
Beaches 15 May 36 vale US
VIRGINIA
Willoughby Spit, Norfolk 20 Nov 37 482 US
Colonial Beach, Potomac River © 24 Jan 49

S&S

24

Published in
Location Completed House Doc. Congress

NORTH CAROLINA

Fort Fisher 10 Nov 31 204 72
Wrightsville Beach 2 Jan 34 218 3
Kitty Hawk, Nags Head, &

Oregon Inlet 1 Mar 35 15) 14
State of North Carolina 22 May 47 763 80

SOUTH CAROLINA

Folly Beach 31 Jan 35 156 74
GEORGIA

St. Simon Island 18 Mar 40 820 76
FLORIDA

Blind Pass (Boca Ciega) 1 Feb 37 187 US

Miami Beach 1 Feb 37 169 5 |

Hollywood Beach 28 Apr 37 253 WS)

Daytona Beach 15 Mar 38 571 : 75

Bakers Haulover Inlet 21 May 45 527 719

Anna Maria & Longboat Keys 12 Feb 47 760 80

Jupiter Island 13 Feb 47 765 80

Palm Beach (1) 13 Feb 47 772 80

MISSISSIPPI
Hancock County 3 Apr 42
Harrison County — Initial 15 Mar 44

Supplement 16 Feb 48 eos2 80

(1) A cooperative study of experimental steel pile groins was also
made, under which methods of improvement were recommended in an
interim report dated 19 Sep 1940. Final report on experimental
groins was published in 1948 as Technical Memo. No. 10 of the
Bsach Erosion Board.

25

Location

Grand Isle

Galveston

Galveston Bay, Harris County

Santa Barbara —- Initial
Supplement
Final

Ballona & San Gabriel
River (Partial)

Orange County
Coronado Beach
Long Beach

Mission Beach

Presque Isle Peninsula,
Erie (Interim)

Erie County - Vicinity of
Huron

Lake Erie Shore — Michigan
Line to Marblehead

Cities of Cleveland &
Lakewood

Milwaukee County

Punta Las Marias, San Juan

Completed
LOUISTANA

28 Jul 36
TEXAS
10 May 34
RA Jul 34
CALIFORNIA

15 Jan 38
18 Feb 42
22 May 47
-1l May 38
10 Jan 40
4 Apr 41
3 Apr 42
4 Nov 42

PENNSYLVANIA

3 Apr 42

26 Aug 41

30 Oct 44

22 Mar 48
WISCONSIN

21 May 45
PUERTO RICO

5 Aug 47

26

Published in

House Doc. Congress

92 ©
4,00 73
74 74
552 8
761 80
637 76
636 Ue
220 US)
We 79
526 79
769 80

COOPERATIVE BEACH EROSION STUDIES IN PROGRESS

NEW HAMPSHIRE

HAMPTON BEACH. Cooperating Agency: New Hampshire Shore and Beach
Preservation and Development Commission.

Problem: To determine the best method of preventing further
erosion and of stabilizing and restoring the beaches;
also to determine the extent of silting and erosion
in the harbor.

MASSACHUSETTS

METROPOLITAN DISTRICT BEACHES, BOSTON. Cooperating Agency; Metropoli-
tan District Commission (for the Commonwealth of Massachus—
etts).

Problem: To determine the best methods of preventing further
erosion, of stabilizing and improving the beaches, and
of protecting the sea walls of Lynn Shore Reservation,
Nahant Beach Parkway, Revere Beach, Quincy Shore, Nan-
tasket Beach.

SALISBURY BEACH. Cooperating Agency: Department of Public Works (for
the Commonwealth of Massachusetts).

Problem; To determine the best methods of preventing further
beach erosion. This will be a final report to report
dated 26 August 1941.

CONNECTICUT
STATE OF CONNECTICUT. Cooperating Agency: State of Connecticut
(Acting through the Flood Control and Water Policy Com-
mission).

Problem: To determine the most suitable methods of stabilizing
and improving the shore line. Sections of the coast
will be studied in order of priority as requested by
the cooperating agency until the entire coast is in-
cluded.

NEW JERSEY
ATLANTIC CITY. Cooperating Agency: City of Atlantic City.

Problem: To determine the best methods of preventing further
beach erosion.

27

QCEAN CITY.

Problem:

Cooperating Agency: City of Ocean City.

To determine the causes of erosion or accretion and
the effect of previously constructed groins and
structures, and to recommend remedial measures to
prevent further erosion and to restore the beaches.

VIRGINIA

VIRGINIA BEACH. Cooperating Agency: Town of Virginia Beach.

Problem:

To determine methods for the improvement and pro-
tection of the beach and existing concrete sea
wall.

SQUTH CAROLINA

STATE OF SQUTH CAROLINA. Cooperating Agency: State Highway Depart-
ment. :

Pro blems

To determine the best method of preventing erosion,
stabilizing and improving the beaches.

LOUISIANA

LAKE PONTCHARTRAIN. Cooperating Agency: Board of Levee Commission-
ers, Orleans Levee District.

Problem:

To determine the best method of effecting necessary
repairs to the existing sea wall and the desirability
of building an artificial beach to provide protection
to the wall and also to provide additional recreational
beach area.

TEXAS

GALVESTON COUNTY. Cooperating Agency: County Commissioners Court
of Galveston County.

Problem:

To determine the best method of providing a permanent
beach and the necessity for further protection or
extending the sea wall within the area bounded by the
Galveston South Jetty and Hight Mile Road.

CALIFORNIA

STATE OF CALIFORNIA. Cooperating Agency: Division of Beaches and
Parks, State of California.

Problem:

To conduct a study of the problems of beach erosion and
shore protection along the entire coast of California.

The initial studies are to be made in the Ventura-—Port

Hueneme area and the Santa Monica area.

28

WISCONSIN
RACINE COUNTY. Cooperating Agency: Racine County

Problem: To prevent erosion by waves and currents, and to deter-
mine the most suitable methods for protection, re-
storation and development of beaches.

ILLINOIS

STATE OF ILLINOIS. Cooperating Agency: Department of Public Works
and Buildings, Division of Waterways, State of Illinois.

Problem: To determine the best method of preventing further
erosion and of protecting the Lake Michigan shore
line within the Illinois boundaries.

OHIO

STATE OF CHIQ. Cooperating Agency: State of Ohio (Acting through
the Superintendent of Public Works).

Problem: To determine the best method of preventing further
erosion of and stabilizing existing beaches, of
restoring and creating new beaches, and appropriate
locations for the development of recreational
facilities by the State along the Lake Erie shore
line.

PENNSYLVANIA

PRESQUE ISLE. Cooperating Agency: State Parks and Harbor Commission
of Erie (for the Commonwealth of Pennsylvania).

Problem: To determine the best method of preventing further
erosion and stabilizing the beaches of Presque Isle
Peninsula at Erie, Pennsylvania. This will be a
supplemental report to the report dated 3 April 1942.

TERRITORY OF HAWAII

WAIKIKI BEACH. Cooperating Agency: Board of Harbor Commissioners,
Territory of Hawaii.

Problem: To determine the most suitable method of preventing
: erosion, and of increasing the usable recreational
beach area, and to determine the extent of Federal

aid in effecting the desired improvement.

29

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