Technical Report CHL-99-1

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January 1999

US Army Corps

of Engineers
Waterways Experiment
Station

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Coastal Inlets Research Program

Ponce de Leon Inlet, Florida, Site
Investigation

Report 1
Selected Portions of Long-Term Measurements, 1995-1997

by David B. King, Jr., Jane M. Smith, Adele Militello,
Donald K. Stauble, Terry N. Waller

Approved For Public Release; Distribution Is Unlimited

repared for Headquarters, U.S. Army Corps of Engineers

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.

ER) cannes ON RECYCLED PAPER

Technical Report CHL-99-1
January 1999

Coastal Inlets
Research Program

Ponce de Leon Inlet, Florida, Site
Investigation

Report 1
Selected Portions of Long-Term Measurements, 1995-1997
by David B. King, Jr., Jane M. Smith, Adele Militello, Donald K. Stauble, Terry N. Waller

U.S. Army Corps of Engineers
Waterways Experiment Station
3909 Halls Ferry Road
Vicksburg, MS 39180-6199

Report 1 of a series
Approved for public release; distribution is unlimited

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Men

NINN

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

Under CIRP Inlet Field Investigations WU 32931

a

US Army Corps
of Engineers
Waterways Experiment
Station

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Waterways Experiment Station Cataloging-in-Publication Data

Ponce de Leon Inlet, Florida, site investigation. Report 1, Selected portions of long-term measurements,
1995-1997 / by David B. King ... [et al.] ; prepared for U.S. Army Corps of Engineers.

147 p. : ill. ; 28 cm. — (Technical report ; CHL-99-1 rept. 1)

Includes bibliographic references.

Report 1 of a series.

1. Ocean waves — Measurement. 2. Wind waves — Measurement. 3. Inlets — Florida. 4. Ponce de
Leon Inlet (Fla.) 1. King, David B. (David Byron) II. United States. Army. Corps of Engineers. Ill. U.S.
Army Engineer Waterways Experiment Station. IV. Coastal and Hydraulics Laboratory (U.S. Army
Engineer Waterways Experiment Station) V. Coastal Inlets Research Program (U.S.) VI. Series:
Technical report (U.S. Army Engineer Waterways Experiment Station) ; CHL-99-1 rept.1

TA7 W34 no.CHL-99-1 rept.1

Contents

| PURE PAYO/Shy © heey ST EIS PTE TCU a pet trl an Cg UO UPA OR Are SAUD RS Cre ix
LR TVET Ch CH Go Maeda ersvrctircnssotawvecsoevorsecwh cis PRIA rast calc va AY Sara AM RRA A a 1
Ponceide Leoninleti Field |Studys- 4.) 5 ao pee eae ee 1

DEO CAT OMe any Toe Mea ek eee ea ata UAT Ey ve a ares USSD cone 1

NET HHIStORY Wy ts, sees sl eercces eusietvy aud gah a NCA PRESS 5 a 3
PataiCollectionwhimesPeriodsm eae ee een 3

20 VRebruaryj20MarchslO 9G eee eee eae 3

MTulye=S Au custelO9G vee ie serape est sucdeien sy al ears peueeers 4

leAucust— 3 ileOctoberlOO7ee wey iee-sen en aicne)saraea 4

ScOMCIOMREP ONE ees rege tee es oi oash Go eit eee) eS eee Ramet) uke gene!

De lnstrumentationsandyProceduresys a Geis aie ee iio eee oleae 5
INStrumentylocations! Ags ces ae See Sh es oie) Suances aya Giclee ene 5

ata) Collection:System\! 3.4014 utes was fee es apse ol ae 5

Wave Measurementss oii), byucis aha oes ea Sy des on 7

Water Level Measurements ..............20.0000000- 9
@urrentsMeasurementste saris cicesese-warcnen eerie ceil eae 10

Meteorological Measurements ....................... 12

Bathymetnyi iin. teeite stele ete seu sed aay aper Aesecrustteess aptapele's| .t BE aes 13

Sediment’ Collections: ve 95 ic ng, Sista ae a atyt iva come iel sh coca ae 13

Wisualblima gine ant eteted ou huide arty Said usp el ieemteaript cpraiN a): Laws 14
BeExamplesresultssand’Discussionyes See ena eo oie aie 16
IWiaverResultsie: syseen rite saute: pe. sys fad eey) terrae pey samy al, hl cab 16

Waverhel ght nists Waveveinmencietana iia al sets del gealaus 16

Wave MeniOdiaty: stra sy tintuck tera werd Sic 5 RES Ait V7

Wiaverdinectiom ysis) iiss lereiw ars yey abbe, au eelantalin eo eDI i7/

WiatenWevellJRESULESK Mie) sulle is lit lea elas hl Mrdaniailid Sieh Ms Ls) say 37
GunrrenteResultsim ages ee ay ear Oren a este eur mmNC LANL Rune 48

RETETENCES Hie Ss ie PE RAST Hane Catia oa ot) ellgL AN as Acne a ae Pete 64

Appendix A: Velocity and Discharge Measurements at Ponce de Leon Inlet,
|e) (0) 0 (ce ae ar a ee eRe IMBPEE i < Du owe LG we, Bh Al

Append xg Aerial BehOtoStap hyaeeseie eer ei eeiel erie T eine ar mene ee Bi

SF 298

List of Figures

Figure: (Study locations: 3c. </aeaeee een eeee soe ate cle nay naee 2
Figure:2.:. a Siteamapy sc) 3 ise cased epee eer Sua is al See eee ee. cutetao et eecene 2
Figures see leocationiofinstrumentsm eae araeee em in) tee eine 6

Figure 4. | Zero-moment wave height at the offshore gauge for 20 February -

20KMarch: 1996." sis 3 seine Syke cps te meen, Pmt ie) Gleieaie 18
Figure 5. | Zero-moment wave height at the ebb shoal gauge for 20 February -

ZO March’ 1996 pcan raiescoess, als ra h5 ES PARE oh SIE ce Mea ea 18
Figure 6. | Zero-moment wave height at the inlet throat gauge for 20 February -

Z2O;Marchal99G: s <.:. cs Ses sean eA arte ROE seu tel eau 19
Figure 7. | Zero-moment wave height at the offshore gauge for July 1996 ..... 19
Figure 8. _Zero-moment wave height at the ebb shoal gauge for July 1996..... 20
Figure 9. | Zero-moment wave height at the inlet throat gauge for July 1996... . 20
Figure 10. Zero-moment wave height at the offshore gauge for August 1996 ... 21

Figure 11. Zero-moment wave height at the ebb shoal gauge for August 1996... 21
Figure 12. Zero-moment wave height at the inlet throat gauge for August 1996 . . 22
Figure 13. Zero-moment wave height at the ebb shoal gauge for August 1997 .. . 22

Figure 14. Zero-moment wave height at the ebb shoal gauge for
September 1997 or ics haze cache Mio: Gcea secu cheat ase Cena ReeT EE aE 23

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.

Figure 32.
Figure 33.

Figure 34.

Zero-moment wave height at the ebb shoal gauge for

October ve ek a eos elise eis ailen eee vies is) clash aiien class weenie ene 23
Peak wave period at the offshore gauge for 20 February -

{NIN Erica OMG a pseatey cite ommienc cera caemcncrouare (olaasinenlo at ono cleave 24
Peak wave period at the ebb shoal gauge for 20 February -

DOM ATC BLDG! arceterryes es cerca en ep tirer ay-c sy ev omteprtkay ous, alles set olgey neem ets 24
Peak wave period at the inlet throat gauge for 20 February -

XO) MITOTIC) S glgre ofe- wacdve Orolals os ardace seale ol Senet eo ole didi ono! oro 25
Peak wave period at the offshore gauge for July 1996 ........... 25
Peak wave period at the ebb shoal gauge for July 1996 .......... 26
Peak wave period at the inlet throat gauge for July 1996 ......... 26
Peak wave period at the offshore gauge for August 1996 ......... Di
Peak wave period at the ebb shoal gauge for August 1996 ........ Dill
Peak wave period at the inlet throat gauge for August 1996 ....... 28
Peak wave period at the ebb shoal gauge for August 1997 ........ 28
Peak wave period at the ebb shoal gauge for September 1997 ...... 29
Peak wave period at the ebb shoal gauge for October 1997 ........ 29
Frequency spectra measured at the offshore, ebb shoal, and inlet

throat wave gauges on 28 August 1996 at 1800 hr GMT ......... 30
Peak wave direction at the offshore gauge for 20 February -

DOIMarch el OO Ghee deserve on te yen cute ne reice epee eum ete cat ole e 30
Peak wave direction at the ebb shoal gauge for 20 February -

AD) IME MONG bdo cloo os cdarweacsesoboocoaccgdso es 31
Peak wave direction at the inlet throat gauge for 20 February -

DOW arch wlOSGwarrrcisy cise cra sie corms orcuc ie cavalier egrsineueeloMet rele as 31
Peak wave direction at the offshore gauge for July 1996 ......... 32
Peak wave direction at the ebb shoal gauge for July 1996......... 32

Peak wave direction at the inlet throat gauge for July 1996........ 33

vi

Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.

Figure 41.

Figure 42.

Figure 43.

Figure 44.

Figure 45.

Figure 46.

Figure 47.

Figure 48.

Figure 49.

Figure 50.

Figure 51.

Figure 52.

Peak wave direction at the offshore gauge for August 1996 ....... 33
Peak wave direction at the ebb shoal gauge for August 1996....... 34
Peak wave direction at the inlet throat gauge for August 1996 ...... 34
Peak wave direction at the ebb shoal gauge for August 1997 ....... 35
Peak wave direction at the ebb shoal gauge for September 1997 .... 35
Peak wave direction at the ebb shoal gauge for October 1997 ...... 36

Water level at offshore gauge for 7 March (JD 67) -
DOUMar che 99G i ia ied Ache Rok ss mule pe Una eh ati, 2 Coody: ae a 38

Water level at ebb shoal gauge for 7 March (JD 67) -
PONMaTCRBIOOG Sarre aire tats Cea eee CET ENCE eth) 5.05)1a2t, oe 38

Water level at inlet throat gauge for 7 March (JD 67) -
POUT eH 996. io.) 0s, Hoa ae NP ON Ee ere a ON cue a me 39

Water level at river north gauge for 7 March (JD 67) -
19 Marchi. 99G i), ncuy ai -aa septa retrsmtenebie ie Pius AS) Spomtoinsiyc me yesureoeae 39

Water level at river west gauge for 7 March (JD 67) -
ES March 996i kis, 3s bn i liga MM Le ce aki at AP Sos ogra eae 40

Water level at river south gauge for 7 March (JD 67) -
M9, March 19 9G jos Sos beylird wert tenes etree ae het ae eee oa a 40

Water level at Coast Guard station gauge for 7 March (JD 67) -
LO! Marchyl 996 ii.c Sates ars ee ee ute roto nets: Sei S Le CICS tee metins 4]

Water level at offshore gauge for 3 July (JD 185) -
SU AUSUSt EQ9G Sei fee ies ilerno halo eeuelvat sl elaey oneedg ak sas cee Reames 42

Water level ebb shoal gauge for 3 July (JD 185) -
SI Augustyh O96) pacha ie kanca al tran ole ce-ch oe ue lies Cem ata 43

Water level at inlet throat gauge for 3 July JD 185) -
ST August 1996) oie ai luiceats Muses CaicesiA cy ecrey eeUe en enone aes 44

Water level at river north gauge for 3 July (JD 185) -
B WuAupust L9G hice hes cede ea ove lh eras ok tole ale isa ROR Ae 45

Water level at river west gauge for 3 July (JD 185) -
SleAUgustlO9G Perey aa cine ea Nee yas Clea a bee este (Caen ZEIT 46

Figure 53.

Figure 54.

Figure 55.

Figure 56.

Figure 57.

Figure 58.
Figure 59.
Figure 60.
Figure 61.
Figure 62.
Figure 63.

Figure 64.

Figure 65.
Figure 66.
Figure 67.
Figure 68.
Figure 69.

Figure 70.

Water level at river south gauge for 3 July (JD 185) -

SIMA OUSTHOOG eee es ceil cetieits curichs Milian chal ame ete alae

Current at inlet throat gauge for 5 July (JD 188) - 1 August 1996

Current at inlet throat gauge for 1 August (JD 214) -

BpAUpUst L9G: oak ils, nica: it AIR BI RRR EAA

Current at ebb shoal gauge for 5 July (JD 188) - 1 August 1996

Current at ebb shoal gauge for 1 August (JD 214) -

Mi Septemberjl99G resis ieee ee hes Means eshte etal A aslavewta ye Aah ku
Wind speed at the Battelle site for 20 February - 20 March 1996 ....
Wind speed at the Battelle site for July 1996 ...............
Wind speed at the Battelle site for August 1996 .............
Wind speed at the Battelle site for August 1997 .............
Wind speed at the Battelle site for September 1997 ...........

Wind speed at the Battelle site for October 1997 ............

Wind direction at the Battelle site for 20 February -

ZOUMAT CHUNG OS Gira en tr eee kate VPM ene Aerien aire eae iO ou ea Seee goa
Wind direction at the Battelle site for July 1996 .............
Wind direction at the Battelle site for August 1996 ...........
Wind direction at the Battelle site for August 1997 ...........
Wind direction at the Battelle site for September 1997 .........

Wind direction at the Battelle site for October 1997 ..........

Location of sediment samples at Ponce de Leon Inlet, Florida.

Bathymetry from SHOALS survey 1995 .................

oi

59

vil

viii

List of Tables

Table 1. Gauge Wocations oes i) seis Len er oR RN de 2 7
Table 2. Wave DatavAvailability si teed aoa sei acces ck ane Bt 9
Table 3. Water, Levelt DatayAvailabilitys qe rates ak ed eS ae 11
Table 4. Current/DatavA vailability, 45) ueordlaree eel Se ecco nee 12
Table 5. Meteorological)DatayAvatlability yee coe 13
Table 6. ‘AerialiPhotography Sets; coe saps eaten eee ee 15
Table 7. Ponce de Leon Inlet Sediment Samples .................... 60
Table Al. Ponce de Leon Inlet Discharge Rates on 25 August 1997 ........ A8
Table A2. Ponce de Leon Inlet Discharge Rates on 26 August 1997 ........ A10
Table A3. Ponce de Leon Inlet Discharge Rates on 27 August 1997 ........ Al3
Table A4. Ponce de Leon Inlet Discharge Rates on 28 August 1997 ........ Al4
Table A5. Ponce de Leon Inlet Discharge Rates on 29 August 1997 ........ A15
Table A6. Ponce de Leon Inlet Discharge Rates on 15 September 1997 ...... Al6
Table A7. Ponce de Leon Inlet Discharge Rates on 16 September 1997 ...... Al7
Table A8. Ponce de Leon Inlet Discharge Rates on 17 September 1997 ...... Al8
Table A9. Ponce de Leon Inlet Discharge Rates on 18 September 1997 ...... A19
Table A10. Ponce de Leon Inlet Discharge Rates on 19 September 1997 ...... A22

Preface

The study described herein was conducted by the U.S. Army Engineer Waterways
Experiment Station (WES), Coastal and Hydraulics Laboratory (CHL). The work was
performed under Work Unit 32931 “Inlet Field Investigations” (IFI) in the Coastal
Inlets Research Program (CIRP). Additional funding for field work was supplied by
the U.S. Army Engineer District, Jacksonville (SAJ).

During the design, site selection, and deployment phase of the project, Mr. Gary L.
Howell of the Coastal Sediments and Engineering Division (CS&ED), CHL, was the
CIRP Principal Investigator (PI) of the IFI Work Unit. Mr. W. Jeff Lillycrop of the
Coastal Evaluation and Design Branch (CE&DB), CHL, was the Technical Area
Leader responsible for the work unit. Following a reorganization of CIRP in 1997,
Mr. Thad C. Pratt of the Hydraulic Analysis Group (HAG), CHL, became the PI of
the IFI Work Unit, and Dr. Nicholas C. Kraus (CS&ED), CHL, the Technical
Coordinator. The CIRP Program Manager during the study was Mr. E. Clark
McNair, Jr. Technical Monitors of CIRP at Headquarters, U.S. Army Corps of
Engineers, were Mr. John P. Bianco, Mr. Charles B. Chesnutt, and Mr. Barry W.
Holliday.

Several WES personnel made substantial contributions to the data collection effort.
Planning for the data collection and deployment was managed by Mr. Paul Puckette,
formerly of the Prototype Measurement and Analysis Branch (PMAB), CHL. The
field data collection computers were programmed by Mr. Troy Nelson, formerly of
PMAB. Construction and deployment of the field instrumentation were supervised by
Mr. William E. Grogg, formerly of PMAB. Field deployment team members included
Mr. Ralph E. Ankeny, Mr. Larry G. Caviness, and Charles J. Mayers, all of PMAB.
Mr. Lillycrop and the Scanning Hydrographic Operational Airborne Lidar Survey
(SHOALS) team performed the bathymetric surveys. Mr. Michael W. Leffler of the
WES Field Research Facility (FRF) coordinated the beach profile surveys. Dr. Donald
K. Stauble (CE&DB) coordinated the collection of sediment samples. Mr. Kent K.
Hathaway (FRF) coordinated the collection of video imagery. Time series data
collection, analysis, and quality control were coordinated by Mr. William D. Corson,
along with Ms. Rhonda Lofton and Mr. James P. McKinney, all of PMAB.

Several persons outside WES also participated. Mr. Thomas Martin (SAJ) was the
project liaison with the Jacksonville District. Mr. Daniel O'Brien of the Ponce de
Leon Port Authority provided local coordination and assistance obtaining permission
for occupying the gauge sites. The U.S. Coast Guard station at New Smyrna provided

valuable support as well as the site for the data collection trailer. Mr. Larry Devers of
the Inlets Condominium coordinated the use of the building for the video cameras.

Mr. Henry Pate of the Battelle Institute paint test facility provided the meteorological
data. Aerial photography and image rectification were provided by Spacecoast Micro
Map Corporation and Aerial Cartographics of America, Inc. Evans-Hamilton, Inc.
provided both installation support and on-site maintenance for the duration of data
collection. Dr. Gary Zarillo of the Florida Institute of Technology, working under
contract through Evans Hamilton, Inc., collected extensive additional data during the
August-October 1997 short-term experiment.

Dr. David B. King, Jr. (PMAB), along with Dr. Jane M. Smith of the Coastal
Processes Branch (CPB), CHL, Ms. Adele Militello of the Coastal Hydrodynamics
Branch (CHB), CHL, and Dr. Stauble wrote the body of the report. Mr. Terry N.
Waller, along with Mr. Pratt, Ms. Clara J. Coleman, and Mr. Tim L. Fagerburg, all
of HAG, wrote Appendix A. Ms. J. Holley Messing (CPB) coordinated report
preparation.

Supervision of various aspects of the data collection and report preparation was
performed by the following division and branch personnel: Mr. Thomas W.
Richardson, Chief, CS&ED; Mr. William A. Birkemeier, Chief, FRF; Mr. Bruce A.
Ebersole, Chief, CPB; Ms. Joan Pope, Chief, CE&DB; Mr. William L. Preslan,
Chief, PMAB; Mr. C. E. Chatham, Jr., Chief, Navigation and Harbors Division;
Dr. Martin C. Miller, Chief, CHB; Mr. William H. McAnally, Jr., Chief, Estuaries
and Hydroscience Division; and Mr. Fagerburg, Chief, HAG.

The Director and Assistant Director of CHL were Dr. James R. Houston and
Mr. Charles C. Calhoun, Jr., respectively. At the time of this report publication,
WES Commander was COL Robin R. Cababa, EN, and the WES Director was
Dr. Robert W. Whalin.

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.

1 Introduction

Ponce de Leon Inlet Field Study

The Coastal Inlets Research Program (CIRP) was initiated in 1993 by the U.S. Army
Engineer Waterways Experiment Station (WES) of the U.S. Army Corps of Engineers
(USACE) as the first comprehensive program to study inlet behavior since the General
Investigation of Tidal Inlets Program of the 1970's. The Inlet Field Investigations work
unit within CIRP was tasked with choosing an initial inlet for field study. Careful
planning was required to balance limited resources with investigator needs. Both technical
and operational characteristics of candidate inlets from around the country were evaluated.
Criteria for selection included such factors as the availability of historical data sets,
engineering problems at the inlet, and suitability of the inlet for field measurements and for
physical model studies. At the time of the selection process, a physical model study of
Ponce de Leon Inlet was underway at WES (Harkins, Puckette, and Dorrell 1997). Asa
result of the lengthy selection process, Ponce de Leon Inlet was recommended and
approved as the initial CIRP field study site.

The long-term comprehensive monitoring program at Ponce de Leon Inlet began in
September 1995, and ran through October 1997. The data collection consisted of
multiple gauge sites to collect data on wave height, wave period, wave direction, water
level, current velocity, and wind velocity. Additional data were provided through
bathymetry surveys, the collection of sediment samples, and inlet monitoring with
video imagery and aerial photography.

Location

Ponce de Leon Inlet is located along the east coast of Florida at Latitude 29°05'N,
Longitude 80°55'W. The inlet is in Volusia County approximately 20 km south of
Daytona Beach, 75 km northeast of Orlando, and 80 km north-northwest of Cape
Canaveral. The inlet connects the Atlantic Ocean with the Halifax and Indian Rivers, both
of which join the Intracoastal Waterway. Ponce de Leon Inlet is the only inlet to drain the
Halifax River Lagoon to the north and is the principal inlet for the Indian River to the
south. Rockhouse Creek is a short channel to the dredged Intracoastal Waterway bypass
to the west. The location of the inlet and a site map are shown in Figures | and 2,
respectively.

Chapter 1 Introduction

Daytona Beach

Deltona
t=)

Sanford
fa

itamonte
n°
% LA Titusville
Orlando a

ix}

~<#== Ponce de Leon Inlet

Cape Canaveral

Figure 1. Study location (1 cm equals approximately 17 km)

Figure 2. Site map (1 cm equals approximately 500 m)

Chapter 1 Introduction

Inlet History

Ponce de Leon Inlet has existed as a natural inlet in its approximate present location
since at least the time of the Spanish explorer Ponce de Leon when he noted the inlet in his
log in 1513 (Jones and Mehta 1978). The first major bathymetric survey was done in May
1925 by the Coast and Geodetic Survey. In 1932/33, the Intracoastal Waterway was
rerouted to the west of the inlet by dredging a bypass channel, due to problems navigating
through the dynamic flood shoal. The inlet became non-navigable and was dredged and
surveyed in August 1943 and again in October 1944 by the U.S. Army Engineer District,
Jacksonville (SAJ), for the war effort. Prior to jetty construction in 1968, the inlet was
recognized as difficult and dangerous to navigate with controlling depths over the ebb
shoal of typically 1.2 to 1.8 m.

Funding for a weir jetty system at Ponce de Leon Inlet was authorized under the River
and Harbor Act adopted 27 October 1965. The weir system was designed so that sand
moving down from the north would pass through the weir section of the north jetty and
deposit in the adjacent impoundment basin. This basin was to be periodically dredged and
the sand placed south of the inlet. Construction occurred from 1967 to 1972. Following
construction, the project did not perform as anticipated. As early as August 1972 riprap
was placed beside sections of the north jetty to provide scour protection. Because the weir
section was not functioning as planned, it was partially closed in 1979 and fully closed in
1984. The inlet continues to experience shoaling, scour, and navigation problems today.

There have been several previous field studies of Ponce de Leon Inlet. A partial list of
published reports includes: U.S. Army Engineer District, Jacksonville (1963, 1967, 1983),
Purpura et al. (1974), Purpura (1977), Hemsley and Briggs (1988), Taylor (1989), Taylor
et al. (1990), Taylor, Yanez, and Hull (1992), and Waller et al. (1997) (which is
included in this report as Appendix A).

Data Collection Time Periods

Three time periods within the 2-year deployment (September 1995 to October 1997)
were selected for detailed analyses. These time periods were selected based on data
requirements for numerical model development and validation. The parameters for
selecting the time periods included: time periods when most or all the in situ gauges were
functioning, storm conditions, near-continuous spring-neap tidal cycles, and data
coincident with short-term data collection in the fall of 1997.

20 February - 20 March 1996

This period was selected because it included a major storm during 8-14 March. The
storm’s peak on 11 March produced wave heights over 5 m, a storm surge of 0.5 m, and a
wind speed of 17 m/sec. During this time period all the wave and water level gauges were
working, except for one wave gauge on the ebb shoal that failed during the peak of the
storm. The current meters were not operational. The main interest in this time period was
in modeling the shoaling, refraction, and breaking of the storm waves.

Chapter 1 Introduction

Data from this period were used to test two Coastal and Hydraulics Laboratory
numerical models at WES; ADCIRC and STWAVE. The ADCIRC (Advanced
Circulation) model is a two- or three-dimensional (2- or 3-D) coastal circulation model,
and the STWAVE (Steady-state Spectral Wave) model is a spectral wave model with
wave-current interaction. These applications are discussed in Smith, Militello, and Smith
(1998).

1 July - 31 August 1996

This period was selected to include two full spring-neap tidal cycles with all wave,
water level, and current gauges operating. The period provided additional data for
numerical model validation. During the 2-month period, a storm on 11 July had wave
heights over 2.5 m, and three other events (on 17 July, 21 August, and 31 August) had
wave heights exceeding | m. Winds exceeded 16 m/sec during the 17 July and 21 August
events. The winds during these 2 months show a typical land and sea breeze pattern.

1 August - 31 October 1997

This period was selected to coincide with short-term measurements made at Ponce
de Leon Inlet. The short-term measurements included current and bathymetry surveys
over the ebb shoal, inlet throat, and in bay channels during neap tide (25-29 August) and
spring tide (15-19 September) conditions. The short-term measurements also included a
72-day deployment (21 August - 31 October 1997) of six additional wave and current
gauges located in the inlet throat and in the bay to supplement the long-term wave, water
level, and current measurements. Unfortunately, many of the long-term gauges were
inoperable. During this time period there were three large wave events: 1.5-m waves on
27 August, 2.3-m waves on 5 September, and waves exceeding 1 m during 8-18 October.

Scope of Report

The purpose of this report is to document the available data, document the data
collection and processing procedures, and present examples of the long-term field data
collected at Ponce de Leon Inlet. These data are currently being applied in CIRP analyses
and modeling studies, and it is anticipated that they will continue to be used extensively in
the future. Potential users include not only researchers in the CIRP and at WES, but also
SAJ, the State of Florida, and others in industry and academia.

Chapter 2 of this report discusses the types of data collected, the instruments used, and
the processing procedures. Chapter 3 discusses examples of the data. Appendix A is a
report on current measurements made at the inlet in August and September 1997.
Appendix B presents selected aerial photos.

Chapter 1 Introduction

2 Instrumentation and Procedures

The long-term comprehensive monitoring program consisted of multiple gauge sites
to collect data on wave height, wave period, wave direction, water level, current
velocity, and wind velocity. Additional data were provided through bathymetry
surveys, sediment sample collection, and inlet monitoring with video imagery and
aerial photography.

Instrument Locations

Figure 3 shows the locations of data collection gauges at Ponce de Leon Inlet.
Wave gauges were at Sites A, B, and C; and current meters were at Sites B and C.
Site A was north of the inlet in about 15 m of water in a region where the bathymetric
contours are relatively straight and parallel to shore. This site was intended to
measure the incident wave conditions. Site B was centered on the seaward face of the
ebb shoal in about 7 m of water. Site C was in the outer inlet throat at about the 5-m
depth. A stilling well water level gauge was at the Coast Guard Station at Site D.
Pressure type water level gauges were at Sites E, F, and G. The wave gauges at Sites
A, B, and C were also used to obtain water levels. Wind speed and direction, air
temperature, relative humidity, and barometric pressure were measured at the
meteorological station operated by the Battelle Institute at Site H. The data acquisition
electronics were housed in a trailer located at Site J, which also had a barometer. The
coordinates of these locations are given in Table 1.

Data Collection System

Data from the wave, water level, and current gauges were collected continuously (in
real-time mode) and transmitted to WES in Vicksburg, MS, via the Internet for daily
processing. Data from the ebb shoal and inlet throat pods, Sites B and C, were cabled
directly to the data collection trailer (Site J). The north pod (Site A) was cabled to
shore at the Battelle site (Site H). These data were sent to the data trailer via telephone
line. The data from the pressure tide gauges at Sites E, F, and G were also transmitted
to the data trailer via telephone line. Data from the tide gauge at the Coast Guard
station (Site D) were radioed to the data trailer. The Ethernet network in the data
trailer was connected to the Internet via a leased line to SAJ. The meteorological data
from the Battelle site were separately transmitted to WES via telephone line.

Chapter 2 Instrumentation and Procedures

PONCE DE LEON INLET

\

\

ee \

0 1000 2000 = 3000 FT \
Es
D) 400 800 1200 M

Figure 3. Location of instruments

Chapter 2 Instrumentation and Procedures

Table 1
Gauge Locations
29° 05.462 'N 80 ° 54.620' W DWGIINT1

Ebb Shoal 29° 04.565' N 80 ° 53.902’ W
ADCPEBB1
Inlet Throat 29° 04.605’ N 80 ° 54.489' W

| 0 | coosteves | avroazren | eovsesoow | vmusava
| = | Rivernorn | aovosassn | sovsesszw | sprseavs

29° 03.944' N 80 ° 56.322' W SPRSBAY2
River South 29° 02.266' N 80 ° 54.299' W SPRSBAY3

Battelle 29° 04.933' N 80 ° 55.581' W Meteorology
Data Trailer 29° 03.868' N 80 ° 54.902' W

The data were received by a WES computer located in the Prototype Measurement
and Analysis Branch (PMAB), Coastal and Hydraulics Laboratory (CHL), using a
standard data acquisition, analysis, and storage routine (McKinney and Howell 1996).
The entire system was designed to operate automatically and to provide high
reliability. Extensive automated checks were incorporated to determine if the system
was operating normally. If a problem was detected, automated E-mail warning
messages were sent. Furthermore, the status of various systems in the on-site data
collection trailer could be queried from WES. For a further description of this system,
see Howell (1996).

Wave Measurements

Continuous, long-term wave measurements were made from 1995 to 1997 using
three DWGI's, a gauge developed by PMAB. Each gauge consisted of three
Paroscientific Digiquartz piezo-electric (Paros) pressure sensors mounted on a trawler-
resistant seafloor pod in an equilateral triangle distribution. These gauges performed
limited onboard data processing, then transmitted the information to shore through a
cable, which also supplied power to the systems. The DWGI is further described in
Howell (1992). In all cases, pod orientation (necessary to determine wave direction)
was determined by divers following deployment and checked during retrieval.
Datasonic acoustic releasing transponders were used to assist in locating and recovering
the equipment pods.

The output wave parameters were derived from a two-dimensional (2-D) power density

spectrum of the sea surface using spectral analysis of the sensors' output and linear wave
theory. The raw DWG1 wave data were collected at 5 Hz for 1 hr (17,000+ data points

Chapter 2 Instrumentation and Procedures

for each sensor). These were converted onboard to millimeters of seawater. After arrival
at WES, the data were stored in a database.

A copy of the data was then automatically put through a routine analysis procedure.
The data were first decimated to 1 Hz, then truncated to the first 2,048 decimated data
points. An edit routine checked for spikes and flat spots. The data were then converted to
pressure (newtons per square meter), detrended, and demeaned. An auto- and cross-
correlation matrix was produced using a Welch method to produce 31 data segments
(50 percent overlapping segments of 128 points each). Thus, the frequency resolution for
this analysis was 1/128 sec or 0.00781 Hz. A 10-percent cosine taper (window) was
applied to each segment. The resulting 2-D spectrum was then surface corrected on a
frequency-band by frequency-band basis using linear wave theory. This spectrum was
truncated when the surface correction factor exceeded 100. Because the three gauge sites
were at different depths, each had a different minimum cut-off period; approximately
4 3 sec for the offshore gauge, 2.9 sec for the ebb shoal gauge, and 2.5 sec for the throat
gauge.

The co-spectrum was then integrated to obtain the wave height. The frequency band of
the co-spectrum with the maximum energy was used to designate the peak period. The
quad-spectrum was used to determine the wave direction of the peak frequency. These
wave parameters are defined as follows (see Earle, McGehee, and Tubman (1995) for
additional information):

a. Zero Moment Wave Height (H,,.): Spectrally-derived wave height, in meters;
equivalent to time-domain-derived significant wave height in deep water.

b. Peak Wave Period (7,): Peak spectral period, in seconds; inverse of the frequency
of the peak (highest energy) of the one-dimensional (1-D) power spectrum.

c. Peak Wave Direction (D,): Peak spectral direction, in degrees clockwise from true
north; mean direction from which energy is coming at the peak of the 1-D power
spectrum.

The time stamp associated with these products refers to the time at the beginning of the
|-hr data record.

During very low-energy wave conditions, while H,,. can be calculated, the calculation
of other wave parameters is difficult, subject to greater relative error, and may be
misleading. Therefore, wave period and direction calculations were omitted from the data
set whenever the wave height dropped below a threshold of 0.2 m.

Application of these wave parameters to engineering solutions requires judgement
and understanding of their limitations. Critical decisions should take all available
information, such as the directional spectra of the original measured time series, into
account. However, heuristic rules of thumb have evolved among the wave measurement
community that may be of assistance in utilizing these data. Reasonable assumptions for
typical engineering applications with these data are that the uncertainty in significant wave
height is on the order of 10 percent, and on the order of 10 deg for peak direction.

Chapter 2 Instrumentation and Procedures

Uncertainty in peak period is affected more by resolution than measurement error.
Peak period is the inverse of the center of the frequency band with the most total energy.
This band, whose width is set by the analysis procedure, effectively averages energy from
multiple discrete frequencies; and the true peak period could lie anywhere within that band.
Conceivably, the spectrum could contain another discrete peak within another band that
approaches, or even exceeds, the energy of any discrete frequency in the peak period band.
Small variations in the values of these energies from hour to hour sometimes cause rapid
changes in the reported peak period, particularly at low wave heights.

Examples of these wave data are given in Chapter 3. Table 2 shows the months for
which the wave gauges were operational. Files containing these wave data are avail-
able on the World Wide Web at (http://sandbar.cerc.wes.army.mil/). Directional (2-D)
wave spectral plots, which are not included in the examples shown in Chapter 3 or on the
World Wide Web site, can also be obtained from the archived raw data.

Table 2
Wave Data Availability

Evan] Feb | mar | apr | may | Jun | sut | aug | sep | oct | Nov | Dec!
Pome ols la ee
Offshore
ee ae icles
Ebb Shoal
Fee it ol nal ana eo ela
Inlet Throat
ESRB Abes
ems [LD ee

DWG10TH1
Inlet Throat

DWGI1INT1
DWG1EBB1
Inlet Throat

X indicates that a full or partial data set is available for that month.

Water Level Measurements

Water level was measured at four locations inside the inlet as shown in Figure 3. At
three of these measurement stations (Sites E, F, and G), Paros pressure sensors were
deployed; the same type of sensors as were used in the wave gauges. Each gauge was
housed in a protective steel sleeve and attached to a piling. The fourth water level gauge
was located at the Coast Guard Station just inside the inlet entrance (Site D). This gauge

Chapter 2 Instrumentation and Procedures

10

was a Vitel Model WLS2 stilling well tide gauge with an air acoustic sensor to measure
the water surface elevation. These four gauges were surveyed in and their vertical datums
referenced to National Geodetic Vertical Datum (NGVD) 1929 as described in John E.
Chance & Associates (1996). The inlet throat and ocean wave gauges were also used as
tide gauges. However, these were not surveyed in. Instead, long-term average values were
used as reference mean water levels as described in Howell (1996).

The bay pressure gauges were sampled at a 1-Hz rate. Water levels were reported as
6-min averages of these samples (360 data points). Measurements made between 1:00 and
1:06 were reported as the 1:06 average. Water levels obtained from the six pressure
gauges needed to be corrected for changes in atmospheric pressure. This adjustment was
made by using another Paros pressure gauge housed in the data trailer as a barometer and
subtracting out the air pressure. Table 3 shows the availability of the water level data.
For the fully analyzed data, the elevations are available in meters relative to NGVD 1929
(approximately mean sea level).

The Paros gauges were calibrated before deployment. Their resolution is approxi-
mately +2 mm, and their precision is on the order of +1 cm. Examples of the water level
data from the three time periods of interest are given in Chapter 3.

Current Measurements

The current meters were RD Instruments broad band 1,200-kHz Acoustic Doppler
Current Profilers (ADCPs). These instruments were mounted horizontally on the same
pods as the DWGIs and were oriented upward-looking through the use of a nght angle
head. Each shared a data and power cable with the wave sensors. For further information
on this instrument, see the RD Instruments World Wide Web site (http://www.adcp.com/).

The ADCPs divided the water column into a maximum of 13 vertical bins, each 0.5 m
long, and computed velocities in each bin. As is typical with ADCPs, data collected at the
top and bottom bins were not usable. The ADCPs sampled at 1 Hz. The samples were
first decimated to 0.1 Hz, then averaged in 6-min intervals, then bins 3 through 5 were
averaged together (creating a 6-min average of the velocity between 1.0 and 2.5 m above
the bed). The east/west and north/south components of these 6-min averages were
reported in meters per second (north and east directions are positive). The time stamp
associated with each average refers to the time at the beginning of the average.

Table 4 shows the availability of the current data. However, these data have recently
been found to have a problem with the time code. This problem is under review, and thus,
these data are not generally available for public release.

Chapter 3 gives examples of these data. In addition, Appendix A contains a report of
the ADCP current measurements made during the short-term experiment (August and
September 1997). A neap tide current survey was conducted on 25-29 August, and a
spring tide current survey was conducted 2 weeks later on 15-19 September 1997.

Chapter 2 Instrumentation and Procedures

Table 3
Water Level Data Availability

Perro | ne oe [my [te | [i [eee | om [Joes

‘
DWG1INT1
DWG1EBB1
DWG10TH1
Inlet Throat
VITLBAY3
Coast Guard

SPRSBAY1
River North

SPRSBAY2
River West

SPRSBAY3
River South

A indicates that a full or partial data set is available for that month.
X indicates that a full or partial data set is available for that month, however, the data have not been
elevation corrected to NGVD and have not had a final quality control check.

Chapter 2 Instrumentation and Procedures

11

7

Table 4
Current Data Availability

een
DWG1EBB1
Ebb Shoal
1995
DWG10TH1
Inlet Throat
DWG1EBB1
1996
DWG10TH1
DWG1EBB1
Ebb Shoal
1997
DWG10TH1
Inlet Throat
X indicates that a full or partial data set is available for that month.

Meteorological Measurements

Wind speed and direction, air temperature, humidity, and barometric pressure were
monitored at the Battelle site throughout the long-term data collection experiment.
Barometric pressure was also measured at the data trailer.

The Battelle wind gauge was an R. M. Young Model 05103-U swivel propeller gauge
mounted at an elevation of 10 m. The station is located approximately 200 m landward of
the shoreline. The intervening terrain contains three rows of sand dunes which reach a
maximum height of approximately 3 m. The Battelle meteorological station used a Vaisala
Model CS105 gauge to measure barometric pressure and a Vaisala HMP 35 gauge to
measure air temperature and relative humidity. The data trailer barometric pressure gauge
was a Paros sensor of the same type used in the wave and water level gauges.

The Battelle gauges for the wind, barometric pressure, relative humidity, and air
temperature were all sampled by the same method. One measurement for each parameter
was obtained every 10 sec. These measurements were then averaged over an hour (with all
data weighted equally), and this average hourly value was reported. Maximum wind gusts
were also reported as the maximum 10-sec sample in the hour. The wind direction was a
vector average of the direction the wind was coming from, measured clockwise from north.

Measurements made between 1:00 and 2:00 were reported as the 1:00 average. If a data
record had gaps, no average was reported for that hour. Gauges were calibrated yearly.

Chapter 3 gives examples of these meteorological data and their availability are shown
in Table 5. In this table, “wind” refers to average speed and direction, and maximum gust
speed and direction; “temperature” refers to temperature and relative humidity.

Chapter 2 Instrumentation and Procedures

Se (a a
[esta] ee es
Re a ee a ee
ie i ih eM EEE
=e ee
[tenperre | x | x | x | x [x | x [x | x | x
he ee Ee ae a

5) (Eom eC ee
| temperate | x | x{x{x] | [| [x] x

X indicates that a full or partial data set is available for that month.

Bathymetry

Two rod and level beach profile surveys were conducted, one in September 1995, and
the second in September 1996. During each survey, the same 33 profiles were measured
north and south of the inlet. Profile lines were run from the State of Florida, Department
of Environmental Quality, beach profile bench mark numbers R-121 to R-176, Volusia
County. Profiles near the inlet (R-139 to R-148 and R-150 to R-160) were run at every
bench mark. Further north (R-121 to R-136) and south (R-164 to R-176) of the inlet,
every third bench mark was used. All profile lines ran north 60 deg east from the bench
marks. Most profiles started at the bench mark and extended out to approximately 2 m
depth.

Bathymetry throughout the inlet, back bays, beaches, and ocean was obtained during
four SHOALS surveys, in July 1994, September 1995, September-October 1996, and
December 1997. The SHOALS system consists of a helicopter-mounted laser that rapidly
obtains above- and below-water vertical elevations using differential Global Positioning
System (GPS) for horizontal control. The SHOALS Airborme Lidar Hydrographic Survey
System is described in more detail in Irish, Lillycrop, and Parsons (1996) and Lillycrop,
Parsons, and Irish (1996). See also the World Wide Web site (http://bigfoot.wes.army.
mil/6022 html). The July 1994, Ponce de Leon SHOALS survey data are discussed in
Irish, Parsons, and Lillycrop (1995) and Stauble (1998).

Sediment Collection

A set of 105 sediment samples was collected at Ponce de Leon Inlet from
18-22 September 1995. (A second set of 106 samples collected from
15-18 September 1997, at similar locations, has not been analyzed). Differential
GPS was used to locate surface grab samples, which were collected by boat with a

Chapter 2 Instrumentation and Procedures

13

14

bucket dredge on the ebb and flood shoals and in the inlet throat. Surface grab
samples were collected with a hand-held scoop on both the updrift and downdrift
beaches and on some of the exposed flood deltas. These samples represent the
present-day surface sediment distribution. Several patterns of sampling were
applied, depending on the area of the inlet.

On the ebb shoal a radial pattern was sampled extending from the throat
seaward over the back face, crest, and front face of the shoal on five radial lines for
a total of 28 samples. Figure 70 and Table 7 (see Chapter 3, p. 58 "Sediment
Results" Section) use the same notation presented in the following station
descriptions. Line N (north transect) and Line NE (northeast transect) both had
three samples. Line CL (the center line of the inlet channel) and Line SE
(southeast transect) both had seven samples. Line S (south transect) had five
samples. Three samples were also collected on a line parallel to the north jetty
(NJ 1 to 3) to characterize the nearshore shelf sediment north of the jetty and ebb
shoal. Three samples were taken on each of four transect lines across the inlet
throat for a total of 12 samples. These channel samples were designated CH Al
through D3. Samples were collected in two environments at the flood shoal. Four
samples were collected in each of three deeper flood tidal channels, which are for
navigation into the Halifax River Lagoon to the north (NFC), Rockhouse Creek in
the center (CFC), and in the Indian River North Lagoon, to the south (SFC). Five
samples were collected on the two roughly triangular shaped flood tidal shoals,
which were exposed at low tide and were designated as the north flood shoal
(NFS) and south flood shoal (SFS). Twelve samples were collected in the flood
channels and ten on the flood shoals. Inlet-adjacent beaches were also sampled
along Florida Department of Environmental Protection profile lines, at the high-
tide (HT), mid-tide (MT), low-tide (LT), and nearshore (OS) located approxi-
mately 61 to 76 m (200 to 250 ft) seaward of the mid-tide sample at time of low
tide. Four profiles were located up to 1,829 m (6,000 ft) north of the inlet (R142
to R148) and six lines (R150 to R160) were located up to 3,048 m (10,000 ft) to
the south.

Four additional beach samples were collected at the mid-tide location at sites
south of the inlet: at R176 in New Smyrna Beach 6.9 km (11 miles) south of the
inlet, at two sites at Bethune Beach 14.5 and 16.1 km (23.2 and 25.8 miles) south
of the inlet, and at Canaveral National Seashore 30.6 km (49 miles) south of the
inlet.

Visual Imaging

Six video cameras were set up on top of the Inlets Condominium just south of the inlet
in positions that had clear views of the north and south coasts, the inlet, and the flood and
ebb shoals. The cameras operated for most of the days between 28 February and
13 August 1996, when a presumed lighting strike destroyed some of the electrical
components. During daylight hours the cameras were operated sequentially with each

Chapter 2 Instrumentation and Procedures

camera capturing one 6-min time-averaged video every hour. These images highlighted
regions of significant wave breaking as bands of white. This imaging was of interest in
determining regions of substantial wave energy dissipation to infer locations of substantial
sediment transport. Control points in the video images along with camera locations have
been surveyed in as discussed in Wood (1996a) and Wood (1996b). The video images
have not yet been rectified or analyzed.

Five sets of aerial photographs were obtained during this study. All but the last were
recorded as digital images. An index to these photo sets is given in Table 6. Examples of
these images are shown in Appendix B. A source for a listing of older aerial photos of
Ponce de Leon Inlet is included in Barwis (1975).

Table 6
Aerial Photography Sets

No. of Photos Coverage

Spacecoast Micro Map Corp.
P.O. Box 6484
9/20/95 Titusville FL 32782 29 Inlet, north and south beach
407-383-0405

3/21/96 Spacecoast Micro Map Corp. North beach
8/24/96 Spacecoast Micro Map Corp. North beach and flood shoal

9/24/96 Spacecoast Micro Map Corp. ee oo aan sere

Aerial Cartographics of America, Inc.
1722 W. Oak Ridge Road
9/10/97 Orlando, FL 32809 3 Inlet and shoals
407-851-7880

22
5
1

Chapter 2 Instrumentation and Procedures

15

16

3 Example Results and
Discussion

This chapter provides example results and discussion of the wave, water level, current,
and wind data collected in the three time periods (February-March 1996, July-August
1996, and August-October 1997). Plots of most of these data are shown. This chapter
also includes a discussion of the sediment data collected in September 1995.

Wave Results

Wave height, period, and direction parameters are of interest for navigation safety and
predicting sediment transport rates. Analyzed wave measurements are presented in plots
of wave height, period, and direction at the offshore, ebb shoal, and inlet throat gauges
(Sites A, B, and C, respectively, in Figure 3). Discussion of the measurements is arranged
by wave parameter.

Wave height

Zero-moment wave heights for the offshore, ebb shoal, and inlet throat gauges for
20 February to 20 March 1996 are shown in Figures 4-6. The July 1996 data are shown
in Figures 7-9; and the August 1996 data are shown in Figures 10-12. In the fall of 1997,
only the ebb shoal wave gauge was operational. The ebb shoal wave heights for August,
September, and October 1997 are given in Figures 13-15. The maximum wave height
measured during the three time periods was 5.4 m at the offshore gauge on 11 March 1996
(Figure 4).

In general, the wave heights increase 20 to 30 percent between the offshore and ebb
shoal gauges due to shoaling and refraction as the waves transform from a region of
parallel contours and 15-m depth to the outer portion of the ebb shoal at a depth of 7 m.
Between the ebb shoal gauge and inlet throat gauge at a depth of 5 m, the wave height
generally decreases 10 to 20 percent due to wave focusing on the ebb shoal (south of the
throat gauge). Wave height at the inlet throat gauge, and to a lesser degree at the ebb
shoal gauge, increases at low tide due to greater wave shoaling. During high wave events,
such as the peak of the March 1996 storm, this trend is reversed due to depth-limited wave
breaking and the wave height is higher at high tide and lower at low tide (Figures 4-6).
Wave height modulation of up to 1 m occurs at the inlet throat gauge, due to the tide.

Chapter 3 Example Results and Discussion

During the peak of the 5.4-m wave event in March 1996, the waves were depth limited
across the entire ebb shoal and near-inlet region. The height decreased 20 percent between
the offshore and ebb shoal gauges and an additional 40 percent between the ebb shoal and
inlet throat gauges at the peak of the event. This storm was numerically modeled for
validation of wave and circulation models by Smith, Militello, and Smith (1998). In the
6 months of analysis, there are five events with wave heights exceeding 2 m. Some of
these events are short in duration (e.g., the 5 September 1997 event, with a peak height of
2.3 m, exceeded | m in height for 3 days (Figure 14)). Others are much longer (e.g., the
11 October 1997 event, with a peak height of 2 m, exceeded 1 m in height for 11 days
(Figure 15)). As expected, the large wave events are highly correlated to strong local
winds.

Wave period

Peak wave periods from the three gauges for the three time periods are shown in
Figures 16-27. The measured periods ranged from 3 to 21 sec. Generally, the peak
periods are consistent from gauge to gauge for each time period and vary slowly with time.
However, the difference in wave period between two gauges or between 2 hr at one gauge
may vary by as much as 5 sec. These large variations typically occur at times when there
are multiple frequency peaks in the spectra. This is evident in the frequency spectra for
28 August 1996 at 1800 Greenwich Mean Time (GMT), shown in Figure 28. The lower
frequency peak (16-sec period) dominates at the offshore gauge, and the low-frequency
peak becomes larger at the ebb shoal gauge due to shoaling and remains dominate. In the
outer inlet throat, the higher frequency peak (9-sec period) dominates, due to refraction and
possibly sheltering by the north jetty. Jumps in the peak period also occur at times with
very low wave energy. Also, the high-frequency cutoff is different at each gauge because
of the different water depths.

Wave direction

Peak wave directions from the three gauges for the three time periods are shown in
Figures 29-40. The figures give the peak spectral direction from which the waves
propagate, relative to true north. The wave direction normal to offshore depth contours at
Ponce de Leon Inlet is about 60 deg. The average wave direction for the 6 months of data
was approximately 70 deg. Most of the large wave events have north or northeast wave
directions. At the offshore and ebb shoal gauges, the wave direction often varies by 5 to
10 deg from hour to hour. The variability at the inlet throat gauge is higher with hour-to-
hour oscillations of 10 to 20 deg. Greater variability in wave direction (similar to the
variability in wave period) is seen in some cases with multiple wave trains or cases with
very low wave energy.

Chapter 3 Example Results and Discussion

Ua

Offshore

| 96/Sz/e

QG/ET/E

7 96/LZ/E

+ 96/6 L/E

+

+ 96/LL/E

I 96/SL/E

+ 96/EL/E

+ 96/LL/E

| 96/6/E

7 96/L/E

7 96/S/E

+ 96/E/E

+ 96/L/e
{ 96/82/Z

I 96/92/Z
IL
+ 96/Pz/Z

7 96/27/2

+ 96/02/Z
°

Date

Zero-moment wave height at the offshore gauge for 20 February -

20 March 1996

Figure 4.

Ebb Shoal

+ 96/SZ/E
At

+ 96/ET/E

+ 9B/LZ/E

+ 96/6 L/E

7 Q6/LL/E

+ 96/SL/€

+ 9G6/EL/E

+ 96/LL/E

7 96/6/E

7 96/L/E

+ 96/S/E

+ 96/E/E

+ 96/L/E

+

1, 96/872/Z
i 96/92/2

+ 96/P7/Z

+ 96/27/Z

+ 96/02/Z
°

Date

Zero-moment wave height at the ebb shoal gauge for 20 February -

20 March 1996

Figure 5.

Chapter 3 Example Results and Discussion

18

Throat

+ 96/SZ/E

+ 96/E7/E

+ 96/LZ/E

+ 96/6L/E

+ 96/LL/E

+ 96/SL/E

+ Q6/EL/E

db

7 96/LL/E

7 96/6/E
al
+ 96/L/E

+ 96/S/E

+ 96/E/E

+ 96/L/E

I 96/82/~
+ 96/97/2
+ 96/72/e

+ 96/22/~

+ 96/02/Z
°

Date

Zero-moment wave height at the inlet throat gauge for 20 February - 20

March 1996

Figure 6.

Offshore

pp

7 96/LE/L
+ 96/62/2
+ 96/ZZ/L
+ 96/SZ/L
7 96/ET/L
+ 96/L2/2
+ 96/6 L/L
+ QBIZL/L
I Q6/SL/Z
+ Q6/EL/L
i 96/b 1/2
+ 96/6/Z

+

+ 96/Z/Z

96/S/Z

+ 96/E/Z

25 4

Che.

+ 9B/L/L
°

Date

Zero-moment wave height at the offshore gauge for July 1996

Figure 7.

19

Chapter 3 Example Results and Discussion

Ebb Shoal

+ 96/LE/Z

+ 96/67/2

+ 96/Z2/2

96/S2/L

+ 96/E?/L

+ 96/b2/2

96/6 1/2

Q6/LL/2

Q96/SL/Z

Q6/EL/L

; 9B/L L/L

| Q6/6/Z

96/L/Z

96/S/Z

96/E/2

| 96/L/Z

Date

Zero-moment wave height at the ebb shoal gauge for July 1996

Figure 8.

Throat

25 |

+ 96/6C/L

+

96/LE/Z

96/Z2/2

96/S2/2

- 96/EC/L

96/L 2/2

96/6 1/2

7 Q6/Zb/L

| 96/SLIL

- 9B/EL/L

96/E 1/2

| 96/6/Z

| Q6ILIL

» 96/S/L

~ 96/E/L

96/L/2

Date

Zero-moment wave height at the inlet throat gauge for July 1996

Figure 9.

Chapter 3 Example Results and Discussion

20

Offshore

|

Tey, ¥.

+ 96/LE/8

+ 96/62/8

96/Z2/8

96/SZ/8

+ 96/E7/8

+ 96/12/8

+ 96/6 1/8

+ 96/L1/8

+ 96/SL/8

7 96/EL/8

7 96/LL/8

+ 96/6/8

7 96/2/8

+ 96/S/8

+ 96/E/8

1.4 5

24
1

065

0.4

02 |

+ 96/1/8
°

Date

Figure 10. Zero-moment wave height at the offshore gauge for August 1996

)
|
|
|
|
|
|

Ebb Shoal

| ge/le/e

+ 96/67/28
| 96/2z/8

+ 96/SZ/8

+ 96/EZ/8

+ 96/12/8
+ 96/6 1/8

+ 96/ZL/8

+ 96/SL/8

+ 96/E1/8

+ 96/LL/8

+ 96/6/8

+>

+ 96/2/8

+ 96/S/8

ak

+ 96/E/8

96/1/8

Date

Zero-moment wave height at the ebb shoal gauge for August 1996

Figure 11.

21

Chapter 3 Example Results and Discussion

Throat

i 96/LE/8

+ 96/62/8

+ 96/L2/8

+ 96/S2/8

Jt

+ 96/E7/8

db

+ 96/L2/8

+ 96/61/8
+

+ 96/Z1/8

I 96/S1/8

+ Q6/EL/8

+ 96/L 1/8

+ 96/6/8

+ 96/L/8

+ 96/S/8

+ 96/E/8

db

+ 96/L/8

Date

Figure 12. Zero-moment wave height at the inlet throat gauge for August 1996

Ebb Shoal

0.2 4

oO

L6/LE/8

L6/6Z/8

L6/L2/8

L6/S2/8

L6/E7/B

L6/L2/8

L6/61/8

LE/LL/8

L6/SL/8

LE/EL/8

LZ6/L 1/8

L6/6/8

L6/L/8

26/S/8

L6/E/8

Z6/L/8

Date

Zero-moment wave height at the ebb shoal gauge for August 1997

Figure 13.

Chapter 3 Example Results and Discussion

22

@
ie)
£
”n
2
fe}
WwW

+ L6/6Z/6
I LGILZ/6
| L6ISZI6
AL

+ L6/€Z/6
+ L6/12/6
+ LEI6LIG
+ LILVIG
+ 16/SLI6
+ LIELIG
+ LEILLG
+ 16/6/16
+ LGILIG
+ LEISIG

+ L6/€/6
|

2.5

+ L6/L/E
°

Date

Zero-moment wave height at the ebb shoal gauge for September 1997

Figure 14.

Ebb Shoal

+ L6/LE/OL

+ L6/6Z/OL

7 L6/ZZ/OL

+ L6/SZ/OlL

+ L6/EZ/OL

7 L6/L2/0L

+ L6IGL/OL

+ LEIZL/OL

+ L6/SH/OL

7 L6/EL/OL

7 L6/LL/OL

+ L6/6/0L

+ L6/LIOL

+ L6/S/OL

7 L6/E/OL

2.5

+ LE/L/OL
°

Date

Zero-moment wave height at the ebb shoal gauge for October 1997

Figure 15.

23

Chapter 3 Example Results and Discussion

Offshore

|

Peak wave period at the offshore gauge for 20 February - 20 March 1996

+

1

1

96/SZ/E

- 9B/EZ/E
96/LZ/E

+ 96/6 L/E

Q6/LL/E

+ 96/SL/E
+ 96/EL/E
~ 96/LL/E

- 96/6/E

96/L/E

96/S/E

96/E/E

+ 96/L/E

96/8Z/2

96/97/Z

96/7 T/Z

96/27/Z

96/02/2

Date

Figure 16.

16 +—

Ebb Shoal

14 |

12 -

+ 96/SZ/E

Q6/ET/E

+ 96/LZ/E

96/6 L/E

7 QBIZL/E

96/SL/E

QB/EL/E

96/L L/E

96/6/E

96/L/E

96/S/E

Q6/E/E

96/L/E

96/82/Z

96/92/72

96/7 2/2

96/Z7/7

* 96/0C/Z

Date

Peak wave period at the ebb shoal gauge for 20 February - 20 March

1996

Figure 17.

Chapter 3 Example Results and Discussion

24

Throat

+ geszie
| geezie
+ gevtze
+ 9e/6L/e
+ ge/zLe

7 96/SL/E

7 YB/EL/E

n

- 96/LL/E
| 96/6/E
+ 96/L/E
+ 96/S/E
7 96/E/E
+ 96/L/E
+ 96/82/72
+ 96/92/7

+ 96/2/2

+ 96/2z/~

16

14 5

+ 96/02/Z
°

Date

Peak wave period at the inlet throat gauge for 20 February - 20 March

1996

Figure 18.

Offshore

| 96/LE/Z
- 96/67/L
+ 96/L7/2
96/S2/Z
+ 96/E7/L
96/L-2/2
if 96/6 1/2
7 Q6/Zb/2
+ 96/SL/Z
+ 96/EL/Z
7 96/EL/Z
+ 96/6/Z
+ 96/Z/Z

+ 96/S/Z

+ 96/E/Z

+ 96/L/Z

25

20 5

oO

Date

Peak wave period at the offshore gauge for July 1996

Figure 19.

25

Chapter 3 Example Results and Discussion

Ebb Shoal

7 96/LE/Z

+ 96/67/L

ab

+ 96/LZ2/2

+ 96/S2/2

+ 96/EC/L

+ 96/L2/2

+ 96/6 L/Z

+ Q6/ZL/Z

7 96/SL/Z

7 96/EL/2

7 96/bL/2

7 96/6/Z

+ 96/L/Z

+ 96/S/Z

+ 96/E/L

25

20 5

96/1 /2
°

Date

Figure 20. Peak wave period at the ebb shoal gauge for July 1996

Throat

+
+ 96/6 L/2

— + 96/LZ/L

+ 96/LE/Z
{

96/62/LZ

+ 96/LZ2/L

|
+

+ 96/S2/L

+ 96/Ec/L

7 96/L2/L

+ 9B/ZL/Z

+ 96/SL/LZ

+
+ QB/EL/L

7 96/L L/L

7 96/6/2Z

t

96/S/2Z

+ 96/E/2

25

20 +

d

+ 9B/L/Z
°

Date

Peak wave period at the inlet throat gauge for July 1996

Figure 21.

Chapter 3 Example Results and Discussion

26

al

Offshore

Pa

Date
Peak wave period at the ebb shoal gauge for August 1996

16

+ 96/LE/8 + Q6/LE/8
+ 96/62/98 + 96/6Z/8
+ 96/22/8 + 96/27/8
IL Oo db
o
+ 96/SZ/8 oy + 96/S2/8
AL % a
+ 96/€7/8 = + 96/E7/8
3
I ? |
96/12/8 s + 96/12/28
+ = af
o
+ 96/61/28 =) + 96/61/8
+ is) ab
io)
+ 96/218 2 ow + 96/21/8
SS
+ a ra ak
96/S1/8 2 + 96/SL/8
| 5 |
o
+ 96/EL/8 = + 96/EL/8
— ab
| i)
96/1 1/8 3 + 96/1 1/8
+ = = +
+ 96/6/8 a a= + 96/6/8
al v {
+ 96/L/8 g es = + 96/Z/8
is] AL
JL S g
3)
+ 96/5/28 o rr + 96/S/9
Al, oO r) +
Oo
+ 96/e/8 : wi + 96/e/8
N +
+ N
+ 96/L/8 2 1 ; - r + 96/1/8
(~) =] (<2) tT N (=) (o) w+ (>)
LL (9as) di

Figure 23.

Chapter 3 Example Results and Discussion

Throat

16

14 5

+ 96/LE/8

+ 96/62/8

+
+ 96/Z2/8

+ 96/SZ/8

+ 96/E7/8

- 96/L2/8
If 96/61/8
+ 96/ZL/8
| 96/S1/8
7 Q6/EL/8
+ 96/LL/8
7 96/6/8

; 96/L/8

+ 96/S/8

+ 96/E/8

96/L/8

Date

Peak wave period at the inlet throat gauge for August 1996

Figure 24.

Ebb Shoal

+ L6/LE/B
JE
+ L6/62/8

+ LZ6/Z7/8

+ L6/SZ/8

+ L6/E7/e

+ L6/LZ/8

L6/61/8

- LEILL/8

1

L6/SL/8

+ LE/EL/S

1

~ LE/LL/8

}

+ L6/6/8
+ L6/L/I9
+ L6/S/8

+ 16/€/8

+} 6/118
o

Date

Peak wave period at the ebb shoal gauge for August 1997

Figure 25.

Chapter 3 Example Results and Discussion

28

Ebb Shoal

16

144

12 +

+ L6/6C/E

+ L6/L2/6

+

+ L6/S2/6

+ L6/EZ/E

+ L6/L/E

+ LE/GL/E

| LE/LL/6

+ L6/SL/6
+ LEE LIE
+
+ LE/LL/6

+ L6/6/6

+ L6/L/I6

+ L6/S/6
AL
+ LEE
a

+ L6/L/6
°

Date

Peak wave period at the ebb shoal gauge for September 1997

Figure 26.

Ebb Shoal

+ L6/LE/OL

+ L6/6Z/OL

+ L6/ZZ/Ob

+ L6/SZ/OL

+ L6/EZ/OL

+ LE/LZ/OL

+ L6/6L/OL

+ L6/LL/OL
AL
+ L6/SL/OL
+
+ L6/EL/OL

+

+ L6/LL/OL
dl.

7 26/6/01

+

7 26/2/01

+ L6/S/OL

+

+ L6/E/OL

16

+ L6/L/OL
°

Date

Peak wave period at the ebb shoal gauge for October 1997

Figure 27.

29

Chapter 3 Example Results and Discussion

03

B
ce
2H tt
” ao °
Bae
We
ae
i]
: ~ ~ :
8 S % 3 8
(ZH/Z vw) Ayjsueg ABseuR

Frequency (Hz)

Figure 28. Frequency spectra measured at the offshore, ebb shoal, and inlet throat

wave gauges on 28 August 1996 at 1800 hr GMT

Offshore

7 96/SZ/E

+7 96/ET/E

_————— ee

——— TF rr

96/6 L/E
I

+ 96/LL/E

=

+ 96/SL/E

+ 96/EL/E

+ 96/LL/E
S6/6/E

+ 96/Z/E

+ 96/92/2

7 96/PZ/~

+ 96/22/~

:

+

8
(Ni 6ep) dq

120] |

96/02/Z
°

60 5

Date

Peak wave direction at the offshore gauge for 20 February - 20 March

1996

Figure 29.

Chapter 3 Example Results and Discussion

30

Ebb Shoal

+ 96/SZ/e

7 96/ET7/E

+ 96/LZ/E

+ 96/6 LIE

ats

i 96/Lb/E

7 9B/SL/E

7 SB/EL/E
=— dE

+ QB/LL/E

7 96/6/E

S6/L/E
96/S/E
7 S6/E/€

+ S6/L/E

i 96/82/~
I 96/92/2
| 96/77/2

+ 96/C2/%

100 5

20 5
0

5 8 8
(Na 6ep) dq

Date

Figure 30. Peak wave direction at the ebb shoal gauge for 20 February - 20 March

1996

Throat

+

i

|

{

+

120 7—

100 +
80

(Ni 5ep) dq

=P

oO

96/SZ/E

96/ET/E

96/L C/E

96/6 L/€

96/ZL/E

96/SL/E

Q6/EL/E

96/1 L/E

96/6/E

96/L/E

96/S/E

96/E/E

96/L/E

96/82/2

96/9Z/~

96/P7/2

96/ZZ/Z

96/02/C

2
a

Peak wave direction at the inlet throat gauge for 20 February - 20 March

1996

Figure 31.

31

Chapter 3 Example Results and Discussion

Offshore

+ 96/LE/Z

96/62/L

+ 96/Z2/L

7 96/S2/2

+ 96/E7/L

> Q6/LE/L

+ 9B/6L/Z

7 96/LZL/2

+ 9B/SL/Z

+ 96/EL/L

7 Q6/L L/L

+

96/6/2

+ 96/L/Z

+ 96/S/L

+ 96/E/L

300 5

x

20 5

8 &
(Ni Sep) dq

96/L/Z
°

Date

Peak wave direction at the offshore gauge for July 1996

Figure 32.

Ebb Shoal

=
=

+

96/LE/Z

+ 96/62/2

96/Z2/2L

it

+

{

96/SZ/L
7 Q6/EC/L
7 Q6/LZ/Z
7 96/EL/Z
7 Q6/Z1/2
+ 96/SL/Z
7 96/EL/L
> Q6/L L/L
+ 96/6/2
96/Z/Z
96/S/Z

+ 96/E/2

160

140 +

120 +

38 See. s
(NL Sep) dq

+ 96/L/L
oO

Date

Peak wave direction at the ebb shoal gauge for July 1996

Figure 33.

Chapter 3 Example Results and Discussion

32

Throat

+ 96/LE/Z
96/62/2
7 96/L2/L
96/S7/L
| 96/E7/L
+ 96/bC/L

7 96/6L/Z
I Q6/ZL/Z
7 G6/SL/Z
7 96/EL/L

+ 9B/L L/L

7 96/6/Z

+ 96/L/L
SS |

|

+ 96/S/Z

96/E/2

160

140 ;

120 +

- = - = + Q6/L/L
o

(Ni Sep) dg

20 5

Date

Peak wave direction at the inlet throat gauge for July 1996

Figure 34.

Offshore

I 96/LE/8
7 96/62/8
7 96/Z7/8
7 96/SZ/8
+ 96/€7/8
+ 96/L7/8

7+ 96/6 1/8

7 96/Z1/8

7 96/S1/8

7 96/EL/8

+ 96/L 1/8

+ 96/6/8

+ 96/2/8

+ 96/S/8

+ 96/E/8

120 |

(NL 5ep) dq

+ 96/1L/8

to)
N

Date

Peak wave direction at the offshore gauge for August 1996

Figure 35.

33

Chapter 3 Example Results and Discussion

Ebb Shoal

{

+

I

+
+

{

+

140 7

120 +

ae
?
>
%

(NL 6ep) dq

&

96/LE/8

96/62/8

96/L72/8

96/S2/8

96/E€7/8

96/12/8

96/61/8

96/Z1/8

96/SL/8

96/EL/8

96/1 1/8

96/6/8

96/2/28

96/S/8

96/E/8

96/1/8

Date

Peak wave direction at the ebb shoal gauge for August 1996

Figure 36.

Throat

I 96/LE/8

+ 96/62/8
a
7 96/Z7/8

+

7 96/S2/8

+

7 96/E7/8

+

96/L 2/8

7 96/61/8

7 Q6/ZL/8

7 96/SL/8

7 96/EL/8

7 96/LL/8

+ 96/6/8

+ 96/2/38

+ 96/S/8

+ 96/€/8

140

120 5

(Ni Sep) dq

96/1/8

20

Date

Peak wave direction at the inlet throat gauge for August 1996

Figure 37.

Chapter 3 Example Results and Discussion

34

Ebb Shoal

7 LZ6/LE/8

+ L46/67/8

+ L6/L7z/8

+ Le/s7/e

+ L46/e7/8

+ L6/Lc/8

dL

+ L6/6L/8

ae

7 L6/L1/8
+
+ L6/SL/8

+ LE/EL/S

+ LE/LL/8

+ L6/6/8

7 L6/L/8

7 26/S/2

I L6/E/8

I L6/L/8

360 +

:

ae

g

3
(NL 5ep) dq

120 4

oO

Date

Peak wave direction at the ebb shoal gauge for August 1997

Figure 38.

360

Ebb Shoal

300

o So
N

nN = =
(NL 5ep) dq

40
8

60

L6/62/6

LE/LZ/6

L6/SZ/6

LE/EZ/E

L6/LZ/6

LE/EL/6

L6/LL/6

L6/SL/6

L6/EL/6

LG/LL/6

L6/6/6

L6/L/I6

L6/S/6

LE/E/6

L6/L/6

Date

Figure 39. Peak wave direction at the ebb shoal gauge for September 1997

35

Chapter 3 Example Results and Discussion

| Z6/LE/OL

+ L6/6Z/01

+ LE/LZ/OL

+

L6/SZ/OL
+ L6/EZ/OL

+ L6/LZ/OL

+ LE/6L/OL
ale
+ L6/LL/OL
+ L6/SL/O1
+ LE/EL/OL
+ LE/LL/OL
; L6/6/01

~ LG/L/OL

+ L6/S/OL

+ L6/E/OL

360

300 +

240

(NL 5ap) dq

120 +

60 >

Z6/L/O1

Date

Figure 40. Peak wave direction at the ebb shoal gauge for October 1997

Chapter 3 Example Results and Discussion

36

Water Level Results

Water level data were collected at 6-min intervals at seven sites in the region of
Ponce de Leon Inlet. Two sites, offshore (DWGIINT1) and ebb shoal (DWGI1EBB1),
were located in the coastal ocean; one site was located in the outer throat of the inlet
(DWG10TH1); and four sites, river north (SPRSBAY 1), river west (SPRSBAY2), river
south (SPRSBAY3), and Coast Guard station (VITLBAY3), were located in the back bay
(see Figure 3 and Table 1). The regional coverage provides information on the tide wave
and storm surge as they propagate through the inlet and into the back-bay channels. The
data coverage also allows for hydrodynamic model calibration in the vicinity of the inlet.
These data are plotted in Figures 41-53.

Figures 41-43 show the water levels offshore, at the ebb shoal, and at the inlet throat
for the time period 7-19 March 1996 (Julian days 67-79). A storm passed through the
study site during this time and elevated the water level for approximately 3 days (Julian
days 71-73). The increase in coastal ocean water level was approximately 0.3 m. In the
back bay, the superelevation was approximately twice that amount at 0.6 - 0.7 m
(Figures 44-47).

The storm that passed through the study area on 12 July 1996 (Julian Day 194)
elevated the ocean water level by approximately 0.3 m (Figures 48-50), whereas in the
back bay the water rose approximately 0.4 m above the pre-storm water level (Figures 51-
53). The July/August data also provide information on the variation of the tidal range over
a spring-neap cycle. During the neap tide, the tidal range is approximately 0.7 m, whereas
during the spring tide, the tidal range is approximately 1.3 m. The monthly variation in
water level is expected to induce corresponding changes in current velocity in the inlet
throat.

Chapter 3 Example Results and Discussion

37

38

Water Level, m (MSL)

Julian Day, 1996
Figure 41. Water level at offshore gauge for 7 March (JD 67) - 19 March 1996

15

Fz 10

(ep)

=

= 05

=

5 00

o 0

G

= 05
10

66 68 70 72 74 76 78 80

Julian Day, 1996
Figure 42. Water level at ebb shoal gauge for 7 March (JD 67) - 19 March 1996

Chapter 3 Example Results and Discussion

Water Level, m (MSL)

Julian Day, 1996
Figure 43. Water level at inlet throat gauge for 7 March (JD 67) - 19 March 1996

Water Level, m (MSL)

Julian Day, 1996

Figure 44. Water level at river north gauge for 7 March (JD 67) - 19 March 1996

Chapter 3 Example Results and Discussion

39

40

Water Level, m (MSL)

Julian Day, 1996

Figure 45. Water level at river west gauge for 7 March (JD 67) - 19 March 1996

Water Level, m (MSL)

66 68 70 72 74 76 78 80

Julian Day, 1996

Figure 46. Water level at river south gauge for 7 March (JD 67) - 19 March 1996

Chapter 3 Example Results and Discussion

Water Level, m (MSL)

Julian Day, 1996

Figure 47. Water level at Coast Guard station gauge for 7 March (JD 67) - 19 March 1996

Chapter 3 Example Results and Discussion

41

(TSW) w ‘]eA97 Ja}eM

(TSW) wW ‘}ene7 J987eM

(TSW) Ww ‘jene7 1872

Gauge: DWGINT1

Julian Day, 1996

Figure 48. Water level at offshore gauge for 3 July (JD 185) - 31 August 1996

Chapter 3 Example Results and Discussion

42

(TSW) w ‘jeAe7 19872

(ISW) wi ‘jaAe7 1a7e MM

(TSW) W ‘}eAe7 JexeEM

Gauge: DWGEBB1

Julian Day, 1996

- 31 August 1996

)

Water level ebb shoal gauge for 3 July (JD 185

Figure 49.

43

Chapter 3 Example Results and Discussion

(1SW) Wi ‘}aA287 J87eM

205

200

195

190

185

o
—)

s °
(=) o

-0.4

(ISI) Wi ‘}ane7 Jaye

-0.8

225

220

215

210

205

oo
r=)

4
()

(ASW) W ‘Jane7 JaVE MA

-0.8

245

240

235

230

225

Gauge: DWGOTH1

Julian Day, 1996

Water level at inlet throat gauge for 3 July (JD 185) - 31 August 1996

Figure 50.

Chapter 3 Example Results and Discussion

44

(SW) Ww ‘jane7 sa7eM

(ASW) wW ‘}eAe7 JEVeN\\

(ISI) WwW ‘}eAe7 JExeNA

Gauge: SPRSBAY1

Julian Day, 1996

Water level at river north gauge for 3 July (JD 185) - 31 August 1996

Figure 51.

45

Chapter 3 Example Results and Discussion

(TSW) W ‘}eAe7 182M

(TSW) Ww ‘}ane7 187eA\

sw

) w ‘jaAe7 IAEA

Gauge: SPRSBAY2

Julian Day, 1996

Figure 52. Water level at river west gauge for 3 July (JD 185) - 31 August 1996

Chapter 3 Example Results and Discussion

46

ma

—SS

Ky ALAA ly ANAM
rT

Julian Day, 1996 Gauge: SPRSBAY3

igure 53. Water level at river south gauge for 3 July (JD 185) - 31 August 1996

48

Current Results

Currents were measured in the inlet throat and on the outer edge of the ebb shoal, at
Sites B and C (see Figure 3). During the three periods of interest, current data were only
available for July and August 1996. The north/south and east/west components of these
currents are shown in Figures 54-57. Positive values indicate north and east for each
component. During the 12 July storm (Julian Day 195), the north-south component of the
current at the inlet gauge (Figure 54) flowed southward, indicating the wind and
wave-driven alongshore current for about 2 days. During a typical tidal cycle, peak inlet
throat currents reached approximately 0.8 m/sec, but current speed was measured as
strong as 1.3 m/sec during the spring tide on 29 August (Julian Day 242, Figure 55). In
general, the currents at this location exhibit ebb dominance.

Currents measured at the ebb shoal gauge are reduced in magnitude as compared with
those measured at the inlet throat. In addition, on the ebb shoal, the north-south and
east-west components are generally of equal magnitude; whereas in the inlet throat, the
current was directed predominantly along an east-west axis (aligned with the inlet).
During the storm of 12 July (Julian Day 195), the ebb shoal data showed a strong current
reaching 1.2 m/sec toward the south and comparatively unorganized current motion in the
east-west component (Figure 56). This signal indicates a strong southward wave-driven
flow that dominated the current and suppressed the tidal current through the inlet. Two
other south flowing events occurred in August (Figure 57).

Chapter 3 Example Results and Discussion

“ihe Ih i Mh : ,
mM

“i

ADCPOTHI

Wi | A ik i ii hil
yn il ) Wi Halll

Chapter 3 Example Results and Discussion

ti m

Hin i iy sil

— East-West Conponent

————_——————————
————

++ Sree ONO
i

Julian Day 1996

———

——————————————
a =

50

Current Speed, m/s

ADCPEBB1 East-West Component
-- North-South Component

Wi
Hil : |
|

Julian Day, 1996

Figure 56. Current at ebb shoal gauge for 5 July (JD 188) - 1 August 1996

nt Speed, m/s

Curre

1.0
ADCPEBB1 East-West Component
SS North-South Component
0.5 i
i
Hf i shi

it
an

a eee Se Ee

Julian Day, 1996
Figure 57. Current at ebb shoal gauge for 1 August (JD 214) - 1 September 1996

Chapter 3 Example Results and Discussion

Wind Results

Wind measurements are of interest at coastal inlets because the winds can force
longshore and cross-shore currents, storm surge, local wave generation, and wind-blown
sand transport. Plots of the measured wind speed at the Battelle gauge (Site H in
Figure 3) for the months of February/March 1996, July 1996, August 1996, August 1997,
September 1997, and October 1997 are given in Figures 58-63; and directions for the
same months are given in Figures 64-69. In the March 1996 wind speed plot (Figure 58),
the most prominent feature is the high winds associated with the storm event that peaks
on 11 March. The wind speed peaks early on 11 March at 16 m/sec and then peaks again
22 hr later at 17 m/sec. During the 11 March storm, strong winds from the north were
sustained over 3 days, which generated 5.4-m waves. In July and August 1996, the
maximum wind speeds measured were 8 m/sec (Figures 59 and 60). An event on 11 July
had winds from the north, and an event on 21 August had east-northeast winds over a
5-day period (Figures 65 and 66).

The wind speed has a strong 24-hr cycle, with the maximum wind speed typically
occurring between 1700 and 2100 GMT (1200-1600 Eastern Standard Time (EST),
1300-1700 Eastern Daylight Time (EDT)) and the minimum wind speed occurring
between 0500 and 0900 GMT (0000-0400 EST, 0100-0500 EDT). During this daily
cycle, the maximum winds typically blow onshore and the minimum winds blow
offshore. This is a typical sea breeze and land breeze cycle caused by the warming of the
land during the day and cooling at night. The diumal shift in direction is shown in the
wind direction plots (Figures 64-69).

Chapter 3 Example Results and Discussion

51

dL
7 96/S2/E

I Q6/ET/E
+ 96/LZ/E
+ QB/6L/E
+ 96/LL/E
I 96/SL/E
7 96/EL/E
+ 96/LL/E
+ Q6/6/E
7+ 96/L/E
96/S/E
I 96/E/E

~ 96/L/E

| 96/8z/z
+ 96/922
+

+ 96/P7/~

+ 96/27/Z

18 +

oO
=

vt
of

T aaa T

N (=) co Ke}

(9as/w) peeds pulm

vT

+ 96/02/Z
°

Date

Figure 58. Wind speed at the Battelle site for 20 February - 20 March 1996

©

ae

wo vT oO

(sas/w) peeds pul

a

+

96/LE/Z

96/62/2

96/L7/L

96/SZ/L

96/E7/L

96/1 72/2

96/6 1/2

- OB/Z L/L

Q6/S1L/Z

Q6/E L/L

96/LL/Z

+ 96/6/L

96/L/2

- 96/S/L

- 96/E/L

| 96/L/Z

Date

Figure 59. Wind speed at the Battelle site for July 1996

Chapter 3 Example Results and Discussion

52

o

ite)
(990s/wW)

vT o

peeds Pulm

N

+ 96/LE/8

Jt

+ 96/62/8

+ 96/L2/8

+ 96/S2/8

+ 96/E7/8

+ 96/L2/8

+ 96/61L/8

+ 96/Z1/8

7 96/SL/8

7 96/EL/8

If 96/1 1/8

I 96/6/8

+ 96/L/8

+ 96/S/8

7 96/E/8

96/1/28
°

Date

Figure 60. Wind speed at the Battelle site for August 1996

(ses/w) peeds Pulm

+ L6/LE/8

+ L6/62/8

+ L6/L2/8

7 L6/SZ/8

> L6/E7/8

+ L6/L2/8

+ L6/6L/8

+ L6/LL/8

+ L6/SL/8

+ L6/EL/8

+ L6/LL/8

+ L6/6/8
+ L6/LI8
ar
+ L6/S/8

+ L6/E/8

+ L6/L/8
fo) (e) N © Te) vt (2) N“ =

oO

Date

Wind speed at the Battelle site for August 1997

Figure 61.

53

Chapter 3 Example Results and Discussion

+ L6/6Z/6

+ L6/L2/6

+ L6/S2/6

+ L6/E7/6

7 L6/L2/6
Al

+ LE/GL/E

+ L6/LL/E

+ L6/S1/6

+ LE/EL/E

7 LE/LL/6

+ L6/6/6

+ L6/L/6

+ L6/SI6

| L6/E/6

12

10 5

(ses/w) peeds pul

+ L6/L/E
°

Date

Figure 62. Wind speed at the Battelle site for September 1997

+ L6/LE/OL

+ L6/6Z/01

+ L6/LZ/01

+ L6/SZ/OL

+ LE/EZ/OL

+ L6/LZ/OL

+

+ LE/6L/OL

+ LE/LL/OL

+ L6/SL/OL

+ L6/EL/OL

+ L6/LL/OL

+ L6/6/OL

+ L6/L/OL

+ L6/S/OL

+ L6/E/OL

~ i<e) wo vT oO

(ses/w) peeds pul

26/1/01

Date

Figure 63. Wind speed at the Battelle site for October 1997

Chapter 3 Example Results and Discussion

54

|

at

+

JL

if

8

—— ——————

g 8 &

N =

(NL Bap) uonseu1qg PUI

8

96/SZ/E

96/ET/E

96/1 Z/€

96/6 L/E

SE/LL/E

9B/SL/E

Q6/EL/E

96/L L/E

96/6/E

96/L/E

96/S/E

96/E/E

96/L/E

96/82/2

96/92/2

Date

Figure 64. Wind direction at the Battelle site for 20 February - 20 March 1996

T a=

—— aaa
(Ni Bap) uojse1g PUI

8

+ Q6ILE/L

+ 96/6Z/Z

7 Q6ILZZ/L

7 96/SZ/Z
al

7 S6/E7/Z

7 S6/L2/Z

+ Q6/GL/Z

I Q6/ZL/Z

+ S6/SL/Z

7 S6/EL/Z

S6/LL/Z

+ 96/6/Z

| 96/Z/Z

+ 96/S/Z

{se

S6/L/Z
°

Date

Figure 65. Wind direction at the Battelle site for July 1996

55

Chapter 3 Example Results and Discussion

ances

+ 96/672/8

+ 96/L2/8

+ 96/S2/8

+ 96/E7/8

+ 96/L2/8

+ 96/61/8
dt,

+ 96/Z 1/8
+ 96/S1/8
+
+ 96/EL/B

7 96/LL/8

7 96/6/8

7+ 96/L/8

+ 96/S/8

+ 96/E/8

60 4

¢ @ a
Nn - -

(99s/w) UO}De41G PUM

96/L/8
°

Date

Figure 66. Wind direction at the Battelle site for August 1996

+ L6/LE/8

I L6/6/8

> L6/L7c/8

it L6/SZ/8

+ L6/ET/8

+ L6/LZ/8

+ L6/61/8

+ L6E/LL/8

Jt

+ L6/SL/8

+ L6/EL/8

+ L6/LL/8

+ L6/6/8

+ 26/2/98

+ L6/S/8

Z6/€/8

T

e. 2. ae

N -

(NL Bap) uoNda41q PUIM

+ L6/L/8
°

Date

Wind direction at the Battelle site for August 1997

Figure 67.

Chapter 3 Example Results and Discussion

56

eto

+ L6/6Z/6

| 26/Z2/6

7 L6/SZ/6

+ L6/E7/6

+ LE/L 2/6
+ L6I6LIE
+ L6/LL/6

7+ LEISL/E

+ L6/EL/E

+ LE/LL/6

7 L6/6/6

+

7 L6/L/6

I L6/S/6

+ L6IE/6

360 +

300 5

Te Ta T
i=)
fia ae aera

(NL Bap) uonsda41Gg PULA

+ L6/L/6
°

Date

Wind direction at the Battelle site for September 1997

Figure 68.

360 4

T T

x 8 &
(NL Bap) UoRde1Ig PUIM

20 4

T

8

+ L6/LE/OL

+
; L6/6Z/Ol

7 L6/ZZ/01
7 L6/SZ/OL
7 L6/ET/OL
+ L6/LZ/OL
+ LE/6L/0L
+ L6/ZL/01
+ L6/SL/OL
+ LE/EL/OL
+ L6/LL/OL

+ L6/G/OL

+ L6/LZ/01

| L6/S/OL

L6/E/OL

+ L6/L/OL
°

Date

Wind direction at the Battelle site for October 1997

Figure 69.

37

Chapter 3 Example Results and Discussion

58

Sediment Results

All samples were sieved at quarter-phi (%4 @) intervals. Sediment statistics were
calculated using the method of moments (Friedman and Sanders 1978). Mean
(the average grain size) and standard deviation (a measure of uniformity or sorting
of the sediment) values were calculated for each sediment sample. Ponce de Leon
Inlet had a narrow range of mean grain sizes, most centered in the fine sand range,
with little shell and no gravel size components. Most of these samples were well
sorted and the mean and median were similar. Only the few coarser sand samples
generally had poorer sorting. Samples from the flood and ebb shoals were
relatively finer than the throat and flood channels, and most of the beach samples.
For the flood and ebb shoals, the average mean grain size was around 0.15 mm
(2.70 o), for the throat and flood channels and beaches, around 0.18 mm (2.45 g).
A few low tide samples and the south flood channel (SFC3) sample contained
shells and shell fragments and were substantially coarser (up to 0.42 mm, 1.26 g).
Figure 70 shows the sample locations. Table 7 lists data on sample location and
sediment statistics. Further details on sediment analysis can be found in Stauble
and Cialone (1997).

Chapter 3 Example Results and Discussion

59

S661 AeAins STWOHS Woy AjewAyyeEg “epuoj ‘jajU| U0E7] ap adU0d je Sajdwes juaUIpas jo uoNe07 “OZ eunbi4

EAS (w>) St 0
0

(33) 000

RS!

ateas

Sa[tdwes Juawtpas e

NV390
IILNVILV

VQIwWO IS
L3SINI NO31 99 39NO0d

Chapter 3 Example Results and Discussion

60

Table 7
Ponce de Leon Inlet Sediment Samples

Ebb Shoal

Location a el a) aaa yetay

N

a |9°
& 8

N N
g 8

Sheet 1 of 4

Chapter 3 Example Results and Discussion

Table 7 (Continued)

0.

41

33 0.20
muon eee ea bee
ie Pace eee ie bene
uel waren meres es len Ie
Ba bane timer fee len fae

1.28

0.53

43

2
Flood Shoals
2

NFS 1 522271 .26202 1722311.47664 Ea

Sheet 2 of 4

s2essa.96108 | 1719017 63761 ee ee ka
527297 .33359 1717454.64045

Chapter 3 Example Results and Discussion

61

62

Table 7 (Continued)

oO

oa }]o}]o]o o lo
& g B13

3

w

R142HT
R142MT
R142LT
R1420S
R144HT
R144MT :
R1440S
R146HT
R146MT
R1460S

R148HT

oO
“I

R148MT

R148LT

oO
o

R1480S

R1SOHT 528056.08767 1722441 52106
R1SOMT 528233.31699 1722530.13000 sta orem

R150LT
R1500S 528452.94600 1722695.62790 2.30
Sheet 3 of 4

ui
N
oO
Ww
WwW
@
Z
(oy)
pss
=
IN
3
on
wo
an
S
ai
fs
a
NO

oS
fon)
@

Chapter 3 Example Results and Discussion

R152HT

)
Sq [eon [ee er den ee
ce
Ea
=

A

aa fo

RITEMT
BBSHMT 113

CNSSMT 566900.00000 1652830.00000

(Sheet 4 of 4)

NOTE: Translated Coordinates on NAD 27 Florida East State Plane Zone,U.S. FOOT

Chapter 3 Example Results and Discussion

63

64

References

Barwis, J. H. (1975). “Catalog of tidal inlet aerial photography,” GITI
Report 75-2, U.S. Army Engineer Waterways Experiment Station,
Vicksburg, MS, and U.S. Army Coastal Engineering Research Center, Fort
Belvoir, VA.

Earle, M. D., McGehee, D. D., and Tubman, M. W. (1995). “Field wave gaging
program wave data analysis standard,” Instruction Report CERC-95-1, U.S.
Army Engineer Waterways Experiment Station, Vicksburg, MS.

Friedman, G. M., and Sanders, J. E. (1978). Principals of sedimentology.
John Wiley and Sons, New York.

Harkins, G. S., Puckette, P., and Dorrell, C. (1997). “Physical model studies of
Ponce de Leon Inlet, Florida,” Technical Report CHL-97-23, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.

Hemsley, J. M., and Briggs, M. J. (1988). “Tidal elevations and currents at Ponce
de Leon Inlet, Florida,” Miscellaneous Paper CERC-88-8, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.

Howell, G. L. (1992). “A new nearshore directional wave gauge.” Proceedings, 23
International Conference on Coastal Engineering. American Society of Civil
Engineers, Venice, Italy, 295-307.

Howell, G. L. (1996). “A comprehensive field study of tidal inlet processes at
Ponce de Leon Inlet, Florida.” Proceedings, 25th International Conference on
Coastal Engineering. Chapter 257, American Society of Civil Engineers,
3,323-36.

Irish, J. L., Lillycrop, W. J., and Parsons, L. E. (1996). “Accuracy of
sand volumes as a function of survey density,” Proceedings, 25th
International Conference on Coastal Engineering, Orlando, FL, 3,736-49.

Irish, J. L., Parson, L. E., and Lillycrop, W. J. (1995). “Detailed bathymetry of
four Florida inlets.” Proceedings, 8th National Conference on Beach
Preservation Technology. FSBPA, Tallahassee, FL, 243-58.

References

John E. Chance & Associates. (1996). "Ponce de Leon Inlet gauge elevations,
New Smyrna Beach, Florida," Contractor Report, U.S. Army Engineer
Waterways Experiment Station, Contract No. DACW39-92-D-0016.

Jones, C. P. and Mehta, A. J. (1978). "Ponce de Leon Inlet: Glossary of
Inlets Report No. 6," Florida Sea Grant Report Number 23, Gainesville, ‘wD
FL.

Lillycrop, W. J., Parsons, L. E., and Irish, J. L. (1996). "Development and
operation of the SHOALS airborne lidar hydrographic survey system,
"Laser remote sensing of natural waters: From theory to practice; "
Proceedings, the International Society for Optical Engineering, V.1. Feigels
and Y.I. Kopilevich, eds., Vol 2964, 26-37, SPIE, Bellingham, WA.

McKinney, J. P., and Howell, G. L. (1996). "A data acquisition and analysis
system for coastal ocean measurements." Proceedings, Oceans 96.
Ft. Lauderdale, FL, IEEE.

Purpura, J. A. (1977), "Performance of a jetty-weir improvement plan."
Proceedings, Coastal Sediments ‘77. American Society of Civil Engineers,
330-49.

Purpura, J. A., Beechley, B. C., Baskette, C. W., Jr., and Roberge, J.C.
(1974). "Performance of a jetty-weir improvement plan." Proceedings,
14th Coastal Engineering Conference. American Society of Civil
Engineers, Chapter 86, 1,470-90.

Smith, J. M., Militello, A., and Smith, S. J. (1998). "Modeling waves at
Ponce de Leon Inlet, Florida." Proceedings, 5” International Workshop on
Wave Hindcasting and Forecasting. Environment Canada, Downsview,
Ontario, 201-14.

Stauble, D. K. (1998). “Evaluation of pre- and post-jetty inlet shoal evolution.”
Proceedings, 11th National Conference on Beach Preservation Technology.
Florida Shore and Beach Preservation Association, Tallahassee, FL.

Stauble, D. K., and Cialone, M. A. (1997). "The tale of three inlets:
Sediment management techniques," New Insights into Beach Preservation,
Proceedings of the 10” National Conference on Beach Preservation
Technology, L. S. Tait, ed., Florida Shore and Beach Preservation
Association, Tallahassee, FL, 199-214.

Taylor, R. B. (1989). "Program development report for Port District Inlet
management program," prepared by Taylor Engineering, Jacksonville, FL.

Taylor, R. B., Yanez, M. A., and Hull, T. J. (1992). "Port District Inlet
management plan, phase III technical addendum," Ponce de Leon Port
Authority, Taylor Engineering, Jacksonville, FL.

References

65

66

Taylor, R. B., Yanez, M. A. Hull, T. J., and McFetridge, W. F. (1990).
"Engineering evaluation of Ponce de Leon Inlet," Final Phase II Report,
Taylor Engineering, Inc., Jacksonville, FL.

U.S. Army Engineer District, Jacksonville. (1963). "Survey review report on
Ponce de Leon Inlet, Florida," Serial No. 61, Jacksonville, FL.

. (1967). "General and detail design memorandum, Ponce de
Leon Inlet, Florida," Serial No. 17, Jacksonville, FL.

. (1983). "General and detail design memorandum, Ponce de
Leon Inlet, Florida," Addendum 1 (Adjustment to Weir), Jacksonville, FL.

Waller, T. N. (1998). "Velocity and discharge measurements at Ponce de
Leon Inlet, Florida," Memorandum for Record, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.

Wood, B. C. (1996a). "Project report, photo control: Ponce de Leon Inlet,"
Project No. 073-001-96, Subcontractor report, GeoBase Control, Inc., for
Evans-Hamilton, Inc., U.S. Army Corps of Engineers Waterways
Experiment Station, Vicksburg, MS.

. (1996b). "Report of specific purpose survey, Ponce Inlet,
Volusia County, FL," Project No. 073-002-96, Subcontractor report,
GeoBase Control, Inc. for Evans-Hamilton, Inc., U.S. Army Corps of
Engineers Waterways Experiment Station, Vicksburg, MS.

References

Appendix A

Velocity and Discharge
Measurements at Ponce de Leon
Inlet, Florida

This appendix contains a revised copy of a memorandum for record dated 26 January
1998, regarding velocity and discharge measurements at Ponce de Leon Inlet, FL.

Introduction

Short-term field measurements were conducted at Ponce De Leon Inlet, FL, to support
the Inlet Modeling System work unit for development and validation of the circulation and
wave model. The subject field investigation, which consisted of two 1-week Acoustic
Doppler Current Profiler (ADCP) surveys during the periods 25-29 August 1997 and
15-19 September 1997, was conducted by the staff of the Coastal and Hydraulics
Laboratory (CHL) at the U.S. Army Engineer Waterways Experiment Station. Results
from these activities are discussed herein. Additional information was obtained from
several sources. A 2-month deployment of six in situ pressure and two-component velocity
gauges (PUV’s) was conducted by Florida Institute of Technology. The SHOALS team
performed a high-resolution bathymetric survey. Aerial photographs were taken by Aerial
Cartographics of America, Inc. of Orlando, FL: Dr. Donald Stauble obtained sediment
samples from the interior and exterior of the inlet. Finally, meteorological data were
obtained from the Battelle Paint Test Facility adjacent to the inlet.

The ADCP and bathymetric data surveys were conducted by Messrs. Howard Benson,
Thad Pratt, and Terry Waller, CHL. Other participants in the surveys from CHL included

Ms. Adele Militello and Dr. Jane Smith. The boat and boat operator were supplied by
DIMCO, Inc.

Bathymetric Survey and Tide Data

The bathymetric data collected during this effort were not comprehensive and,
therefore, do not represent a full bathymetric survey. The bathymetric data were mainly

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL Al

A2

collected along each of the ADCP transect lines. The areas in which these transect lines
were located include the north and south bays, the Intracoastal Waterway (ICWW), the
inlet, and on the ebb shoal. Additional bathymetric data were collected between each of
the inlet transect lines, many of the north and south bay transect lines, along depth
contours in the inlet and ebb shoal, and along the center lines of the bay and inlet channels.
These data were collected to aid in the interpretation of the ADCP results, as well as
provide information for updating the 1996 SHOALS survey in designated critical areas.
The constant presence of swells, particularly in the area of the ebb shoal, made for poor
surveying conditions. As a result, the depth soundings recorded the up and down
movement of the boat and gave the appearance of sand waves forming on the shoal. The
bathymetric data were collected concurrent with the ADCP data collection using a
200-kHz Echotrac fathometer.

These data were corrected to National Geodetic Vertical Datum using information from
CHL’s Prototype Measurement and Analysis Branch (PMAB) water-level gauges. Time-
history plots of the tide data from one of the PMAB water-level gauges during the two
ADCP and bathymetric survey periods (August and September) are shown in Plates Al
and A2. The PMAB water-level gauge located near the Coast Guard Station in the south
bay area was used due to its relative proximity to the inlet. Data are plotted in Eastern
Standard Time (EST) for correlation with the ADCP data. The maximum neap tide range
during the week of 25 August was 1.05 m. The maximum spring tide range during the
week of 15 September was 1.35 m.

ADCP Surveys

ADCP surveys were performed to measure the current distributions (variations across
the channel and through the vertical) and discharges in the inlet system. These roving
measurements provide a means for obtaining comprehensive information on the spatial
variability throughout the inlet system, unlike the more limited in situ gauges (tide and
PUV), which provide data on the temporal variability at only a few locations. The two
1-week ADCP surveys were conducted during 25-29 August and 15-19 September. These
dates coincided with periods of neap and spring tide conditions, respectively.

An RD Instruments Broadband ADCP was used to obtain the velocity magnitude and
direction profiles for each transect. This instrument uses a 1,200-kHz operating
frequency. The equipment is mounted over the side of the boat with the acoustic
transducers submerged and data are collected while the vessel is under way.

The ADCP transmits sound bursts into the water column which are scattered back to
the instrument by particulate matter suspended in the flowing water. The ADCP listens
for the returning signal and assigns velocity to the received signal based on the change in
the frequency caused by the moving particles. This change in frequency is referred to as a
Doppler shift. The ADCP is also capable of measuring vessel direction, current direction,
and bottom depth. Communications with the instrument for setup and data recording are
performed with a portable computer using manufacturer-supplied software, hardware, and

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

communication cables. The manufacturer-stated accuracy for current speed measurement
is+ 0.2 cm/sec.

The data collection boat was outfitted with a Global Positioning System (GPS) receiver
antenna. U.S. Coast Guard GPS transmitter beacons, positioned at various locations
along the Florida coast, provided differential GPS positioning for a higher level of
accuracy during the data collection. The outputs from these instruments were interfaced to
a laptop computer using a hydrographic surveying software system known as HYPACK.
This combination permitted accurate logging of location from a known GPS starting
coordinate at each velocity profile transect. The data collection boat traversed the transect
line at a slow constant speed (approximately 4-7 km/hr) to obtain the best possible spatial
coverage.

The data collection transect lines throughout the study area were located to provide the
best information to support the modeling effort. However, certain field conditions were
encountered, such as shallow flats, marshes, and shoal migration near the inlet, that
necessitated transect line locations be moved, shortened, or lengthened in order to obtain
the full discharge and flow patterns within the cross sections.

Neap Tide Data Collection

Plate A3 illustrates the location of the areas monitored for the data collection effort
during trip one. During this first survey, a priority was placed on the collection of
bathymetric information, as well as the ADCP data. Therefore, the first day's effort
covered numerous transect lines in the bay areas. Table Al summarizes the ADCP data
collected on 25 August 1997. It contains line numbers, times (EST), and discharges for
the areas in the south bay, north bay, and ICWW. Direction of the total discharge flow
listed in this table is presented as flood or ebb flow and indicated by + and -, respectively.
Except for the summary table of the intensive surveys, the tables and Plates summarizing
the data collection are presented in chronological order and not in order of line number.
Chronological order presentation of the data was selected because the transects were not
monitored by sequential line number order. Plates A4-A7 present the depth-averaged
velocity vector plots for data collected on 25 August. The integration of the GPS
coordinates for each vertical profile along the transect line accurately defines the location
of the velocity vector data shown in the Plates. Transect lines with velocity vectors that do
not plot from bank to bank indicate that either bank movement or shallow water areas were
encountered during the data collection. For the purposes of data presentation, the arrow
shows flow direction and the velocity magnitude is indicated by the adjacent number. All
the Plates showing velocity vectors are plotted at the same scale. The Plates for each day
are in order of time.

The intensive ADCP survey of the inlet area was conducted on 26 August. The
discharge data are summarizeqin Table A2, but are not plotted. Table A3 presents a
summarizes of the 27 August data collection effort, which was concentrated in the north
bay and the ICWW areas during ebb flow conditions. Depth-averaged velocity vector data
for the transects in these areas are shown in Plates A8-A12. Bathymetric and ADCP data
were collected on the ebb shoal on 28 August. The ADCP discharges for this area are

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

AG

summarized in Table A4 and the depth-averaged velocity vectors are plotted in
Plates Al3-A16. Data collected in the south bay area on 29 August are summarized in
Table A5 and plotted in Plates A17-A20.

The following is a detailed daily summary of the data collection effort conducted in the
respective areas during this first trip (neap tide).

Inlet surveys

On 26 August an intensive data collection effort was conducted. ADCP transect lines
1-9 (shown in Plate A21) in the inlet were repeated at approximately 1-hr increments over
a 12-hr period. (Note: Inlet transect lines 1-9 differ from transect lines 1-9 in the bay
area.) The transect lines began at the north jetty and ran to the south. Each set of
transects required approximately 30-45 min to complete. Waves in the outer portions of
the inlet were generally 1 m high with short periods; however, conditions deteriorated
during periods of ebb flow. Data collection efforts at the most seaward transect line (7),
which ran between the seaward ends of the jetties, were hampered by the high wave
conditions and only a few hours of data were obtained at this location. The waves in the
inner inlet area were significantly smaller and more conducive to longer periods of data
collection. Data collected at transect lines 8 and 9 occurred near the time of the peak flood
currents and captured the division of flow between the north and south portions of the bay,
respectively. Hourly results of the intensive survey are summarized in Table A2.

Ebb shoal surveys

ADCP transect lines 69 and 77-84 (in the ebb shoal area) were monitored on
28 August. Morning measurements at these transects were made under ebb flow
conditions and the afternoon measurements were made under flood flow conditions. These
transect lines were up to 3.0 km long, requiring approximately 4 hr to conduct each set of
transects. During the morning survey, transect line 80 had to be shortened due to breaking
waves on the shoal. The offshore waves were 1.2 m in height with periods of 7-8 sec, and
winds were light. Large breakers were focused on the ebb shoal just seaward of the south
jetty. Table A4 presents the discharges for each set of measurements and the data are
plotted in Plates A13-A16. The data generally illustrate the wave direction; however, near
the end of the jetties, the velocity vectors indicate the tidal current direction.

North bay surveys

On 25 August, a partial flood flow condition survey, which included transect lines
26-31, was made in an area of the north bay located between the inlet and extending
1.6 km to the north (Plates A5 and A6). To complement the data set, a longitudinal
transect along the channel center line was also obtained. On 27 August, selected ADCP
transect lines in north bay (beginning at the inlet and extending approximately 8 km to the
north) were monitored during ebb flow conditions (Plates A8-A10).

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

South bay surveys

On 25 August, ADCP transect lines 1-10 in the south bay were monitored during flood
flow conditions (Plates A4 and A5). On 29 August, the south bay transect lines 4, 5, 7, 9,
and 10 (beginning 5 km south of the inlet and extending to the inlet) were monitored during
ebb flow conditions (Plates Al7 and A18).

ICWW surveys

On 25 August, ADCP transects in the ICWW were monitored during flood flow
conditions and slack conditions (Plates A5-A7). The transect lines are located in the area
between the confluences of the ICWW with the north and south bay channels and the
feeding channels behind the inlet. On 27 August, ICWW transect lines 13, 17, and 19
were repeated during flood flow conditions (Plates All and Al2). During this period,
longitudinal transects along the main channel and side channel center lines were also
monitored.

Spring Tide Data Collection

During the week of 15-19 September, the data collection effort was conducted for a
spring tide condition. The majority of the ADCP transect lines, monitored during the neap
tide period, were repeated for this data collection effort. For the spring tide measurements,
a greater priority was placed on obtaining data during periods of peak ebb and flood
currents. Additionally, the transect lines at the inlet (96), the entrance to the north bay
(30), and the entrance to the south bay (4) were repeated frequently in an effort to
determine current direction and magnitude both before and after each data set was
collected. Plate A22 identifies the locations for each area monitored during this spring tide
data collection period. On 15 September, ebb and flood flow conditions were monitored in
the south bay area. These data are summarized in Table A6, and the depth-averaged
velocity vectors are presented in Plates A23-A28. During the morning of 16 September,
transect lines on the ebb shoal were monitored for ebb flow conditions. These data are
summarized in Table A7, and the depth-averaged velocity vector plots are presented in
Plate A29. During the afternoon of 16 September, currents for ebb flow conditions were
monitored in the north bay area. These data are also summarized in Table A7, and the
depth-averaged velocity vector plots are presented in Plates A30-A33. Measurements on
17 September began on the ebb shoal during flood flow conditions. Afternoon
measurements, on this same day, were made on the ICWW during ebb flow conditions.
The data are summarized in Table A8 and plotted in Plates A34-A38. On 18 September,
an intensive 13-hr data collection effort was conducted in the inlet area. These data are
summarized in Table A9 but are not plotted. The data collection efforts for 19 September
were designed to cover transect lines located in areas of the north bay and the ICWW
during flood flow conditions. The data obtained for this period are summarized in
Table A10, and velocity vector plots are presented in Plates A39-A42.

The following is a detailed daily summary of the data collection effort conducted in the
respective areas during the period of the second trip (spring tide).

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL A5

A6

Inlet survey

On 18 September, the inlet survey was conducted at a peak spring tide. Table A9
summarizes the discharges. The total number of transect lines monitored in the inlet area
were identical to those from the neap tide survey. However, due to extreme wave and
current interactions, the outside (seaward) lines were determined to be too dangerous to
run. Transect lines 8 and 9, which determined the splitting of the flow to the north and
south bay areas, were monitored at or near periods of peak ebb and flood flow conditions.

Ebb shoal surveys

The ebb shoal depth-averaged velocity vector data are plotted in Plates A29 and A34.
The number of lines monitored during this period was reduced to five from the original
eight. The five transect lines that were monitored include: 77, 80, 81, 82, and 83. Line
77 extends eastward from the jetty. The remaining four lines are oriented from north to
south and are nearly perpendicular to the axis of the main channel. Each data set for these
five lines required approximately 2.5 hr to complete. During the ebb flow condition, the
waves (swell) were about | m high and from an east-northeast direction. At the beginning
of the flood tidal survey, the waves (swell) were about 0.5 m high from the east. The
depth-averaged velocity vector Plates depict the maximum currents near the jetties.
Further away from the end of the jetties, the influence of the waves appears to override the
tidal current velocities.

North and south bay surveys

North and south bay channel surveys were performed on flood and ebb tide. The total
number of transect lines surveyed in these areas was reduced from those from the neap tide
survey period. This reduction in transect lines was done to provide adequate time to
complete the north bay channel section. The omitted lines were near and similar to
adjacent lines so that no vital information was lost. The north and south bay channel
surveys were usually started by monitoring transect lines 96, 4, and 30, in that order, to
determine the flow distribution between the inlet, the south channel, and the north channel,
respectively. During the flood flow conditions in the north bay area, the transect lines at
the extreme north end of the bay were not surveyed in order that measurements of
velocities in the ICWW areas could be obtained. The ebb flow data in the south bay are
shown in Plates A23 and A24, while the flood flow data are shown in Plates A27 and A28.
The north bay ebb flow data are shown in Plates A30-A33 and the flood data are shown in
Plates A39-A41.

ICWW survey
The reach of the ICWW located between the confluences with the north and south bay

channels was surveyed for ebb and flood tidal conditions on 17 and 19 September,
respectively. The velocity vector plots for the data obtained on these dates are shown in

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

Plates A35-A37 and Plates A39-A41, respectively. The ICWW survey also included
transect lines (11 and 32) in the creeks located between the ICWW and the inlet.

General Observations

During the neap and spring ADCP and bathymetry surveys, the following observations
were made:

a. During the neap tide intensive ADCP survey the maximum discharges measured
through the inlet were about 1,700 cu m/sec on flood and 1,300 cu m/sec on ebb. The
spring tide intensive survey measured maximum discharges of 2,200 cu m/sec on flood and
1,600 cu m/sec on ebb. In the bay area, approximately half of the flow goes to the south
at near maximum flood flows. The remainder of the flow is split between the north bay
and the creeks flowing into the ICWW. These creeks are located on ADCP transect lines
11 and 32.

b. There was significant wave action throughout the neap tide measurement period.
Waves were breaking over the north jetty almost the whole week, and at high tide, waves
were propagating over the jetty causing very rough conditions in the throat of the inlet.
The ebb shoal was found to be extremely shallow just seaward and south of the south jetty.
As a result, it was very common to have 2.0- to 2.5-m waves breaking in this region.

c. During both the neap and spring surveys of the ebb shoal area, ebb currents were
observed to be deflected to the south near the tips of the jetties. This was probably due to
the waves from the northeast. Also evident in the data were reversals in the current
directions north and south of the inlet. The somewhat erratic current direction offshore is
also influenced by the waves present during the data collection.

d. Very strong currents were found to exist throughout the entire study area. Current
speeds of 60 cm/sec north and south of the inlet in the bays were commonly observed.
Peak currents observed in the inlet were approximately 100 cm/sec.

e. There is a large difference in tidal phase between the water level and current during
spring tide. Strong currents in the ebb direction were observed while the water level
continued to rise in the bay. The water level had risen substantially from the low tide
elevation and the currents were still observed to be in an ebb direction. A similar
phenomenon was observed for the falling tide; the water level would decrease and the
current continued in the flood direction.

f. The flows in the ICWW were generally observed to be from south to north when the
flood currents in the inlet were strong . The flows were from north to south when the ebb
currents in the inlet were strongest.

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

A7

A8

Table A1
Ponce de Leon Inlet Discharge Rates on 25 August 1997

Pome Nee: [iil wl a
Line No. EST m*/sec
South Bay - see Plates A4 and A5

8/25/97

8/25/97

8/25/97

(Continued)

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

Table A1 (Concluded)

ee
Line No. EST m/sec
arse7

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

AQ

A10

Table A2
Ponce de Leon Inlet Discharge Rates on 26 August 1997

Time Discharge
Line No. al m/sec
iti areas | Throats - see Plate A21

8/26/97

(Sheet 1 of 3)

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

Table A2 (Continued)

Time
Date Line No. EST

Inlet Throats (Continued)

Discharge
m/sec

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

(Sheet 2 of 3)

All

Table A2 (Concluded)

er eee

Line No. EST m/sec
Ce a
a oo

A12 Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

Table A3
Ponce de Leon Inlet Discharge Rates on 27 August 1997

SS eS eS
Line No. EST m*/sec
North Bay - see Plates A8, A9, and A10

8/27/97

8/27/97

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL A13

A14

Table A4
Ponce de Leon Inlet Discharge Rates on 28 August 1997

Line No. EST m/sec
Ebb Shoal - Ebb Tide- see Plates A13 and A14

8/28/97

8/28/97

290.5

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

Table AS
Ponce de Leon Inlet Discharge Rates on 29 August 1997

Time Discharge
Line No. EST m/sec
South Bay - see Plates A17 and A18

8/29/97

8/29/97

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL A15

A16

Table A6
Ponce de Leon Inlet Discharge Rates on 15 September 1997

Line No. EST m*/sec
South Bay - see Plates A23 and A24

9/15/97

9/15/97:

153
1542 +12645

9/15/97

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

Table A7
Ponce de Leon Inlet Discharge Rates on 16 September 1997

eran OL aa a
Line No. EST m/sec
Ebb Shoal - Ebb Tide - see Plate A29

9/16/97

9/16/97

** Data not available

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL A17

A18

Table A8
Ponce de Leon Inlet Discharge Rates on 17 September 1997

Line No. EST m*/sec

Ebb Shoal - Flood Tide - see Plate A34

9/17/97

9/17/97

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

Table A9
Ponce de Leon Inlet Discharge Rates on 18 September 1997

ee ee
Line No. EST m/sec

Inlet Throats - see Plate A21

fe jee
eae cn

(Sheet 1 of 3)

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

A19

Table A9 [Table ag(Contnued) =
Line No. Se m/sec

Inlet Throats Pear eee a |

9/18/97

+1178.0

A20 Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

Table A9 (Concluded)

Peau a
Line No. EST m/sec
Inlet Throats (Continued

5 9/18/97

** Data not available

Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL A21

Table A10
Ponce de Leon Inlet Discharge Rates on 19 September 1997

(mmm fem ea oS
Line No. EST m/sec
North Bay - see Plates A39, A40, and A41
a
a aio
fe ae

Intracoastal Waterway - see Plates A39, A40, A41, and A42

9/19/97

+1461.4

A22 Appendix A Velocity and Discharge Measurements at Ponce de Leon, FL

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Appendix B
Aerial Photography

Appendix B Aerial Photography

B1

B2

Photo B1.

Ponce de Leon Inlet, 10 September 1997

Appendix B Aerial Photography

Photo B2. North jetty, 21 March 1996

Appendix B Aerial Photography

B3

B4

Appendix B Aerial Photography

Appendix B Aerial Photography

Bb

B6

Photo B5. Floods

Site

oals, 24 September 1996

eaxieebalin Weiter ues wT

Appendix B Aerial Photography

]
REPORT DOCUMENTATION PAGE Aap aa sen |

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Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

January 1999 Report 1 of a series
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
Ponce de Leon Inlet, Florida, Site Investigation; Report 1, Selected Portions of
Long-Term Measurements, 1995-1997

6. AUTHOR(S)
David B. King, Jr., Jane M. Smith, Adele Militello, Donald K. Stauble,

Terry N. Waller
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
U.S. Army Engineer Waterways Experiment Station cues NUMBER
3909 Halls Ferry Road Technical Report CHL-99- 1
Vicksburg, MS 39180-6199
|9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING
AGENCY REPORT NUMBER

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

11. SUPPLEMENTARY NOTES
Available from National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.

12b. DISTRIBUTION CODE

12a. DISTRIBUTION/AVAILABILITY STATEMENT
Approved for public release; distribution is unlimited.

|

13. ABSTRACT (Maximum 200 words)

The U.S. Army Corps of Engineers, Coastal Inlets Research Program, conducted a long-term comprehensive monitoring
program at Ponce de Leon Inlet, Florida, beginning in September 1995 and ending in October 1997. The monitoring program
consisted of multiple gauge sites to collect data on wave height, wave period, wave direction, water level, current velocity,
and wind velocity. Additional data were obtained through bathymetry surveys, the collection of sediment samples, and inlet
monitoring with video imagery and aerial photography. This report describing the available data, discusses the data
collection and processing procedures used, and presents examples of the data collected during three time periods of interest.

14. SUBJECT TERMS 15. NUMBER OF PAGES
Bathymetry data Ponce de Leon Inlet, Florida 147
Coastal Inlets Research Program Sediment data
Current data Water level data 16. PRICE CODE
Field data Wave data

Inlets, Florida Wind data

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

OF REPORT OF THIS PAGE OF ABSTRACT
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