An examination of flood deltas in Florida's tidal inlets

UFL/COEL-99/015

AN EXAMINATION OF FLOOD DELTAS AT
FLORIDA'S TIDAL INLETS

by

Erica Eva Carr de Betts

Thesis

1999

AN EXAMINATION OF FLOOD DELTAS AT FLORIDA'S TIDAL INLETS

By

ERICA EVA CARR de BETTS

A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF
FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

1999

ACKNOWLEDGMENT

I would like to express my highest gratitude to my supervisory committee chair,

Dr. Ashish Mehta, whose immense help was key in the completion of this thesis. I would

also like to thank members of my committee, Dr. Robert G. Dean and Dr. Thieke. Dr.

Dean was always available to identify an inlet from a photograph, provide support, or just

utter a kind word. I am grateful to Dr. Thieke for stretching my brains in his fluids class,

and for serving as the goalie on the soccer team.

I would like to recognize Helen Twedell who was a joy to work for in the Coastal

Engineering Archives and who is the friendliest, most helpful resource in all of Coastal

Engineering. My appreciation goes to all of my fellow coastal students who were always

available to stop working and to play soccer-Guillermo, Roberto, Rodrigo, Justin, Vadim,

Kevin, Al, Ki Jin, Edward, L.J., Daniel, Chris, Peter, Sun, Ding, Dave, Joel and Hugo.

I am forever thankful for my mom, dad, aunt Treva, my grandparents, and brother

Eric, who instilled in me the value of education, and supported me in every aspect of my

life. My family has truly been my greatest asset as they have provided me with a life full

of love, humor, happiness and opportunity without limits.

Finally, my deepest gratitude goes to Daniel Augusto Betts, who came to study at

the University of Florida because I wanted to be a coastal engineer. Perhaps his greatest

contribution to this thesis came in his ability to show his support, respect and love at

every turn.

TABLE OF CONTENTS
Page

A CKN OW LED GM EN T ............................................................................................. ii

LIST OF FIGU RES ......................................................................................................... vii

LIST OF TABLES ....................................................................................................... x

LIST OF SYM BOLS ...................................................................................................... xiv

A BSTRA CT .................................................................................................................... xvi

CHAPTERS

1 INTRODUCTION

1.1 Problem Statem ent ........................................................................................... 1
1.2 Objectives and Scope ......................................... ................ ........................... 2
1.3 Outline of Presentation .......................................................................................... 3

2 APPROACH

2.1 Inlet Flood Delta .............................................................................................. 4
2.2 Method of Calculation Flood Delta Area and Volume........................................... 9
2.2.1 Calculation of Flood Tidal Delta Area ..................................... ............ 9
2.2.2 Calculation of Flood Tidal Delta Volum e ............................................ 15

3 FLORIDA'S INLETS

3.1 Introduction ................................................................................................... 19
3.2 St. M arys Inlet................................................................................................. 20
3.3 N assau Sound ................................................................................................. 20
3.4 Ft. George Inlet............................................................................................... 20
3.5 St. Johns Inlet.................................................................................................. 21
3.6 St. Augustine Inlet .......................................................................................... 22
3.7 M atanzas Inlet................................................................................................. 22
3.8 Ponce de Leon Inlet ........................................................................................ 23
3.9 Port Canaveral Inlet ........................................................................................ 24
3.10 Sebastian Inlet................................................................................................. 24

iii

3.11 Ft. Pierce Inlet............................................................................................... 25
3.12 St. Lucie Inlet.................................................................................................. 25
3.13 Jupiter Inlet .................................................................................................... 26
3.14 Lake W north Inlet............................................................................................. 27
3.15 South Lake W north Inlet ...................................................................................... 28
3.16 Boca Raton Inlet .................................................................................................. 28
3.17 H illsboro Inlet ............................................................................................... 29
3.18 Port Everglades Entrance ........................................................... ................... 30
3.19 Bakers Haulover Inlet ........................................................................................... 30
3.20 Governm ent Cut.................................................................................................... 31
3.21 N orris Cut.............................................................................................................. 32
3.22 Bear Cut ................................................................................................................ 32
3.23 Sands Cut.............................................................................................................. 33
3.24 Caesar Creek................................................................................................. 33
3.25 Old Rhodes Channel ............................................................................................. 33
3.26 Broad Creek .................................................................................................... 33
3.27 Angelfish Creek .................................................................................................... 34
3.28 Snake Creek .................................................................................................... 34
3.29 Key Vaca Cut.................................................................................................. 34
3.30 Caxam bas Pass............................................................................................... 35
3.31 Big M arco Pass ..................................................................................................... 36
3.32 Capri Pass.............................................................................................................. 36
3.33 Hurricane Pass ............................................................................................... 36
3.34 Little M arco Pass .................................................................................................. 36
3.35 Gordon Pass .................................................................................................... 37
3.36 D doctors Pass.......................................................................................................... 37
3.37 Clam Pass.............................................................................................................. 37
3.38 W iggins Pass ......................................................................................................... 38
3.39 Big Hickory Pass............................................................................................. 38
3.40 N ew Pass ............................................................................................................... 39
3.41 Big Carlos Pass ............................................................................................... 39
3.42 M atanzas Pass ................................................................................................. 39
3.43 San Carlos Inlet............................................................................................. 40
3.44 Blind Pass ...................................................................................................... 40
3.45 Redfish Pass.................................................................................................... 40
3.46 Captiva Pass .......................................................................................................... 41
3.47 Boca Grande Inlet ........................................................................................... 42
3.48 Gasparilla Pass ............................................................................................... 42
3.49 Stum p Pass...................................................................................................... 42
3.50 Venice Inlet........................................................................................................... 43
3.51 Big Sarasota Pass ........................................................................................... 43

3.52 N ew Pass......................................................................................................... 44
3.53 Longboat Pass ................................................................................................. 45
3.54 Passage Key Inlet............................................................................................ 45
3.55 Southw est Channel.......................................................................................... 46
3.56 Egm ont Channel.............................................................................................. 46
3.57 Bunces Pass..................................................................................................... 46
3.58 Pass-A -Grille................................................................................................... 47
3.59 Blind Pass ......................................... ................................. ............................. 47
3.60 Johns Pass ....................................................................................................... 48
3.61 Clearwater Pass............................................................................................... 49
3.62 W illy's Cut...................................................................................................... 50
3.63 Hurricane Pass ................................................................................................ 50
3.64 Anclote Pass South ......................................................................................... 50
3.65 Anclote Pass.................................................................................................... 51
3.66 East Pass Carrabelle...................................................................................... 51
3.67 Sikes Cut......................................................................................................... 51
3.68 W est Pass ........................................................................................................ 52
3.69 St. Joseph Bay................................................................................................. 52
3.70 M exico Beach ................................................................................................. 52
3.71 St. Andrew Bay East Channel............................................. .......................... 53
3.72 Panam a City Channel..................................................... ............................... 53
3.73 Phillips Inlet.................................................................................................... 54
3.74 East Pass Destin............................................................................................ 54
3.75 Pensacola Pass ................................................................................................ 55

4 FLOOD DELTAS IN FLORIDA

4.1 Introduction .................................................................................................... 56
4.2 Tidal Prism Based Relationships............................................. ..................... 57
4.3 Variability in Prism Based Relationships......................................... ......... ... 61
4.3.1 Dredging Histories ................................................................................... 65
4.3.2 Bay Filling Capacity ................................................... ......................... 67
4.4 Tim e-Evolution of Flood Delta .................................................................. 72
4.5 Delta Approach to Possible Equilibrium Configuration .................................. 77
4.6 Growths of "N ear-field" and "Far-field" Deposits ........................................... 78

SUMMARY AND CONCLUSIONS

5.1 Sum m ary......................................................................................................... 80
5.2 Conclusions .................................................................................................... 81

5.3 Recommendations for Further Studies ........................................... ........... ... 83

APPENDICES

A INLETS IN FLORIDA AND ASSOCIATED PHYSICAL PARAMETERS ..... 86
B FLOOD DELTA AREA AND VOLUME DATA FOR THE FLORIDA
TIDAL INLETS EXAMINED .................................................................... 91

BIBLIO G RA PH Y .................................................................................................... 118

BIOGRAPHICAL SKETCH ................. ......................................................................... 125

LIST OF FIGURES

Figure Page

2.1 Morphology of the flood delta .................................................................... 5

2.2 St. Lucie Inlet flood delta growth over time ..................................... ............. 7

2.3 Redfish Pass flood delta distinction between near-field and far-field areas ........ 10

2.4 Hypothetical semi-conical flood delta used in the calculation of the error
associated with the use of aerial photographs for the determination of
the flood delta area ......................................................................................... 11

2.5 Maximum error in the calculation of the flood delta area using aerial
photographs of unknown stage in tidal cycle................................... ........... .. 12

2.6 St. Lucie Inlet (1971) with the near-field and far-field deltas identified............. 15

2.7 Two models of the flood tidal delta, one with a flat bottom topography
and the other with a sloped bottom topography ................................................. 16

2.8 Error in total volume calculation for Ceasar Creek using various
uniform depth contours ..................................................... ........................... 17

2.9 Example of method of volume calculation for Redfish Pass ............................. 18

3.1 Florida's tidal inlets where deltas have been examined ................................... 19

3.2 Key Vaca Cut looking towards Florida Bay .................................... ........... 35

3.3 Redfish Pass in Lee county on the west coast ............................................... 41

3.4 Blind Pass in Pinellas county looking towards the Gulf of Mexico .................. 48

3.5 Johns Pass in Pinellas county looking towards Boca Ciega Bay...................... 49

4.1 Near-field delta area versus spring tidal prism using both east and west
coast inlet data................................................................................................. 57

4.2 Far-field delta area versus spring tidal prism using both east and west
coast inlet data................................................................................................. 58

4.3 Total delta area versus spring tidal prism using both east and west
coast inlet data................................................................................................. 59

4.4 Near-field delta volume versus spring tidal prism using both east and west
coast inlet data................................................................................................. 59

4.5 Far-field delta volume versus spring tidal prism using both east and west
coast inlet data................................................................................................. 60

4.6 Total delta volume versus spring tidal prism using both east and west
coast inlet data................................................................................................. 60

4.7 Total delta area versus spring tidal prism using east coast inlet data ............... 63

4.8 Total delta volume versus spring tidal prism using east coast inlet data............ 63

4.9 Total delta area versus spring tidal prism using west coast inlet data ................. 64

4.10 Total delta volume versus spring tidal prism using west coast inlet data ............ 64

4.11 Comparison of bays with differing effective areas but the same
hydraulic areas ............................................................................................... 67

4.12 St. M arys Inlet................................................................................................. 69

4.13 Old Rhodes Channel .................................................................................... 70

4.14 B ig H ickory Pass ........................................................................................... 71

4.15 West Pass ...................................... ....................... ......... 71

4.16 Sikes C ut ........................................................................................................ 72

4.17 Flood delta area growth at Sikes Cut ............................................ ............ ... 73

4.18 Flood delta volume growth at Sikes Cut ......................................... .......... ... 73

4.19 Big Marco Pass and Capri Pass in Collier County ............................................ 74

viii

4.20 Flood delta volumes versus time at Big Marco Pass ......................................... 75

4.21 Flood delta mean depth of near-field deposit versus time for Big Marco Pass ... 76

4.22 Time-evolution of the mean depth ot thickness of sediment deposit
for St. M arys Inlet .......................................................................................... 77

LIST OF TABLES

Table Page

4.1 Comparison of two inlets with similar tidal prisms but different total
volumes of flood delta deposit................................................................... 61

4.2 Parameters for representative cases of Florida's east and west
coast inlets....................................................................................................... 62

4.3 Volumes of dredged material from Florida's east coast Inlets ......................... 65

4.4 Volumes of dredged material from Florida's west coast Inlets ........................ 66

4.5 Hydraulic bay area and the effective available bay area for two east coast
inlets and two west coast inlets .................................................................. 68

4.6 Flood delta data for St. Augustine Inlet .......................................... .......... ... 77

4.7 Flood delta data for San Carlos Inlet ............................................ ............ ... 78

4.8 Sikes Cut mean depths of near-field and far-field deltas ................................. 79

4.9 South Lake Worth Inlet depths of near-field and far-field deltas ................... 79

A.1 Listing of inlets in Florida and associated physical parameters ........................ 86

B.1 Flood delta data for St. Marys Inlet.............................................. ............ .... 93

B.2 Flood delta data for Ft. George Inlet.......................................................... 93

B.3 Flood delta data for St. Augustine Inlet.......................................... ........... ... 94

B.4 Flood delta data for Matanzas Inlet ............................................... ............ 94

B.5 Flood delta data for Ponce de Leon Inlet........................................ ........... ... 95

B.6 Flood delta data for Sebastian Inlet ............................................... ............ 95

B.7 Flood delta data for St. Lucie Inlet ................................................ ............. 96

B.8 Flood delta data for Jupiter Inlet................................................................... 96

B.9 Flood delta data for South Lake Worth Inlet .................................... .......... 96

B.10 Flood delta data for Boca Raton Inlet.............................................. ........... 97

B.11 Flood delta data for Hillsboro Inlet............................................................... 97

B.12 Flood delta data for Bakers Haulover Inlet...................................... .......... ... 98

B.13 Flood delta data for Norris Cut................................................................... 98

B.14 Flood delta data for Bear Cut........................................................................ 99

B.15 Flood delta data for Sands Cut...................................................................... 99

B.16 Flood delta data for Caesar Creek............................................................... 99

B.17 Flood delta data for Old Rhodes Channel....................................... ........... 99

B.18 Flood delta data for Broad Creek........................................................................ 100

B.19 Flood delta data for Angelfish Creek.................................................................. 100

B.20 Flood delta data for Snake Creek........................................................................ 100

B.21 Flood delta data for Key Vaca Cut ................................................................... 100

B.22 Flood delta data for Caxambas Pass ................................................................. 101

B.23 Flood delta data for Big Marco Pass................................................................. 101

B.24 Flood delta data for Capri Pass ......................................................................... 101

B.25 Flood delta data for Hurricane Pass Collier.................................................... 102

B.26 Flood delta data for Little Marco Pass.............................................................. 102

B.27 Flood delta data for Gordon Pass........................................................................ 103

B.28 Flood delta data for Doctors Pass ..................................................................... 103

xi

B.29 Flood delta data for Clam Pass ........................................................................... 103

B.30 Flood delta data for W iggins Pass .................................................................... 104

B.31 Flood delta data for Big Hickory Pass.............................................................. 104

B.32 Flood delta data for New Pass Lee ................................................................. 105

B.33 Flood delta data for Big Carlos Pass.............................................................. 105

B.34 Flood delta data for M atanzas Pass Lee ......................................................... 105

B.35 Flood delta data for San Carlos Inlet ................................................................ 106

B.36 Flood delta data for Blind Pass Lee............................................................ ... 106

B.37 Flood delta data for Redfish Pass........................................................................ 106

B.38 Flood delta data for Captiva Pass........................................................................ 107

B.39 Flood delta data for Boca Grande Inlet............................................................... 107

B.40 Flood delta data for Gasparilla Pass.................................................................... 108

B.41 Flood delta data for Stump Pass.......................................................................... 108

B.42 Flood delta data for Venice Inlet ...................................................................... 109

B.43 Flood delta data for Big Sarasota Pass.............................................................. 109

B.44 Flood delta data for New Pass Sarasota........................................................... 110

B.45 Flood delta data for Longboat Pass.................................................................... 110

B.46 Flood delta data for Passage Key Inlet ................................................. ......... 111

B.47 Flood delta data for Southwest Channel...................................... ........ ..... 111

B.48 Flood delta data for Egmont Channel............................................................... 111

B.49 Flood delta data for Bunces Pass .................................................................... 111

B.50 Flood delta data for Pass-A-Grille.................................................................... 112

B.51 Flood delta data for Blind Pass Pinellas......................................................... 112

B.52 Flood delta data for Johns Pass ......................................................................... 113

B.53 Flood delta data for Clearwater Pass ................................................................ 113

B.54 Flood delta data for W illy's Cut ....................................................................... 114

B.55 Flood delta data for Hurricane Pass Pinellas.................................................. 114

B.56 Flood delta data for Anclote Pass South........................................................... 114

B.57 Flood delta data for Anclote Pass ..................................................................... 115

B.58 Flood delta data for East Pass Carrabelle....................................................... 115

B.59 Flood delta data for Sikes Cut............................................................................. 115

B.60 Flood delta data for W est Pass............................................................................ 116

B.61 Flood delta data for St. Joseph Bay .................................................................. 116

B.62 Flood delta data for M exico Beach................................................................... 116

B.63 Flood delta data for St. Andrew Bay East......................................................... 116

B.64 Flood delta data for Panama City Channel ....................................................... 117

B.65 Flood delta data for Phillips Inlet........................................................................ 117

B.66 Flood delta data for East Pass-Destin ............................................................... 117

B.67 Flood delta data for Pensacola Pass.................................................................. 117

LIST OF SYMBOLS

AB Hydraulic bay area (m2)

AB' Effective bay area (m2)

Ae Throat area (m2)

Amw Mean area of deposit (m2)

AF Far-field area of flood delta deposit (m2)

AN Near-field area of flood delta deposit (m2)

AT Total area of flood delta deposit (m2)

d depth (m)

dc Depth at the throat (m)

dso Median grain size on adjacent beaches (mm)

E East Coast

H Characteristic wave height (m)

L Length of the inlet (m)

Lat. Latitude

Long. Longitude

MHW Mean High Water

MLW Mean Low Water

P Spring tidal prism (m3)

Q Net littoral drift (m3/yr)

Rb Bay spring tide range (m)

Rhw Radius of flood delta at high water

Riw Radius of flood delta at low water

Ro Spring tidal range (m)

VF Far-field volume of deposit (m3)

VN Near-field volume of deposit (m3)

VT Total volume of deposit (m3)

W West Coast

We Width at the throat (m)

Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the degree of Master of Science

AN EXAMINATION OF FLOOD DELTAS AT FLORIDA'S TIDAL INLETS

By

Erica Eva Carr de Betts

August, 1999

Chairperson: Dr. Ashish J. Mehta
Major Department: Coastal and Oceanographic Engineering

The flood delta is an integral component of a tidal inlet. The growth of the flood

delta over time is examined at Florida's inlets. The areas of flood delta deposit have been

determined through aerial photographs and bathymetric charts. Delta volumes are

obtained from bathymetric charts using a method developed and applied to ebb deltas.

The application of this method to flood deltas and the associated errors are discussed.

Relationships between the spring tidal prism and the area and volume of the flood

delta deposit are developed. There is an evident trend of increasing area and volume of

deposit with increasing tidal prism for all inlets combined. When the east coast inlet data

are separated from the west coast data, no correlation is found for the east coast data, but

the trend of increasing area and volume with increasing prism is found for the west coast

data. There are several likely reasons for the lack of correlation for the east coast data

including effects of dredging, bay area available for sediment deposition, and depths in

the bay before a new inlet was opened. An examination of delta area and volume change

over time indicates a general trend of monotonic delta growth. This trend contrasts cases

of inlets where delta growth did not have the same pattern. Episodic events such as the

opening of an inlet in the vicinity of an old inlet, or reduction in delta volume due to

dredging are examples of unusual trends in delta variation with time. The possibility of

the flood delta attaining an equilibrium configuration is discussed, as well as the mode of

filling of the flood delta in its near and far field regions.

xvii

CHAPTER 1
INTRODUCTION

1.1 Problem Statement

Much research has been conducted on the ebb tidal shoals or deltas, which form

outside of inlets through the deposition of littoral and riverine sedimentary materials.

Thus, for example, ebb delta shapes as well as the manner in which they form and their

growth over time have been examined. The flood delta, defined as sediment accumulation

on the landward side of an inlet, is also a significant part of the inlet, and can also provide

an indication of the stability and navigability of the inlet. In Florida, where riverine

supply of sediment tends to be low, flood deltas are formed largely by landward transport

of (mostly sand-sized) littoral material by tidal flood currents.

Despite its importance, the flood delta has not in general been as thoroughly

researched as the ebb delta. In Florida this is possibly due to the fact that, with some

noteworthy exceptions, the flood delta is now not the primary source of borrow sand for

beach nourishment due to the high growth rate of vegetation on the flood shoals and

associated generation of aquatic habitat. Characteristically however, the flood delta plays

the'role of a sink for large amounts of high quality beach sand that is removed from the

littoral system, which in turn leads to the erosion of nearby beaches. The flood delta also

influences the navigability of the inlet interior.

There is a need for a greater understanding of the mode of formation of the flood

delta, as well as a demand for data on volumes and areas of historical flood deltas. In

1

2
addition, presently there appears to be no single document that provides a compilation of

both historical delta volumes and associated spread areas along with recent hydraulic and

geometric properties of Florida's inlets. Such a collection of information should prove

beneficial to the coastal engineering community and readership interested in the inlets in

Florida. The development of such a compilation was the main motivating factor for this

study.

1.2 Objectives and Scope

This research had two objectives. The first was to compile information on

Florida's inlets including their locations, hydraulic parameters, dimensions and the

volumes and areas of their sandy flood deltas. The second objective was to make an

attempt to examine likely relationships between the volume and area and the tidal prism,

and to explain the resulting trends in terms of other inlet-related physical parameters and

processes.

Data were gathered from available sources for most inlets in Florida on both the

east and the west coasts. Inlets that were closed at the time of this study were not

considered. In addition, inlets with large scale dredging operations, where the flood delta

has virtually been eliminated through mechanical removal of sediment, were not

considered for their delta volume and area, but are included in Appendix A detailing their

hydraulic and geometric properties. Additionally, these dredged inlets are included in the

historical summary provided in Chapter 3.

3
Some of the inlets included may not be familiar to many readers; however, all

have been noted in the coastal engineering literature, and all have been examined here

from numerous available bathymertic charts and aerial photographs.

1.3 Outline of Presentation

Chapter 2 discusses the general characterization of the inlet flood delta, including

its shape and features in addition to its overall importance to the inlet. The calculation

method for the delta volume and area is also provided. Chapter 3 includes a historical

summary of the inlets of Florida. Chapter 4 presents the principal results. Chapter 5

summarizes the findings of this study and gives recommendations as to areas where

further work is needed.

Appendix A consists of a table listing Florida's inlets, beginning with St. Marys

Inlet on the northeast corer of the state, proceeding south along the Atlantic east coast,

around the southern tip of Florida, then continuing north up the Gulf of Mexico west

coast to the western edge of the panhandle, ending with Pensacola Pass. In this table,

inlet latitude and longitude are given as well as important hydraulic and geometric

parameters and sediment size information on the beaches in the vicinity of each inlet.

Appendix B contains flood delta area and volume values for a large number of inlets in

Florida over time. These areas and volumes are broken down into "near-field" and "far-

field" components (defined in Chapter 2) and the totals ("near-field" plus "far-field") for

each delta.

CHAPTER 2
APPROACH

2.1 Inlet Flood Delta

A flood tidal delta is defined here as sediment accumulation formed on the

landward side of an inlet by flood-tidal currents. Hayes (1980) describes the typical

morphology of a flood delta as consisting of a flood ramp, flood channels, ebb shields,

ebb spits, and spillover lobes (Figure 2.1). The flood ramp is a seaward facing slope on

the body of sediment over which the main force of flood current is directed. The

bedforms of this feature are flood-oriented sand waves, which cover the flood ramp. The

flood channels are dominated by flood currents, which branch off of the flood ramp. The

ebb shield is a topographically high border around the tidal delta that effectively prevents

modifications of the inner portion of the delta through the action of ebb currents. Ebb

spits are elongated depositional features formed by ebb-tidal currents. Spillover lobes are

lobate bodies of sediment formed by uni-directional currents. They are formed on the

inside of the inlet when the prevailing conditions at the inlet allow for the deposition of

sediment during flood tide.

While the shape and volume of the ebb deltas can be delineated with a reasonable

degree of certainty from bathymetric charts (Marino and Mehta 1986), and their spread

areas identified from photographs as well (Davis and Gibeaut 1990), identification of

flood deltas can be more tedious for several reasons.

Dominant Tidal
Current Direction
S-Dominant Tidal
S Ebb Shield Current Direction

Spillover /Tidal Flat
Lobe

:Flood Dominant Tidal
Current Direction

Ebb Spit T Ebb Spit

Flood Channel Inlet
Flood Channel

Figure 2.1 Morphology of the flood delta (based on Hayes 1980).

Firstly, the borders and bathymetry of the interior waters even in the absence of

the delta may be complex. At ebb deltas this is often not a significant constraint, because

the "pre-inlet" bathymetry, i.e., beach profiles adjacent to the deltas, tends to be more

uniform (Dean and Walton 1973). Secondly, while at ebb deltas sea waves tend to

"mold" the delta shape, especially in the microtidal environment, similar molding is often

absent at flood deltas. Finally, in areas where the source of sediment can be oceanic as

well as riverine, the shape of the flood delta can be complex.

There are some important differences between the growth behaviors of ebb deltas

versus flood deltas. Consider a newly cut channel across a barrier island. At the time of

the breach no ebb or flood deltas exist; however, where littoral/riverine sand is present

deltas begin to form, initially at comparatively rapid rates. As the delta "fills up", i.e., as

more and more sediment is deposited, the rate of growth decreases. At ebb deltas formed

by littoral sand supply only, the delta volume eventually tends to a quasi-equilibrium

6
value, with episodic fluctuations about this value on a seasonal basis (Dombrowski and

Mehta 1994). At flood deltas the rate of growth likewise tends to decrease with time;

however, the filling process appears to be somewhat different. A characteristic delta

morphology (depicted in Figure 2.1) develops in the vicinity of the inlet channel as

increasing amount of sand is deposited. Eventually, the delta may approach a "terminal"

shape and volume; however, sand often continues to arrive at the delta, being controlled

by the channel hydraulics. Hence sand continues to spread beyond the region of "near-

field" delta, into the surrounding "far-field" region which may eventually become large.

Corroborative evidence of the above nature of flood delta growth is found in the

observations of Dean and Walton (1973) at St. Lucie Inlet on the east coast of Florida.

This is shown in Figure 2.2, in which sand deposition (in cubic meters) is plotted as a

function of years since the opening of this barrier cut in 1892. Additional data were

added to the original Dean and Walton plot (covering the 1892 1943 period) using

bathymetric charts from 1981, 1989, and 1991. Observe the "near-field" delta growth

curve in the vicinity of a 1.2km radius of the inlet. The initial deposition rate of

3.0x105m3/yr decreased to 3.5x104m3/yr by the 1990s. The "total" deposit, i.e., sum of

"near-field" and "far-field", over the region from 3.2km north of the inlet to 1.6km south

of the inlet, initially grew at a very rapid rate, but subsequently the rate of growth

approached that of the "near-field" zone.

9.00E+06 -
*.,* Data of Dean and Walton (1973)
8.00E+06 A' Present Data A

7.00E+06

2 6.00E+06 Covers region from 3.2km north of
C inlet to 1.6km south of the inlet

0. 5.00E+06

S4.00E+06

3.00E+06 Covers region in the vicinity
of 1.2km radius of the inlet
2.00E+06

1.00E+06

0.00E+00
1880 1900 1920 1940 1960 1980 2000
Year

Figure 2.2 St. Lucie Inlet flood delta growth over time.

From the observations in Figure 2.2, it appears that in order to examine the time

evolution of flood delta growth, one may examine "near-field" and "far-field" growths

separately as well as combined. This manner of dividing the flood sand deposit is

inherently approximate and is prone to subjective interpretation; yet it makes problem

analysis more tractable, hence useful as an observational process.

Flood delta morphology is, for the most part, dependent on the tidal range and

prism, the morphology of the inlet channel, and the bay containing the delta. Davies

(1964) gives a classification of coastal regions based on their tidal range. The microtidal

coast is the class of shoreline where the tide is less than 2m, and the mesotidal coast

occurs with ranges between 2m and 4m. Finally, the macrotidal coast has a tide range

greater than 4m. Microtidal inlets are present in Florida and typically have small ebb

deltas close to the shore, wide throats with multiple sand bodies, and comparatively large

8
flood deltas. The growth of the flood delta is related to inlet interaction with tidal current,

sand transport and waves. As Postma (1967) has noted, as the sea water level rises, the

flood current enters through the inlet taking the path through which it encounters the least

resistance. This path is most often around the border of the flood delta deposit.

The flood delta has great significance for the inlet as a whole. The greater the

amount of sediment in the flood delta, the less navigable the inlet will eventually become.

If the flood delta volume interferes with passage through the inlet, there may be a need

for maintenance dredging. If left to grow, the flood delta has the potential of causing an

inlet to close.

The flood delta is a potential source of borrow material for beach nourishment

application. The benefit to use of flood delta sediment is that this material is in a

protected area and would make the dredge less vulnerable to breaking waves. In Florida,

inlets such as Sebastian and Jupiter have designated areas in the flood delta region that

are periodically dredged for the dual purpose of maintaining a navigable channel and

providing sand for nourishing the nearby beach. It should however, be pointed out that

there might be a difficulty with the use of flood delta material for beach nourishment

applications, because of the environmental and possible wetland impacts in the inlet. As

noted earlier, typically, the flood delta has a higher rate of vegetation growth than the ebb

delta because the latter is subjected to greater wave action. This vegetation growth can

make the flood delta a more environmentally difficult borrow area. In fact, in Florida,

new "sand traps" in the flood delta areas are currently not permitted without providing a

strong justification for the need for such traps.

9
2.2 Method of Calculation of Flood Delta Area and Volume

Flood delta areas and volumes were calculated for a total of 67 inlets in Florida.

Areas of the flood deltas were determined from photographs and nautical charts, and

volumes were determined through the "no-inlet" contour method of Dean and Walton

(1973). This method is a relatively simple procedure for the determination of depths of

accumulated sediment volume over a pre-determined area. Existing contours, retrieved

directly from nautical charts, provide a basis for the determination of the bottom

topography in the case where the inlet exists, called "with the inlet" case. A set of

separate contours is developed, using as a guide the contours that exist inside of the bay

far from the inlet. Contours from both sides of the inlet are connected together and an

approximate contour field is estimated for the case if the inlet had not existed at all; this

is called the "without the inlet" case.

Nautical charts and aerial photographs available in the Coastal Engineering

Archives at the University of Florida were used for the information they gave on Florida's

inlets. Charts provided both area and volume values for the flood deltas, while from the

photographs only the area of the delta could be determined.

2.2.1 Calculation of Flood Delta Area

Areas of the flood tidal deltas were determined using aerial photographs over

various years. From the photographs the flood deltas were visually determined making

certain consistency was maintained for the areas between the years for each inlet. The

"near-field" flood delta could easily be identified at most inlets due to its compact nature.

The "far-field" delta often takes the shape of a bat wing or hand due to the spillover

10
lobes, which distinguishes itself from other sediment within the bay. The "near-field"

delta can be identified as localized in the center of the inlet while the "far-field" delta

"spreads out" from the "near-field" and has a greater area. The nautical chart of Redfish

Pass seen in Figure 2.3 shows this delineation between "near-field" and "far-field" deltas.

The identification of the areas was clear in most circumstances; however, an error

is inherent since the photographs were not all taken at the same point in the tidal cycle.

Florida nautical charts are developed with a mean low water (MLW) reference and the

photographs of the deltas characteristically vary throughout the tidal cycle. To identify

the error that occurs when photographs are used without an indication of the tide, it is

necessary to closely examine the photographs. In the majority of the aerial photographs

7 YRG'3A,7
lZ;J -.1 I.--- 7 7 7
--7

Figure 2.3 Redfish Pass flood delta distinction between "near-field" and "far-field" areas.
r GFavft Area a

Scale: cm 347m.

used, the deltas were seen as fully submerged; however, in most cases the visibility of the

water was such that the delta could be seen in detail. This level of visibility increases the
4 7 6 1 66
4to4

_a II it

19

Figure 2.3 Redfish Pass flood delta distinction between "near-field" and "far-field" areas.
Scale: lcm = 347m.

used, the deltas were seen as fully submerged; however, in most cases the visibility of the

water was such that the delta could be seen in detail. This level of visibility increases the

11
accuracy of the area determination so the error may have been minor in many cases.

However, in general, when the flood deltas are not fully submerged and the visibility of

the water is not perfectly clear, an error can occur in the determination of the area of the

flood delta. In order to quantify this error (e) the average slope of various flood deltas in

Florida were determined, and these were found to follow a 1 to 30 slope. This average

slope was used to map out a hypothetical flood delta that is semi-conical in shape as seen

in Figure 2.4, where Rhw is the radius of the delta at high water and Riw is the radius of

the delta at low water. The area of the half-circle was determined at its maximum area

BB'D (representing mean low water MLW) for a range of radii values. To determine the

corresponding area AA'C at high water three typical tide ranges (Rb) were used, 0.5m,

1.0m and 1.5m.

Rhw

1

B
D

Rlw C

Rhw
B A A' B'
Figure 2.4 Hypothetical semi-conical flood delta (semi-circular discs AA'C and BB'D)
used in the calculation of the error associated with the use of aerial photographs for the
determination of flood delta area.

This elevation in tide correspondingly decreased the size of the semi-conical delta

that would be visible in the photograph. These areas were used in the determination of an

error for a range of low water areas, Alw. The maximum likely error is plotted in Figure

2.5 for different tidal ranges. The equation corresponding to this plot is given in Equation

2.5, where E is the error, Rb represents the spring tidal range in the bay, and Ahw and Alw

are the area of the flood delta at high water and low water, respectively. As noted, this

equation represents the maximum error that would occur if the aerial photograph were

actually taken at high water, since a mean low water tide level is assumed in all cases.

Equation 2.1 gives the value of the vertical axis in Figure 2.5.

20.0

18.0

16.0

14.0
0
12.0

10.0

8.0 Rb = 1.5m
II
6.0

4.0 Rb 1.

2.0 Rb=0.5m
2.0
0.0 i i 1 i I I I I I I I I I I I I 1 1 1
0.00E+00 2.00E+06 4.00E+06 6.00E+06 8.00E+06 1.00E+07 1.20E+07 1.40E+07 1.60E+07
Aw (m2)
Figure 2.5 Maximum percentage error in the calculation of the flood delta area using
aerial photographs of unknown stage in the tidal cycle.

Equation 2.2 relates the area of the delta at high water Ahw to the radius of the

delta at high water. Equation 2.3 relates the area of the delta at low water, Alw, to the

13
radius of the delta at low water, Riw. Equation 2.4 relates the radius of the delta at high

water to the radius of the delta at low water with an assumed slope of 1:30.

= [1- (Ahw/Alw)] *100 (2.1)

Ahw = (7 Rhw2 )/2 (2.2)

Al = (n RIw2 )/2 (2.3)

Rhw = Riw 30(Rb) (2.4)

S= [1- ((Alw- 307Rb(2Alw/T)1/2 + 4501Rb2)/Al)]* 100 (2.5)

The general trend in the plot is due to the fact that as the radius of the delta

increases the tide has the ability to cover less of the delta as the water level rises. Flood

deltas with smaller radii are more completely covered during high tide. As the tide level

increases the errors also increase since there is a greater height difference between the

low tide level and the high tide level. As seen in Equation 2.4, a larger tidal range is

directly related to the increase in difference of the delta radius at low water and the delta

radius at high water.

The "near-field" and "far-field" areas were defined using the same criterion over

all of the photographs examined to ensure uniformity results. The "near-field" area was

identified as the area of sediment deposition at the entrance of the bay. The "near-field"

area distinguished itself in the bay as the location of the principal deposition of sediment

from the littoral system. Once the sediment settles out of the water column it deposits in

the "near-field" delta initially, then "spreads" to the "far-field" delta as the "near-field"

delta reaches its sediment carrying capacity. Typically, the "near-field" delta is not

vegetated and has a "bird foot" or "hand" that aids in its identification. The "far-field"

14
delta surrounds the "near-field". Visually the combination of "near-field" and "far-field"

deltas often appears as a smaller hand placed on top of a larger hand.

Although the "near-field" delta was identified relatively easily, the "far-field"

delta was not always visible in the aerial photographs. This visual distinction would

produce a result of greater depth of sediment (meaning more sediment deposit) in the

"near-field" than in the "far-field". In some cases, however, sediment was visible in the

very bayward sections of the delta. This visible sediment was clearly not in the "near-

field" area of the delta deposit, since the sediment could not initially have deposited so

far into the bay. In some cases the "far-field" deposit was found to be large and also

vegetated. Such for instance is the case of St. Lucie Inlet on the east coast of Florida (see

Figure 2.6). Here, the vegetated area is clearly formed over what is considered the "far-

field" delta. Other vegetated areas which did not seem to form from sand spread (i.e.,

were not what is considered here a "far-field" delta) were not included in the calculation

for the area or the volume of the delta. Once the area of the flood delta was identified, a

grid consisting of 1.2cm by 1.2cm squares was placed over a tracing from the photograph

of the flood delta. Using the scale of the photograph, the actual area of the grid square

was determined. When scales were not provided directly on the aerial photograph, it

became necessary to determine the scale manually. This was done with the help of a

stationary object such as a bridge of known length. Once the area of the grid square was

known, the total grid boxes that encompassed the flood delta were added, and the sum

multiplied by the area of each box. This gave the area (reported in square meters) of the

flood delta for the year of the photograph.

"near-field"]
Area

"far-field"
Area

Figure 2.6 St. Lucie Inlet (1971) with the "near-field" and "far-field" deltas identified.
Scale: Icm = 661m.

The flood delta areas were also determined from nautical charts. The existing

flood delta was identified and a grid was laid over the delta area. The number of grid

boxes within the delta area were counted and recorded. Similar to the calculation for the

photographs, the total number of boxes was multiplied by the area for each box.

The areas were also broken down into separate sections, the "near-field" area of

the delta and the "far-field" area. The values of these two portions were summed to

determine the total area of flood delta material. These values are given for each inlet in

Appendix B.

2.2.2 Calculation of Flood Delta Volume

The determination of flood delta volume was done in conjunction with the areas.

Initially, idealized no-inlet contour lines were constructed on a 1.2cm by 1.2cm square

grid. As explained in Section 2.3.1, no-inlet contour lines indicate the assumed

bathymetry of the location behind the inlet if no inlet were to have existed. For many of

16
the inlets where the no-inlet bottom appeared to be relatively flat, it was feasible to

assume an average no-inlet depth over the entire flood delta area. Figure 2.7 shows a

model of the flood deltas. The right-hand inlet section gives an example of the case where

it is possible to use the uniform bottom assumption, while the left-hand inlet model

shows a sloping bottom for which actual no-inlet contours would have to be constructed.

e in bay topography No slope in bay topography

Figure 2.7 Two models of the flood tidal delta, one with flat bottom topography (right)
and the other with sloped bottom topography (left).

An error can occur when the uniform bottom estimation method is used. The case

of Caesar Creek is used to illustrate this error. The delta at the inlet was initially

contoured assuming a flat bottom. The plot of the error between the total delta volume

calculated using different flat bottom depths and the volume obtained by using the actual

no-inlet contours is shown in Figure 2.8. The uniform depths were at 0.9, 1.2, 1.4, 1.5,

1.7, and 1.8m. It is seen that the correct uniform depth contour was 1.16m. This figure

gives an indication of the likely error induced when selecting a uniform no-inlet contour.

Thus, it is evident that an accurate assessment of the uniform no-inlet contour is a

necessary step in the calculation of delta volume.

17

60

50

40

30

20

2
10

0 0 0.80 1.00 1.20 1.40 1.60 1.80 2.)0

-10

-20

-30
Selected Uniform Depth Contour (m)

Figure 2.8 Error in total volume calculation for Ceasar Creek using various uniform depth
contours.

An additional error can arise between the areas from the nautical charts and those

from the photographs. In the photographs if sediment was not visible that particular area

was not included as part of the delta area. Gaps of sediment visibility in the delta often

exist in the photographs since the sediment usually does not have a consistent depth. In

the nautical chart, however, no such gaps exist since the depths are found for the entire

delta. Thus, in the nautical charts the delta area is always noticeable. Hence, this error

was minimal in most cases, since the entire flood delta could be seen.

Figure 2.9 Example of method of volume calculation for Redfish Pass. All depths are
reported in feet.

In the calculation of the volume of the flood delta the no-inlet contours were

placed over existing contour lines and the differences in depths at each grid intersection

were calculated, interpolating when necessary. An example is shown in Figure 2.9.

These four depths per square grid box were averaged, thus producing an average

sediment accumulation depth over the individual grid box. Depths were calculated in this

manner over the entire flood delta area. The total volume was then determined by

multiplying the averaged grid block depth by the area of that block and summing the

volumes of all of the grid blocks. As defined in Section 2.3.1, determinations of the delta

volume, like the area computations, were separated into the "near-field" and the "far-

field" components. The sum of these two components yielded the total delta volume.

CHAPTER 3
FLORIDA'S INLETS

3.1 Introduction

The following is a collection of historical information on Florida's tidal inlets.

Figure 3.1 shows the locations of the inlets examined.

/ --- -I.-- -- -St Marys nilet
SNassau Sound
S\ I I ~\ -Ft. George Inlet
--St Johns Inlet
--=,=o,,nle

East Pass- Destin -' I Augustne Inlet
Pensacola Pass Philips Inlet/ Matanzas Inlet

St. Andrew Bay East Entran ;\
Mexico Beach Inet
St Joseph Bay Entance \\ East Paw Ponce de Leon Inlet
SSikes Cut --
WIstPass '
Andote Pass1
Andate Pass South
Hu rricaneP \ I Port Canaveral Inlet
Cleawater Pass
Johns Pras^s I
ms..... Seasken Inlet
Pass-A-Grlle Int - Sebastian nlet
Bunces Parss
Egmont Inl-et '''- - Ft- - FI. Pierce Inlet
Southwest Channed
Passage Key Inlet ISt. Lucie Inlet
Longboat Pass ~ --~
BigSar S aJupi er Inlet
Vespi Inlet- O Lake th Inlet
Gaspla Pass south Lake Worlh hIlet
Boca Grande Inlet------ I ,-
Captive Pas t- Boca Raton Inlet
SindPass- -t -___ ---~ isboro Inlet
Matanzas Pass -.Part Everglades Entrance
BigCarlosPass -----
New Pass -.Bakers Haulover Inlet
Big Hickory Pass - Government Cut
Wg-insPass ///
Clam PsI Noris Cut
Doctors Pass Bear Cut
Ut 'G Poass Sand* Cut
adrrS s a Ceasar Creek
Big aro Pas Rhodes Channel
CesambPs
B I road Creek
lish Creek
F,-;-i -^ Snake Creek
Key VacaCut

Figure 3.1 Florida's tidal inlets where deltas have been examined.

20
3.2 St. Marys Inlet

St. Marys Inlet is located in the northeast of Florida in Nassau County on the

border between Florida and Georgia, and connects the Atlantic Ocean with Cumberland

Sound. The inlet has remained navigable throughout its recorded history.

Prior to the stabilization of the channel by the construction of jetties in 1927, St.

Marys Inlet was fronted on its seaward side by a very large bar formation, which was cut

by two relatively stable channels. The north and south jetties are 5,840m and 3,415m in

length, respectively. There has been periodic maintenance dredging of the inlet. A

description of the history of construction projects preformed at the inlet can be found in

Hou (1974), Olsen (1977), Florida Coastal Engineers, Inc. (1976), and Parchure (1982).

3.3 Nassau Sound

Nassau Sound entrance in Nassau County, is a natural inlet that connects the

Nassau River and the Amelia River to the Atlantic Ocean. Over the past century, the

major changes have been the recession of the southern portion of Amelia Island to the

north, the accretion of Little Talbot Island to the south, and the emergence of Bird Island.

This inlet has not been altered through dredging or the construction of jetties. It is

presently 1,700m wide with variable depth. The maximum depth is 7m. There are many

tidal flats in the inlet mouth region. Further description may be found in Marino (1986).

3.4 Ft. George Inlet

Ft. George Inlet, in Duval county, has not been stabilized except by the presence

of the north jetty of the St. Johns River and the construction of a bridge across Ft. George

21
River. This inlet has a variable bathymetry due to shifting shoals. In 1934, a concrete

monolithic cap was constructed for the north jetty to resist the movement of sand through

the jetty. Most of the flood tidal delta formation occurred after this period. Much of the

coastal engineering history of Ft. George Inlet is tied to the improvements made to St.

Johns River entrance. The main channel is approximately 2m deep. For more information

the reader is referred to Kojima and Hunt (1980) and Devine and Mehta (1995).

3.5 St. Johns River Inlet

St. Johns River Inlet is a natural inlet located in Duval County. It is a federal

navigation project. In 1881, two jetties were constructed at this inlet. The north jetty was

2,900m long and the south jetty was 2,075m in length. These jetties were submerged at

the seaward end. In 1895, the jetties were lengthened to 3,360m and 3,230m,

respectively. In the early 1900s the channel was dredged to 7m. This was completed in

1910 when authorization was granted for deepening to 9m. In 1934, the north jetty was

capped with concrete and holes were plugged to make the jetty less permeable. In 1937,

the jetties were extended to 4,360m to 3,410m, respectively. In 1965 the channel was

deepened to 13m in conjunction with the Mayport Naval Air Station. The U.S. Army

Corps of Engineers maintains the channel. Over the period 1980-1985, an average of

163,800m3/yr of beach quality sand dredged for maintenance was placed on the nearby

shoreline. For more information the reader is referred to Marino (1986).

22
3.6 St. Augustine Inlet

St. Augustine Inlet, in St. Johns County, existed as a natural inlet prior to its

relocation in 1940. In that year, a new inlet was constructed approximately 600m north of

North Point. In 1941, the north jetty was constructed. By 1946, the old inlet to the south

showed signs of deterioration and shoaling. The old ebb delta had begun to move

shoreward to form Conch Island. In 1957, the south jetty was constructed, and by that

time the old inlet had almost completely closed. Accretion has occurred in all regions,

with no significant erosion until a point approximately 6.5km south of the inlet in the

vicinity of St. Augustine Beach. The entrance channel is 60m wide and 5m deep. The

north jetty is 480m and the south jetty is 1,130m.

The inlet is maintained by the Corps of Engineers and is connected to the

Intracoastal Waterway. For more information the reader is referred to Marino and Mehta

(1986).

3.7 Matanzas Inlet

Matanzas Inlet in St. Johns County is a natural inlet located approximately 21km

south of St. Augustine and 64km north of Daytona Beach. This inlet exists without

jetties. A by-pass channel 2,880m long through the marsh west of the inlet was

constructed to link the inlet with the Intracoastal Waterway in 1932. In 1964, hurricane

Dora struck the St. Johns County coastline on September 9th causing widespread erosion,

as well as the undermining of the coast and structures. This hurricane was responsible for

a breakthrough at Rattlesnake Island that caused significant changes in the area. The

breakthrough had widened to 75m by 1972. Erosion along both sides of the inlet had

23
taken place, although it was more significant at Summer Haven. The breakthrough was

closed in 1976 with the construction of a steel, sheet pile dike. A channel was dredged

through the shoal in 1977, and 1,000m of the south beach were nourished. The inlet is

approximately 290m wide with a maximum depth of 5 to 6m. For further the reader is

referred to Mehta and Sheppard (1977).

3.8 Ponce de Leon Inlet

Ponce de Leon Inlet is located on the coastline of Volusia County and lies 156km

south of Jacksonville and 92km north of Canaveral Harbor. The first dredging of inlet

channel was done in 1943, and the construction of north and south jetties was completed

in 1971, with each jetty approximately 1,200m in length. The north jetty had a 550m

weir section to produce an impoundment basin. In addition the inlet stabilization program

called for the dredging of a navigation channel through the inlet to the Intracoastal

Waterway. During the construction of the stabilization project the inlet adjusted to the

jetties in an unexpected way. The shoreline south of the inlet built out and extended far

beyond the originally expected shoreline. The shoreline grew northward to such an

extent that it covered sections of the south jetty. The area where the shoreline advanced

north of the south jetty and into the channel is termed the south shoal area. There has

been a tendency for the navigation channel to shift northward as the south shoal has

grown.

A northeast storm breached a channel through the north side shoal in 1973. This

breach was closed by dredging 1974. In 1984, the north jetty weir section was closed.

The inlet is 490m wide at the jetty entrance and as narrow as 300m inside the inlet shoals.

24
The channel is 5m deep and 60m wide. For more information the reader is directed to

Bruun (1991), Wang et al. (1996), Marino (1986) and Jones and Mehta (1978).

3.9 Port Canaveral Inlet

Port Canaveral is an artificial inlet located in Brevard County. It was cut in 1951.

Because of rapid shoaling problems and severe beach erosion, bank revetments and 350m

long jetties were constructed between 1953 and 1954. The initial project depth was 8m

and the channel width was 90-120m. In 1956, the channel was deepened to 10m in the

inner channel and 1lm in the approach channel. In 1961, the inner approach channels

were deepened to 1 m and 12m, respectively. In 1974, the approach channel was

deepened to 13m, in conjunction with construction of the Trident submarine turning

basin. Approximately 1.7 million cubic meters of dredge material was placed on the

south beach for nourishment purposes. Port Canaveral Harbor is a federal navigation

project and is maintained by U.S. Army Corps of Engineers. In 1994 the port initiated a

widening and deepening construction project, and all of the dredged material was placed

in the nearshore disposal area. More information can be found in Bruun (1991), Jones and

Mehta (1977) and Marino (1986).

3.10 Sebastian Inlet

Sebastian Inlet is an artificial inlet located in Brevard County. In 1924 two local

rock jetties were constructed 183m apart on the ocean side and 122m apart on the

landward side. In 1939, a channel approximately 2m deep was dredged from the Indian

River to within 90m deep of the ocean. The inlet was closed by a northeast storm in 1941

25
or 1942. In 1947 a channel 2.4m deep by 3.0m wide at the ocean was opened. In 1948

the inlet closed in February because dredge spoil had been placed on the banks of the

channel. The inlet was opened in 1948 on a new northeast/southwest alignment; this

alignment is its current state. In 1952, a new rubble-mound north jetty was completed. In

1962, a sand trap was dredged 760m west of the inlet throat. The jetties were extended

between 1968 and 1970. The inlet is maintenance dredged. Further information can be

found in Bruun (1991), Mehta, et al. (1976a), Stauble et al. (1988) and Monroe (1987).

3.11 Ft. Pierce Inlet

Ft. Pierce Inlet located in St. Lucie County was constructed in 1921. The channel

was 30m wide and lm deep. Tidal currents quickly scoured the channel to 4m in depth.

Jetties were constructed, 120m long and 180m apart. Due to storm damage at the inlet,

the jetties had to be reconstructed 275m apart in 1926. They were 550m and 360m long

on the north and south sides, respectively. In 1938, the inlet channel was dredged to 8m.

Regular maintenance dredging is necessary to maintain project dimensions. The current

project depth is 8.2m. Fort Pierce Inlet has been a federal navigation project since 1935.

For more information the reader is directed to Marino (1986).

3.12 St. Lucie Inlet

St. Lucie is an artificial inlet in Martin County that was cut through the barrier

island in 1892, thus connecting the Indian River and the Atlantic Ocean. At that time the

dimensions were 9m width and 2m depth. The inlet continued to widen through natural

means to a width of 520m by 1898. By 1922, it had widened to 800m. The shoreline had

26
moved westward approximately 600m from 1892 to 1926, on both sides of the inlet. The

north jetty was constructed between 1926 and 1929 and was 1,014m long. In 1962, a

severe storm caused a breakthrough in the barrier beach at Peck Lake, about 6km south of

the inlet. The breakthrough had widened to 215m with a depth of 4m within a year and

St. Lucie Inlet began to shoal. In 1965, emergency dredging restored the St. Lucie

channel to a 2m depth. In 1982, new jetty construction was undertaken. A 275m "dog-

leg" extension was added to the north jetty and the natural weir section was closed. A

150m long detached breakwater was constructed near the center of the inlet. A south

jetty, 450m in length, was also constructed. St. Lucie Inlet is a federally maintained

navigation project with authorized channel dimensions 1.8m deep by 30.5m wide.

The inlet has resulted in severe erosion to the north beaches of Jupiter Island. For

many years, this erosion was the most rapid in the state. Until approximately 1980 the

sand drifting through and depositing inside the porous south jetty appeared to be equal to

the net longshore sediment transport. Since 1980, erosion has been acute north of the

north jetty. Further information can be found in Dean and O'Brien (1987a).

3.13 Jupiter Inlet

Jupiter Inlet is a natural inlet in northern Palm Beach County. The inlet connects

the Loxahatchee River and the southern portion of the Indian River Lagoon system to the

Atlantic Ocean. Rock jetties were constructed in 1922 that were 120m long and 100m

apart. In 1929, the jetties were extended to 60m and 25m, respectively. In 1941, a 2m

deep channel, 18m wide was dredged close to the south jetty. The inlet closed in 1942

and was reopened in 1947. It is likely that the construction of St. Lucie and Lake Worth

27
Inlets and other waterways in the area caused a reduction of the flow through Jupiter Inlet

and its long-term stability was most likely reduced. Jupiter Inlet District records indicate

that maintenance dredging has been performed since the early 1940's. Between 1952 and

1964, approximately 368,100m3 of material were dredged from the inlet and placed on

the beach south of the inlet. Since 1966, all maintenance dredging has taken place in a

sand trap area landward of the jetties. The flood tidal delta is elongated, extending into

the estuary past the U.S. 1 Highway Bridge. The channel is 60m wide, 2m deep and

requires regular maintenance dredging. More information can be acquired from Stauble

(1993) and Jones (1977).

3.14 Lake Worth Inlet

Lake Worth Inlet is located in Palm Beach County. It was cut in 1917, where a

natural inlet was believed to have existed until the early to mid-1800's. The inlet was cut

through the narrow barrier island between Singer and Palm Beach Islands and connected

the northern part of a former fresh water Lake Worth with the Atlantic Ocean.

The inlet was stabilized with bulkheads and jetties between 1918 and 1925. The

north jetty traps southward-moving longshore sand transport and has created an updrift-

offset. The north portion of the flood shoal extends between Peanut Island and Singer

Island. Peanut Island is made up of dredged material disposal and flood tidal shoal. The

southern portion of the flood shoal has, for the most part, been dredged to accommodate

the turning basin for the Port of Palm Beach. Since 1936, the U.S. Army Corps of

Engineers has maintained the inlet. A sand transfer plant was installed in 1958. The

reader is referred to Stauble (1993) and Marino and Mehta (1986) for more information.

3.15 South Lake Worth Inlet

South Lake Worth Inlet, also called Boynton Inlet, is an artificial cut located in

Palm Beach County near the town of Boynton Beach. Two jetties and concrete-capped

sheet pile revetments were constructed in 1927; and jetties were rebuilt in 1936. A sand

transfer pant was installed in 1937. The old plant was replaced in 1948 with a capacity of

56 m3/hr. The jetties were extended seaward in 1967. The poorly defined flood tidal delta

consists of a dredge material island and some shoals at the landward end of the jetties.

An interior sand trap at the landward end of the south jetty has been dredged in the past

and sand has been placed on the south side of the inlet to mitigate erosion. More

information on the inlet can be found in Bruun (1991), Jones and Mehta (1977) and

Stauble (1993).

3.16 Boca Raton Inlet

This inlet, located in Palm Beach County, originally used to open only after heavy

rainfalls. It was very shallow and only marginally navigable by small craft. Two jetties

were constructed in 1930 that oriented the channel in an east-west direction. Since 1972,

the inlet has been maintained with a hydraulic pipeline dredge. The dredge maintains a

channel at 1.8m and disposes the dredged material on the beach south of the south jetty.

The north jetty was extended 55m seaward and south jetty was reinforced in 1975. In

1980 a weir section was installed in the north jetty to allow sand to flow over the jetty

and impound on the northern edge of the inlet throat. Photographs indicate that the flood

shoal has been reduced by dredging to maintain navigation. The inlet connects Lake

29
Boca Raton with the Atlantic Ocean. More information can be found in Marino and

Mehta (1986).

3.17 Hillsboro Inlet

Hillsboro Inlet, located in Broward County, is a natural inlet that connects the

Atlantic Ocean to the Intracoastal Waterway. It lies 8km south of Boca Raton Inlet and

approximately 56km north of Miami. The inlet throat section has a northwest-southeast

orientation. The inlet has been under the jurisdiction of the Hillsboro Inlet District since

1957.

The flood delta sand has deposited inside of the inlet throat on the southwest side

between the A1A Bridge and the mouth of the inlet. Most of the flood deposit has been

dredged and a sand trap is now located in this area.

The ebb shoal is asymmetric to the south of the inlet and influenced by a natural

Anastasia rock reef. The reef has an exposed length of 177m on the north side of the

inlet, dips as it crosses the navigation channel and rises once again about 183m south to

the inlet, where it is partially exposed at low water. The reef on the north side of the inlet

acts as a "sand spillway" for littoral material, which washes across the reef and settles in

a sheltered area west of it. From that impoundment area, the sand is bypassed via

hydraulic pipeline dredging and disposed to the beach south of the south jetty. The

Hillsboro Inlet Improvement and Maintenance District was established by the Florida

Legislature in 1957. The reader is referred to Bruun (1991), Jones (1977), Marino (1986)

and Coastal Engineering Laboratory (1958b) for more information.

30
3.18 Port Everglades Entrance

Port Everglades, located in Broward County, is an artificial inlet, which was cut

through the barrier island in 1926-1928 to connect Lake Mabel to the Atlantic Ocean.

Local interests initiated the construction of Port Everglades Harbor. Jetties were also

constructed at this time. Two long converging submerged breakwaters are located at 3m

to 4.5m below mlw outside of the jetties.

The project depth in 1993 was 13.7m. No flood tidal delta exists due to dredging

operations in the port turning basin and the limited amount of sand that enters the inlet.

The entrance channel was dredged seaward some 1,500m over the first and second reef.

The dredged channel, jetties, submerged breakwaters and a dredge material disposal

shoal have created an almost complete blockage of littoral drift. The reader is referred to

Stauble (1993) for other information on this inlet.

3.19 Bakers Haulover Inlet

Bakers Haulover Inlet, in Dade County, was cut in 1925 to improve water quality

of the northern end of Biscayne Bay. The inlet is located about 15km north of Miami

Harbor and 23km south of Port Everglades Harbor. The jetties were also constructed at

this time. In 1926, a storm almost completely destroyed the inlet and adjacent seawalls.

Jetties were reconstructed and spaced 100m apart in that same year. In 1928, a steel

sheet-pile bulkhead was driven parallel to the shore northward from the inlet for a

distance of about 210m and southward for a distance of about 225m with an additional

30m wing wall. In 1963, the north jetty was reconstructed as a rubble mound structure

and a revetment was added. The south jetty was reconstructed and relocated in 1964.

31
The inlet was widened to 120m. A rubble mound groin was installed 60m south of the

jetty. In 1975, the south jetty was extended curving to the south and five adjustable

groins were installed along the south beach. The north jetty was extended seaward 85m

with an additional 30m "dog-leg" extension to the north at the seaward end in 1986. The

south jetty was extended in 1975 and the north jetty was extended in 1986. The inlet

throat section is around 284m long and 137m wide and has seawalls on both sides

between the bay and the ocean. There are sand fillets on both the north and south sides of

the inlet with a slight downdrift offset, due to the longer south jetty. The reader is referred

to Marino (1986) Harlem (1979), and Coastal Engineering Laboratory (1958a) for more

information on this inlet.

3.20 Government Cut

Also called Miami Harbor Entrance, this artificial inlet, located in Dade County,

was cut across the southern tip of Miami Beach in 1902. Fisher Island, which originally

was the 800m southern spit of Miami Beach, was separated by the cut. The original work

consisted of a land cut 6m deep across the Miami Beach peninsula and a north jetty. The

project was modified, in 1907 and 1912, to include a south jetty, extension of both jetties,

and a 6m by 90m channel from Biscayne Bay to the Atlantic Ocean. In 1925, the channel

was deepened to 8m. In 1935, the channel was again deepened and widened to 12m and

150m, respectively. The north jetty is 900m long, while the south jetty is 600m in length.

Due to the large number of fill islands and dredged channels in Biscayne Bay, there is no

definable flood delta. A dredged navigation channel extends between the jetties then

turns to a more northeasterly direction. The channel between the islands is completely

32
revetted with a length of 1,260m and a width of 300m. The U.S. Army Corps of

Engineers performs maintenance on the inlet. The reader is referred to Marino (1986) and

Olsen and Associates (1989) for more information on this inlet.

3.21 Norris Cut

Norris Cut is a natural inlet between Fisher Island and Virginia Key in Dade

County. The throat area of this inlet is oriented in a northwest-southeast direction. The

area behind Virginia Key within Biscayne Bay is very shallow and may be associated

with deposition of the flood shoal. The proximity to the Port of Miami dredged

navigation channels and Government Cut has modified the northern end of the delta. The

throat section is revetted on the Fisher Island shoreline. No jetties exist at the inlet. The

length of the inlet channel between the islands is around 1,234m and the width is around

640m. Stauble (1993) provides information on this inlet.

3.22 Bear Cut

Bear Cut is oriented in a northeast-southeast direction and separates the barrier

islands of Virginia Key from Key Biscayne in Dade County. The large flood shoal is

bisected by several channels. The channel length is 1,555m and the width is 1,158m.

There are no jetties at this inlet. Seagrass beds are present along the ocean shoreline of

Key Biscayne and the inlet shoals. For information on this inlet the reader is referred to

Stauble (1993).

33
3.23 Sands Cut

Sands Cut is located on the Atlantic coast in Dade County. It separates Sands Key

from Elliott Key and connects Hawk Channel in the Atlantic Ocean to Biscayne Bay.

Limited historical information on this inlet can be found in Coastal Engineering

Laboratory (1959).

3.24 Caesar Creek

Caesar Creek is located 40km south-southeast of Miami. This inlet is in Dade

County and joins the Atlantic Ocean to Lower Biscayne Bay. It separates Elliott and

Adams Keys to the north from Old Rhodes and Totten Keys to the south. Information on

this inlet can be found in Taylor and Dean (1974) and Warzeski (1976).

3.25 Old Rhodes Channel

Old Rhodes Channel is located in Dade County. This inlet allows for tidal

exchange between Card Sound and the Atlantic Ocean. The sediments in the channel

bottom consist of carbonate sand and shell. In this channel, bedrock outcroppings

frequently penetrate thin layers of sand. The channel bottom has less vegetation than

other inlets of the area. Taylor (1971) gives more information on this inlet.

3.26 Broad Creek

Broad Creek is located in Monroe County and connects the Atlantic Ocean to

Lower Biscayne Bay. It lies in Monroe County. Taylor (1971) gives more information on

this inlet.

3.27 Angelfish Creek

Angelfish Creek is located in Monroe County. This inlet connects the Atlantic

Ocean to Card Sound in the Lower Biscayne Area. Taylor (1971) gives more information

on the inlet.

3.28 Snake Creek

Snake Creek is located in Monroe County and connects the Atlantic Ocean to the

Florida Bay. It separates Plantation Key to the southwest from Windley Key to the

northeast. Snake Creek is controlled by the Atlantic tide on the east end and the Florida

Bay tide on the west end in such a way as to cause a fast current through the inlet

channel. Further information can be found in Michel (1973) and Coastal Engineering

Laboratory (1959).

3.29 Key Vaca Cut

Key Vaca Cut is located in Monroe County. It separates Vaca Key, also known

as Marathon Key, from Fat Deer Key. This inlet is shown in Figure 3.2. More

information on Key Vaca Cut can be found in State of Florida Department of Pollution

Control (1973).

Figure 3.2 Key Vaca Cut looking towards Florida Bay.

3.30 Caxambas Pass

Prior to 1952, Caxambas Pass on the Gulf of Mexico west coast in Collier County

was stable with no significant changes occurring in the configuration. A massive seawall

was constructed in 1958-1959 adjacent to this inlet. Between 1967 and 1976, portions of

the Marco Island shoreline retreated up to 101m. In the late 1970s it was determined that

the seawall was responsible for the large scale changes in the shape and function of the

inlet. An unnaturally high-energy wave field was caused by wave amplification due to

reflection from the wall. An inlet management plan was developed in 1981 to restore the

natural inlet and the Marco Island shoreline. Dean and O'Brien (1987b) and Stephen

(1995) provide more information on the inlet.

36
3.31 Big Marco Pass

Big Marco Pass is a natural inlet located on the west coast of Florida in Collier

County. This inlet has not been dredged or modified, nor is it federally or locally

maintained. More information on Big Marco Pass can be found in Coastal Engineering

Consultants (1991), van de Kreeke (1990), Yanez (1989) and U.S. Army Corps of

Engineers (1994).

3.32 Capri Pass

Capri Pass was opened in 1967 as a result of a severe storm. Since its opening,

Big Marco Pass nearby has gradually lengthened as a result of the deposition of sediment

on the outer shoals. Capri Pass is located in Collier County and connects the Gulf of

Mexico with Johnson Bay. The reader is referred to van de Kreeke (1990) for more

information on this inlet.

3.33 Hurricane Pass

Located on the west coast of Florida in Collier County, Hurricane Pass joins the

Gulf of Mexico with Johnson Bay and separates Little Marco Island from mangrove

islands. Limited information is available on this inlet in Coastal Engineering Consultants,

Inc. (1991).

3.34 Little Marco Pass

Little Marco Pass is located on the west coast of Florida in Collier County. This

inlet has changed greatly in both morphology and location since the late 19th century.

37
There exists a flood delta associated with the older location of this inlet. The reader is

referred to Davis and Gibeaut (1990) for more information on the inlet.

3.35 Gordon Pass

Gordon Pass, which separates Naples Beach (north) from Keewaydin Island,

became a federal navigation project in 1963. It is located in Collier County. Between

1963 and 1985, dredging from the channel amounting to 841,500m3 was carried out. The

dredged material was placed on Keewaydin Island to the south. The south jetty was

constructed in 1969. Based on shoreline change history, it appears that the channel traps

more than the net longshore sediment transport. The reader is referred to Dean and

O'Brien (1987b) for more information on this inlet.

3.36 Doctors Pass

Doctors Pass is located on the west coast in Collier County. This inlet was

dredged twice in the 1960s. In the years since 1960, the tidal prism increased. In the late

1960s rock was removed from the channel. During 1959-1960 the inlet was straightened

and jetties were constructed. In 1984 the inlet was dredged to remove its shoals and

9,950m3 of dredged material were deposited offshore. The reader is referred to Dean and

O'Brien (1987b) for more information on this inlet.

3.37 Clam Pass

Clam Pass is located on the west coast of Florida in Collier County. Between

1954 and 1970 this inlet migrated almost 183m to the north. It closed naturally in 1976

38
and in 1981. Each time the channel was re-opened by a dragline. The dredged sand was

placed on the south beach. Clam Pass is a very small, shallow natural pass which is not

federally or locally maintained. The reader is referred to Dean and O'Brien (1987b) for

more information on this inlet.

3.38 Wiggins Pass

Prior to 1952 Wiggins Pass, located on the west coast in Collier County,

experienced frequent closures and was not navigable throughout most of the year. In

1952, changes in channels connecting the inlet increased the tidal prism by 50 percent;

this increase caused the throat area to increase and closures were eliminated. The tidal

prism further increased in the period 1960 to 1970. In 1983, 36,700m3 of material were

dredged and placed on the beach of the adjacent state park. At the time of this dredging

the channel was 61m wide by 2.4m deep. Wiggins Pass is not maintained federally or

locally. The reader is referred to Dean and O'Brien (1987b) for more information on this

inlet.

3.39 Big Hickory Pass

Big Hickory Pass, located in Lee County, separates Little Hickory Island from

Big Hickory Island and connects Estero Bay to the Gulf of Mexico. Between 1953 and

1958, the location of the inlet remained relatively unchanged. During the late 1960s Big

Hickory Pass developed an updrift-offset as sediment was built up on the south side of

the pass. In the 1970s the shoaling in this inlet increased. It first closed in 1976 and

reopened in that same year two months later, only to re-close in 1979. This inlet is not

39
maintained federally or locally. The reader is referred to Dean and O'Brien (1987b) and

Jones (1980) for more information on the inlet.

3.40 New Pass

From 1963 to 1965, construction of a causeway between Fort Myers and Bonita

Beach caused closure of several small inlets between Big Carlos Pass and New Pass that

caused the tidal prisms of the latter two inlets to increase. New Pass, located on the west

coast in Lee County is not federally maintained. The reader is referred to Dean and

O'Brien (1987b) and Jones (1980) for more information on this inlet.

3.41 Big Carlos Pass

Big Carlos Pass, located in Lee County on the west coast of Florida, has remained

largely unchanged during the past century. There has been no dredging of the channel or

construction of jetties at this inlet. The tidal prism increased when several small inlets to

the south were closed by construction of a causeway between Fort Myers and Bonita

Beach. Big Carlos Pass is not federally or locally maintained. The reader is referred to

Dean and O'Brien (1987b) and Jones (1980) for more information on this inlet.

3.42 Matanzas Pass

Matanzas Pass is located in Lee County near San Carlos Inlet. It connects San

Carlos Bay and the Gulf of Mexico to Estero Bay and is located between Estero Island

and San Carlos Island. The U.S. Army Corps of Engineers placed over 586,800m3 of

40
material on Estero Island between 1962 and 1987. The reader is referred to Hine (1987)

for more information on this inlet.

3.43 San Carlos Inlet

San Carlos Inlet is located in southern Lee County and serves as the entrance to

San Carlos Bay. It separates Sanibel Island (north) from Ft. Meyer's Beach (south). The

reader is referred to Dean and O'Brien (1987b) for more information on this inlet.

3.44 Blind Pass

Blind Pass, located in Lee County, separates Captiva Island to the north from

Sanibel Island. The pass is not federally or locally maintained. Between 1859 and 1961

a spit from the south end of Captiva Island became attached to Sanibel Island at least

three times. During these times the entire inlet migrated to the south. A new channel was

opened by a storm that breached the spit near the original location of the inlet. The spit

formed again and once again became attached to Sanibel Island. The inlet was opened by

Hurricane Agnes in 1972, and a small terminal structure was constructed on the north

side by the Department of Transportation to protect a bridge abutment. The reader is

referred to Dean and O'Brien (1987b) for more information on this inlet.

3.45 Redfish Pass

Redfish Pass separates North Captiva Island from Captiva Island in Lee County.

This inlet was formed by a severe hurricane in 1926. This pass has not been altered with

the exception of some limestone rip-rap that has been placed at north end of Captiva

41
Island. The pass is not maintained federally or locally. The reader is referred to Dean and

O'Brien (1987b) and Coastal Planning and Engineering, Inc. (1992) for more information

on this inlet.

Figure 3.3 Redfish Pass in Lee County on the west coast. The flood delta "open hand"
shape can easily be seen in this aerial photograph. Scale: 1cm = 370m.

3.46 Captiva Pass

Captiva Pass, located in Lee County, separates Cayo Costa from North Captiva

Island and is not federally or locally maintained. This is a natural inlet with no structures,

and has not been modified for navigational purposes. The reader is referred to Dean and

O'Brien (1987b) and Coastal Engineering Consultants, Inc. (1991) for more information

on this inlet.

42
3.47 Boca Grande Inlet

Boca Grande Inlet, located on the west coast in Charlotte County, separates

Gasparilla Island from Cayo Costa. Until 1912, this inlet was a stable, natural channel

with a depth of 5.8m. In 1924, the channel was dredged to 7.3m. In 1927, the channel

was dredged to 8.2m, and in 1937 it was dredged to 9.1m. Currently it is a federal

project. The modifications of Boca Grande Inlet have placed erosional stresses on

Gasparilla Island to the North. From 1930 to 1970 the southwest tip of Gasparilla Island

eroded more than 457m. Two small terminal structures, which were constructed at the

south end of Gasparilla Island in early 1970s, have been effective in reducing erosion to

the north. The reader is referred to Dean and O'Brien (1987b) for more information on

this inlet.

3.48 Gasparilla Pass

Gasparilla Pass is located in Charlotte County on Florida's west coast. There has

not been any dredging or modification of this inlet. No significant erosion has been

recorded updrift or downdrift of the pass. The reader is referred to Hine (1987) and Dean

and O'Brien (1987b) for more information on this inlet.

3.49 Stump Pass

Stump Pass, located in Sarasota County, separates Manasota Key (north) from

Knight Island (south). It was a natural inlet until 1980, when it was dredged to provide a

channel 45.7m by 3.0m deep. Stump Pass is not a federal navigation project. Port

Charlotte State Park, to the north of the inlet, has eroded and sand placed on beach tends

43
to be drawn back into the inlet. The reader is referred to Dean and O'Brien (1987b) for

more information on this inlet.

3.50 Venice Inlet

Venice Inlet, located in Sarasota County, is a natural inlet whose origin predates

available maps and was originally known as Casey's Pass. This inlet separates Casey Key

(north) from Manasota Key to the south. Between 1937-1938, the U.S. Army Corps of

Engineers constructed twin jetties and dredged the channel. In the 1960's groins were

constructed on Manasota Key to halt downdrift erosion. In 1962-1968 the Intracoastal

Waterway was dredged and 600,000m3 were dredged and placed on adjacent beaches.

About 90% of this dredged material was placed on Casey Key. In 1964, 16,800m3 were

dredged from the channel and 90% placed on Venice Beach. In 1971 the channel was

once again dredged but the volumes were negligible. In 1983, the jetties were repaired.

The U.S. Army Corps of Engineers performs the maintenance dredging. Venice Inlet has

caused severe erosion to the beaches to the south. The reader is referred to Dean and

O'Brien (1987b) for more information on this inlet.

3.51 Big Sarasota Pass

Big Sarasota Pass in Sarasota County separates Lido Key to the north from Siesta

Key to the south. This inlet can be traced back more than 3,000 years before present and

is believed to have its origin during the birth of the west-central barrier island chain. The

prevailing direction of sand transport southward has caused a large shoal to grow from

Lido Key toward Siesta Key. This shoal has resulted in a deep channel adjacent to the

44
north end of Siesta Key as well as an erosional tendency in that same location. There has

been no dredging of Big Sarasota Pass to date, and neither federal nor local agencies

maintain the pass. Between 1940 and 1960, a majority of the southern shoreline had been

hardened by concrete seawall and limestone rip rap. The reader is referred to Dean and

O'Brien (1987b) for more information on this inlet.

3.52 New Pass

New Pass, located in Sarasota County, was opened by a hurricane in 1848, and

currently separates Longboat Key (north) and Lido Key (south). In 1926 the channel was

dredged to a width of 75m and depth of 6.7m to fill in Cerol Isle, thus artificially closing

at least two secondary channels between Big Sarasota Pass and New Pass to form Lido

Key. In 1964, 95,000m3 of dredged material were taken from the channel and placed on

north Lido Beach. In 1970, a rock anchor groin was constructed on the north channel

bank to protect property. In 1974, 188,000m3 of material were dredged from the channel

and placed on central Lido Beach. In 1977, 306,000m3 of material were dredged from the

channel and placed on central Lido Beach. The channel was again dredged in 1982 and

142,000m3 of material were placed on Lido Beach and Longboat Key. In 1982, the U.S.

Army Corps of Engineers relocated the channel to the south, which resulted in severe

erosion of the southern channel shoreline. A revetment was constructed to stabilize the

channel shoreline and protect property. In 1985, 183,000m3 of material were dredged

from the channel. In 1990-1991, 248,000m3 of material were dredged. Again in 1997 the

channel was dredged. The reader is referred to Dean and O'Brien (1987b) and Davis and

Gibeaut (1990) for more information on this inlet.

3.53 Longboat Pass

Longboat Pass in Manatee County separates Anna Maria Island to the north from

Longboat Key to the south. Surveys since 1876 show many changes in the location of

this inlet and the two adjacent islands. The channel was dredged in 1951. In 1958 a

bridge spanning the inlet and the north jetty were constructed. Longboat Pass became a

federal navigation project in 1977. The area immediately south of the inlet was badly

eroded in the mid 1970's. However, beach nourishment projects were able to alleviate

the erosion in the immediate vicinity of the pass (Whitney Beach), but severe erosion

persists farther south. In 1977, 232,000m3 of material were dredged from the channel

mouth to the Intracoastal Waterway and placed on the north end of Longboat Key and the

south end of Anna Maria Island. In 1982 the channel was dredged again and 153,000m3

of material were placed on adjacent islands. In 1985, 130,000m3 of dredged material were

placed on Anna Maria Island. In 1990, 153,000m3 were dredged from the channel. In

1996 the channel was again. The U.S. Army Corps of Engineers maintains the

maintenance dredging operation at this inlet. The rate of material deposition into the inlet

is estimated at 33,000m3 per year. The reader is referred to Dean and O'Brien (1987b)

and Davis and Gibeaut (1990) for more information on this inlet.

3.54 Passage Key Inlet

Passage Key Inlet, located in Manatee County, predates available maps. This

inlet has never been dredged and is not maintained by any level of government. The

reader is referred to Dean and O'Brien (1987b) for more information on this inlet.

3.55 Southwest Channel

Southwest channel is located in Manatee County. Available surveys showing this

inlet date from 1877. It is not maintained. The reader is referred to Davis and Gibeaut

(1990) for more information on this inlet.

3.56 Egmont Channel

Available surveys of Egmont Channel, located in Manatee County, date from

1877. This inlet connects Tampa Bay to the Gulf of Mexico. It is the main shipping

channel for the Tampa Bay area and is part of a federal navigation project. The U.S.

Army Corps of Engineers maintains the channel. The channel has been dredged since

1951. All dredged material has been placed in the Gulf of Mexico. The reader is referred

to Davis and Gibeaut (1990) for more information on this inlet.

3.57 Bunces Pass

Bunces Pass is one of two entrances to Pass-A-Grille. Shell Key separates the two

entrances. Bunces Pass, located in Manatee County, is the entrance towards the south.

Between 1926 and 1948, Shell Key migrated 548.6m northward. There is no federal

maintenance at this time of this inlet. The reader is referred to Dean and O'Brien (1987b)

for more information on this inlet.

47
3.58 Pass-A-Grille

Pass-a-Grille Inlet has its origin before 1873. It is located to the south of Shell

Key in Pinellas County. The jetty, which was built on the south tip of Long Key in 1959,

was extended in 1962. In 1960, 122,000m3 of material were dredged from channel and

placed offshore. Passage Key Inlet became a federal navigation project in 1964. In 1975,

the channel was sealed off by shoaling at North Bunces Key. In 1982 North Bunces Key

was breached and overwashed significantly during winter frontal systems and Pass-A-

Grille Channel reopened. This inlet is not maintained by any level of government. The

reader is referred to Davis (1995) and Dean and O'Brien (1987b) for more information on

this inlet.

3.59 Blind Pass

The origin of Blind Pass located in Pinellas County predates available maps. It is

not a federal navigation project, but has been designated as a borrow area for beach

nourishment projects. Figure 3.4 shows Blind Pass looking toward the Gulf of Mexico.

The flood delta can be seen in the photograph as a change in color of water. The

photograph was taken at low tide.

48

Chmsange In a
Iodica Bes

Figure 3.4 Blind Pass in Pinellas County looking toward the Gulf of Mexico.

Between 1969 and 1991, 707,000m3 of material were dredged from Blind Pass, which

connects Boca Ciega Bay to the Gulf. In 1937 a low jetty was built on the north side. In

1962 a jetty was built on the south side, and was extended in 1986. The reader is referred

to Dean and O'Brien (1987b) and Mehta, et al (1976b) for more information on this inlet.

3.60 Johns Pass

Johns Pass is located in Pinellas County on the west coast of Florida. This inlet

connects the Gulf of Mexico to Boca Ciega Bay and separates Sunshine Beach from

Madeira Beach. It was formed by a severe hurricane in 1848. Johns Pass became a

federal navigation project in 1964. The north jetty is 140m long and was built in 1962.

The south bank was revetted over the length of 280m in 1966.

Figure 3.5 Johns Pass in Pinellas County looking toward Boca Ciega Bay.

Changes in Blind Pass have affected the flow area, tidal prism and sedimentary regime of

Johns Pass. The reader is referred to O'Brien et al. (1975) and Mehta, et al. (1976b) for

more information on this inlet.

3.61 Clearwater Pass

Clearwater Pass, located in Pinellas County, became a federal navigation project

in 1960, but was de-authorized in 1983. From 1950 to 1985, 980,000m3 of channel-

dredged was placed on the adjacent Sand Key and Clearwater beaches. The supply of

sediment to the flood delta has been reduced by the 1975 construction of a south jetty.

The reader is referred to Ross and Dorzbak (1986), Newman (1983) and Davis and

Gibeaut (1990) for more information on this inlet.

r..l
I ~;~~~~ w, i~7.

50
3.62 Willy's Cut

Willy's Cut, located in Pinellas County, was opened by Hurricane Elena in 1985.

The inlet appears to be slowly increasing in size. The inlet is not currently maintained.

More information on this inlet can be found in Davis and Gibeaut (1990).

3.63 Hurricane Pass

This inlet in Pinellas County was formed by a 1921 hurricane, which breached

Hog Island. The flood delta is lobate in shape and has remained essentially unchanged

since formation. The inlet widened after formation until the mid 1960's, when a

causeway constructed between Honeymoon Island and the mainland reduced the tidal

prism and caused the inlet to decrease in width. Hurricane Pass has remained relatively

stable since that time. There is some indication of narrowing of the inlet caused by the

development of Willy's cut immediately to the south. There has been little historical

change to the overall morphology of this inlet. It is not maintained federally or locally.

Honeymoon Island, which lies updrift to the north of the inlet, is a state park and the

south end of this island is eroding. In 1969, 1.14 million cubic meters of material were

dredged from the ebb-tidal delta and placed on Honeymoon Island. In 1970, rip-rap was

placed on north side of channel to stabilize the southern end of Honeymoon Island. More

information can be found in Ross and Dorzbak (1986) and Davis and Gibeaut (1990).

3.64 Anclote Pass South

The origin of Anclote Pass South, located in Pinellas County, predates available

maps. In the 1960's a small navigation channel was dredged from mouth of the Anclote

51
River to the south of the channel. In 1997 the channel was on the verge of closure.

Anclote Pass South has never been dredged and is not maintained by any level of

government. The reader is referred to Barnard (1998) for more information.

3.65 Anclote Pass

Anclote Pass is located to the north of Anclote Pass South in Pinellas County.

This inlet existed before 1873. The inlet has never been dredged and is not maintained

by any level of government. The reader is referred to Barnard (1998) for more

information.

3.66 East Pass Carrabelle

East Pass is a natural inlet and a federal navigation project located in Franklin

County. From 1905 to 1963, 765,000m3 of dredged material from the inlet were

deposited offshore. The reader is referred to Dean and O'Brien (1987b) for more

information on this inlet.

3.67 Sikes Cut

This inlet, located in Franklin County, was opened through St. George Island in

1954. In 1956 two jetties were constructed. The east jetty was 259m long and the west

jetty was 305m long, extending into the Gulf of Mexico. The U.S. Army Corps of

Engineers dredges Sikes Cut and places dredged material both in the Apalachicola Bay

and in the Gulf of Mexico and on the beach west of the inlet. Zeh (1980) gives an

extended history of this inlet.

3.68 West Pass

West Pass is located in Franklin County on the Gulf coast of Florida. Maintenance

at this inlet was discontinued when Sikes Cut became the main navigation channel in this

area. Between 1900 and 1948, 356,500m3 of material were dredged from this inlet and

disposed offshore. The reader is referred to Dean and O'Brien (1987b) for more

information on this inlet.

3.69 St. Joseph Bay

St. Joseph Bay, located in Bay County, is a federal navigation project authorized

for a 91m to 152m wide and 10.7m to 11.3m deep channel, from St. Joseph Bay to the

Gulf of Mexico with an additional silting basin. A portion of the present channel runs

very close to the St. Joe Spit. This inlet is natural and is an area of considerable shoaling.

Dredging and removal of the material inside the inlet is believed to have increased

erosion on St. Joe Spit. The reader is referred to Dean and O'Brien (1987b) for more

information on this inlet.

3.70 Mexico Beach

Mexico Beach Inlet is a small inlet lying approximately 50km southeast of

Panama City in Bay County. The inlet at one time was a small creek that occasionally

discharged into the Gulf of Mexico. It was stabilized with short jetties when the interior

lowland was developed into a canal system. The west jetty was constructed to be 45.7m

long, and the east jetty to be 39.6m long. The west jetty extends 30.5m farther offshore

53
than the east jetty. Sand transfer has been required to keep the channel navigable by small

craft. From 1972 to 1975, a dragline was used to maintain the channel open. The dredged

material was placed on the west side of the inlet. Mexico Beach Inlet was a site where the

U.S. Army Corps of Engineers Waterways Experiment Station (in Vicksburg,

Mississippi) tested a jet pump during 1973-1974. The jet pump installation was of the

truck-mounted type, and bypassed approximately 15,300m3 over several months during

this period. The city of Mexico Beach soon thereafter began constructing a fixed jet

pump system at the inlet. In 1987 a small floating dredge was used for bypassing. The

reader is referred to Bruun (1991), Jones (1977) and Dean and O'Brien (1987b) for more

information on this inlet.

3.71 St. Andrew Bay East

St. Andrews Bay East Inlet, located in Bay County, is a natural inlet which

connects the Gulf of Mexico to St. Andrews Bay. From 1911 to 1934 the total dredged

volume of material from the channel was 4.7x106m3. Maintenance dredging by the U.S.

Army Corps of Engineers was discontinued in 1934. The reader is referred to Dean and

O'Brien (1987b) for more information on this inlet.

3.72 Panama City Channel

Panama City Channel located in Bay County was dredged in 1934. Two jetties

were constructed in 1934. This entrance has caused erosion of the downdrift (west)

shoreline. Starting in 1972, some of the maintenance dredged material has been placed

on the downdrift shoreline. In the period 1976-1986, 97,920m3/yr were dredged and all

54
material was placed on the beach. The available information suggests that the jetties at

this entrance may be quite permeable allowing sand to enter the channel at rates greater

than the net longshore sediment transport. The reader is referred to Dean and O'Brien

(1987b) for more information on this inlet.

3.73 Phillips Inlet

Phillips Inlet is a small inlet located in Bay County that connects Lake Powell to

the Gulf of Mexico. It is located approximately 32km to the north of Panama City.

During periods of high sedimentation deposition a bar builds up at the entrance and

blocks the tidal flow. In times of high rainfall, lake overflow reopens the channel and

allows tidal flow to enter. The reader is referred to Lin (1988) for more information on

this inlet.

3.74 East Pass-Destin

East Pass is a natural inlet located in Okaloosa County that provides an entrance

to the Gulf of Mexico from Choctawatchee Bay. The inlet was formed in 1928 and 1929

during a severe storm when there was a breach through the eastern end of Santa Rosa

Island. Another inlet that existed about 2.4km east of the present-day East Pass gradually

shoaled, and finally closed during 1983. The improvement of the inlet was authorized by

the U.S. Congress in 1965 and was completed in 1969. East Pass was stabilized with two

jetties, one of which contained a low, weir section with an adjacent deposition basin.

This weir jetty was constructed on the west side of the inlet, because it was the contention

at the time that the predominant direction of littoral transport was from west to east.

55
However, there is a clear indication that the predominant drift direction is from east to

west. The reader is referred to Dean and O'Brien (1987b), Morang (1992) and Jones

(1977) for more information on this inlet.

3.75 Pensacola Pass

Pensacola Pass is a natural entrance, located in Santa Rosa County, which became

a federal navigation project in 1881. This pass connects the Gulf of Mexico to Pensacola

Bay and is bordered by Perdido Key to the west and Santa Rosa Island to the east.

Dredging of the inlet began in 1883. Between the years 1989 and 1991 more than

9.5x106m3 of beach quality sand were dredged from the channel. This dredging work,

completed in 1991, left the channel with a depth of 14.6m and a width of 244m to

accommodate the home-port of a U.S. Navy aircraft carrier. The reader is referred to

Browder (1999) and Dean and O'Brien (1987b) for more information on this inlet.

CHAPTER 4
FLOOD DELTAS IN FLORIDA

4.1 Introduction

The determination of the flood delta volumes and areas for the considered tidal

inlets in Florida provides two avenues for analysis of the data. Firstly, the flood delta

volume and area for each inlet examined is plotted versus the tidal prism of the respective

inlet, and the results analyzed. Secondly, the time-evolution history of the delta is

examined with reference to candidate inlets.

Hayes (1975) has classified most of Florida's inlets as microtidal i.e., with a tidal

range < 2m. These have well-defined flood deltas, a good example being Redfish Pass

shown in Figure 3.3. Such deltas have the typical "bat wing" or "open hand" shape with

sediment deposit concentrated in the middle of the delta forming the "near-field" area,

and in the sediment that has "spread out" from the "near-field" area forming the "far-

field" area. The flood delta receives sand from the littoral system through the inlet

channel and deposits in the "near-field" area. This area can "fill up" and reach a non-

silting, non-scouring sedimentary equilibrium depth where subsequent growth is limited.

When this occurs the newly arriving sand spreads out to the "far-field" delta. It is

instructive to analyze patterns of delta growth and point out changes in the inlet evolution

patterns. Often, changes in the littoral environment itself can be seen in the response of

the flood delta growth pattern.

57

4.2 Tidal Prism Based Relationships

An attempt is made here to determine likely relationships between the spring tidal

prism and the various categories of areas and volumes of the flood delta deposit.

Accordingly, flood delta "near-field", "far-field" and total areas as well as "near-field",

"far-field" and total volume have been plotted versus the respective tidal prisms for

selected inlets in Figures 4.1 through 4.6. The data accompanying these plots are found in

Appendix B. For all of the inlets, the area and volume versus tidal prism plots the final

year for which data were available was selected. This value would effectively be closer to

the "equilibrium value" of deposit for the delta.

The "near-field" area of deposit versus spring tidal prism plot shown in Figure 4.1

(in log-log coordinates) exhibits a trend of increasing "near-field" area (AN) with

increasing tidal prism (P), although there is a considerable degree of data scatter.

AN = 14500P0.254
1 o0E+07

CL
E

Z I.0E+05
S 1.00E+04

100E+05 1.00E+06 I.00E+07 1.00E+0 100E+09 100E+10
Tidal Prism (m3)

Figure 4.1 "Near-field" delta area versus spring tidal prism using both east and west coast
inlet data.

58

Equation 4.1 is the trend-line equation for the Figure 4.1 data, and was determined

using the least-squares fit method of data interpolation resulting in the value of the

correlation coefficient R2 = 0.21.

AN= 14,500 P 0.254 (4.1)

In Figure 4.2 the "far-field" area of deposit (AF) is plotted against tidal prism (P).

Equation 4.2 describes the trend-line with R2 = 0.21.

AF= 34,100 P 0.244 (4.2)

1.00E+08

AF = 34100P0.244
E
1.00E+07

o *

1.00E+06

1.00E+05
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10
Tidal Prism (m3)

Figure 4.2 "Far-field" delta area versus spring tidal prism using both east and west coast
inlet data.

The total area of the deposit (AT) versus tidal prism (P) plot is shown in Figure

4.3. The trend-line of this plot is described by Equation 4.3.

AT= 47,600 P 0.249 (4.3)

The R2 value for this plot is 0.22.

59

1.00E+08

SAT= 47600P.249
11.00E+07 *

1.00E+05
Ot-

1.00E+05
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10
Tidal Prism (m3)

Figure 4.3 Total delta area versus spring tidal prism using both east and west coast inlet
data.

The "near-field" volume (VN) versus tidal prism (P) plot is shown in Figure 4.4.

The trend-line is given by Equation 4.4.

VN= 4060 P 0.314 (4.4)

The R2 value for this relation is 0.23.

1.00E+08

SVN = 40600.314
1.00E+07
0
o *

4- .
1.00E+06 *
E%* *.

S1.00E+05 *
a)
z

1.00E+04 i
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10
Tidal Prism (m3)
Figure 4.4 "Near-field" delta volume versus spring tidal prism using both east and west
coast inlet data.

60

Figure 4.5 shows the plot of "far-field" volume of deposit (VF) versus tidal prism

(P). The accompanying trend-line is shown in Equation 4.5 with R2 = 0.22

VF= 15,000 P 0.291 (4.5)

1.00E+08

VF =15000P0.291
A-

1.00E+07

*6
a)

a 1.00E+06
-6
L.

1.00E+05 I Iiiii -- ii i 111--------i
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10
Tidal Prism (m3)

Figure 4.5 "Far-field" delta volume versus spring tidal prism using both east and west
coast data.

Figure 4.6 shows the plot of total volume (VT) versus tidal prism (P).

1.00E+08

1.00E+07

1.00E+06

1 0n0nE+

1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10
Tidal Prism (m3)

Figure 4.6 Total delta volume versus spring tidal prism using both east and west c
inlet data.

The trend-line is given by Equation 4.6 with a corresponding R2 value of 0.25.

VT= 20,400 P 0.296 (4.6)

oast

St. Joseph Bay
VT= 20400P.296 o

* H.* *
- *,

Sakers Haulover

4.3 Variability in Prism Based Relationships

Figures 4.1 through 4.6 indicate that, in general, the larger the tidal prism the

larger the volume and area of deposit. However, these plots have low correlation

coefficients, which thus implies there is not a clear relationship between the tidal prism

and the delta areas and volumes independent of other factors.

An effect that may result in a low correlation is due to the initial depth of the bay

before the opening of an inlet. Thus, if an inlet began with a comparatively large initial

depth in the bay the "no-inlet" contours would be deep, and there would be a greater

available space for sediment to deposit. Two inlets indicated in Figure 4.6 have very

different total volumes of deposit but comparatively similar tidal prisms. St. Joseph Bay

entrance has a considerably larger total volume of deposit (VT = 2.35E+07m3) than

Bakers Haulover (VT = 4.39E+05m3), even though the prisms are not too different, i.e.,

P=1.9E+07m3 for St. Joseph Bay and 1.lE+07m3 for Bakers Haulover Inlet. Bakers

Haulover not only has a smaller bay area available for sediment deposition than St.

Joseph Bay as seen from Table 4.1 but, in addition, the mean no-inlet depth for St. Joseph

Bay (7.3m) is much larger than that of Bakers Haulover (2.1m).

Table 4.1 Comparison of two inlets with similar tidal prisms but different total volumes
of flood delta deposit.
Inlet Spring tidal Total volume Area available for Mean no-
prism (P) of deposit sediment deposition inlet
(m3) (m3) (Ab') (2) Depth (m)
St. Joseph Bay 1.9E+07 2.35E+07 1.5E+08 7.3
Bakers Haulover 1.1E+07 4.39E+05 9.9E+05 2.1

Thus it can be concluded that St. Joseph Bay is a larger "sink" for sediment than

Bakers Haulover.

62

In order to better examine the relationships between the flood delta volume and

area with the tidal prism, it is logical to separate the east coast data from the west coast

data. Some representative coastal physical parameters on the east and west coasts of

Florida's are given in Table 4.2 with reference to four inlets. Additional information of

this nature for the east coast and can be found in McBride (1989). When the four inlets in

Table 4.2 are compared it is seen that the east coast inlets are different from the inlets on

the west coast in these parameters, which are important in delta formation. In particular,

on the east coast the wave heights are greater than on the west coast and, as a result, the

littoral drift is also characteristically higher. This in turn may imply a different response

of the inlet channel cross-section to tidal prism on the east coast inlets than on the west

(Jarrett, 1976). Also, the corresponding rates of sand influx through the channel may be

different as well. Finally, note that while the tide along the east coast is semi-diurnal, that

on the west coast is either mixed or diurnal.

Table 4.2 Parameters for representative cases of Florida's east and west coast inlets.
East Coast West Coast
Inlet Jupiter St. Augustine Gordon Panama City
Spring tide range (m) 0.9 1.63 0.85 0.4
Wave height (m) 1.0 1.0 0.5 0.7
Net littoral drift (m'/yr) 1.79E+05 3.13E+05 5.34E+04 8.40E+04

Figure 4.7 plots the flood delta area of deposit versus tidal prism for east coast

inlets. Since there is a large degree of scatter among the data points, a trend-line equation

cannot be fit with any reasonable degree of correlation. There are a number of factors that

may cause the observed scatter and lack of correlation, as discussed later.

1.OOE+08 -

1.OOE+07

1.OOE+06 -

Figure 4.7 Total

1.00E+05 II ,
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09
Tidal Prism (m3)

delta area versus spring tidal prism using east coast inlet data.

1.00E+07
Old Rhodes Channel

E St. Marys Inlet

0)

05 1.00E+06
a)
E

0

I-

1.00E+05
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09
Tidal Prism (m3)

Figure 4.8 Total delta volume versus spring tidal prism using east coast inlet data.

As with Figure 4.7, the total volume versus tidal prism for the east coast data in

Figure 4.8 exhibit a large degree of scatter, hence it is not appropriate to fit a trend-line

equation.

*

S64

Figure 4.9 is a plot of the total area of flood delta deposit versus the

corresponding tidal prism for the west coast inlets. The trend-line for this plot is given in

Equation 4.7 with R2 = 0.31.

AT= 20,600 P 0.310 (4.7)

1.00E+08

A, = 20600Po.310

t1.00E+07

< 1.00E+06

1.00E+05
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10
Tidal Prism (m3)

Figure 4.9 Total delta area versus spring tidal prism using west coast inlet data.

1.00E+08

VT = 8350 p0.362 West Pass
E *
I 1.00E+07 *
o *o

o 1.00E+06

Big Hickory

1.00E+05
1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10
Tidal Prism (m3)

Figure 4.10 Total delta volume versus spring tidal prism using west coast inlet data.

65

Figure 4.10 gives the plot of total volume of deposit versus spring tidal prism for

the west coast inlets. The equation for the trend-line is with R2 = 0.39. It is evident that

VT= 8,350 P 0.362 (4.8)

this plot exhibits a higher correlation than the combined east and west coast total volume

versus tidal prism plot (Figure 4.6). Some reasons for the observed differences in

correlation between east and west coast inlets are examined in the following paragraphs.

4.3.1. Dredging Histories

Tables 4.3 and 4.4 give volumes of dredged material of many of Florida's inlets

from the east and west coasts, respectively (Dean and O'Brien 1987a,b). Because the

inlets have been dredged at different schedules, the column labeled "years" indicates the

period over which the corresponding volume of dredged material was removed.

Table 4.3 Volumes of dredged material from Florida's east coast inlets.
Inlet Years Volume of dredged material (m3)
St. Marys Inlet 1903-1985 9.85E+06
St. Johns Inlet 1925-1985 2.02E+07
St. Augustine Inlet 1940-1985 1.22E+06
Ponce de Leon Inlet Not given 2.75E+06
Sebastian Not given 1.37E+06
Ft. Pierce 1930-1985 2.44E+06
St. Lucie Inlet Not given 2.29E+06
Jupiter Inlet 1952-1977 8.40E+05
Lake Worth Inlet 1929-1986 3.97E+06
Boca Raton Inlet 1940-1985 8.40E+05
Hillsboro Inlet Not given 1.68E+06
Bakers Haulover Inlet 1937-1978 2.06E+06
Government Cut 1957-1982 5.65E+06

As can be seen in Tables 4.3 and 4.4, the east coast inlets have had a greater

quantity of material removed from them than the inlets on the west coast. The average

66

volume of dredged material for the east coast was 4.24E+06m3 compared to 3.1E+06m3

for the west coast. This increased dredging on the east coast indicates that the calculated

east coast flood delta may not be as accurate a representation of the sediment

accumulation inside the inlet as on the west coast, where less volume of material has been

removed. In fact, eight of the inlets on the west coast documented by Dean and O'Brien

(1987b) that are not listed in Table 4.4 have no history of dredging. These inlets are:

Gasparilla Pass, Big Sarasota Pass, Captiva Pass, Blind Pass in Lee County, Big Carlos

Pass, New Pass, Big Hickory Pass and Big Marco Pass.

Table 4.4 Volumes of dredged material from Florida's west coast inlets.
Inlet Years Volume of dredged material (m3)
Caxambas Pass 1982 2.44E+05
Gordon Pass 1963-1985 8.40E+06
Doctors Pass 1984 9.92E+03
Wiggins Pass 1983 3.66E+04
San Carlos Inlet 1980,1985 5.60E+04
Redfish Pass 1981 5.84E+05
Boca Grande Pass 1912-1984 6.72E+06
Stump Pass 1980 1.07E+05
Venice Inlet 1937-1938, 1964 7.02E+04
New Pass 1964-1985 9.11E+05
Longboat Pass 1977-1985 4.98E+05
Egmont Channel 1951-1987 1.03E+07
Pass-A-Grille Inlet 1960 1.22E+05
Blind Pass 1964-1975 5.61E+05
Johns Pass 1960-1983 3.31E+05
Clearwater Pass 1960-1985 1.22E+06
Hurricane Pass Not given 8.70E+05
East Pass Carrabelle 1905-1963 7.63E+05
Sikes Cut 1956-1986 9.76E+05
West Pass 1900-1948 3.56E+05
St. Joseph Bay Not given 9.47E+06
St. Andrews Bay East 1911-1934 4.66E+06
Panama City Channel 1976-1986 9.77E+04
East Pass Destin 1931-1984 3.36E+06
Pensacola Pass 1883-1985 2.72E+07

4.3.2 Bay Filling Capacity

A method of explaining the data spread seen in the plots of tidal prism versus

delta volume and area is to compare the "hydraulic bay area" Ab (m2) to the "effective

bay area" Ab' (m2) available for delta formation. Figure 4.11 defines the relevant

quantities with reference to two idealized inlets.

The area over which tidal prism distributes itself inside the bay can be determined

through the division of the tidal prism, P, by the tidal range inside the bay, Rb. This value,

Ab, is compared to the area of the bay where it would be possible for sediment to form an

identifiable delta.

Hydraulic Area, Ab

Effective
Area, Ab'

Effective
Area, Ab'
Sea Sea

Hydraulic Area, Ab

(a) (b)

Figure 4.11 Comparison of bays with differing effective areas but the same hydraulic
area. Bay (b) has a greater possibility of having a larger identifiable flood delta than bay
(a), since the area available for delta formation is greater in (b).

Table 4.5 gives values of Ab' and Ab for four inlets in Florida, two on the east

coast and two on the west coast. The inlets selected for examination were at opposite

ends of their respective plots; Figure 4.8 for the east coast inlets and Figure 4.10 for the

west coast inlets.

Table 4.5 Hydraulic bay area (Ab) and the effective bay area (Ab') for two east coast inlets
and two west coast inlets.
Inlet Name Coast P (m') Rb (m) Ab (m2) Ab'(m2) Ab'/Ab
St. Marys Inlet East 2.78E+8 2.11 1.30E+8 1.90E+7 0.146
Old Rhodes East 1.99E+5 0.43 4.63E+5 4.63E+5 1.00
Channel
Big Hickory West 4.30E+5 0.762 5.60E+5 5.60E+5 1.00
Pass
West Pass West 1.00E+9 0.437 2.29E+9 8.46E+7 0.037

From these data it can be seen the inlets smaller the Ab' to Ab ratio, i.e., the ratio

of effective bay area to the hydraulic bay area, the greater the area for the sediment to

form an identifiable delta, and the greater the opportunity for the volume and area of the

delta to grow. In the case where the effective area is small compared to the hydraulic

area, the delta is limited in capacity for the formation of an identifiable delta. The

sediment in an area such as Figure 4.11 (a), where the effective bay area to hydraulic bay

area ratio is smaller than in case (b), would be "pushed" down the narrower portions of

the bay due to the low effective bay area. This sediment may travel so far from the mouth

of the inlet that it would no longer be identified as the flood delta according to the

definition of the delta selected in this study.

69

Figure 4.12 shows St. Marys Inlet. As seen in Table 4.5, this inlet has a small

Ab'/Ab value, i.e., the effective area is small relative to the hydraulic area, especially

because the hydraulic area is large due to the large tidal prism. In contrast, Old Rhodes

Channel (Figure 4.13) has a larger available area of deposit relative to the hydraulic area

(which is small because of small tidal prism) and a larger Ab'/Ab value.

Figure 4.12 St. Marys Inlet. Scale: Icm = 772m.

IFigure 4.13 Old Rhos C l. S :

Figure 4.13 Old Rhodes Channel. Scale: cm = 440m.

A similar pattern can be seen in the comparison of Big Hickory Pass and West

Pass on the west coast of Florida. Big Hickory Pass has a comparatively larger available

area for delta formation, while West Pass has a small effective area relative to hydraulic

area. This effect of Ab'/Ab ratio on delta area and volume implies that the tidal prism is

not the only factor influencing the delta area and volume. Apparently, the effect of Ab'/Ab

on area and volume is more significant on the east coast than on the west coast. If so, this

would explain the poorer correlation between the delta area and volume with the prism

found on the east coast.

Figure 4.14 Big Hickory Pass. Scale: 1cm = 332m.

Figure 4.15 West Pass. Scale: Icm = 648m.

13

72

4.4 Time-Evolution of Flood Delta

The variations of volume and area of the flood delta with time can give a perspective

into the local littoral processes, or changes in the local littoral environment over time. In

other words, the flood delta behavior can serve as a surrogate for other coastal events in

the vicinity of the inlet.

Consider Sikes Cut in Franklin County (Figure 4.16) as a "typical" mode of the

flood delta growth in Florida. Figure 4.17 shows the flood delta area growth over time for

this inlet, and Figure 4.18 shows the corresponding flood delta volume growth over time.

7 M 71 2'1,' -
1 71 8 9 10 a A-r
r 990 3
SgL A C .--- -, A
8y 9 a
S10
8. a V 9 9' 3
89 10 0

/ 9 10 E Int G 6se

.0 QkFIG2 27
/ '' o "" ', -r3 '2
I % 2 3 2

Figure 4.16 Sikes Cut. Scale: 1cm = 1235m.
,o "" t,,3 13 .2 - -, 26

FItgre 4.13 2. 5t 25 26 S e 1

1.20E+07

1.00E+07

8.00E+06

6.00E+06

4.00E+06

2.00E+06

0.OOE+00
1950

1955 1960 1965 1970 1975 1980 1985 1990

Year

17 Flood d

9.00E+06

8.00E+06

7.00E+06

6.00E+06

5.00E+06

4.00E+06

3.00E+06

2.00E+06

1.00E+06

0.OOE+00
19i

elta area growth at Sikes Cut.

1955 1960 1965 1970 1975 1980 1985 1990

Year

Figure 4.18 Flood delta volume growth at Sikes Cut.

Sikes Cut has exhibited an approximately monotonic increase in both the delta

area and volume through time. Both the area and volume plots have steep slopes

Figure 4.

5-
E

o
U)
Q
a-
E
o
0

Total Volume

Far-field Volue

r-field Volume

50

74

indicating that a large amount of sediment continues to be deposited on to the flood delta

since 1954. This behavior can be expected since there is a large available space for

sediment to deposit.

St. Lucie Inlet in Figure 2.2 is an older inlet which shows the possibility that for

the delta volume may have reached an equilibrium configuration. These "typical" delta

growth plots of Sikes Cut and St. Lucie Inlet may be compared to other plots to examine

changes specific to the inlets that cause a deviation from the typical trend.

,, ". ,, A' ,,"^," ;*/, .'

"21 , '- ,, ./ '. /
,, " Gulf of Mexico iA, o fi^ /

Figure 4.19 Big Marco Pass and Capri Pass in Collier County. Scale: 1cm = 556m.

Big Marco Pass in Collier County on the west coast of Florida (Figure 4.19)

showed a rapid growth in the flood delta volume in the late 1960's and the early 1970's

(Figure 4.20). This trend is also seen in the mean depth of deposit, which also increased

rapidly during this period (Figure 4.21).

75

Capri Pass, located about 1km to the north of Big Marco, was cut by a severe

storm in 1967, and from that time began to overtake the role of Big Marco Pass as the

main navigation channel in that area. Big Marco Pass, which until then was a stable inlet

(van de Kreeke 1990), became hydraulically less efficient and its delta received

considerable sand from the littoral drift. By the mid to late 1980's Big Marco flood shoal

had seemingly adjusted to the opening of Capri Pass.

4.50E+06
Total Deposit A
4.00E+06

3.50E+06

E 3.00E+06
o Far-field
o 2.50E+06
a) Deposit
0
2.00E+06
E
: 1.50E+06
0
1.00E+06

5.00E+05 i /Capri Pass
Near-field Deposit Cut 1967
0.00E+00 i i I i I I I
1880 1900 1920 1940 1960 1980 2000
Year
Figure 4.20 Flood delta volumes versus time at Big Marco Pass.

This example is demonstrative of how patterns in the time-evolution plots of the

flood delta can be used to aid in the interpretation of changes in the adjacent shoreline

processes. In addition to its usefulness in describing past events, the delta evolution plots

are also useful in the prediction of the ways by which other deltas may react when

subjected to similar conditions. To illustrate this point, consider the example of a new

inlet that is planned near an existing main navigation channel, which needs to remain

76

open and has conditions similar to those at Big Marco Pass. Thus, in such a situation it is

useful to keep in mind the response of the flood delta at Big Marco Pass to the opening of

Capri Pass and, in addition, to make the comparison of the new case with the historical

one. It is pertinent to also consider what measures may be necessary to maintain the old

navigational inlet open and clear of sediment.

1.60

1.40

1.20

1.00

a 0.80
Z
o6 0.60

0.20
Capri Pass
,ut 1967

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
Year
Figure 4.21 Flood delta mean depth of "near-field" deposit versus time for Big Marco
Pass.
Another example of the way by which flood delta volume data illustrate processes

occurring in the region is the case study of St. Marys Inlet (Figure 4.12). From the data in

Table B.1, observe that the total volume of the flood delta as well as the total depth of

deposit, has decreased, while the area of the deposit has remained approximately the

same. This behavior can be traced to the continual dredging of this inlet (Parchure 1982).

Figure 4.22 shows the mean thickness of the flood delta over time. From this figure the

pattern of dredging can be gleaned, and the advantage of the knowledge of the growth

pattern of the flood delta is recognized.

1.8

1.6

1.4

g 1.2

1.0

0.8

0.6

0 0.4

S0.2

0.0
1965 1970 1975 1980 1985 1990 1995
Year
Figure 4.22 Time-evolution of the mean depth or thickness of sediment deposit (dT) for
St. Marys Inlet.

4.5 Delta Approach to Possible Equilibrium Configuration

St. Augustine Inlet (Table 4.6) is considered here as an example of an inlet flood

delta that appears to be reaching an equilibrium configuration. This is apparent from data

given in Table 4.6. Figure 2.2 shows that a similar condition may exist at St. Lucie Inlet.

Table 4.6 Flood delta data for St. Augustine Inlet.
Percent change VT (m3) Percent change
Year AT (m) VT (mi)
in area in volume
1940 0.00E+00 0.00E+00
1947 4.69E+05
1949 4.61E+05 -2%
1951 4.81E+05 +4%
1956 4.74E+05 -2%
1962 7.95E+05 +40%
1967 8.71E+05 +9%
1974 1.08E+06 +19% 1.35E+06____
1989 1.63E+06 +34% 1.33E+06 -1%
1992 1.35E+06 -21% 1.34E+06 +1%

78

Not all of the inlets examined show a trend toward equilibrium. In Table 4.7 the

total area and volume of the flood delta at San Carlos Inlet are given. No "equilibrium"

seems to have been achieved. It could be expected that older inlets would have had the

time to become filled with sediment and have a well-developed flood delta. Although San

Carlos is an older inlet, its flood delta continues to grow in both volume and area. Since

the age of the inlet seems to have little to do with the possibility of it reaching an

equilibrium configuration, other factors must also be examined. Some likely effects have

been reviewed previously in this chapter. Effects of sea level rise must also be

considered.

Table 4.7 Flood delta data for San Carlos Inlet
Year AT ( 2) Percent change VT (m3) Percent change
in area in volume
1975 2.42E+07 2.47E+07
1978 3.17E+07 +24% 2.45E+07 -1%
1979 3.30E+07 +4% 2.85E+07 +14%
1982 3.15E+07 -5% 2.90E+07 +2%
1986 3.40E+07 +8% 3.09E+07 +7%
1987 3.60E+07 +6% 3.55E+07 +15%

4.6 Growths of "Near-field" and "Far-field" Deposits

The flood delta grows through the supply and deposition of sediment from the

littoral system. Initially, the "near-field" delta is filled, and as this portion of the delta

"saturates" the sediment "spreads out" to the "far-field" region. The "near-field" and the

"far-field" deltas have been identified in the photograph of St. Lucie inlet (Figure 2.5)

and in the nautical chart of Redfish Pass (Figure 2.3).

The "near-field" deposit, which begins at the exit of the inlet channel, is directly

influenced by the flood current, and comprises an active zone of sediment deposition.

79
The "far-field" section of the delta is in a less active zone and often becomes partly

vegetated, e.g., at St. Lucie Inlet. The "far-field" section of the delta receives sediment

from the "near-field" zone over the tidal cycle and over longer, episodic time-scales.

An example of this mode of delta development can be seen in the Table 4.8,

which gives the mean depth of the "near-field" and "far-field" deltas at Sikes Cut. This

inlet was opened by dredging in 1954, thus beginning with no delta and no depth of

deposit. It can be seen that the "near-field" delta filled at a faster rate than the "far-field"

delta, and by 1979 the "near-field" depth of sediment was much greater than the "far-

field" depth of deposit. The sediment coming into the bay from the littoral system

initially filled the "near-field" delta. As this "near-field" delta was filled, sediment

spread further into the bay forming the "far-field" delta. By 1985 the depths were

approximately equal. A similar pattern is seen in the growth of the South Lake Worth

Inlet flood delta (Table 4.9).

Table 4.8 Sikes Cut mean depth of"near-field" and "far-field" deltas.
Year dN (m) dF (m)
1954 0.0 0.0
1979 0.97 0.60
1985 1.05 0.99

Table 4.9 South Lake Worth Inlet mean depth of "near-field" and "far-field" deltas.
Year dN (m) dF (m)
1927 0.0 0.0
1990 0.72 0.59
1994 0.78 1.54

CHAPTER 5
SUMMARY AND CONCLUSIONS

5.1 Summary

A compilation of information, including hydraulic and geometric properties as

well as brief historical sketches, of many of Florida's inlets is presented. Calculations of

flood delta volume and area growths over time are made for the Florida inlets examined,

and these data have been analyzed.

A distinction is made between the "near-field" flood delta deposit and "far-field"

delta deposit. The corresponding volumes and areas are determined from nautical charts

and bathymetric maps through the use of a modified Dean and Walton (1973) "no-inlet"

contour method developed for ebb deltas. In the method used, the no-inlet contours are

compared to the existing delta contours in order to calculate the volume. Aerial

photographs are analyzed both for the identification of the "near-field" delta and the "far-

field" delta, and to determine the corresponding delta areas for the year in which the

photograph was taken. A description of the procedure for calculation of flood delta

volumes and areas is given, and errors associated with this procedure have been

examined.

Flood delta "near-field" area, "far-field" area, total area, "near-field" volume,

"far-field" volume and total volume are plotted against the tidal prism on the spring range

for all of the inlets examined along both the east and west coasts. Data corresponding to

the most recent year available have been used for this purpose. The plots are analyzed

80

81

and mean trend-lines are fit to the data points where the data make this possible. Next, the

east coast data are separated from the west coast, and plots of total area and total volume

versus tidal prism are given for each coast. A greater correlation is seen for the west coast

delta area and volume versus tidal prism than for the east coast. Reasons for this

correlation difference are examined.

The area and volume growths with time are plotted to show a "typical" inlet flood

delta growth behavior. This pattern is contrasted to the examples of the growth curves at

two of Florida's inlets. Big Marco Pass is a natural inlet where volume and area of

deposit increased dramatically in the late 1970's. This increase is shown to signify

changes in the surrounding environment. St. Marys Inlet is provided as an example of

how flood delta volume change data can give an indication of the anthropogenic

processes occurring at an inlet.

The likelihood of a flood delta approaching an equilibrium configuration is briefly

examined. In that regard, flood delta development at four inlets is reviewed. Also

examined is the likely way by which sand filling occurs in the "near-field" and "far-field"

deposit zones.

5.2 Conclusions

The following are the main conclusions of this study:

1. The following relations for all inlets concerned were found between the spring tidal

prism and area and volume of flood delta deposit:

a. Area versus prism (Figure 4.1 through Figure 4.3):

AN = 14532 P0.254 Equation 4.1

82

Ar = 34122 P0.244 Equation 4.2

AT = 47585 P0.249 Equation 4.3

b. Volume versus prism (Figure 4.4 through Figure 4.6):

VN = 4056 p0.314 Equation 4.4

VF = 15337 p0.314 Equation 4.5

VT = 20389 P0.296 Equation 4.6

2. The east coast data, when plotted exclusively, show little correlations between the

volume and area of deposit and the tidal prism (Figures 4.7 and 4.8). Thus no trend-

line equations could be determined.

3. The west coast data, when plotted exclusively, show better correlation between the

volume and area of deposit and the tidal prism, than the east coast data (Figures 4.9

and 4.10):

AT = 20578 PO.310 Equation 4.7

VT = 8350 P0.362 Equation 4.8

4. The inlets on the east coast have greater volumes of sediment dredged from them and

more of them are maintenance dredged than on the west coast (Dean and O'Brien

1987b). This dredging practice on the east coast may account in part for the lack of

correlation between delta area and volume and tidal prism on the east coast.

5. The effective bay area (Ab') to hydraulic bay area (Ab) ratio concept was employed to

compare the data from inlets identified at opposite sides of the tidal prism versus total

volume of deposit plots for the east and west coasts. It was seen that the smaller the

effective bay area compared to the hydraulic bay area, the lesser the likelihood of a

large, clearly discernable, flood delta. In the case of an inlet with a small effective bay

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