Technical Report CHL-99-19

September 1999

US Army Corps

of Engineers
Engineer Research and
Development Center

DMS: Diagnostic Modeling System

Report 2
Reduction of Sediment Shoaling of the Entrance Channel

at East Pass, Florida

by Mark S. Gosselin, Kenneth R. Craig, R. Bruce Taylor,
Taylor Engineering, Inc.

Approved For Public Release; Distribution Is Unlimited

TA
ae
wat ,

CHE Prepared for Headquarters, U.S. Army Corps of Engineers
AA -iH +4

The contents of this report are not to be used for advertising,
publication, or promotional purposes. Citation of trade names
does not constitute an official endorsement or approval of the use
of such commercial products.

The findings of this report are not to be construed as an

official Department of the Army position, unless so desig-
nated by other authorized documents.

& PRINTED ON RECYCLED PAPER

Technical Report CHL-99-19
September 1999

DMS: Diagnostic Modeling System

BL/WHOI

M

It

NM

Report 2
Reduction of Sediment Shoaling of the Entrance Channel

at East Pass, Florida
by Mark S. Gosselin, Kenneth R. Craig, R. Bruce Taylor

UMN

tifinn

O 030)

Taylor Engineering, Inc.
9000 Cypress Green Drive
Jacksonville, FL 32256

Final report
Approved for public release; distribution is unlimited

Prepared for U.S. Army Corps of Engineers
Washington, DC 20314-1000

Monitored by Coastal and Hydraulics Laboratory
U.S. Army Engineer Research and Development Center
3909 Halls Ferry Road, Vicksburg, MS 39180-6199

Engineer Research and Development Center Cataloging-in-Publication Data

Gosselin, Mark S.

DMS : Diagnostic Modeling System. Report 2, Reduction of sediment shoaling of the entrance channel
at East Pass, Florida / by Mark S. Gosselin, Kenneth R. Craig, R. Bruce Taylor ; prepared for U.S. Army
Corps of Engineers ; monitored by Coastal and Hydraulics Laboratory, U.S. Army Engineer Research and
Development Center.

63 p. : ill. ; 28 cm. — (Technical report ; CHL-99-19 rept.2)

Includes bibliographic references.

1. DMS (Computer system) 2. East Pass Inlet (Fla.) 3. Inlets — Florida. 4. Dredging — Florida —
East Pass. 5. Sedimentation and deposition — Florida — East Pass —Computer simulation. |. Craig,
Kenneth R. Il. Taylor, R. Bruce. Ill. United States. Army. Corps of Engineers. IV. U.S. Army Engineer
Research and Development Center. V. Coastal and Hydraulics Laboratory (U.S.) VI. Title. VIl. Title:
Reduction of sediment shoaling of the entrance channel of East Pass, Florida. VIII. Series: Technical
report CHL ; 99-19 rept.2.

TA7 W34 no.CHL-99-19 rept.2

Contents

Del ed Bie he care aga es ey he ees a re a ea v1
Conversion Factors, Non-SI to SI Units of Measurement ...00.......00..00ceccccecceesceeseeeeeeeeeeeees Vil
l—BackeroundiandiProb lems tatericntessee eee ner enn ne 1
BBC Sr OU ie ae ees I eR a adie ade eect Naach eg eect eetne eSedee a ae 1
DMS) STOVer vai cw eee eee ee TN ee oe ee aE Ne ree 2

ast Rass RIStony nears le aU et i rete nates a RN Pe nie Ee eS PN 3

Bast) Rassi— physical processes ie reek ee ee if

East) Passi dred sin oi histony- sie oc se ae iets sree ee eae ea el 9
PrODlemmS tatermen tees cee see ere eee na er ere ocd e Me neato tale ud es RoR Ue ee 13
Objectives and Procedures of this Study «.............0...0.cccccccccccescesceseesceseseseesenseeeseeseneess 14
2=—DMS-Datail Vian ater sees ee cet oad ced ats tee oi Oh ual reat ee eee 16
DatayManacen Oy ctw cw pee see ent ie ara cP. EO ee 16
SOftwale! Te quit cients me eee ec cres tecc ON carefree ees nd eg 16

Bata require ments) sees cece eects ae ce a ac el ee Oe eS 17

|B Fo feyep9 00] 0 eee a et I ea ROI Da ei 17
Bathymetric, surveys ose Reson te tehc ia on aout woe Mian an Mactan tours, vo ee 17

Dred Sin FreCOTdS eee sere Ege As RNS ah se ava na Waa nae Reece eee 17

Disitali photooraphs sex .29. cies lac occa eM as lease eies ie Mitek c lotene ssa nivae vets 18
IMS Cell arco tas sree eae ee ae a al ae als LER ae ta nen re eR 18
@aseiStudy —EastiPass#Kloriday 2 2 eS a ee 18
3D) MS= Maria Semaes ceae tr icnh )eete 5 a ta ara hs BN Ga ce te Aa oe 23
Manual Descripttonte ia: a he LAR eS ad a NORE Re A ete 23
Manuallstmictiire) 220 Me cto) nude sac Aamo heh Rie aa duane SMart ae 23
Maniualittse 22.288 Seceto oe sree 2 RR ms ce nit ohn ta: get torment aE 24
Example Application — East Pass Inlet 22. ............ecccscesesesesesesesesessvecseersvscsesesesesecees 29
Arca sle: Outermb arn sen ces eee i Peay ey ARR es i ema etapa TU. sais 29

Areal? Channel Bend 2.2) 2. .h.2 -y A SIG N ee I SN Ae SAS oe 30

ATC aS Ol iP asset Fe oi hee on. Se sere EL 3. oh AN eee PR 30

4-—DMS-Analytical! T ool DOx <sac.22 0.2 eaces ress se eee ee 32

Analytical Toolbox Description! sx: :2-:5cc2.45o se ot cose 32
Moolboxicontents:: 25:2 Ae Ok SER ee sa oer ea eee ae 32
TOOIDOX USE seine es See ee te ea Re SOT OE 37

Example Application — East Pass Inlet .............. ce ecccceccececececeececeeeeseeeeeecesteceeeseaeeeteees 38
Inlet hydrodynamics soe. oes een cs as ae ee ee ee 38
Wave-retracthion'model! 0). ee ee eee ee 48

S—— SUMMA aNd RX CCOMMENG ALLOMS eee a eee ee ee 51
SSAA aay 92s ea oe ee i a ere 51
Recommendations 3222 sce osc esate ete oe cat ad ce Re RE EER Ee 52

IRE LCT OM CES ei saeco este case eyes Se reat nea es poe oa eee eT CATE DR ee ee 54

SF 298

List of Figures

Figure 1. Location map for the study site and the Gulf of Mexico ................eece 4
Figure 2. Dredging locations and placement sites ..................:ecccececeeceeeeeeeeeeeeeeeeteees 10
Figure 3. Diedsedhvolumesiby/sitc eee ee 1]
Figure 4. Dredge-material placement by Site ..........0.....cecccecececcececeeceeeeeeeeeeeeseeeteeenes 12
Figure 5. Shoaling. hot/spotsiat,EastyPassin: ee we ee oie oe eee ee 15
Figure 6. Example of data formats available in the DMS-Data Manager.................. 19
Figure 7. Bathymetric survey comparisons, 1985, 1990, 1997...0.0.....ecceeeeertee: 20
Figure 8. Normiego Point shoreline evolution ....0......0..0..0ccccccccecceccecceceesceseeeceseeseeneens 22

Figure 9. Example page of the DMS-Manual (Horizontal Expansions: Expansion
into Ocean — Ebb Tidal Shoal) ...........2.c20c00c00cc0csccsecevseseeseecseeseeesesenscneeneeees 25

Figure 10. Example page of the DMS-Manual (Horizontal Expansions: Areas of
Shoreline RECESSION) eine ik ea PNA a ts ae eee ae ee 26

Figure 11.

Figure 12.

Figure 13.
Figure 14.
Figure 15.

Figure 16.

Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.

Figure 30.

Figure 31.

Example page of the DMS-Manual (Vertical Expansions: Cross Channel

FEO W) eee ree lasts eer ee rR a aC a aie aN ot tac po eee eae Dif,
Example page of the DMS-Manual (Enhanced Sediment Forcing:

UCT LLOT CIGD 1s fi) jeer eaten te cer PCR ge le oe a eee 28
Examplejofstime-Schics|p lot =e a 34
Example of two-dimensional velocity vector plot...................::ceseeeee: 34
Example of false-color bathymetry with velocity vector overlay................ 35
Example of false-color velocity magnitude contour plot with velocity

VECLOIROV ET AV escent Oe ace a Pe re art er ed OT one ee ulienea nine eee 35
Example of comparison of solutions .............-...2-c:c:ccccscecccececeeeeceeeseceeeeseees 36
Example of contours of sediment transport ................-.:c:e:cececeeeseeeeeeeeeeeeee 38
RMA2 solution mesh for East Pass Inlet and vicinity ..................0..... 39
Velocities through East Pass Inlet on spring flood ................. eee 4]
Velocities through East Pass Inlet on spring ebb .............. eects 41
Velocities at channel bend on spring flood............0.......ccceceeeeteeeeeteeeeees 42
Velocities at channel bend on spring ebb ..................eeecceeeeeeeeeteee cette 42
Velocities at Old Pass on spring flOOd «0.00.00... 0. cceeceeceeceseeeteeeeteeeesetetsenes 43
Welocitiesiat OldjBassion\sprineebb eee ee 43
Sediment transport during spring flood at the channel bend....................... 46
Sediment transport during spring ebb at the channel bend ......................... 46
Sediment transport during spring flood at Old Pass ..................seeeeeee 47
Sediment transport during spring ebb at Old Pass............0.0....e sees 47

RCPWave wave-refraction diagrams of offshore region (above) and
INIEL thr Oat! (DELO Ww) ee aoe anes se eat cai Pe ee ae see 49

RCPWave wave-refraction diagram in the vicinity of Norriego Point ....... 50

vi

Preface

The study described in this report was performed under the Diagnostic Modeling System
(DMS) Work Unit of the Coastal Sedimentation and Dredging Program administered by the
Headquarters, U.S. Army Corps of Engineers (HQUSACE). Research and Development
activities of the DMS are being conducted at the U.S. Army Research and Development
Center (ERDC) Coastal and Hydraulics Laboratory (CHL), Vicksburg, MS. HQUSACE
Program Monitors are Messrs. Earl Eiker, Charles B. Chesnutt, and Barry W. Holiday.

Work was performed by Dr. Mark S. Gosselin, Mr. Kenneth R. Craig, and Dr. R. Bruce
Taylor of Taylor Engineering, Inc., Jacksonville, Florida. The Contract Monitor and
Principal Investigator of the DMS work unit was Dr. Nicholas C. Kraus, Coastal Sediments
and Engineering Division (CSED), CHL. Dr. Kraus provided direction for and technical
review of this report.

Work at CHL was performed under the general supervision of Dr. James R. Houston,
Director, and the administrative supervision of Mr. Thomas W. Richardson, Chief, CSED,
CHL.

At the time of publication of this report, Dr. Lewis E. Link was Acting Director of
ERDC, and COL Robin R. Cababa, EN, was Commander.

Conversion Factors, Non-Sl
to SI Units of Measurement

Non-SI units of measurement used in this report can be converted to SI units as follows:

To Obtain

I
0.02831685 cubic meters

| miles (U.S. statute 1.609347 RIKiNrrictes eae We maT

square miles 2.589998 square kilometers

vii

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1 Background and Problem
Statement

This report documents a joint case study conducted by the U.S. Army
Engineer Research and Development Center (ERDC) Coastal and Hydraulics
Laboratory (CHL) and Taylor Engineering, Inc., to assess the functioning of the
Diagnostic Modeling System (DMS). In this case study, shoaling patterns at a
Federal waterway at East Pass, Florida, provide an evaluation site for tnal
application of the DMS. The shoaling at the entrance channel at East Pass Inlet
serves as the second exercise and evaluation of the DMS concept (for the first
application, see Kraus, Mark, and Sarruff (In preparation)).

Background

The DMS is being developed under the Coastal Sedimentation and Dredging
Program administered by the U.S. Army Corps of Engineers (USACE). The
DMS is intended to provide the USACE with a rapid, yet reliable, capability to
develop and evaluate navigation channel operations and maintenance (O&M)
alternatives based on limited information on the hydrodynamic and sediment-
transport conditions at a site.

The DMS gives a rapid evaluation or diagnosis of a problem shoaling area
and provides guidance for determining possible solutions. The economic lever
underlying the DMS concept is that a low-level analysis, possibly supplemented
by a modest numerical modeling effort, can yield substantial cost savings without
interrupting ongoing O&M activities and schedule. That is, the DMS is intended
to provide feasible alternatives for reducing O&M costs within the dredging
cycle of the subject project. The application time and effort in applying the DMS
are relative to the maintenance time of the project.

Taylor Engineering is currently developing the State-mandated inlet manage-
ment plan for East Pass in cooperation with the City of Destin, Okaloosa County;
the Florida Department of Environmental Protection, Bureau of Beaches and
Coastal Systems; and the U.S. Army Engineer District, Mobile. The Mobile
District identified a study site in East Pass, Florida, where dredged volume is
increasing and navigation is becoming more difficult. This report describes the
application of a DMS approach to East Pass.

This chapter begins by presenting an overview of the DMS methodology and
follows with a description of the case study area. This description includes a
short history of the area, a discussion of the physical processes, and a listing of

Chapter 1 Background and Problem Statement

the dredging history. This information is intended to facilitate discussion of the
application of the DMS in ensuing chapters. The chapter concludes with the
problem statement and the objectives and procedures of the investigation.

DMS — overview

The DMS will provide a quick and concise capability to identify, categorize,
and evaluate navigation channel sediment-deposition hot spots for correction.
The DMS will incorporate established public-domain coastal hydrodynamic
models to be applied, as necessary, in combination with a suite of analytical tools
and procedures. The strategy behind this concept is to develop an experience-
based methodology for treatment of shoaling problems. The tools included in the
DMS will help engineers identify problem areas of shoaling, characterize the
causes of these problems, and develop practical, cost-effective solutions.

The DMS methodology relies upon the use of established public-domain
coastal hydrodynamic models, typically developed by the USACE, in
combination with a suite of engineering analyses and procedures founded upon
principles of fluid dynamics and sediment transport. For this reason, the
methodology is referred to as the Diagnostic Modeling System, or DMS. The
DMS is intended to be a common-sense diagnostic tool that is easily applied by
engineers directly engaged in the planning, design, and maintenance of
navigation projects and waterways to do the following:

a. Identify potential problem areas of shoaling.
b. Identify characteristic causes of these problems.

c. Assist with the development of practical engineering solutions that will
decrease the cost of project maintenance by enhancing project
performance.

As such, the DMS is not intended to provide the level of detailed information
required for final design or in-depth study. Rather, it is intended to quickly
diagnose the problem, categorize it according to its key characteristics, and
identify corrective actions that can be taken within project authorization. The
diagnostic procedure should be capable of completion within a time span shorter
than the project dredging cycle.

This investigation makes no effort to develop or advance numerical modeling
techniques for the evaluation of sediment deposition. The literature contains
numerous examples of the considerable effort expended in this arena. Rather, the
DMS will combine established hydrodynamic modeling techniques with
specialized output formats and back-end sediment-transport analytical procedures
to arrive at an effective diagnostic methodology to quickly characterize and
evaluate sediment-deposition behavior. Several coastal hydrodynamic models
can provide reliable information of sufficient accuracy to perform the work
envisioned. The heart of the research lies in the application of such model to
obtain the type and format of the information required, the engineering
experience gained through observation, and the development and application of
concise, easy-to-use analytical procedures to systematically diagnose
characteristic sediment-deposition problems.

As envisioned, the DMS comprises three components: the DMS-Data
Manager, the DMS-Manual, and the DMS-Analytical Toolbox. The DMS-Data

Chapter 1 Background and Problem Statement

Manager, a GIS-based computer program, allows the user to organize and view
all the relevant information within a project area. Examples of the data kept in
the DMS-Data Manager include digitized bathymetries, aerial photographs, GIS
coverages, and shoaling history. This component gives “one-stop” access to all
graphical and numerical information associated with a maintained channel.

The DMS-Manual is a reference document containing diagrams and example
photographs of different shoal categones. This “field guide” to shoaling
problems helps identify the types of shoals by giving the user comparable
examples. In addition to providing diagrams and examples, the DMS-Manual
also gives descnptions of the sediment shoaling and shoals, and the mechanisms
that create these features.

The DMS-Analytical Toolbox is a suite of analytical tools and
recommendations in graphical formats for quick diagnosis of shoaling problems
and investigation of possible solutions. This toolbox includes a collection of
computer software (e.g., hydrodynamic models, wave refraction/diffraction
models) and analytical models (e.g., sediment-transport equations, wind-
generated wave models). In addition, the toolbox contains recommended output
formats from the models. By standardizing output formats, mechanisms that
contribute to shoaling will become easier to identify. The use of standardized
output formats facilitates the building of an experience base with which to
compare future shoaling investigations. Applied in parallel, these three
components provide for rapid and systematic assessment of shoaling hot spots.
Application of each component to the shoaling hot spots at East Pass, Florida, is
the focus of the present study.

East Pass — history

Application of the DMS requires familiarization with the study area. This
may be accomplished through a literature search, site visits, and discussion with
persons familiar with the area. This process discovers and assembles the
available data for the study area. The data will subsequently become input for
the DMS-Data Manager. This section familiarizes the reader with the study area
by providing a brief history of the pass and of the work performed there.

East Pass is the only direct tidal link between the Gulf of Mexico and
Choctawhatchee Bay. Measuring approximately 4,000 ft long and 1,000 ft across
between the tips of the jetties, East Pass is located about 45 miles east of
Pensacola and 50 miles northwest of Panama City. Figure 1 shows the configur-
ation of East Pass and adjacent areas. Situated at the coordinates 30°23’N and
86°31°W, East Pass is positioned between Santa Rosa Island to the west and
Moreno Point to the east. At 45 miles, Santa Rosa Island, the second longest
barnier island on the Gulf Coast, spans from East Pass on the east to Pensacola
Pass on the west. Averaging between 1,000 and 1,500 ft in width, this long,
narrow island shelters Santa Rosa Sound located directly north. Santa Rosa
Sound is a natural waterway connecting Choctawhatchee and Pensacola Bay.

The easternmost 4 miles of the island compmise Eglin Air Force Base and, for the
most part, remain undeveloped. Moreno Point is the western edge of a headland
separating Choctawhatchee Bay from the Gulf of Mexico. The City of Destin is
located on Moreno Point north of the inlet. On the east side of the pass near the
jetties is a sand spit, known as Norniego Point, that formed in 1935. This spit and

Chapter 1 Background and Problem Statement

the beach directly east is known as Holiday Isle. The spit has been developed
with roads, canals, and condominiums since the 1970s.

Choctawhatchee Bay, landlocked except for East Pass and Santa Rosa
Sound, has an area of 122 square miles, is approximately 30 miles long, and
averages 4 miles in width north to south. The Gamiers, Boggy, Rocky, and
La Grange Bayous to the north and the Choctawhatchee River to the east

Reference: NOAA Hydrographic
Chart #11388, Choctawhatchee
Bay and Approaches, 16th Editio
Dec. 23, 1995

oe Rs v8 = © = ; 70 a oO 5 ms re < cS
4 « R ao

ee ES Ss ° “3. 7) GuiForMexico

Figure 1. Location map for the study site and the Gulf of Mexico

provide freshwater influx into the bay. The Intracoastal Waterway connects to
the eastern edge of the bay, and Santa Rosa Sound attaches at the southwest edge.
East Pass links the Gulf of Mexico to the bay at the bay’s southwest edge.

The stability of East Pass is of great significance to local interests. Traffic
through the inlet includes charter vessels, a fishing fleet, recreational craft, some
freight traffic, and military vessels. The tourism and real estate industries also
have a vested interest in the condition of the inlet, specifically, the inlet’s eastern
side consisting of Holiday Isle and Normego Point.

A review of East Pass history and the surrounding area gives the natural
behavior of the inlet as well as an account of the inlet’s response to previous
stabilization attempts. As the only inlet for 100 miles on this stretch of the
Florida panhandle, East Pass has provided a passageway for vessels since the
early 1800s. The first hydrographic map of the area, made by John Williams in
1827, indicates that Moreno Point occupied much the same position as it does
today (Morang 1992). In addition, the location of a flood shoal and the northern
terminus of the pass was also situated at its current position adjacent to Moreno
Point. The southern terminus, however, has changed significantly. The 1827
inlet mouth entered the Gulf of Mexico 1.5 miles east of its current position.
Dunming this time, the inlet had a more northwest to southeast orientation. The
brackish pond 0.5 miles east of the 1827 inlet mouth implies that in the past, the

Chapter 1 Background and Problem Statement

inlet entered the Gulf at least 2 miles from its current location. From 1871 to
1929. East Pass migrated approximately 2,500 ft westward. In addition,
progressive erosion occurred at Moreno Point. These two mechanisms
effectively bent the channel and created a much less efficient hydraulic state.

In April 1928, severe storms and high tides caused a breach in a low narrow
portion of Santa Rosa Island at about the location of the present inlet. This
breach soon shoaled and the original inlet remained open. In 1929, another
heavy rainstorm flooded the Choctawhatchee Bay. High-water marks indicated
that water levels had risen to as much as 5.4 ft above mean low water (mlw).
The local inhabitants dug a pilot channel along the 1928 breach to allow the high
waters of the bay to rush into the Gulf (U.S. Engineer Office 1939). Because the
new channel provided a more direct route to the Gulf, it became more
hydraulically efficient. As such, it soon captured the tidal flow in and out of the
bay and remained open.

Following the breach, changes in the shoreline occurred rapidly. By 1935,
the new inlet had grown to 2,500 ft wide. The old inlet soon shoaled and, by
1938, completely closed. The east side of the new inlet had receded 500 ft
eastward from its original 1929 position (U.S. Engineer Office 1939). In
addition, by 1931, a sand spit (later named Norniego Point) had formed along the
eastern edge of the inlet and stretched northward to a point within 500 ft of
Moreno Point. The reduced depth between the spit and the mainland required
dredging approximately 20,000 cu yd of material to create a channel (hereafter
referred to as Old Pass) 6 by 100 ft to connect Old Pass Lagoon to East Pass.
This was the first in a long history of dredging projects at East Pass.

Navigation through the newly formed East Pass proved perilous for small
vessels. The crescentic bar at the outermost edge of the ebb-tidal shoal had a
history of shifting significantly during storms. In addition, Government
acquisition of Valpariso Airport, which would later become Eglin Air Force
Base, meant that channels through the pass required modification and mainten-
ance to allow passage of military vessels. Before 1945, dredging occurred
periodically to maintain a 6- by 100-ft channel through East Pass. In June 1945,
the Air Force paid the USACE to dredge a channel 12 ft deep and 180 ft wide
through East Pass (U.S. Congress, House 1950). In 1951, Congress authorized
the dredging of a 6- by 100-ft channel extending from the east end of the U.S.
Highway 98 bridge through Old Pass into Old Pass Lagoon. These channel
dimensions continue to the present. The rapidly shoaling East Pass channel
quickly returns to about 7 or 8 ft deep at mlw. Consequently, maintenance
dredging must be continuously scheduled.

To improve the inlet’s navigational safety and to reduce annual maintenance
costs, the 1963 USACE survey report recommended constructing jetties to
protect the entrance to the Gulf of Mexico. The report also recommended a
substantial amount of dredging to coincide with jetty construction. The total
estimated cost of the project was $1.87 million. Jetty construction and dredging
began in December 1967 and ended in January 1969. The jetties featured a
converging design constructed to the -6-ft mlw contour that ends with an opening
1,000 ft across (Mobile District 1967). A 1,000-ft weir was placed in the west
jetty near the landward end to allow littoral drift to enter a deposition basin on
the opposite (east) side of the weir. Within the shelter of the jetties, a dredge

Chapter1 Background and Problem Statement

could pump sand to renourish the downdnft beach. A regular dredging schedule
would minimize the interruption of littoral dnft by the jetties/inlet and the
accumulation of sediment at the updrift side. A deposition basin was dredged to
provide a 2-year supply of sediment, an estimated volume of 300,000 cu yd.

Between Apmil and June 1969, a few months after completion of the jetties, a
100-ft section of the weir collapsed. The collapse caused a deep trough to be
scoured away through the breach. As a temporary remedy, 67,000 cu yd of sand
was pumped from the deposition basin onto the jetty. This sand temporanly
blocked the entire weir; however, all the sediment had eroded by March the
following year. The weir was permanently repaired in September 1970. Since
its construction, the deposition basin was dredged only twice, in 1970 and 1972.
Differing opinions as to the source of the sediment filling the basin and the
direction of longshore drift caused the end of maintenance dredging of the
deposition basin. In addition, at this time, concern grew over the continuing
erosion of Norriego Point and the western tip of Moreno Point. Popular opinion
held that the weir allowed large waves to pass through and erode the point.
Under pressure by local interests, the USACE recommended weir closure in its
1983 Reconnaissance Report, East Pass Channel, Destin, Florida (Mobile
District 1983). In 1985, the USACE permanently closed the weir by covering it
with a rubble-mound trunk section identical to that placed on the rest of the jettv.

By Apmil 1977, erosion of the East Pass eastern shoreline (Normego Point)
required immediate attention. A report on shoreline improvement and dune
stabilization was submitted to the USACE South Atlantic Division Engineer.
This report recommended the construction of a groin field consisting of six
structures located at the northern end of Norriego Point (Mobile District 1977).
It claimed that wind-generated waves traveling through the mouth of the inlet
caused the most severe erosion along the point. The authors specifically did not
identify the weir as playing a role in the erosion. This recommendation was
rejected. However, the continued easterly channel migration had eroded the
eastern shoreline to a point where the east jetty was in danger of being flanked.
General inlet maintenance occurred in 1977 with the construction of a 300-ft
rubble-mound spur that attached at a nght angle to the landward end of the east
jetty. The purpose of the spur was to divert flow away from the landward
terminus of the jetty. By the 1980s, scour holes had formed at the tip of the spur
as well as at the tip of the west jetty (Lillycrop and Hughes 1993). Until 1993,
maintenance of the spur jetty had been limited to the placement of dredge
matenal, mprap stone, and concrete rubble in the scour hole. More extensive
repairs were completed in 1994.

On 4 October 1995, Hurricane Opal made landfall at 1700 Central Daylight
Time. The eye of this Category III (at landfall) hurricane passed near the town of
Mary Ester located approximately 12 miles west of East Pass. Opal generated
winds with gusts in excess of 150 mph and produced a storm surge reaching
14.6 ft above mlw. Following the storm, the USACE deployed their Scanning
Hydrographic Operational Airborne Laser System (SHOALS) to assess Opal’s
damage at East Pass. Morang, Insh, and Pope (1996) separated storm damage
into two categones: subaerial changes caused by the storm surge during the
height of the storm, and subaqueous changes caused by the draining of the
flooded Choctawhatchee Bay.

Chapter 1 Background and Problem Statement

Subaeral changes included the following:

a. The overwashing of Santa Rosa Island and the landward side of the west
jetty, an action that led to the creation of a large depositional fan in the
lee of the island and the accumulation of sand in the area previously
occupied by the deposition basin.

b. The breaching of Norriego Point with deposition of sediment in Old Pass
Lagoon.

c. The overwashing of the beach east of the east jetty, an action that
flattened dunes and carried sediment into the area eroded near the spur
jetty and further into the thalweg of the channel.

d. Minor damage to the jetties involving the settling of the capstones.

Morphological subaqueous changes associated with the ebb jet and post-
recovery included the following:

a. The formation of a contraction-induced scour hole at the inlet throat
between the jetties.

b. The westward movement of the thalweg away from the shoreline and
subsequent channel straightening.

c. The further deepening of the scour holes at the tips of the west jetty and

spur jetty.

Notably, Hurricane Opal caused no significant change in the ebb shoal’s
growth pattern. In contrast to this assessment, the local USACE office reported
no apparent deepening of the scour holes as a result of Hurricane Opal. More
information concerning the damage caused by Hurricane Opal is contained in
Leadon, Nguyen, and Clark (1998) and Leadon (1996).

The preceding account of the history of the inlet has accomplished three
goals. First, it pomted out the need for the DMS system. Considerable money
and effort have been expended at East Pass to improve the navigational safety of
the Federally maintained channel. The use of the DMS at certain stages in this
channel’s history may have pointed to better solutions than the ones attempted
(e.g., the weir jetty). Second, it validated the choice of East Pass — a location
where maintenance efforts have expended considerable time and money — an
appropriate demonstration site for application of the DMS methodology. Finally,
it has familiarized the reader with the study area to facilitate later discussion.

East Pass — physical processes

Knowledge of the physical processes in the study area also aids in the
diagnosis of shoaling problems. Notably, the DMS intends to address the
mechanisms that cause shoaling rather than simply treat the shoaling itself. In
this regard, application of the DMS is a proactive rather than the traditional
reactive approach to addressing shoaling. As such, knowledge of the channel’s
physical processes that cause the shoaling is essential in finding a defensible and
successful shoaling mitigation method. This section characterizes the physical
processes at East Pass through a literature search.

To comprehend an inlet’s tidal hydrodynamics, one must document not only
the tidal ranges and their consequences but also the influences of bay geometry,

Chapter 1 Background and Problem Statement

freshwater influx, wind forcing wave setup, and storm surge. Several sources
(e.g., Wright and Sonu 1975 and Mobile District 1986) have reported a diurnal
astronomical tide in East Pass with a mean range of 0.6 ft and a maximum spring
tidal range of 0.9 ft.

In addition to these sources, the USACE has documented the results of
several tide-monitoring efforts including measurements from 1938, 1983-1984,
and 1987. These measurements show that the bay’s geometry plays a role in the
tidal amplitude and phase within the bay as compared with tidal records in the
Gulf. The Mobile District report Monitoring Program, East Pass Channel
(1986) documents that measured tidal ranges in Choctawhatchee Bay
corresponding to 0.5 and 1.5 ft have associated tidal ranges in the Gulf of Mexico
of 1.2 and 2.5 ft. These values respectively translate to a 40- to 60-percent
reduction in amplitude between the bay and the Gulf. In addition, an estimated
5.7-hr phase difference occurs between the tidal elevation in the bay and in the
Gulf. These differences are mostly attributable to the bay’s large surface area
(~122 square miles) and particular channelization. The 1939 U.S. Engineer
Office report Study of East Pass Channel, Choctawhatchee Bay, Florida offers
the most comprehensive analysis of this phenomenon. The report attributes the
reduced amplitude to the large hydraulic resistance through East Pass (mainly a
function of the flood-tidal shoal). The report also attributes the phase lag to that
part of the bay’s tidal inflow that travels along the much longer route to
Pensacola Bay via Santa Rosa Sound.

The two known sources of tidal current measurements are the 1939 U.S.
Engineer Office report and the 1992 USACE study (Morang 1992). The 1939
report presents the results of float studies performed at various times during the
tidal cycle. In the main body of the text, the authors report measured maximum
flood velocities of 1.97 and 4.37 ft/sec (two different field measurements) and a
maximum ebb velocity of 3.39 ft/sec. In a table found im the report, however, the
reported maximum flood and ebb velocities through East Pass — 1.5 and
1.7 ft/sec — are presumably based on measurements of the maximum discharges
through the inlet and a representative cross-sectional area. Morang (1992)
reports the results from field investigations in 1983, 1984, and 1987. Maximum
currents measured during flood tide across the inlet were between 4.5 to
5.0 ft/sec at the surface and 2.5 to 3.0 ft/sec at the bottom (measured at a distance
of 0.2 times the water depth from the bottom). Maximum currents during ebb
were between 4.5 to 5.0 ft/sec at the surface and 3.0 to 3.5 ft/sec at the bottom.

As the literature identifies, only two sources have developed estimates of the
tidal prism through East Pass: the 1939 U.S. Engineers Office report and the
1992 USACE study (Morang 1992). The 1939 report estimates 1.23 x 10” cu ft
of water moves through the inlet on flood and 1.59 x 10° cu ft on ebb. These
estimates correspond to maximum discharges of 50,000 cfs on flood and
53,000 cfs on ebb. The discrepancy between the two is attributed to artesian
wells located in Choctawhatchee Bay and freshwater runoff into the bay.
Adjacent tidal inlets may also play a minor role. The 1992 study does not present
computed estimates of the total tidal prisms. However, it does present graphs of
the measured discharge through the pass. Numerical integration of the discharge
curves for 16 May 1984 and 16 April 1987 gives flood tidal prisms of 2.49 x
10° cu ft and 1.25 x 10° cu ft, respectively (with maxima of 88,000 cfs and
63,000 cfs), and ebb prisms of 4.16 x 10° cu ft and 3.40 x 10° cu ft (with maxima
of 99,000 cfs and 76,000 cfs).

Chapter 1 Background and Problem Statement

Again, the only studies of East Pass current patterns identified in the
literature review are reported in the 1939 U.S. Engineer Office report and the
1992 USACE study (Morang 1992). These two field investigations bracket the
construction of the jetties. The 1939 study documents the results from drogue
studies performed during different times in the tidal cycle. Dlustrations of drogue
paths show that before jetty construction, the current intensified on the east side
of the inlet throat during both flood and ebb tides. The report states that despite
their release location, all the drogues that passed through the inlet moved toward
the east side of the inlet where they experienced high velocities.

The 1992 USACE report (Morang 1992) details experiments performed in
the years 1983, 1984, and 1987. Plots of the currents in East Pass Channel again
show an intensification of current velocity on the east side of the pass. Morang
(1992) suggests the ebb current impinging on the east bank is the main cause of
the rapid erosion of Norriego Point. In addition, Morang (1992) observes that the
300- to 120-deg orientation of the flood and ebb current directions in the northern
end of the inlet is almost identical to the 295- to 115-deg orientation of the
entrance to Old Pass Lagoon.

This section outlined the tidal hydraulics of East Pass Inlet. Unfortunately,
except for the Wave Information Study (WIS) hindcast data, little is known about
the wave climate inside the inlet or in the Gulf. In the application of the DMS,
the information from this section will aid in the identification of the shoaling
mechanisms, as well as provide input into the model applied in the DMS-
Analytical Toolbox.

East Pass — dredging history

Reduction of dredging amounts and frequency is the objective of this
research. Thus, knowledge of the channel’s dredging history is paramount to
understanding the behavior of shoaling. As with other pertinent channel
information, the channel’s dredging history becomes key input data for the DMS-
Data Manager. This section documents the dredging activity at East Pass and
identifies the areas of shoaling that serve as the test case for the DMS.

Between 1931 and 1995, dredging removed approximately 4 million cubic
yards of sediment — about 64,000 cu yd/vear — from the project channel.
Figure 2 illustrates the locations of the dredge sites and disposal placement areas
that encompass all dredging activity at East Pass. Figures 3 and 4 categorize the
dredged and placed volumes by site. Some of the designations required consider-
able estimation. As is usually the case, the dredging records (especially early
records) were incomplete. Figures 3 and 4 show that dredging frequency has
decreased, while the magnitude of volume dredged has increased. This trend is
explained by advances in economic dredging practice. Notably, before 1964,
Open Water/Surf Zone designation characterized much of the dredge-matenal
placement. Figure 2 does not denote this area because no reliable record exists of
the actual placements. Also, during its early history, side-cast dredges were used
to maintain the channel. Thus, the placement area depended on the maintenance
location. Table 1 summarizes the dredging activity at East Pass throughout its
history.

Chapter 1 Background and Problem Statement

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V2 Chapter 1 Background and Problem Statement

Table 1
| Summary of Dredging Activity at East Pass (1931-1995)
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Table 2 summarizes channel-dredging operations since jetty construction. Notably, most of
the material dredged came from the main channel and Old Pass Channel. The overwhelming
majority of material-placement activity occurred on Norniego Point. As a comparison, Norriego
Point received more than three times as much material as the material bypassed (Nearshore Site).

Examining the dredge plans from recent years in more detail identifies the location of
several shoaling “hot-spots,” areas where dredging activity has been concentrated as evidenced
by recurrence in the dredging plans. Figure 5 illustrates these locations (crosshatched areas).
The three areas have been given names to facilitate discussion. These shoaling hot spots will be
analyzed using the DMS in order to test the validity of the methodology.

Problem Statement

The USACE maintains thousands of miles of navigation channels throughout the coastal
waters of the United States and its territories. These Federally maintained channels comprise the
maritime heart of the Nation’s waterbome commerce and national defense. As such, their
maintenance commands a major share of the USACE O&M budget every year. With the
continued ebb and flood of the tide, sediments enter and deposit in these channels, often in areas
neither welcomed nor anticipated. Excessive deposition causes shoaling that reduces channel
depths, leading to navigational hazards that require frequent and expensive dredging.

Traditionally, once designed and constructed, channels and their ancillary structures have
rarely benefited from evaluation against expected performance standards or efforts to reduce
their maintenance cost by improving their performance. Consequently, frequent dredging of
channel shoals is routinely prosecuted as part of the USACE annual O&M budget at ever
increasing cost.

Experience indicates a majority of the most frequently maintained channel reaches and
structures share key characteristics that define localized hydraulic conditions and attendant
sediment deposition. This tendency for commonality suggests that a reasoned diagnostic

Chapter 1 Background and Problem Statement

13

14

methodology applied to channel hydraulics and associated sediment transport may produce
significant benefits, leading to reduced maintenance costs and enhanced project performance.

To be effective, this methodology must be easily applied, capable of quickly identifying
problems, able to classify problems by key characteristics, and able to facilitate the identification
of realistic engineering solutions common to each problem category.

Table 2
Summary of Dredging Activity at East Pass (1969-1995)
Location Total Volume, cu yd Rate of Activity, cu yd/year

Dredging Activity Summary

Basin/East Pass Channel 96,727
East Pass Channel 29,233
Old Pass Channel 27,859
Outer Bar 16,046

East Jetty

Spur Jetty Scour Hole 135,489 :
Weir West Jetty 92,791 }
Total Material Dredged 2,304,341

The DMS attempts to embody this methodology by taking a three-pronged approach to the
evaluation of shoaling problems. The DMS-Data Manager component consolidates all the
pertinent information concerning maintained channels in one place and in an easily interpreted
graphic format. The DMS-Manual, an encyclopedia for shoaling signatures, simplifies the
classification of shoaling mechanisms through comparisons with generalized illustrations,
example photos, and case studies. The DMS-Analytical Toolbox contains a suite of programs
and analytical models for advanced analysis of shoaling problems. In addition, this component
provides recommendations for output format to facilitate diagnosis of shoaling mechanisms and
investigation of solutions.

This report seeks to evaluate the DMS concepts through the application of each of the DMS
modules on a demonstration site, the shoaling hot spots at East Pass Inlet (Figure 5).

Objectives and Procedures of this Study

The objective of this study is to determine the causes of the shoaling in the maintained
channels at East Pass Inlet and to recommend a solution that will reduce the frequency and cost

Chapter 1 Background and Problem Statement

of dredging, and improve navigation safety. The objective is met through the application of
DMS concepts and methodology.

Bend}

——

TAYLOR ENGINEERING INC.
9000 Cypress Green Drive
Jacksonville, Florida 32256

tlh

Figure 5. Shoaling hot spots at East Pass

This second DMS application employed the following procedure:

a. Make site visits, review the existing literature, discuss the physical processes with those
possessing local knowledge, and enter all available information into the DMS-Data
Manager.

b. Based on the information displayed in the DMS-Data Manager, classify the types of
shoals by reference to the DMS-Manual.

c. Applying tools in the DMS-Analytical Toolbox, perform an analysis of the shoaling
patterns that includes a hydrodynamic model, a wave refraction model, and simple
sediment-transport calculations.

d. Synthesize information and results from Items a-c and make recommendations for
reduction of channel shoaling.

This report documents the results of this DMS application. Chapter | gives a background of
the DMS methodology, a description of the study area including the inlet history and physical
processes, and the problem statement and study objectives. Chapter 2 contains a description of
the DMS-Data Manager and the example application at East Pass. Chapter 3 reviews the DMS-
Manual and employs it to classify the shoaling problems at East Pass. Chapter 4 outlines the
DMS-Analytical Toolbox and presents the application of a few of its tools to the shoaling at East
Pass. Chapter 5 presents conclusions and recommendations.

Chapter1 Background and Problem Statement

15

16

2 DMS-Data Manager

Data Manager Overview

The DMS is intended to assist those responsible for inlet and channel design
and maintenance in assessing both the root causes of shoaling and the implica-
tions of proposed changes to such systems. One important component of the
DMS is the Data Manager, a graphically based tool that allows the user to view
all relevant data representing conditions within the area of concern. This
software tool brings modern data visualization technology to the user’s desktop
— as such, it leverages recent advances in Geographic Information Systems
(GIS).

The Data Manager is a customized extension of the commercially available
GIS software package ArcView from Environmental Systems Research Institute
(ESRI), Redlands, California. Taylor Engineering, Inc., of Jacksonville, Florida,
in conjunction with the CHL is developing the Data Manager. In combination
with the Data Manager User’s Guide (presently under development), the software
assumes the user has minimal experience with GIS systems, and as such,
development has proceeded with the end user in mind. Numerous wizards aid
the user during assembly of a comprehensive project database. Data Manager
leverages the flexibility of data formats available for use within ArcView to
minimize format conversions and simplify the assembly process. Additionally,
the Data Manager will incorporate several analysis tools to allow the user to
perform volumetric comparisons to address what-if questions. The Data
Manager offers features that could become an integral part of the daily routine of
those who maintain the country’s waterways.

Report generation is the main product of the Data Manager. Users can
produce consistently formatted reports from their data via the reporting option
available. This option allows examination of past dredging records in a tabular
and/or graphical format to aid in analysis and review of shoaling areas.
Examples of such reports may include anticipated costs of upcoming projects,
daily progress reports of active projects, summary statistics (i.e., total volumes,
annual volumes) for user-defined areas, plus several other reports.

Software requirements

The DMS-Data Manager works on the Windows NT 4.0 operating system
and in conjunction with the latest release of ArcView (presently, Version 3.1) —
extending the base functionality of the ArcView environment. Support of other

Chapter 2 DMS-Data Manager

operating systems is not scheduled at this time. The Data Manager extension will
incorporate ESRI’s 3-D Analyst extension to develop and view bathymetric
surfaces and to calculate sediment volumes. The 3-D Analyst, which is not
necessary to view much of the base map data, is a central element of the DMS-
Data Manager. The CAD Viewer extension, provided with the base ArcView
package, allows incorporation of CAD drawings in AutoCad (.dwg), AutoCad
export (.dxf), and MicroStation (.dgn) formats within the database. Additionally,
the latest version of the software supports many common image formats,
allowing easy viewing of existing and historic site conditions. Finally, the Data
Manager accesses the Crystal Reports for ArcView application to generate many
of the available professional reports.

Data requirements

The Data Manager supports a wide variety of data formats. These include
Arc/Info coverages, shapefiles (ArcView’s native format), AutoCad drawings
(through release 14), MicroStation files, Dbase databases, various text-based data
files, and digital images. The initial step required during development of the
database is selection of a common coordinate system (typically State Plane or
UIM) and units (feet, meters, decimal degrees) to be applied to all the data. This
flexibility provides a common reference for the Data Manager and allows
accurate data layering. The required data falls into five classifications: base map
information, bathymetric surveys, dredging records, digitized photographs, and
miscellaneous. Each classification is discussed in detail below.

Base map

Base map information can be anything the user associates readily with the
project area. Examples include project (channel) boundaries, stationing
information, aids to navigation, shoreline positions, shore-protection structures,
marina and port facilities, sensitive environmental areas, deposition areas,
hazardous areas, shipwrecks, fish havens, reefs, utilities, buildings, roads, and
bridges. Typical formats for base map data will include Arc/Info coverages,
shapefiles, or the two CAD formats. The World Wide Web and in-house GIS
personnel provide numerous sources for base map data from various Federal,
State, and local Government agencies.

Bathymetric surveys

The Data Manager accesses standard bathymetric survey data to develop
surfaces and grids representing the bathymetry in and around the project area.
These data will typically be available in ASCII text files (X, Y, Z) or as contour
lines in a CAD drawing. A bathymetry wizard leads the user step by step
through the surface-generation process.

Dredging records

Historical dredging records are documented in native ArcView database
format and accessed with standard queries through a wizard interface.

Chapter 2 DMS-Data Manager 17

Conversion wizards and data input forms are available to translate data to a
standardized format. Typical records include date, contractor, location

(i.e., station or river mile), horizontal dimensions, depth of cut, design and pay
volumes, disposal location, sediment data, and dredge specifications. Typically,
preparation of this portion of the database will require manual input of printed
data.

One of the advantages to a GIS-based approach is derived from the
geographic relationships inherent in the data. For example, dredging records
document project performance at a location and thus have a geographic
component. Therefore, the data can be referenced to coordinates indicating that
location (i.e., stationing, northing/easting, latitude/longitude). These data can
then be selected for analysis based initially on the location. Specific problem
areas can be isolated and examined to determine trends not readily discernible
through standard tabulated data. Several charts (e.g., dredge production and
historic shoaling) can be generated based on these records.

Digital photographs

Digital photography provides a means to document general and specific
changes to a system over time. These photographs can include aerial
photographs, oblique ground-level shots of specific locations, documentary
evidence of projects — essentially any aspect of the project that will benefit from
photographic evidence. A scanner can convert conventional photographs to
digital format for incorporation in the database. Digital images should be
converted to JPEG format at a standard resolution of 640 by 480 pixels through
third-party software packages. The database includes options to document the
source, date, and description of the photograph. The user may easily scroll
through the images, select and print those of special interest, and incorporate
these images in various reports. Georeferenced aerial photography (1.e., stretched
to match the adopted coordinate system) can be incorporated as an additional
theme in the project base map.

Miscellaneous

Any additional relevant data fall under the miscellaneous classification. This
category can include sediment grain-size curves, tabulated sediment data, a tidal
record time series, datum corrections, and sea-level rise rates based upon survey
epoch. In a manner similar to that used to maintain the dredge records, the end
user incorporates these data into an ArcView database where they become
readily viewable and searchable.

Case Study — East Pass, Florida

The case study of East Pass involved testing and evaluating the concepts
driving Data Manager development. As stated above, the initial step in
developing a DMS-Data Manager project is selection of a common coordinate
system for the data. All data shown on the following pages are referenced to the
State Plane Coordinate System, North American Datum of 1927, Florida North
Zone. Figure 6 shows a typical Data Manager screen. The themes shown along

Chapter 2 DMS-Data Manager

the left side of the screen comprise the Table of Contents of the viewable data
shown in the frame to the right.

@ ArcView GIS Version 21

| “ 1985-shoreline dwg
| _/\/ SHORELINE

iN, CENTER-LINE

DISPOSAL

/’/ DREDGING

/\/ DREDGING-CHANt
STATIONS

| ~ 1985 TIN

Elevation Range
~4.111- 1.2
= -9.422--4.111
(_] -14.733 - -9.422
[Ey -20.044 - -14.733
Hy -25.356 - -20.044
[MY -39.667 - -25.356
Hl -35.978 - -30.667
HM -41.289 --35.978
[EM ~46.6 - 41.289

| “ UsGs Quadjpg
| 1985 txt
© -46.6--32.4
-32.1--23.6

®
e -23.6--181
e -18.1--14.3

Figure 6. Example of data formats available in the DMS-Data Manager

This example illustrates some of the usable data formats in the Data
Manager. First, a georeferenced image of a U.S. Geological Survey (USGS)
7.5-min quadrangle (labeled USGS Quad.jpg) provides the underlying base map.
An AutoCad drawing (Channel.dwg) of the authorized channel and disposal sites
has been layered on top of the base map. Above the CAD drawing, the east and
west jetties are shown as an ArcView shapefile VJetties.shp). Point data from a
comma-delimited X,Y,Z ASCII file (1985 txt) were loaded into the project but
not displayed. However, the point data were used to create a triangulated
irregular network (TIN) to represent the surface defined by a 1985 bathymetric
survey. The TIN has been color coded based on the given elevations to illustrate
depths within East Pass. As this single screen shot shows, multiple data formats
can now be brought together to provide a detailed view of a project.

With the data assembled in one place, the user can first make some simple
observations. First, areas of persistent shoaling become easy to identify.
Although personnel with extensive experience on a given project are likely
familiar with such areas, documentation in a graphical format helps to clarify and
quantify the problem. Figure 7 shows data from bathymetric surveys of East
Pass in 1985, 1990, and 1997. Each of these surveys covers areas outside the
authorized channels. For clarity, the data have been filtered to display only those
falling within the authorized channels. The first two surveys involved standard

Chapter 2 DMS-Data Manager 19

20

Three examples of bathymetric survey point

data. The dots represent areas where the depths
that are shallower than the authorized project depth
(shoaling). Note the persistent shoaling in Old Pass
and at the Channel Bend.

0 1000 2000 Feet

Channel Bend)

1997 Bathymetric Survey

Figure 7. Bathymetric survey comparisons, 1985, 1990, 1997

Chapter 2 DMS-Data Manager

fathometer surveying techniques. The 1997 survey comes from the SHOALS
LIDAR program using airbome laser mapping techniques. Obviously, the data
density is significantly increased in the 1997 survey; however, the user can see
discemible and repeating patterns in each survey. Notably, the Old Pass entrance
channel to Destin Harbor and the Channel Bend within East Pass exhibit
consistent shoaling patterns over each survey. The 1990 survey also indicates
shoaling within the authorized channel as the channel passes across the ebb-tidal
shoal. Once problem areas are identified, they can be compared with the
examples given in the DMS-Manual. Further analyses should then follow the
techniques included in the DMS-Analytical Toolbox to determine the root cause
of the shoaling and to examine potential solutions.

A particular area of concern to the East Pass project engineers is Norriego
Point, one of several sites serving for disposal of the dredged maternal taken from
the authorized channels. Normiego Point shelters Destin Harbor from offshore
waves that propagate through the jetties into East Pass. Sand historically erodes
from Nornego Point into the channels. To document the erosion of Norniego
Point, Figure 8 shows four shoreline surveys taken over a 30-month period. The
August 1995 shoreline shows conditions before the impact of Hurricane Opal.
The January 1996 survey shows conditions following emergency Post-Opal
dredging operations that placed sand on Norriego Point. The August 1996
survey shows some of the initial evolution of the shoreline position following
placement. Finally, the January 1998 survey shows that the shoreline again
approximated 1995 conditions. Chapters 3 and 4 investigate possible
contributions that the eroding Norriego Point may have to the shoaling in the
authorized channels.

The East Pass case study confirmed the utility of the DMS-Data Manager by
providing a quick and simple means to identify problem-shoaling areas. As is
found throughout the remaining chapters, the Data Manager is also useful during
application of the remaining components of the DMS. Development continues
on many of the features identified above. A working beta version of the Data
Manager will be available for application to the Year 2 Case Study in Fiscal Year
1999.

Chapter 2 DMS-Data Manager

21

22

Figure 8. Norriego Point shoreline evolution

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Chapter 2 DMS-Data Manager

3 DMS-Manual

This chapter describes the structure and use of the DMS-Manual. The
chapter also presents the manual’s application to shoaling problems at East Pass
Inlet.

Manual Description

Manual structure

The DMS-Manual is a tool for identifying the type of shoaling problem
encountered on a case-by-case basis. As envisioned, the multipage document
will serve as a field guide to shoaling problems. Each page of the manual
corresponds to a different shoaling pattern. At present, the manual has identified
six main shoal classifications or patterns:

e Horizontal Channel Expansions. Horizontal expansions of channel
boundaries are most times accompanied by an increase in cross-sectional
area of the conveyance. Conservation of flow dictates an accompanying
decrease in velocity. If the currents are transporting sediment, a decrease
in velocity will reduce the sediment-transport capacity and therefore
cause sediment to come to rest. This deposition of sediment creates a
shoal.

e Vertical Channel Expansions. Similar to the previous category, vertical
expansions of channel boundaries are also accompanied by an increase in
cross-sectional area of the conveyance. Again, conservation of flow
dictates an accompanying decrease in velocity. If the currents are
transporting sediment, a decrease in velocity will reduce sediment-
transporting capacity and, therefore, tend to cause deposition of
sediment. This deposition creates a shoal at and after the expansion.

e Sheltered Areas. Protuberances (e.g., headlands and structures) in a
conveyance cause flow to accelerate at the obstruction by reducing the
channel cross-sectional area. This acceleration increases the sediment-
transport potential at the obstruction. Downstream of the obstruction,
complicated flow pattems create regions of low velocity and low
turbulence in addition to flow readjustment to the increased cross-
sectional area. Lower velocities reduce the sediment-transport potential.
This reduction increases the probability of sediment deposition. This

Chapter 3 DMS-Manual 23

24

type of shoaling is usually accompanied by a region of scour or erosion
upstream of the shoal.

e Changes in Channel Alignment. Changes in channel alignment can refer
to either natural changes (meandering) or artificial changes (e.g., struc-
turally redirected flows). A change in channel alignment redirects the
flow momentum. Conservation of momentum dictates the establishment
of secondary currents within the conveyance that spin about the flow
axis. These vortices tend to erode sediment from the outer bank of a
bend and deposit it at the inner bank.

e Multiple Channels. Intersections of watercourses can create complicated
flow patterns. Often, these patterns include areas of flow acceleration
and deceleration. Decrease in velocity implies a decrease in sediment-
transport potential and hence an increase in the probability of shoaling.
Shoaling probability increases where one of the intersecting channels is a
riverine sediment source.

e Enhanced Sediment Forcing. This miscellaneous category of channel-
shoaling classification includes mechanisms that do not fall into the
above categories. These shoaling mechanisms include sediment
transport by winds, waves, storms, and large-scale current patterns.

In the future, each of the above categories is expected to be further divided into
subcategories. Each page of the manual will be devoted to one of the
subclassifications of channel shoaling. As an example, the Horizontal Channel
Expansions category may be divided into three subclassifications: (a) Expansion
into Ocean — Ebb-Tidal Shoal, (b) Expansion into Bay — Flood-Tidal Shoal, and
(c) Areas of Shoreline Recession.

Each page of the manual will feature the same format. Figures 9 through 12
show examples of envisioned manual format. At the top of each page is the main
shoaling classification and subclassification. Below this heading on the left of
the page is a general diagram of the shoaling patterns and forcing mechanisms.
These diagrams are drawn as simply as possible to aid in identification of
shoaling patterns that can vary significantly in size and shape. Below the
drawing is a short description of the shoal. Below this is a short narrative
describing the physical processes that create the shoal. At the bottom left is a
reference containing a case study dedicated to an example of this type of shoal.
An aerial photograph depicting the shoal pattern is located on the night of the
page, below the heading. Below the photograph is a description of the depicted
site, the date of the photograph, and a description of the project and shoaling
history.

Manual use

The DMS-Manual is a diagnostic tool. The engineer responsible for channel
maintenance begins the shoal-classification process by collecting all pertinent
data about the channel. These data will include aerial photographs, channel
hydrographic surveys, and dredging history. Data collection in the DMS-Data

Chapter 3 DMS-Manual

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Chapter 3 DMS—Manual

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Chapter 3 DMS—Manual

28

Manager allows the engineer to obtain a visual picture of the size and location of the
shoal. Upon completion of this task, the engineer then consults the DMS-Manual.
Having obtained a visual image of the shoal, the engineer compares this image with the
general drawings and example photographs. This process results in the selection of one
or more classifications that may describe the shoal. Upon reading the description of the
shoal and the physical processes that created it, the engineer should be able to narrow the
choice even further. Obtained before application of the DMS, knowledge about the
physical processes in the watercourse (e.g., wind and wave climate, storm history, and
current strength and patterns) further simplifies this process.

Identification of the type of shoal is the first step in obtaining more appropriate and
cost-effective shoaling mitigation methods. By identifying the type of shoal, the engineer
has also identified the processes that led to shoal creation. Addressing the processes (the
disease) rather than the shoaling (the symptom) greatly increases the probability of
finding an effective shoaling mitigation method (the cure) in the DMS approach.

Sometimes, shoals may result from several different mechanisms acting in concert.
In such cases, the manual lists the shoal under more than one classification. Here,
addressing either one or both of the processes provides a successful mitigation method.
For example, shoaling occurs in a channel that crosses perpendicular to tidal currents.
However, the sediment in the shoal originates from an upstream shoreline exposed to
waves. Waves erode the shoreline, and tidal currents transport the sediment towards the
channel where the sediment gets deposited because of vertical expansion. Here, the
physical processes at play include tidal currents and waves. By only addressing the
waves, the engineer may be able to cut off the sediment source rather than try to treat
both waves and currents. Regardless, in situations where more than one shoal
classification applies, the manual recommends a more detailed analysis by means of
using the DMS-Analytical Toolbox.

Example Application — East Pass Inlet

As identified in Figure 5, the maintained channels at East Pass Inlet exhibit three
areas of chronic shoaling. In this example, the type of shoaling in each of these areas is
identified using the DMS-Manual and the information collected and contained in the
DMS-Data Manager.

Area 1: Outer Bar

This shoal is located in the maintained channel south of the jetty tips where the
channel crosses the ebb shoal. According to dredging records (Table 2), approximately
16,000 cu yd/year are dredged from this location. Figure 7 illustrates the location of the
outer bar shoal in 1990. Based solely on the shoal’s location, the most likely
classification is Horizontal Expansions: Expansion Into Ocean — Ebb Tidal Shoal
(Figure 9). The sample manual page describes the shoal as follows: “Crescent- or box-
shaped shoal that forms at the seaward end of a tidal inlet. Shape of this shoal depends
on the area’s wave climate.” This description exactly matches the morphology
encountered at this area. Comparing the generalized figure with Figure 7 further
validates this choice.

With the shoal type identified, the next step in the DMS is to identify the shoaling
mechanisms and investigate possible shoaling mitigation methods. In this case, the

Chapter3 DMS-Manual

29

30

physical processes that build the shoal involve the transportation of sediment offshore by
the ebb jet. The sediment source is the littoral drift on either side of the inlet. Because
the only access to Choctawhatchee Bay from the Gulf of Mexico is through the jetties,
location of the channel over the ebb shoal is unavoidable. In dealing with channels over
ebb shoals, the most common means of lowering dredging costs is to perform regular
surveys of the ebb shoal and situate the channel such that it crosses the shoal at the
deepest point. The Mobile District has already incorporated this practice into its regular
maintenance of the channels at East Pass Inlet in its dredging optimization procedure.

Area 2: Channel Bend

Beginning approximately 1,000 ft north of the jetty tips and continuing for 2,000 ft in
a north and then north-northwest direction, this shoaling hot spot is centered around the
southern bend in the project channel. Dredging records do not specify the exact amount
removed from this area. One can safely assume, however, that shoaling in this area
contributes greatly to the ~38,000 cu yd/year (East Pass Channel plus Entrance Channel
categories denoted in Table 2) dredged from the inlet throat. Consultation of the manual
gives two possible categories for shoal classification. The first possible classification is
Horizontal Channel Expansions: Areas of Shoreline Recession (Figure 10). The
configuration of the converging jetties (which diverge as one moves south to north)
prompts selection of this category. Under this classification, sediment-laden currents
travel from an area of flow constriction (between the jetty tips) to an area of low velocity
(north of the jetties where the throat becomes wide). Here, with the transport potential
reduced, deposition occurs. The sediment source may be either the sediment eroded from
the channel between the tips of the jetties or (more likely) the suspended sediment
resulting from the inlet’s interruption of littoral drift.

The second possible classification is Vertical Expansions: Cross Channel Flow
(Figure 11). Under this category, shoals form where flow crosses the channel at an angle
to the channel’s axis. Currents carrying sediments cross from areas of shallow depths to
areas of deeper depths. The change in depth is accompanied by a reduction in velocity
and hence a reduction in sediment-transport potential. Sediment, therefore, deposits
immediately beyond the change in depth. At this channel location, the channel bends
from a north/south to a north-northwest/south-southeast orientation. This change in
orientation increases the likelihood that, at some point (either on flood or on ebb),
currents will cross the channel in a direction other than in line with the channel axis.

Given that the DMS-Manual has identified two possible shoal classifications, this
shoaling hot spot is a good candidate for further investigation using the DMS-Analytical
Toolbox.

Area 3: Old Pass

Figure 5 shows the location of Old Pass channel. The channel attaches to the main
channel just south of the Highway 98 Bridge. From there, the channel runs in a east-
northeast direction until it reaches the tip of Norriego Point. At the tip of the point, the
channel bends south acquiring a southeast orientation as it enters Destin Harbor. From
1969 to 1995, this short channel has accounted for approximately one-third of the
dredging activity at the inlet.

Chapter 3 DMS-Manual

Upon first inspection, classification of the shoaling behavior seems obvious. Vertical
Expansions: Cross Channel Flow (Figure 11) appears to match the geometry of this
channel perfectly. Both on ebb and on flood, currents cross the channel at approximately
right angles. The sediment creating the shoal could come from either Normego Point or
the interior bay (i.e., the flood shoal or the Destin shoreline).

Familiarity with the history of the channel, however, suggests an alternate
classification. Before jetty construction, Norriego Point was fully exposed to waves from
the Gulf of Mexico. In fact, the point is actually a spit formed through wave-induced
sediment transport. The jetties now shelter the spit from waves along certain directions.
However, waves approaching the coast from the south still strike the throat’s eastern
shoreline. Figure 8 shows how much the spit has changed in size and location between
1995 and 1998. Given this information, the classification Enhanced Sediment Forcing:
Littoral Drift (Figure 12) may also apply. Identifying the mechanisms responsible for
shoaling requires application of a wave-refraction model to characterize the wave climate
within the throat and a hydrodynamic model to determine the direction and magnitude of
currents. Both models are available in the DMS-Analytical Toolbox.

The above three examples illustrate application of the DMS-Manual in conjunction
with the DMS-Data Manager for diagnosing shoaling problems. The example pages
from the manual identified the possible shoaling mechanisms for the three shoaling hot
spots found in the maintained channels of East Pass. Identifying possible classifications
has prompted further investigation into shoaling mechanisms through its descriptions of
the physical processes responsible for the shoal’s creation. Finally, the classification
process for Area 3 has underscored the importance of thorough examination of inlet
history before applying the DMS.

Chapter 3 DMS-Manual

31

32

4 DMS-Analytical Toolbox

This chapter describes the DMS-Analytical Toolbox, presently under
development. Included 1s a discussion on the contents of the toolbox and its use.
The chapter presents the application of this DMS component to navigation
channel shoaling at East Pass Inlet.

Analytical Toolbox Description

This component of the DMS consists of a suite of analytical tools for
conducting more detailed analyses of channel shoaling. The toolbox is expected
to contain various utilities ranging in complexity from simple calculations for
determining fetch-limited wave heights to two-dimensional, finite-element,
hydrodynamic flow models. These tools will access the data contained in the
DMS-Data Manager as input. As such, the development of the Data Manager
contains provisions to output information in the appropriate format compatible
with these tools.

Toolbox contents

The following lists examples of anticipated contents of the toolbox. The
label “calculator” indicates that the utility will access the output from one of the
other tools to generate new information. Some of the programs were in the
process of interface development at the time this case study was conducted.

e ADCIRC. The ADCIRC (Luettich, Westerink, and Scheffner 1992)
system of computer programs solves time-dependent, free-surface
circulation, and transport processes in two and three dimensions. The
finite element model is based on the wave-continuity formulation of the
shallow-water equations.

e SMS. The Surface Water Modeling System (SMS) interface is a pre-
and post-processor for ADCIRC (as well as other finite-element
numerical models). SMS is a comprehensive graphical user environment
for performing model conceptualizations, mesh generation, statistical
interpretation, and visual examination of surface water model simulation
results.

e STWAVE. This tool is a time-independent, finite-difference spectral
wave energy propagation model. The STWAVE model (Resio 1987,

Chapter 4 DMS-—Analytical Toolbox

1988: Smith, Resio, and Zundel 1999) also includes steepness-limited
and depth-limited breaking criteria and the wave-current interaction.

e Tidal constituent database. This database (Westerink, Luettich, and
Scheffner 1993) allows the user to manually generate time series of tidal
elevations or to use a program to access the full database to generate the
time series of both tide elevations and currents for any location along the
US. east coast, Gulf of Mexico, Caribbean Sea, or U.S. Pacific coast.
This database drives hydrodynamic models such as ADCIRC.

e Sediment-transport calculator. This utility will calculate sediment-
transport rates as an indicator of areas of erosion and accretion.
Typically, in DMS applications, it yields indicators of transport potential
rather than actual values.

e Initiation of sediment-movement calculator. This tool indicates areas
of sediment movement. Inputs from ADCIRC and wave estimates
determine the shear stress on the bed. From a Shield’s diagram, the
program identifies areas of live bed (sediment motion) or clear water (no
sediment movement).

e Fetch-limited, wind-generated wave model. This tool calculates the
wave height and period associated with locally generated wind waves.
The sediment-transport calculator accesses this information to determine
whether wave-driven sediment transport is a cause of channel shoaling.

e Ebb jet model. This tool examines the ebb jet issuing forth from an
inlet. Based on the work by Ozsoy and Unliata (1982), this program
calculates the velocity distribution of an ebb tidal jet. It takes into
account lateral mixing and entrainment, bottom friction, one-dimensional
bathymetric changes, and ambient currents. Intended for shoaling
problems in channels through tidal inlets, this tool provides estimates of
velocity magnitudes that will drive sediment-transport calculations.

The DMS-—Analytical Toolbox is not just a collection of programs. It also
contains suggestions for display of information generated by these tools. The
format for display of information increases the speed of diagnosis and
investigation of alternative solutions.

An ancillary goal of the DMS-Analytical Toolbox is to improve
interpretetive capabilities through adopting innovative graphical formats.
Typically, graphical display of hydrodynamic information has been limited to
2-D plots of flow vectors and time-series plots of elevations or integrated flow
across an inlet such as in Figures 13 and 14. Although these plots provide some
information about the currents in the area, they do not clearly illustrate how the
bathymetry controls the flow pattern. Inclusion of false-color contouring of the
bathymetry or the velocity magnitude shown underneath the velocity vectors as
in Figures 15 and 16 can greatly enhance the diagnostic utility of these figures.

Chapter 4 DMS-—Analytical Toolbox

33

34

Water Surface Elevation (ft-NGVD)

Tidal Elevations in East Pass Inlet and Vicinity (1996)

50
Time (hrs)

Figure 13. Example of time-series plot

1996 Bathymetry - East Pass Inlet (Flood Velocity Vectors)

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Figure 14. Example of two-dimensional velocity vector plot

Chapter 4 DMS-Analytical Toolbox

Figure 16. Example of false-color velocity magnitude contour plot with velocity vector overlay

Chapter 4. DMS—Analytical Toolbox 35

36

In addition to these types of plots, graphics contours showing differences in
two solution sets can provide informative comparisons. For example, Figure 17
was generated to investigate the change induced by jetty construction by plotting
the difference in velocity magnitude for hydrodynamic model simulations of a
1947 bathymetry (pre-jetty construction) and a 1996 bathymetry (post-jetty
construction). The plot shows the difference in spring ebb-tide velocity
magnitude. Positive values (towards the blue end of the spectrum) denote
increases in velocity magnitude, and negative values (towards the red end) denote
decreases. Units are in feet per second.

*Sonng Ebb Tide Velocity Difference

Figure 17. Example of comparison of solutions

The above examples illustrate the diagnostic utility of selecting the correct
graphical format for output display from the toolbox models. In addition, the
diagnostic benefits gained by adopting the suggested formats increase with the
use of standardized formats. Standardizing output formats permit the
establishment of an experience database. As more case studies investigate the
same tools and display similar information in standard formats, comparisons
between case studies of different shoal types will become easier. This
standardization will expand the state of the science and utility of the DMS
approval.

Chapter 4 DMS-Analytical Toolbox

Toolbox use

In the application of the DMS to channel shoaling, some conditions often
require more detailed analyses of a channel’s physical processes either to better
identify the shoaling mechanisms or to investigate possible mitigation methods.
Obviously, the type and complexity of the investigation will determine the
appropriate tool. For example, if the channel being investigated is located ina
well-sheltered inland waterway, then setting up a wave-refraction model serves
little purpose.

The toolbox is presently in development. With continued application of the
DMS, the contents of the toolbox are expected to change as experience and needs
direct. Certain types of programs are expected to remain in the toolbox. These
include a hydrodynamic model, a wave model, and a sediment-transport
calculator. The DMS-Analytical Toolbox will contain recommendations for the
output format of these three tools. Development of the recommended formats is
ongoing.

Because sediment movement creates shoals, the final form of the DMS-
Analytical Toolbox should contain a method for evaluating sediment-transport
potential under both quasi-steady currents and waves. As with all sediment-
transport investigations, interpreting results requires caution. For example, Yang
and Molinas (1982) compared seven sediment-transport (under steady currents)
formulae with 1,259 measurements from laboratory and field investigations. The
best performing formula predicted sediment-transport rates within a factor of two
of the measured rates in only 68 percent of the cases.

Application of the sediment-transport calculator produces a spatially variable
scalar data set (a contour plot) of magnitude of sediment-transport rate.
Interpretation of contours of sediment-transport magnitude is often difficult. One
must remember that sediment-transport magnitude does not necessarily correlate
to erosion or deposition. Erosion and deposition align more closely to the
gradients of sediment-transport rate in the flow direction. If, for example, in a
specified control volume, the sediment transport entering the volume exceeds the
sediment transport leaving the volume, then most likely, the volume will contain
deposition. The appropriate analogy is that of filling a bucket with a hole in the
side. If water enters the bucket faster than it comes out the hole, the water level
will rise (accretion). If water enters at a slower rate, then the water level will fall
(erosion). The most prudent way to interpret these results is to conclude that
sediment originates in areas showing sediment transport and moves in the
direction of the velocity vectors. Figure 18 illustrates a contour plot of sediment
transport overlaid with the water-velocity vectors.

The DMS-Analytical Toolbox can be the most difficult component of the
DMS to master. Obviously, implementing a hydrodynamic model or a wave-
refraction model requires an investment in learning. The purpose of the toolbox
in the analysis of shoaling problems will be to recommend a model choice, to
assist in the model setup by identifying the required data in the DMS-Data
Manager, and to make suggestions for output formats that best visualize the
physical processes that create the shoal. By following this procedure, the DMS
makes possible the creation of an experience base from which to compare (and
anticipate and avoid) future channel shoaling.

Chapter 4. DMS-Analytical Toolbox 37

38

Figure 18. Example of contours of sediment transport

Example Application — East Pass Inlet

Shoal classification at East Pass Inlet with the DMS-Manual prompted
investigation of the physical processes with two types of models that will become
available in the DMS-Analytical Toolbox. First, a hydrodynamic model
determines the magnitude and direction of the inlet’s currents. Second, a wave-
refraction model characterizes the wave climate in the inlet throat.

Inlet hydrodynamics

As identified in Chapter 1, the maintained channels at East Pass Inlet contain
three channel shoaling hot spots (Figure 5). For two of the areas (Channel Bend
and Old Pass), the application of the DMS-Manual in Chapter 3 gave more than
one classification of shoal type. For both these areas, the physical processes
involved currents through the pass. This prompted the need to investigate the
inlet hydrodynamics. This section details the application of RMA2 (Thomas and
McAnally 1985) to resolve the current patterns at the shoaling areas. RMA2, a
2-D, depth-averaged, finite-element, hydrodynamic numerical model, computes
water-surface elevation and horizontal velocities for subcritical, free-surface
flows. The program computes a finite-element solution to the Reynold’s form of
the Navier-Stokes equations.

Figure 19 depicts the bathymetry input to RMA2. The constructed
bathymetry reflects a combination of the following hydrographic surveys, which
characterize the area given in parentheses:

e 1997 USACE SHOALS Lidar Survey (Inlet Vicinity)
e 1996 USACE SHOALS Lidar Survey (Inlet Vicinity)
e 1987 NOAA Nautical Chart #11385 (Choctawhatchee Bay)
e 1995 NOAA Nautical Chart #11388 (Gulf of Mexico)

Chapter 4 DMS-Analytical Toolbox

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Chapter 4 DMS Analytical Toolbox

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40

Two boundary conditions were specified for the model. Month-long tide gauge
records provided the water-surface elevations at the offshore boundary located
approximately 2 miles offshore. Averaged flow measurements of the freshwater influx
specified the flow boundary condition situated across the Choctawhatchee River Delta on
the eastern border of the bay.

Figures 20 and 21 depict channel currents during spring flood and spring ebb.
Velocity vectors are overlaid on contour plots of the velocity magnitude. The solid black
lines in the figures indicate the location of the maintained channels. Magnifying the
areas of interest, Figures 22 through 25 depict the currents over the shoaling hot spots.

In Chapter 3, the DMS-Manual identified two possible shoal classifications for the
shoaling hot spot at the channel bend. These were shoaling caused by horizontal
expansion of the channel (through shoreline recession) and shoaling caused by vertical
expansion of the water column (i.e., shoaling from currents crossing the channel at an
angle to the channel’s axis). Figures 22 and 23 illustrate current patterns in the vicinity
of this shoal. Examination of the gradient of the velocity-magnitude contours as the flow
enters the inlet on flood tide (Figure 22) tests the accuracy of the horizontal expansion
classification. Figure 22 shows a marked decrease in velocity magnitude traveling north
through the inlet. The velocity magnitude decreases from a value of almost 4 ft/sec near
the jetty tips to less than 2.5 ft/sec at the top of the channel bend. This sharp velocity
decrease over a relatively short distance (~2,000 ft) verifies the choice of this shoal
classification.

To verify the second classification (vertical expansion) requires examination of the
current patterns over the channel. The velocity vectors indicate the existence of a few
areas where currents enter the channel at an angle (e.g., in Figure 22, the flood currents
enter the channel south of the bend at an angle to the channel axis). However, the
perpendicular component of these vectors is small. Also, as currents cross into the
channel, no noticeable decrease in velocity occurs. This observation suggests that the
dominant mechanism causing shoaling in this area is the honzontal expansion of the
channel related to the recession of the banks on either side of the channel.

The second area where the manual identified more than one possible shoal type is in
Old Pass channel. In this area, one of the possible classifications was Vertical
Expansions: Cross Channel Flow. Testing of this classification involves examination of
the current patterns and velocity magnitudes in the channel vicinity. Figures 24 and 25
illustrate the inlet hydrodynamics in this area. Both figures show the currents cross the
channel at almost right angles to the channel axis. In addition, the figures also illustrate
the marked decrease in velocity after currents enter the channel (the shift from green to
blue). Both these behaviors reinforce the selection of this classification.

A further investigation of the shoaling behavior at East Pass involves a simple
treatment of sediment transport. The RMA2 model provides the velocity and water depth
at each node in the finite-element mesh. From this information (together with a
representative sediment size), the sediment-transport rate at each node can be calculated
with an empirical sediment-transport function.

Chapter 4 DMS-Analytical Toolbox

velocity mag 7 : 307.500
gee, 5.90 x

tl

~AANNN OOS
8

—
|

O°;

88

tH

Figure 21. Velocities through East Pass Inlet on spring ebb

Chapter 4 DMS-—Analytical Toolbox

A1

42

Figure 23. Velocities at channel bend on spring ebb

Chapter 4 DMS-—Analytical Toolbox

Figure 25. Velocities at Old Pass on spring ebb

Chapter 4 DMS-—Analytical Toolbox

43

44

The results from the simulation become input into a sediment-transport function. The
function chosen for investigation was the Ackers-White (1973) formula. This total-load
formula is based on dimensional analysis with empirically determined exponents. The
formula takes the form

zt Blea

il Gl | te A
where
OQ, = volume of sediment transport per unit time per unit width
U = depth-averaged velocity
D3; = sediment diameter of the bed greater than 35 percent by weight
of a representative bed sediment sample
d = water depth
ux = shear velocity

In the equation,

I-n

Pe) — || (2)

where
Pp; = density of the sediment
p = density of the fluid

Also, if the function D: is defined as

1/3
p. [PP 8) Dg (3)
Po OF
where
v= kinematic viscosity

Then, for D« > 60,
n=0
A=0.17
m=1.5
C; =0,02

(4)

Chapter 4 DMS-Analytical Toolbox

and for 1<D.<60,
n=1-0.243In(D.)

A=0.14+0.23/,/D. 6)
2)
m=1.34+9.66/D»

C,= exp(2.86 In(D..)- 0.434(In(D..)Y — 8. 13)

Output from the hydrodynamic model supplied the velocity and depth variables.
Sediment sampling suggested an estimate of 0.3 mm for D;;. Assumed values account
for water density and viscosity.

Figures 26 through 29 show contours of sediment transport (in cfs/ft) at the shoaling
hot spots. As a visual aid, vectors were overlaid on the contours. The vectors have the
magnitude equal to the calculated sediment transport, but a direction equal to that of the
ambient currents. The assumption is that the sediment is transported in the direction of
flow (this is usually the case). As mentioned previously, the appropriate indicator of
sediment deposition is the negative gradient of sediment-transport magnitude.

Figures 26 and 27 show the sediment transport during spring flood and ebb near the
channel bend. They confirm the previous conclusion that shoaling in this area results
from the horizontal expansion of the channel. Figure 26 illustrates how sediment is
transported from south to north along the axis of the channel on flood tide. This analysis
has also yielded an unexpected result. Figure 27 also exhibits the behavior associated
with a horizontal channel expansion on ebb tide. Sediment is transported along the axis .
of the northerm section of the channel. This result solidifies the selection of this
classification for shoaling in this area.

Solutions to remedy this type of shoaling vary widely in cost. Shoaling from
shoreline recession causes the channel to meander within the inlet throat. The least-
costly solution is surveying the area regularly to designate the position of the channel by
the location of the meandering thalweg. Another possible solution involves altering the
geometry causing the expansion. The construction of flow-training walls would constrain
the flood jet as it enters the inlet throat. This action would maintain stronger flows
through the throat and hence mitigate shoaling. Notably, a “soft” solution in the same
vein is to build out the shoreline on either side of the throat through the placement of
dredged material. Either of these costly solutions would require a comprehensive
cost/benefit analysis before implementation. One final solution is to treat the source of
the sediment creating the shoal. The east jetty is presently at its sediment-storage
capacity. Sediment that likely bypasses the tip of this jetty gets transported into the throat
on flood tide. Once deposited, it contributes to shoaling. Extension of this jetty or
mining the updrift filet would reduce the contribution from this sediment source.

Figures 28 and 29 illustrate sediment-transport contours and vectors during spring
flood and ebb near Old Pass. These figures show much less variation than the previous
example. Except for a small region to the west of the area during flood (Figure 28), the
contours of sediment-transport magnitude are constant (solid) in almost every area within
and surrounding this shoal. Near-constant sediment-transport magnitude indicates that
little sediment deposits in these areas. This result suggests a need to reevaluate the
classification of this shoal. Examination of the wave climate in this area helps to clarify
the classification.

Chapter 4 DMS-Analytical Toolbox

45

46

Figure 27.

Sediment transport during spring ebb at the channel bend

Chapter 4 DMS-Analytical Toolbox

edgiment Transport (cfs/i)
weet 0.00545

Figure 28. Sediment transport during spring flood at Old Pass

edgiment Transport (cts)
Meee 0.00545 wy)

Figure 29. Sediment transport during spring ebb at Old Pass

Chapter 4 DMS-Analytical Toolbox 47

Wave-refraction model

The USACE-developed model RCPWave (Ebersole, Cialone, and Prater 1986)
provided the means to model wave refraction at East Pass Inlet. RCPWave, a linear wave
propagation model, addresses both refraction and diffraction by bottom contours. The
governing equations of the model are a modified form of the “mild slope” equation for
monochromatic, linear waves and the equation specifying irrotationality of the wave-
phase function gradient. The model accepts as input a representative wave field of wave
height, period, and direction. The program then propagates the wave towards the shore
over a user-supplied bathymetry.

The identical bathymetry used for the hydrodynamic modeling was input into the
wave model. Wave hindcast data from a station located approximately 9 miles due south
of the inlet in 52 ft of water provided the offshore wave conditions. Wave hindcast data
reduction produced representative wave conditions along 22.5-deg direction bands. The
procedure for finding the wave climate in the throat required two applications of
RCPWave. The first application brought the waves from deep water to the tips of the
jetties. The second application, performed with a finer resolution grid, started at the jetty
tips and propagated the wave through the throat. Figure 30 shows an example of both
model applications. In the figure, the wave rays were drawn through interpolation of the
model output.

Figure 31 is a magnified view of Figure 30 in the area of the Old Pass shoal. The
figure illustrates the continued wave impact on Norriego Point despite the protection that
the jetties afford. Qualitatively, the angle with which the waves strike the point and the
magnitude of wave height before breaking suggest a significant amount of sediment
movement or at least sediment suspension. If an adverse wave climate occurs during
flood tide, currents may carry the wave-suspended sediment toward Old Pass.

A program (or “calculator”) evaluating sediment-transport potential by waves was
not available for this case study. This tool would help evaluate the hypothesis outlined in
the preceding paragraph. Development of these types of tools is part of the DMS work
unit.

Conclusions conceming Old Pass shoal are incomplete. The preceding analysis has
indicated that tidal currents cross the channel at a right angle and show an accompanying
deceleration. However, sediment-transport contours indicate no gradients in the area.
Absence of sediment-transport gradients indicates little sediment deposition. The wave-
refraction diagrams show that wave activity may play a significant role in the physical
processes along the point. The synthesis of these facts prompts the hypothesis that waves
suspend sediment along the shoreline and currents transport the sediment toward the pass
where the sediment comes to rest. However, tools to evaluate this hypothesis are under
development.

Chapter 4 DMS-Analytical Toolbox

Angle of Approach =157.5° from North

g
:
3

i

Northing (ft- NAD27)

Easting (ft - NAD27}

511000

> = 5,0 ft Significant Wave Height
Figure 30. RCPWave wave-refraction diagrams of offshore region (above) and inlet
throat (below)

Chapter 4 DMS-Analytical Toolbox

1365000.05 1375006.00 1385000.00 1395000. 00;

49

50

Deep Water Wave Angle of Approach = 157.5° from North

h below NGVD

De

1366500

> =3.0 ft Significant Wave Height

Figure 31. RCPWave wave-refraction diagram in the vicinity of Normego Point

If the hypothesis is valid, a solution to this type of problem is to address the sediment
source. The hydrodynamic analysis indicated that the currents alone were incapable of
creating the shoal. Therefore, reducing the wave-suspended/transported sediment is the
appropriate approach to this problem. Either a reduction in wave activity or a reduction
in the actual transport may address this shoaling problem. Reducing the wave activity
would involve the construction of a breakwater either outside the jetties (preventing
waves from entering the throat) or directly offshore of the point. Obviously, construction
within the throat is less costly than construction offshore. In addition, a breakwater
aligned with the channel and close to shore would have a much smaller impact on the
tidal hydraulics than would a breakwater outside the jetties.

Several actions would reduce the actual sediment transport. First, hardening the
shoreline will prevent sediment movement and thus shoaling. Hardening can take the
form of either a seawall or revetments. Second, the sediment may be intercepted before it
teaches Old Pass. The construction of a small terminal structure at the tip of Nornego
Point would trap the sediment as it moves north.

In conclusion, the application of the tools in the DMS-Analytical Toolbox have
successfully clarified the classification of one of the two problem areas that fell under
more than one shoaling category. The analysis of the second area provided more insight
into the physical processes that create the shoal. However, the analysis also pointed out
deficiencies in the toolbox that require improvement.

Chapter 4 DMS-Analytical Toolbox

5 Summary and
Recommendations

This chapter summarizes the DMS concepts and their application to the high-
shoaling rates in the channels through East Pass Inlet. The case study resulted in
solutions to the shoaling problems developed through the application of each of
the DMS modules: the DMS-Data Manager, the DMS-Manual, and the DMS-
Analytical Toolbox. Application of these modules produced a synthesis of
observations of the morphology, hydrodynamic processes, dredging records, and
hydrodynamic and wave modeling results. This synthesis provides information
and a framework from which to make informed decisions for taking corrective
measures to address sediment shoaling at East Pass.

Summary

The purpose of this research was to evaluate DMS concepts through its
application to the excessive channel shoaling found at East Pass Inlet near
Destin, Florida. The DMS methodology entails a three-pronged approach to
examining shoaling problems:

e DMS-Data Manager. After locating all available data on a maintained
channel, the engineer enters the pertinent information into the DMS-Data
Manager. This GIS-based software tool displays all the information
pertaining to a channel in a graphical format. This tool allows the
engineer to consolidate in one program all the data, which may be
contained in multiple formats, concerning a channel. The software’s
graphical format gives the engineer a visual picture of shoaling hot spots
and their location relative to the geomorphology of the surrounding
areas. The engineer can compare this picture with idealized sketches
found in the DMS-Manual.

e DMS-Manual. This field guide of shoaling problems contains
descriptions, examples, and diagrams of several shoaling classifications.
The engineer matches the picture of the shoaling hot spot created with
the DMS-Data Manager to the correct classification to identify the type
of shoal. The description of the physical processes that create the shoal
will point to possible mitigation methods.

e DMS-Analytical Toolbox. Often, shoaling mechanisms require a greater
understanding than that provided via the DMS-Manual. The

Chapter S Summary and Recommendations

51

DMS-Analytical Toolbox aids the user in those instances when the
DMS-Manual identifies more than one shoaling classification. The
toolbox also provides tools to investigate mitigation methods and gain a
better insight into the physical processes. The DMS-Analytical Toolbox
is a collection of programs and methods for accomplishing a detailed
analysis of the physical processes that create the shoal. It contains
programs that calculate hydrodynamics, wave climate, and sediment
transport. In addition, it contains suggestions for graphical presentation
of the output to help diagnose shoaling problems.

As such, the three components of the DMS aid the engineer in the diagnosis
of shoaling problems and the discovery of a successful mitigation method. The
East Pass Inlet case study showed the application of the DMS to three problem
areas. For two of the areas, the DMS successfully identified the shoal classifi-
cation and pointed to possible mitigation methods. For the third area, the
application produced two possible classifications, perhaps acting together. The
readily available analytical tools do not, at the present time, provide an
unequivocal diagnosis. This unresolved ambiguity indicates the need for further
development of the contents of the DMS-Analytical Toolbox. Despite its
limitation in identifying the distinct shoaling mechanisms at the trial site, the
DMS has provided insight into the possible physical processes responsible for
this shoal’s creation.

Application of DMS methodology led to solutions to the three shoaling
problem areas found in the maintained channels through East Pass Inlet.
Shoaling of the outer bar region of East Pass channel could be mitigated by
conducting frequent surveys of the ebb shoal to find the lowest point in the bar
and redesignating the channel to cross the shoal in that area. Shoaling in the
channel-bend region, caused by horizontal expansions, may be treated in one of
three ways: (a) reducing the flow expansion through construction of training
walls, (b) reducing the flow expansion by building out the shoreline through
dredged-material placement, or (c) preventing material from entering the inlet
through lengthening the east jetty or mining the filet in the updrift beach. The
tools presently available failed to produce definite conclusions conceming the
shoaling in Old Pass channel. If the hypothesis in Chapter 4 concerning the
shoaling in this area is valid, then recommendations would include one of the
following methods: reducing wave activity through the construction of a
breakwater either offshore of the jetties or parallel to the Nornego Point
shoreline, hardening the Norriego Point shoreline through construction of
seawalls or revetments, or preventing littoral transport into the channel by
construction of a terminal groin at the tip of Norriego Point.

Recommendations

This report has shown the utility of the DMS for providing a framework for
formulating solutions to reduce shoaling of maintained channels. The application
of the DMS to this case study has revealed a number of areas requiring further
research and development. These areas are grouped by DMS component:

ChapterS Summary and Recommendations

52

DMS-Data Manager — Research in this area should include the following:

e Developing the software as a stand-alone unit for use as a repository for
all information pertaining to maintained channels regardless of intended
use with the entire DMS.

e Facilitating the use/interface with the DMS-Manual and DMS-Analytical
Toolbox to provide proper definition of shoals.

e Expanding and refining the software to rapidly identify shoaling problem
areas.

e Helping to quantify shoals to evaluate their severity.

e Developing time frames associated with shoaling to aid in scheduling
maintenance dredging.

e Providing feedback with the DMS-Analytical Toolbox to aid in
calibration/validation of the analytical tools.

DMS-Manual — Research concerning this component should include the
following:

e Investigating further shoal classifications.

e Finding relevant case studies for each classification to provide a basis of
comparison.

e Finding appropnate example photographs for documenting each of the
shoal classifications.

DMS-Analytical Toolbox — Research pertaining to this component should
include the following:

e Developing back-end tools that use output from the hydrodynamic and
wave-refraction models to produce definable cause and effect
relationships between the physical processes and the sedimentation
patterns.

e Producing diagnostic pictures of the physical processes in formats that
are easily related to the encountered conditions.

ChapterS Summary and Recommendations 53

References

Ackers, P.. and White, W. R., (1973). “Sediment transport: New approach and
analysis,” Proceedings, Journal of Hydraulics Division 99(HY 11), ASCE,
2041-2060.

Ebersole, B. A., Cialone, M. A., and Prater, M. D. (1986). “Regional Coastal
Processes, Numerical Modeling System; Report 1, RCPWAVE, a linear
wave propagation model for field use,” Technical Report CERC-86-4,
Coastal Engineering Research Center, U.S. Army Engineer Waterways
Expenment Station, Vicksburg, MS.

Kraus, N. C., Mark, D. J., and Sarruff, S. “DMS: Diagnostic Modeling System;
Report 1, Reduction of sediment shoaling by relocation of the Gulf
Intracoastal Waterway, Matagorda Bay, Texas,” Technical Report in
preparation, U.S. Army Engineer Waterways Experiment Station, Vicksburg,
MS.

Leadon, M. E. (1996). “Hurricane Opal: Erosional and structural impacts to
Florida’s Gulf Coast,” Journal of ASBPA, Shore and Beach.

Leadon, M. E., Nguyen, N. T., and Clark, R. R. (1998). “Hurricane Opal: Beach
and dune erosion and structural damage along the Panhandle Coast of
Florida,” Florida Bureau of Beaches and Coastal Systems, BBCS No. 98-
001.

Lillycrop, W. J., and Hughes, S. A. (1993). “Scour hole problems experienced
by the Corps of Engineers: Data presentation and summary,” Miscellaneous
Paper CERC-93-2, Coastal Engineering Research Center, U.S. Army
Engineer Waterways Experiment Station, Vicksburg, MS.

Luettich, R. A., Westerink, J. J., and Scheffner, N. W. (1992). “ADCIRC: An
advanced three-dimensional circulation model for shelves, coasts, and
estuaries; Report 1, Theory and methodology of ADCIRC-2DDI and
ADCIRC-3DL,” Technical Report DRP-92-6, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.

Morang, A. (1992). “A study of geologic and hydraulic processes at East Pass,
Destin, Florida; Volume I, Main Text and Appendices A and B,” Technical
Report CERC-92-5, Coastal Engineering Research Center, U.S. Army
Engineer Waterways Experiment Station, Vicksburg, MS.

54

References

Morang, A., Irish, J. L., and Pope, J. (1996). “Hurricane Opal morphodynamic
impacts on East Pass, Florida: Preliminary findings.” The future of beach
nourishment, proceedings of the 9th national conference on beach
preservation technology, St. Petersburg, Florida, L. S. Tait, ed.

Ozsoy, E., and Unliata, U. (1982). “Ebb-tidal flow characteristics near Inlets,”
Estuarine, Coastal and Shelf Science 14, 251-263.

Resio, D. T. (1987). “Shallow-water waves, I: Theory,” Journal of Waterways,
Port, Coastal, and Ocean Engineering, ASCE, 113(3), 264-281.

. (1988). “Shallow—water waves, II: Data comparisons,” Journal of
Waterways, Port, Coastal, and Ocean Engineering, ASCE, 114(1), 50-65.

Smith, J. M., Resio, D. T., and Zundel, A. K. (1999). “STWAVE: Steady-state
spectral wave model; Report 1, User’s Manual for STWAVE version 2.0,”
Instruction Report CHL-99-1, U.S. Army Engineer Waterways Experiment
Station, Vicksburg, MS.

Thomas, W. A., and McAnally, W. H., Jr. (1985). “User’s manual for the
generalized computer program system; Open-channel flow and
sedimentation: TABS-2, Main Text and Appendices A through O,”
Instruction Report HL-85-1, U.S. Army Engineer Waterways Experiment
Station, Vicksburg, MS.

U.S. Amny Engineer District, Mobile. (1967). “East Pass channel, Florida, Gulf
of Mexico into Choctawhatchee Bay, General Design Memorandum,”
Mobile, AL.

. (1977). “Design report on East Pass channel, Florida,” Mobile,
AL.

. (1983). “Reconnaissance report, East Pass channel, Destin,
Florida,” Mobile, AL.

. (1986). “Monitoring program, East Pass channel, Destin, Florida,”
Mobile, AL.

U.S. Congress, House. (1950). “Letter from the Secretary of the
Army. East Pass from the Gulf of Mexico into Choctawhatchee Bay,
Florida,” 81st Congress, 2nd Session, House Document No. 470.

U.S. Engineer Office. (1939). “Study of East Pass channel, Choctawhatchee
Bay, Flonda,” Gulf of Mexico Division, New Orleans, LA.

Westerink, J. J., Luettich, R. A., and Scheffner, N. W. (1993). “ADCIRC: An
advanced three-dimensional circulation model for shelves, coasts, and
estuaries; Report 3, Development of a tidal constituent database for the
Western North Atlantic and Gulf of Mexico,” Technical Report DRP-92-6,
U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.

Wneght, T. L., and Sonu, C. J. (1975). “Processes of sediment transport and tidal
delta development in a stratified tidal inlet.” Estuarine research, Volume II,
geology and engineering. L. E. Cronin, ed., Academic Press, New York.

Yang, C. T., and Molinas, A. (1982). “Sediment transport and unit stream
power function,” Proceedings, Journal of Hydraulics Division 108(HY6),
774-793.

References

55

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| 1. AGENCY USE ONLY (Leave blank) |2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
! -
| September 1999 Final report

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
DMS: Diagnostic Modeling System; Report 2, Reduction of Sediment Shoaling

| of the Entrance Channel at East Pass, Florida |

| 6. AUTHOR(S)
| Mark S. Gosselin, Kenneth R. Craig, R. Bruce Taylor

|7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
| Taylor Engineering, Inc. REL BNE MEER

| 9000 Cypress Green Drive |
| Jacksonville, FL 32256

4
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING
U.S. Army Corps of Engineers, Washington, DC 20314-1000 BGENCY RSMO NO Walen
U.S. Army Engineer Research and Development Center, Coastal and Technical Report CHL-99-19
Hydraulics Laboratory, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199 |
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| Available from National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.
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| Approved for public release; distribution 1s unlimited.
||

43. ABSTRACT (Maximum 200 words)

This report documents a case study at East Pass, Florida, to assess the concepts and performance of the Diagnostic
Modeling System (DMS), which is presently under development. The DMS is intended to give the capability to identify,
categorize, and evaluate navigation channel sediment-deposition hot spots, from which the system can be applied to identify
corrective actions and perform the appropriate analysis. The level of corrective measures are expected to be within existing
project authorization, and the diagnostic procedure should be capable of arriving at solutions to shoaling problems within the
| project dredging cycle. The system consists of three components: the DMS-Data Manager, the DMS-Manual, and the
| | DMS-Analytical Toolbox, which are described in this report.
| The objective of the case study was to apply DMS concepts and available tools to determine the causes of shoaling in three
maintained channels at East Pass Inlet and to recommend solutions to reduce the frequency and cost of dredging. The DMS
evaluation led to such potential solutions, indicating the viability of the diagnostic method.

| 14. SUBJECT TERMS 15. NUMBER OF PAGES
| Diagnostic Modeling System Sediment deposition 63
Dredging Shoaling 16. PRICE CODE

East Pass Inlet, Florida

| 17. SECURITY CLASSIFICATION | 18. SECURITY CLASSIFICATION|19. SECURITY CLASSIFICATION | 20. LIMITATION OF ABSTRACT |
|

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