• TABLE OF CONTENTS
HIDE
 Cover
 Title Page
 Table of Contents
 Abstract
 Introduction
 Coastal setting
 Tidal inlet features
 Inlet classification
 Inlet evolution
 Summary of inlet dynamics
 Role of inlets in coastal...
 Historical changes in inlets
 References cited






Group Title: Technical paper - Florida Sea Grant College Program ; no. 55
Title: Historical morphodynamics of inlets in Florida
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Permanent Link: http://ufdc.ufl.edu/UF00076602/00001
 Material Information
Title: Historical morphodynamics of inlets in Florida models for coastal zone planning
Series Title: Technical paper Florida Sea Grant College
Physical Description: 81 p. : ill., maps ; 28 cm.
Language: English
Creator: Davis, Richard A ( Richard Albert ), 1937-
Gibeaut, James C
Florida Sea Grant College
Publisher: Florida Sea Grant College
Place of Publication: Gainesville Fla
Publication Date: 1990
 Subjects
Subject: Inlets -- Florida   ( lcsh )
Geomorphology -- Florida   ( lcsh )
Coastal zone management -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 79-81).
Statement of Responsibility: by Richard A. Davis, Jr., and James C. Gibeaut.
General Note: "January 1990."
General Note: "Sea Grant project no. R/C-S-23."
Funding: This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Florida Sea Grant technical series, the Florida Geological Survey series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
 Record Information
Bibliographic ID: UF00076602
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 21257960
lccn - 00457174

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Table of Contents
    Cover
        Cover
    Title Page
        Title Page 1
        Title Page 2
    Table of Contents
        Table of Contents 1
        Table of Contents 2
    Abstract
        Page 1
    Introduction
        Page 2
    Coastal setting
        Page 3
    Tidal inlet features
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
    Inlet classification
        Page 8
        Page 9
        Page 10
        Page 7
    Inlet evolution
        Page 11
        Page 12
        Page 10
        Page 13
        Page 14
    Summary of inlet dynamics
        Page 15
        Page 16
        Page 17
        Page 14
        Page 18
    Role of inlets in coastal management
        Page 18
    Historical changes in inlets
        Page 19
        Page 20
        Hurricane Pass
            Page 21
            Page 22
        Willy's Cut
            Page 23
        Willy's Cut
            Blank
        Dunedin Pass
            Page 24
            Page 25
        Clearwater Pass
            Page 26
            Page 27
        Indian Pass
            Page 28
            Blank
        John's Pass
            Page 29
            Page 30
        Blind Pass (Pinellas Co.)
            Page 31
            Page 32
        Pass-a-Grille
            Page 33
            Page 34
        Bunces Pass
            Page 35
            Page 36
        Egmont/Southwest Channel
            Page 37
            Page 38
        Longboat Pass
            Page 39
            Page 40
        New Pass (Sarasota Co.)
            Page 41
            Page 42
        Big Sarasota Pass
            Page 43
            Page 44
        Midnight Pass
            Page 45
            Page 46
        Stump Pass
            Page 47
            Page 48
        Bocilla and Boca Neuva Passes
            Page 49
            Bland
        Gasparilla Pass
            Page 50
            Page 51
        Boca Grande Pass
            Page 52
            Page 53
        Captiva Pass
            Page 54
            Page 55
        Redfish Pass
            Page 56
            Page 57
        Blind Pass (Lee Co.)
            Page 58
            Page 59
        Big Carlos Pass
            Page 60
            Page 61
        New Pass (Lee Co.)
            Page 62
            Page 63
        Big Hickory Pass
            Page 64
            Page 65
        Wiggins Pass
            Page 66
            Page 67
        Clam Pass
            Page 68
            Page 69
        Gordon Pass
            Page 70
            Page 71
        Little Marco Pass
            Page 72
            Page 73
        Big Marco Pass
            Page 74
            Page 75
        Caxambas Pass
            Page 76
            Page 77
        Explanation of symbols in data tables
            Page 78
    References cited
        Page 79
        Page 80
        Page 81
Full Text
I0\
55


Technical Paper 55






HISTORICAL MORPHODYNAMICS
OF INLETS IN FLORIDA

Models for Coastal Zone Planning

by

Richard A. Davis, Jr. and James C. Gibeaut


MlORIIJ
ldwv


GRANIR
COLLEGE PROGRAM


Research, education and extension for responsible marine resource use
















Historical Morphodynamics of Inlets in Florida:

Models for Coastal Zone Planning


by

Richard A. Davis, Jr. and James C. Gibeaut
Department of Geology
University of South Florida
Tampa, Florida 33620


Sea Grant Project No. R/C-S-23
Technical Paper 55
Florida Sea Grant College



January 1990












HISTORICAL MORPHODYNAMICS OF INLETS IN FLORIDA:
MODELS FOR COASTAL ZONE PLANNING

Table of Contents

Page
Abstract ................. .................... ................. 1
Introduction ......................... ....................... 2
Coastal Setting ............................................. 3
Tidal Inlet Features........................................ 3
Inlet Classification......................................... 6
Tide-dominated Inlets................................... 6
Wave-dominated Inlets................................... 10
Mixed-energy Inlets... ................................ 10
Inlet Evolution ............. ........... ................... 10
Summary of Inlet Dynamics.................................... 14
Role of Inlets in Coastal Management......................... 17
Historical Changes in Inlets................................. 19
Hurricane Pass.......................................... 21
Willy's Cut........................................... 23
Dunedin Pass ........................................... 24
Clearwater Pass....................................... 26
Indian Pass .......................................... 28
Johns Pass ........................... ............... 29
Blind Pass (Pinellas Co.)............................. 31
Pass-a-Grille ........................................ 33
Bunces Pass............................................ 35
Egmont/Southwest Channel.............................. 37
Longboat Pass.......................................... 39
New Pass (Sarasota Co.)................................ 41
Big Sarasota Pass...................................... 43
Midnight Pass.......................................... 45
Stump Pass ........................................... 47
Bocilla and Boca Nueva Passes.......................... 49
Gasparilla Pass ....................................... 50
Boca Grande Pass...................................... 52
Captiva Pass............................................ 54
Redfish Pass............................................ 56
Blind Pass (Lee Co.) ...................................... 58
Big Carlos Pass......................... ............ .. 60
New Pass (Lee Co.) .................................... 62
Big Hickory Pass.......................... ............ 64
Wiggins Pass ........................................... 66
Clam Pass.............................................. 68
Gordon Pass .............................................. 70
Little Marco Pass ... .................................. 72
Big Marco Pass..................................... ..... 74
Caxambas Pass.......................................... 76
Explanation of Symbols in Data Tables.................. 78
References Cited....... ..................................... 79




















ABSTRACT
The west-central barrier coast of peninsular Florida represents
one of the most diverse barrier island systems in the world although it
is a very low energy coast; mean annual wave height is less than 30 cm
and tidal range is less than 1 meter. The diverse morphology of
islands and inlets provides an ideal setting for inlet dynamics.
Historical records show the origin and demise of several inlets as well
as major morphologic changes to numerous others.

Even though there is great range in size and shape of these tidal
inlets, they can be conveniently grouped into a simple classification
with only four types; tide-dominated, wave-dominated and mixed energy
with both straight and offset varieties in the latter. Many of the
inlets along the west-central Florida barrier system have changed from
one category to another over only a few decades. These changes can be
caused by natural or man-related phenomena.

Historical data show a nearly infinite variety of inlet behaviors
along this coast. Some, both large and small, have been essentially
stable whereas most have shown great change. Examples of tide-
dominated becoming wave-dominated as well as major changes in size and
shape have occurred over the past century. Thorough study of the
processes in each inlet coupled with a knowledge of its history can
enable predictions of future inlet behavior.









INTRODUCTION
Tidal inlets are geologically ephemeral environments which act as
dynamic conduits between the sea and coastal bays and which divide the
coast into barrier-island segments. Inlets may close and open, migrate
or become stable on the order of tens of years in response to changing
sediment supply, wave climate and tidal regime, rate of sea level rise,
and back-bay filling or dredging. In turn, the associated sediment
bodies, ebb- and flood-tidal deltas, may rapidly change character.
Because most material making up the inlet sand bodies is taken from the
littoral-drift system which feeds adjacent beaches, changes in inlet
behavior are reflected by changes in adjacent shorelines and overall
barrier-island morphologies.

There are two reasons to consider tidal inlets in a beach
management program: 1) ebb-tidal deltas are prime borrow areas for
beach nourishment projects and 2) inlet throat migration, wave
refraction across ebb-tidal deltas, and sediment trapping by tidal
inlet systems affects sedimentation and navigation along adjacent shore
lines.

Tidal inlets are very dynamic and commonly show major changes in
inlet size and shape, in some cases even without intervention by man's
activities. Changes in wave climate, sediment availability, and
nearshore bottom configuration can cause pertubations in coastal
processes and ,therefore, in the morphology of the inlet or inlets.
Probably the most common and most drastic situation is where a new
inlet is opened by a storm. The inlet may grow and stabilize such has
happened at Hurricane Pass in Pinellas County and at Redfish Pass in
Lee County. Conversely, an inlet may close due to an abundance of
sediment and strong littoral drift coupled with a small tidal prism.
This closure may not only affect the inlet in question but may also
cause changes in adjacent inlets.

A morphodynamic classification of inlets serves to place inlets in
perspective regarding their behavior and effect on adjacent shorelines.
Morphodynamics refers to changes in processes and shapes of subtidal
and intertidal shoals and channels.

Inlets are chiefly shaped by tidal and wave forces, and a thorough
understanding of inlet systems allows the prediction of inlet
morphology given certain process conditions. This prediction is
difficult even with accurate and complete data due to the feed-back
effect that morphology has on processes. For example, an increase in
tidal prism may cause an increase in the size of the ebb-tidal delta;
the larger delta would affect wave refraction and thus sedimentation
along the adjacent shoreline. Therefore, the successful prediction
model must consider the inlet system as a whole.

A morphological classification which is related to tidal and wave
forces and to sediment supply, but which involves overall inlet
morphology, is necessary for the systematic study of inlets in space
and time. It is also the first step in devising comprehensive inlet
sedimentation models.









This report sets forth a preliminary inlet classification model
for the west-central coast of Florida and discusses implications for
shoreline management. It also includes a brief discussion of
historical changes in inlets along the west-central coast of Florida
and an extensive data base on inlet parameters.

COASTAL SETTING
The coast of west-central Florida (Fig. 1) is a microtidal,
mixed-energy coast according to the classification of Hayes (1975,
1979). Mean tidal range along the west-central barrier chain is less
than 1 m and tides are mixed and semi-diurnal. The overall wave energy
is very low with mean annual breaker heights of 25-30 cm (Tanner, 1960;
Davis & Andronaco, 1987). This part of the Gulf of Mexico is subject
to tropical hurricanes and extratropical winter storms associated with
cold fronts. These high-energy events are infrequent but may have a
profound and lasting effect on the coast because of intervening
low-energy conditions.

Sediment type in nearshore and inlet environments is consistent
along the coast and is composed of 90 to 95 percent by weight of fine
to very fine quartz sand. The remaining fraction consist of gravel-
sized shell fragments and a minor amount of biologically produced mud-
sized grains (Evans et al., 1985). Tidal deltas and channels may have
a higher shell content and, therefore, a coarser mean-grain size than
the adjacent shorelines (Lynch-Blosse, 1977). No rivers are inputing
new sediment to the coastal system and the unconsolidated sediment
cover thins rapidly seaward (Davis et al., 1985).

The west-central Florida coast (Fig. 2) has a wide range of
tidal-inlet and barrier-island morphology (Davis, 1988). Because
sediment type and availability and the shoreface setting are relatively
constant along the coast, variations in inlet morphologies are mostly
caused by differences in the relative magnitudes of tidal and wave
energies. Tidal prisms range over nearly four orders of magnitude
(Davis & Hayes, 1984) and are controlled by the size of the bay they
serve.

Seismic profiling in the northern 50 km of the study area (Davis &
Kuhn, 1985; Evans et al., 1985) and in the Charlotte Harbor area (Evans
& Hine, 1986) has shown that the pre-Quaternary surface is an
irregular, karstic surface, and that the location of barrier islands.
Hence, tidal inlets are at least partly controlled by this irregular
bedrock topography.

TIDAL INLET FEATURES
Figure 3 shows the elements that comprise an inlet system using
the commonly accepted nomenclature of Hayes (1975). Outer shoal and
inner shoal, which are terms often found in the engineering literature,
are equilavent to ebb-and flood-tidal delta, respectively.









This report sets forth a preliminary inlet classification model
for the west-central coast of Florida and discusses implications for
shoreline management. It also includes a brief discussion of
historical changes in inlets along the west-central coast of Florida
and an extensive data base on inlet parameters.

COASTAL SETTING
The coast of west-central Florida (Fig. 1) is a microtidal,
mixed-energy coast according to the classification of Hayes (1975,
1979). Mean tidal range along the west-central barrier chain is less
than 1 m and tides are mixed and semi-diurnal. The overall wave energy
is very low with mean annual breaker heights of 25-30 cm (Tanner, 1960;
Davis & Andronaco, 1987). This part of the Gulf of Mexico is subject
to tropical hurricanes and extratropical winter storms associated with
cold fronts. These high-energy events are infrequent but may have a
profound and lasting effect on the coast because of intervening
low-energy conditions.

Sediment type in nearshore and inlet environments is consistent
along the coast and is composed of 90 to 95 percent by weight of fine
to very fine quartz sand. The remaining fraction consist of gravel-
sized shell fragments and a minor amount of biologically produced mud-
sized grains (Evans et al., 1985). Tidal deltas and channels may have
a higher shell content and, therefore, a coarser mean-grain size than
the adjacent shorelines (Lynch-Blosse, 1977). No rivers are inputing
new sediment to the coastal system and the unconsolidated sediment
cover thins rapidly seaward (Davis et al., 1985).

The west-central Florida coast (Fig. 2) has a wide range of
tidal-inlet and barrier-island morphology (Davis, 1988). Because
sediment type and availability and the shoreface setting are relatively
constant along the coast, variations in inlet morphologies are mostly
caused by differences in the relative magnitudes of tidal and wave
energies. Tidal prisms range over nearly four orders of magnitude
(Davis & Hayes, 1984) and are controlled by the size of the bay they
serve.

Seismic profiling in the northern 50 km of the study area (Davis &
Kuhn, 1985; Evans et al., 1985) and in the Charlotte Harbor area (Evans
& Hine, 1986) has shown that the pre-Quaternary surface is an
irregular, karstic surface, and that the location of barrier islands.
Hence, tidal inlets are at least partly controlled by this irregular
bedrock topography.

TIDAL INLET FEATURES
Figure 3 shows the elements that comprise an inlet system using
the commonly accepted nomenclature of Hayes (1975). Outer shoal and
inner shoal, which are terms often found in the engineering literature,
are equilavent to ebb-and flood-tidal delta, respectively.





















1030'N


Figure 1.- Location map of Florida. Tidal inlets considered in this
study are along the west-central barrier chain. From Hine et al.
(1986).
















84 0,)- --1


ANCLOTE KEY.:
I TARPON SPRINGS GENERAL LOCATION
CLEARWATER TIAL /INLETS
HURRICANE PASS I
DUHEDIH PASST------------A'L'^*'* ., TAMPA WECT-C- T^RA l FtL.
CLEARWATER PASS TAMPA WIEST-CENTRAl FL

51 GULF COAST
JOHNS PASS
BLIND PASS'
PASS-A-GRILLE __ _
OUNCES PASS
EOGONT KEY-
SOUTHWEST CHANNEL
PASSAGE KEY INLET
LONOBOAT PASS BRADENTON

NEW PASS SARASOTA
BI0 SARASOTA PASS
MIDNIGHT PASS--
0 VENICE INLET



0 STUMP PASS P A.
GASPARILLA PASS
BOCA GRANDE "

CAPTIVE PASS_ __ FORT MYERS
RED FISH PASS f
BLIND PASS ESTEO PASS
BIG CARLOS PASS SAM CARLOS BAY-
NEW PASS BIG
HICKORY PASS LITTLE
HICKORY PASS WIGGINS PASS
CLAM PASS
DOCTORS PASS
GORDON PASS NAPLES
LITTLE MARCO PASS-
BIG MARCO PASS
CAXAMBAS PASS-
CAPE ROMANO


RMAP



JURSA


280
















27*
















26*N


1 I i I
84* 830 82* 81*W


Figure 2.- Location map of inlets along the west-central Florida
barrier chain. From Hine et al. (1986).


28o


27


260N


R82W


81W


A '























EBB SPIT
SI',
I "~ \ -\ \
EBB SHIELDt .._ ,
% %V SPIT \ -- SWASH BARS
I \ \ PLATFORM ..

FLOOD-TIDAL ,. FLOOD SWASH : EBB-TIDAL
DELTA CHANNEL \ \ PLATFORM '; DELTA
---- -- ---_A _.. .. ,
\ -- MAIN-EBB CHANNEL If
'--;, ,- C', C,,,,'"TERMINAL LOBE
SPILL-OVER LOBE '
-' :/ / "
I MARGINAL-FLOOD
/ CHANNEL
EBB SHIELD ,t I
,'EBB-TIDAL DELTA
I I
I,




Figure 3.- Elements of a tidal inlet using the nomenclature of Hayes
(1979). Not all of the morphological features will necessarily be
present or as well-developed as shown.









The terminology of Hayes (1975) is preferred because of its
comprehensive and simplistic nature. Not all the features shown in
Figure 3 are necessarily present or well developed at all inlets. The
ebb-tidal delta is where tidal and wave processes interact. The
sources of sand for ebb-tidal deltas include material from the bay,
material eroded from the inlet throat, and material moving in the
littoral transport system.

The main-ebb channel is dominated by ebb currents which issue from
the throat in an expanding-jet fashion. The ebb channel shallows
seaward in response to the decreasing competence of the tidal flow to
transport sediment and the increasing importance of onshore wave
energy. Sediment carried by the ebb flow is dropped seaward and is
reworked by waves on the swash platform.

Shoaling waves are the dominant process on swash platforms and
often form landward and alongshore migrating swash bars. These swash
bars may coalesce and weld to the adjacent beach (FitzGerald, 1982).
Where swash bars approach the main-ebb channel, they are truncated by
tidal currents and form channel-margin linear bars.

Marginal channels, where flood-directed tidal flow is reinforced
by wave-generated currents (Davis & Fox, 1981), direct sediment to the
ends of the barrier islands and to the inlet throat (Oertel, 1977).
Spit platforms form at inlets where there is a high littoral drift rate
coupled with a relatively small tidal prism. Growing spit platforms
constrict the inlet throat and cause downdrift migration or closure of
the inlet.

Flood-tidal deltas are relatively static features along the
west-central Florida coast compared to the ebb-tidal deltas. Radially
digitate flood channels and flood-tide deposits (ebb shield) are
modified by ebb currents which form spillover lobes and ebb spits.
Many of the flood-tidal deltas in the study area are stabilized by sea
grasses and mangroves. A schematic diagram (Fig. 4) can be used to
show the distribution of tide-generated and wave-generated current
transport in inlet systems.

INLET CLASSIFICATION
Inlet types are recognized primarily by the morphologies of ebb-
tidal deltas. Varying proportions of tidal and wave energy is the
basic control on morphology. Four inlet categories have been
delineated by inspection of coastal charts and vertical aerial
photographs of west-central Florida inlets (Fig. 5).

Tide-dominated Inlets -
Tide-dominated inlets (Fig. 5) have a well-defined main-ebb
channel with associated sand bodies which are oriented perpendicular to
the shore. Marginal flood channels, which carry sediment to the throat
and the ends of the barrier island, are often present. Redfish pass
(Fig. 6) and Pass-A-Grille (Fig. 7) are examples of tide- dominated
inlets.

























WAVE GENERATED
CURRENT TRANSPORT
FROM SMITH (194)

Figure 4.- Areas of tide- and wave-generated current transport in an
inlet system. Littoral drift is depicted as moving from top to bottom.
From Smith (1984).


Figure 5.- Composite drawings of inlet types for the west-central
Florida barrier chain. Hatching indicates areas along the shoreline
that are most affected by tidal inlet dynamics. The ocean is to the
left and the bays are to the right.




























Figure 6.- Vertical aerial photograph of Redfish Pass (Lee County) in
1975. This inlet is tide-dominated with a distinct main-ebb channel
and an ebb-tidal delta oriented perpendicular to shore. Marginal-
flood channels are also present.


Figure 7.- Vertical aerial photograph of Pass-A-Grille Pass (Pinellas
County) in 1957. This inlet is tide-dominated with a distinct main-
ebb channel and an ebb-tidal delta oriented perpendicular to shore.









Tide-dominated inlets are relatively stable in their throat and
main-ebb channel positions. Usually, the channels are deeply encised.
Because ebb deltas may extend seaward several kilometers, they shield
the adjacent shoreline on the downdrift side from wave attack and a
depositional zone may develop. On the other hand, the prominent and
stable ebb-tidal deltas of tide-dominated inlets are an effective
barrier to littoral drift and may cause beach erosion on the downdrift
barrier island.

Wave-dominated Inlets -
The ebb-tidal deltas of wave-dominated inlets (Fig. 5) are small
and oriented subparallel to the shoreline often asymmetric in the
direction of net-littoral drift. Shore-parallel swash bars may weld to
the downdrift beach, and spit platforms are well-developed extending
from the updrift beach. Blind Pass in 1953 (Fig. 8), Midnight Pass in
1983 (Fig. 9), and Dunedin Pass (Fig. 2) are examples of wave-dominated
inlets.

These inlets are unstable and affect the adjacent shorelines by
erosion on the downdrift island and tenuous extension of beach from the
updrift island. As these inlets migrate, the main channel is
lengthened and becomes hydraulically ineffecient for tidal exchange.
During a storm, a new, more hydraulically efficient inlet may be
breached across the updrift spit causing closure of the former inlet.
Wave-dominated inlets do not cause a significant obstruction to
littoral transport.

Mixed-energy Inlets (Straight. Offset) -
Mixed-energy inlets owe their morphologies to a combination of
tidal and wave forces. Ebb-tidal delta morphology is intermediate
between tide- and wave-dominated inlets (Fig. 5). Littoral drift may
cause shifting orientations of the main-ebb channel and the channel may
adjust to a more hydraulically stable position by ebb-delta breaching
(FitzGerald, 1982). The throat position is relatively stable but
sediment under the influence of wave and flood-generated currents may
move into the inlet opening. Mixed-energy offset inlets (Fig. 5) have
a prominent downdrift offset caused by a local reversal of littoral
drift. Waves refracted around the ebb-tidal delta cause sediment
transport toward the inlet on the downdrift side in the wave shadow of
the ebb-tidal delta (Hayes et al, 1970).

Midnight Pass in 1972 (Fig. 10) and Big Sarasota Pass (Fig. 11)
are examples of mixed-energy offset tidal inlets. Stump Pass in 1981
(Fig. 12) had a small offset and New Pass in 1948 (Fig. 13) had a
mixed-energy straight morphology. Mixed-energy inlets affect the
adjacent beaches most dramatically on the downdrift side where swash
bars weld to the beach. The offset variety may trap a substantial
amount of littoral drift causing progradation and widening of beaches
on the updrift ends and beach narrowing on the downdrift ends of
barrier islands.

INLET EVOLUTION
Inlets may change in character through time as they adjust to
shifting processes. Except for the very large tide-dominated









The terminology of Hayes (1975) is preferred because of its
comprehensive and simplistic nature. Not all the features shown in
Figure 3 are necessarily present or well developed at all inlets. The
ebb-tidal delta is where tidal and wave processes interact. The
sources of sand for ebb-tidal deltas include material from the bay,
material eroded from the inlet throat, and material moving in the
littoral transport system.

The main-ebb channel is dominated by ebb currents which issue from
the throat in an expanding-jet fashion. The ebb channel shallows
seaward in response to the decreasing competence of the tidal flow to
transport sediment and the increasing importance of onshore wave
energy. Sediment carried by the ebb flow is dropped seaward and is
reworked by waves on the swash platform.

Shoaling waves are the dominant process on swash platforms and
often form landward and alongshore migrating swash bars. These swash
bars may coalesce and weld to the adjacent beach (FitzGerald, 1982).
Where swash bars approach the main-ebb channel, they are truncated by
tidal currents and form channel-margin linear bars.

Marginal channels, where flood-directed tidal flow is reinforced
by wave-generated currents (Davis & Fox, 1981), direct sediment to the
ends of the barrier islands and to the inlet throat (Oertel, 1977).
Spit platforms form at inlets where there is a high littoral drift rate
coupled with a relatively small tidal prism. Growing spit platforms
constrict the inlet throat and cause downdrift migration or closure of
the inlet.

Flood-tidal deltas are relatively static features along the
west-central Florida coast compared to the ebb-tidal deltas. Radially
digitate flood channels and flood-tide deposits (ebb shield) are
modified by ebb currents which form spillover lobes and ebb spits.
Many of the flood-tidal deltas in the study area are stabilized by sea
grasses and mangroves. A schematic diagram (Fig. 4) can be used to
show the distribution of tide-generated and wave-generated current
transport in inlet systems.

INLET CLASSIFICATION
Inlet types are recognized primarily by the morphologies of ebb-
tidal deltas. Varying proportions of tidal and wave energy is the
basic control on morphology. Four inlet categories have been
delineated by inspection of coastal charts and vertical aerial
photographs of west-central Florida inlets (Fig. 5).

Tide-dominated Inlets -
Tide-dominated inlets (Fig. 5) have a well-defined main-ebb
channel with associated sand bodies which are oriented perpendicular to
the shore. Marginal flood channels, which carry sediment to the throat
and the ends of the barrier island, are often present. Redfish pass
(Fig. 6) and Pass-A-Grille (Fig. 7) are examples of tide- dominated
inlets.



























Figure 8.- Vertical aerial photograph of Blind Pass (Lee County) in
1953. Blind Pass has a wave-dominated morphology with an ebb-tidal
delta subparallel to the shoreline and a long spit platform.


Figure 9. Vertical aerial photograph of Midnight Pass (Sarasota
County) in 1983. A wave-dominated morphology is displayed with an
unstable channel and nearly nonexistent ebb-tidal delta.





























Figure 10. Vertical aerial photograph of Midnight Pass (Sarasota
County) in 1972. A mixed-energy offset morphology is displayed
with a distinct main-ebb channel and ebb-tidal delta.


Figure 11.- Vertical aerial photograph of Big Sarasota Pass (Sarasota
County) in 1977. This pass is an example of mixed-energy conditions
with a prominent downdrift offset and intertidal shoals in the inlet
opening.









Tide-dominated inlets are relatively stable in their throat and
main-ebb channel positions. Usually, the channels are deeply encised.
Because ebb deltas may extend seaward several kilometers, they shield
the adjacent shoreline on the downdrift side from wave attack and a
depositional zone may develop. On the other hand, the prominent and
stable ebb-tidal deltas of tide-dominated inlets are an effective
barrier to littoral drift and may cause beach erosion on the downdrift
barrier island.

Wave-dominated Inlets -
The ebb-tidal deltas of wave-dominated inlets (Fig. 5) are small
and oriented subparallel to the shoreline often asymmetric in the
direction of net-littoral drift. Shore-parallel swash bars may weld to
the downdrift beach, and spit platforms are well-developed extending
from the updrift beach. Blind Pass in 1953 (Fig. 8), Midnight Pass in
1983 (Fig. 9), and Dunedin Pass (Fig. 2) are examples of wave-dominated
inlets.

These inlets are unstable and affect the adjacent shorelines by
erosion on the downdrift island and tenuous extension of beach from the
updrift island. As these inlets migrate, the main channel is
lengthened and becomes hydraulically ineffecient for tidal exchange.
During a storm, a new, more hydraulically efficient inlet may be
breached across the updrift spit causing closure of the former inlet.
Wave-dominated inlets do not cause a significant obstruction to
littoral transport.

Mixed-energy Inlets (Straight. Offset) -
Mixed-energy inlets owe their morphologies to a combination of
tidal and wave forces. Ebb-tidal delta morphology is intermediate
between tide- and wave-dominated inlets (Fig. 5). Littoral drift may
cause shifting orientations of the main-ebb channel and the channel may
adjust to a more hydraulically stable position by ebb-delta breaching
(FitzGerald, 1982). The throat position is relatively stable but
sediment under the influence of wave and flood-generated currents may
move into the inlet opening. Mixed-energy offset inlets (Fig. 5) have
a prominent downdrift offset caused by a local reversal of littoral
drift. Waves refracted around the ebb-tidal delta cause sediment
transport toward the inlet on the downdrift side in the wave shadow of
the ebb-tidal delta (Hayes et al, 1970).

Midnight Pass in 1972 (Fig. 10) and Big Sarasota Pass (Fig. 11)
are examples of mixed-energy offset tidal inlets. Stump Pass in 1981
(Fig. 12) had a small offset and New Pass in 1948 (Fig. 13) had a
mixed-energy straight morphology. Mixed-energy inlets affect the
adjacent beaches most dramatically on the downdrift side where swash
bars weld to the beach. The offset variety may trap a substantial
amount of littoral drift causing progradation and widening of beaches
on the updrift ends and beach narrowing on the downdrift ends of
barrier islands.

INLET EVOLUTION
Inlets may change in character through time as they adjust to
shifting processes. Except for the very large tide-dominated
























Figure 12.- Vertical aerial photograph of Stump Pass (Charlotte.County)
in 1981. Stump Pass has a mixed-energy morphology with a small offset.


Figure 13.- Vertical aerial photograph of New Pass (Sarasota County) in
1948. New Pass has a mixed-energy straight morphology.


Y









inlets such as Southwest Channel and Boca Grande (Fig. 2), the
west-central Florida inlets are in a delicate balance between tide- and
wave- dominated conditions Fig. 14). These dynamic conditions are
caused by the overall low-energy environment. While slight decrease in
tidal prism may be enough to cause an evolution from tide to
wave-dominated morphology, a change in direction of littoral drift may
cause the devopment of an offset morphology.

In 1972, Midnight Pass (Fig. 10) had a mixed-energy offset
morphology. A distinct main-ebb channel and ebb-tidal delta were
present. By 1983, Midnight Pass (Fig.9) had migrated northward and
displayed a wave-dominated morphology with an unstable channel and a
greatly reduced ebb-tidal delta. Davis et al. (1987) attributed the
change in Midnight Pass to a decrease in tidal prism caused by dredging
of the intracoastal waterway in 1963 and 1964 through the bay served by
Midnight Pass. The dredged channel directed tidal flow north and
south through the bay and away from the pass.

In 1948, New Pass (Fig. 13) displayed a mixed-energy straight
morphology. An increase in southerly littoral drift caused a mixed-
energy offset morphology to develop by 1957 (Fig. 15). A reversal in
littoral drift direction caused New Pass to returned to a mixed-energy
straight morphology by 1983 (Fig. 16).

SUMMARY OF INLET DYNAMICS
The juxtaposition in space and time of different inlet types along
the west-central Florida coast is at odds with previous regional inlet
classification schemes developed for the German and Georgia Bights.
Nummedal and Fischer (1978) noted the orderly geographical change in
inlet type from wave-dominated to tide-dominated morphologies toward
the apex of the bights.

They also observed that tide range increases and wave energy
decreases gradually toward the apexes. Even though tide range and wave
energy shows little variation along the west-central Florida coast,
changes in tidal prism causes tide- and wave-dominated inlets to be
geographically intertwined. Tidal prisms are controlled by the size of
the bays and the number of inlets serving them.

Because barrier island locations and the nature and size of bays
behind them are affected by pre-existing topography (Davis & Kuhn,
1985; Evans et al., 1985; Evans & Hine, 1986), the complicated inlet
morphologies may be partly due to an irregular bedrock surface. The
overall low-energy conditions result in a delicate dynamic balance of
processes and morphology and relatively slight changes in tide or wave
processes cause temporal shifts in inlet types.

Walton and Adams (1976) correlated ebb-tidal delta volumes with
tidal prisms for inlets on the Atlantic, Gulf, and Pacific coasts.
Although the data showed much scatter, a trend of increasing ebb-delta
volume with increasing prism occurred over two orders of magnitude.
Plots of tidal prisms and ebb-delta volumes against inlet types for
some of the inlets in this study are shown in Figure 17. There is much
overlap among the inlet types in tidal prisms and ebb-delta volumes.






















5-
+



++ + +
++++++ .+ + +*:- :
u 3- *..



+ 0 + + +4 + + + + 4 + + + + + +
+ + + + + + + +

S+ + + + .



A'+ +/ + + + +
+ / 4. 4 + + + + +







* I i + + +
Z+ + + + + + + ++ +
S+ + 0 + + + + ++ + + + + + + + 4
A + + + + + + + + + + *
S/ + + I+ + + + *
S+ + + + +




I I* + + + + + . .
.+ + + + . . *. .++ + ++
S + + + + + +++ + + + + + + + + + + + + +
+ ++


++++ ++* + +* +
+++ ++ +*






+ + + + + + + + + + + + + + + + + ++ + + ++ + + + +
+ + + + + + + + + + + + + + + + .
+ + + + + + + + + + + + + ++++ *+ + ++ +



I+ I .+ *


0 100 200
MEAN WAVE HEIGHT (cm)



Figure 14.- Plot of tide range versus mean annual wave height showing
dominant coastal process. The west-peninsular coast of Florida falls
near the lower left corner where energy is quite low and where slight
change in either parameter can cause a significant change in coastal
morphology.






























Figure 15.- Vertical aerial photograph of New Pass (Sarasota County) in
1957. New Pass has a mixed-energy offset morphology. The shift from a
straight morphology in 1948 (Fig. 13) to an offset morphology in 1957
was accomplished by an increase in southerly littoral drift.


Figure 16.- Vertical aerial photograph of New Pass (Sarasota County) in
1983. A restoration of northerly littoral drift eliminated the offset
morphology present in 1957 (Fig. 14).


__

















E 40- +

X 30-
*oE
i "20-

10- +
+
o + + +
0 t
0
Tlde-Dominated Mixed energy Mixed energy Wave-dointed
(straight) (offset)




20- 268
122 +

E 15-

>a +
10o- +
O0 +
OE

6- + + +
o+ +

0-
0
Tide-dominated Mixed energy Mixed energy Wave-dominated
(straight) (offset)


Figure 17 Plots of tidal prism and ebb-tidal delta volumes against
inlet types for some inlets along the west-peninsular Florida barrier
chain. Ebb-tidal delta volumes are from Hine et al. (1986); prisms are
from various sources.


INEEN









inlets such as Southwest Channel and Boca Grande (Fig. 2), the
west-central Florida inlets are in a delicate balance between tide- and
wave- dominated conditions Fig. 14). These dynamic conditions are
caused by the overall low-energy environment. While slight decrease in
tidal prism may be enough to cause an evolution from tide to
wave-dominated morphology, a change in direction of littoral drift may
cause the devopment of an offset morphology.

In 1972, Midnight Pass (Fig. 10) had a mixed-energy offset
morphology. A distinct main-ebb channel and ebb-tidal delta were
present. By 1983, Midnight Pass (Fig.9) had migrated northward and
displayed a wave-dominated morphology with an unstable channel and a
greatly reduced ebb-tidal delta. Davis et al. (1987) attributed the
change in Midnight Pass to a decrease in tidal prism caused by dredging
of the intracoastal waterway in 1963 and 1964 through the bay served by
Midnight Pass. The dredged channel directed tidal flow north and
south through the bay and away from the pass.

In 1948, New Pass (Fig. 13) displayed a mixed-energy straight
morphology. An increase in southerly littoral drift caused a mixed-
energy offset morphology to develop by 1957 (Fig. 15). A reversal in
littoral drift direction caused New Pass to returned to a mixed-energy
straight morphology by 1983 (Fig. 16).

SUMMARY OF INLET DYNAMICS
The juxtaposition in space and time of different inlet types along
the west-central Florida coast is at odds with previous regional inlet
classification schemes developed for the German and Georgia Bights.
Nummedal and Fischer (1978) noted the orderly geographical change in
inlet type from wave-dominated to tide-dominated morphologies toward
the apex of the bights.

They also observed that tide range increases and wave energy
decreases gradually toward the apexes. Even though tide range and wave
energy shows little variation along the west-central Florida coast,
changes in tidal prism causes tide- and wave-dominated inlets to be
geographically intertwined. Tidal prisms are controlled by the size of
the bays and the number of inlets serving them.

Because barrier island locations and the nature and size of bays
behind them are affected by pre-existing topography (Davis & Kuhn,
1985; Evans et al., 1985; Evans & Hine, 1986), the complicated inlet
morphologies may be partly due to an irregular bedrock surface. The
overall low-energy conditions result in a delicate dynamic balance of
processes and morphology and relatively slight changes in tide or wave
processes cause temporal shifts in inlet types.

Walton and Adams (1976) correlated ebb-tidal delta volumes with
tidal prisms for inlets on the Atlantic, Gulf, and Pacific coasts.
Although the data showed much scatter, a trend of increasing ebb-delta
volume with increasing prism occurred over two orders of magnitude.
Plots of tidal prisms and ebb-delta volumes against inlet types for
some of the inlets in this study are shown in Figure 17. There is much
overlap among the inlet types in tidal prisms and ebb-delta volumes.








This demonstrates that although empirical relationships such as those
of Walton and Adams (1976) may predict gross features of inlet
sedimentation. These empirical relationships are not satisfactory for
describing modes of sedimentation and inlet effects on adjacent
shorelines.

The size of ebb-tidal deltas controls the length of shoreline
influence and in part the location of inlet beach sedimentation and
erosion (FitzGerald & Hayes, 1980). The size as well as the type of
inlet must, therefore, be considered in shoreline management. Figure
17 shows there is no simple relationship between scale and inlet
morphology.

ROLE OF INLETS IN COASTAL MANAGEMENT
Most of the attention of managing the open coast tends to be
directed toward problems associated with beaches and adjacent dunes.
This is rapidly changing as we gain greater awareness of inlet dynamics
and their impact on the coast. Inlets represent tremendous sediment
sinks, that is, places where sediment tends to accumulate. Several
inlets along the west-central barriers system in Florida contain
several million cubic meters of sediment in their flood- and ebb-tidal
deltas. Both the fact that the sediment is there and the sediments
potential as borrow material of coastal nourishment
are important considerations in coastal management of inlets.

The fact that inlets present natural interruptions to the littoral
transport system along the coast presents problems for coastal
management. Of course, some inlet types allow for much sediment to
bypass the inlet and continue in this littoral system. However, there
are some inlets, specifically tide-dominated inlets, that act much like
jetties in their prohibition of littoral transport across the tidal
channelss. Such inlets, like Johns Pass in Pinellas County, can yield
considerable borrow material for nourishment but present major barriers
for alongshore transport of material. By way of contrast,
wave-dominated inlets like Midnight Pass and Blind Pass (Lee County)
have almost no ebb-tidal delta and allow virtually all of the littoral
drift sediment to pass by. They, of course, have essentially no value
as borrow sources.

Another important type of management problem associated with
inlets is instability. As inlets become wave-dominated they are
susceptible to considerable migration alongshore; some, such as
Midnight Pass, both Blind Passes and Big Hickory Pass, have migrated
kilometers in less than a century. This causes serious problems along
a developed coast and artificial stabilization is frequently invoked.
Such practice can also cause problems such as inlet shoaling or closure
and local erosion adjacent to the structures installed for stability of
the inlet.

The overall management of inlets must be accomplished in much the
same fashion as for beaches. It is necessary to have a comprehensive
understanding of inlets in general and of specific types; both from the
historical perspective and the current processes operating on the
inlets. This knowledge, coupled with the analogous information on








This demonstrates that although empirical relationships such as those
of Walton and Adams (1976) may predict gross features of inlet
sedimentation. These empirical relationships are not satisfactory for
describing modes of sedimentation and inlet effects on adjacent
shorelines.

The size of ebb-tidal deltas controls the length of shoreline
influence and in part the location of inlet beach sedimentation and
erosion (FitzGerald & Hayes, 1980). The size as well as the type of
inlet must, therefore, be considered in shoreline management. Figure
17 shows there is no simple relationship between scale and inlet
morphology.

ROLE OF INLETS IN COASTAL MANAGEMENT
Most of the attention of managing the open coast tends to be
directed toward problems associated with beaches and adjacent dunes.
This is rapidly changing as we gain greater awareness of inlet dynamics
and their impact on the coast. Inlets represent tremendous sediment
sinks, that is, places where sediment tends to accumulate. Several
inlets along the west-central barriers system in Florida contain
several million cubic meters of sediment in their flood- and ebb-tidal
deltas. Both the fact that the sediment is there and the sediments
potential as borrow material of coastal nourishment
are important considerations in coastal management of inlets.

The fact that inlets present natural interruptions to the littoral
transport system along the coast presents problems for coastal
management. Of course, some inlet types allow for much sediment to
bypass the inlet and continue in this littoral system. However, there
are some inlets, specifically tide-dominated inlets, that act much like
jetties in their prohibition of littoral transport across the tidal
channelss. Such inlets, like Johns Pass in Pinellas County, can yield
considerable borrow material for nourishment but present major barriers
for alongshore transport of material. By way of contrast,
wave-dominated inlets like Midnight Pass and Blind Pass (Lee County)
have almost no ebb-tidal delta and allow virtually all of the littoral
drift sediment to pass by. They, of course, have essentially no value
as borrow sources.

Another important type of management problem associated with
inlets is instability. As inlets become wave-dominated they are
susceptible to considerable migration alongshore; some, such as
Midnight Pass, both Blind Passes and Big Hickory Pass, have migrated
kilometers in less than a century. This causes serious problems along
a developed coast and artificial stabilization is frequently invoked.
Such practice can also cause problems such as inlet shoaling or closure
and local erosion adjacent to the structures installed for stability of
the inlet.

The overall management of inlets must be accomplished in much the
same fashion as for beaches. It is necessary to have a comprehensive
understanding of inlets in general and of specific types; both from the
historical perspective and the current processes operating on the
inlets. This knowledge, coupled with the analogous information on








adjacent beaches, can then permit the best management decisions. It
should be noted that in many cases there are no solutions, just better
approaches that have been applied in the past.

HISTORICAL CHANGES IN INLETS
The coast of Florida has been visited and settled for several
hundred years but it is only during the past century that widespread
and accurate maps have been available for this region. The surveys
that were undertaken and the maps produced by the United States Coast
and Geodetic Survey (now part of NOAA) in the last quarter of the
ninteenth century represent the first reliable charts for this coast.
This time period will be used as the datum for a general discussion of
the trends in inlet changes. The reader must be aware that even as
this discussion is being written changes in inlet morphology are taking
place.

Numerous inlets have been closed during the past century, some
have been formed for the first time and others have experienced both
closure and reopening (Fig. 18). Much of this activity has been due to
natural processes, some has been with the indirect influence of man and
some has been directly by the activities of man. Dredging of one inlet
can "rob" some of the tidal prism, that is, the water budget during a
tidal cycle, from an adjacent inlet. Dredging of the intracoastal
waterway can do the same. The recently abandoned practice of
dredge-and-fill of mangrove and marsh environments on bay margins also
altered the tidal prism by changing the area of the bay. Each of these
activities results in a modification, generally a decrease, in the
tidal prism of affected inlets. The obvious impacts of man that
involve structuring inlets, dredging of the inlet and in some cases,
closing of inlets are also very important factors in the overall
coastal environment.

Figure 18 shows the west-central barrier/inlet system of the
Florida peninsula. The closed triangles represent inlets that have
closed at least once since 1880 and the open triangles represent those
that have been opened during the same time; in both case without direct
influence of man.

Historical information about the role of human activities on each
of the following inlets can be obtained from a report entitled
"Impact of Florida's Gulf Coast Inlets on the Coastal Sand Budget"
(Hine et al., 1986) which was prepared for the Division of Beaches
and Shores, Florida Department of Natural Resources.

The following section includes a brief historical synopsis each
inlet, a recent generalized map showing flood- and ebb-tidal deltas,
and a tabulation of inlet data for the past century. An
explanation of the symbols used in this tabulation is provided on
page 78.


























































Figure 18 Strip map of the west-peninsular Florida barrier coast
showing barrier islands and inlets. Inlet openings and closures during
historical time are shown by the appropriate arrows.

20








Hurricane Pass -
This inlet in Pinellas County was formed by the hurricane of
October, 1921 which breached Hog Island. The flood delta is lobate in
shape, has remained essentially unchanged since formation, and
currently supports a diverse benthic community including sea grasses.

The inlet widened initially after formation until the mid 1960s
when the causeway was constructed between Honeymoon Island and the
mainland. This reduced the tidal prism and caused the inlet to
decrease in width by about 200 m (Lynch-Blosse & Davis, 1977).
Hurricane Pass has remained rather stable since that time with a
maximum depth of nearly 7 m. There is some indication of recent
narrowing of the inlet due to the development of Willy's Cut
immediately to the south after Hurricane Elena in 1985.

Hurricane Pass does not have a prominent ebb delta (Fig. 19) due
in part to its flood-dominated nature (Lynch-Blosse & Davis, 1977) and
to the overall embayed configuration of this local section of barrier
coast. There has been little historical change to the overall
morphology of this inlet during its short existence.

Figure 19 HURRICANE PASS
HURRICANE PASS


m
0 500
0 500







HURRICANE PASS
Diurnal Tide Range: ocean: 88cm bay: 85cm
Net Littoral Drift: 57,300 cubic meters per year, south,

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS.SP PRISON MAXFL MAXEB HIG


697 213

1301 327


1.383


1.454


640 95


740 91







740 96


1.310


520

648

312

800 206

240

1042 259


S100E


2.8

4.0 8.1


9.600


70.0 57.0


4.0 7.4


1951

1957

1958

1962

1963

1972

1975

1976

1977

1977-79

1980

1984

1986

1987


1.537


800 102


1.988


230

220 2.1



192 2.9 5,4


20NW

39.6 50.3 70E


9.848


93.0 88.0


7.362 7.362 52.4 55.8


2

2 0.758








Willy's Cut-
Hurricane Elena did not have landfall on the west central
Florida coast but did have a great effect during August 31 September
2, 1985. It caused a breach on the narrow northern part of Caladesi
Island which initially resulted is a large washover fan with a sediment
volume of 20,000 m3 (Davis et al., in press). Over the following two
years a tidal inlet developed at this breach in the island and appears
to be on its way to stability. The tidal prism appears to be taken
from Hurricane Pass rather than from Dunedin Pass (B. Ross, personal
communication).


The flood tidal delta is a modification of the original washover
fan and is arcuate in shape. There has been little change since
formation except for the excavation of the tidal channel. The inlet
throat was >2 m deep by October, 1988 (Fig. 20). It is somewhat
stabilized in its position by the resistant peat which forms part of
the channel wall on both sides of the inlet. There is a small recurved
spit that persists on the southern or updrift side indicating the
presence of a south to north littoral drift. A small but distinct
ebb-tidal delta has developed that extends about 75 m into the Gulf
(Davis et al., in press). This feature consists of two levee-type
shoals on each side of the inlet channel.

Willy's Cut is the youngest inlet on this reach of coast and its
future is unknown, but it appears to be slowly increasing in size.
There is a possibility that the growth of this inlet will cause a
reduction of size of Hurricane Pass.
0Figure 20
Figure 20 1 /





















THIS PAGE LEFT BLANK

INTENTIONALLY









Dunedin Pass -
Until the 1960s this inlet was known as Big Pass because it
described it well. In the latter part of the 19th century this inlet
was several hundred meters wide and carried a large tidal prism. There
was significant reduction in size as the result of the hurricane of
1921 and the construction of the causeway connecting Clearwater Beach
Island with the mainland in the mid- 1920s (Lynch-Blosse & Davis,
1977). This was followed by further reduction in width after
construction of the Dunedin causeway in the 1960s.

The flood tidal delta of Dunedin Pass is quite large (Fig. 21), it
is stable and it hosts an extensive benthic community including
widespread sea grass beds.

The inlet channel was not only quite wide but was about 5 m deep
in the late 1800s. Even at that time the channel was oriented toward
the northwest indicating a dominance of northerly littoral drift
throughout historical time. The inlet throat became narrower,
shallower and shifted toward the north throughout the past century. As
a result, the southerly end of Caladesi Island experienced considerable
erosion due to the combination of the migrating channel and tidal
currents.

The ebb-tidal delta of Dunedin Pass extended about 700 m into the
Gulf in the latter part of the 19th century. This has gradually been
reduced in size as tidal prism has been reduced in combination with a
decrease in littoral sediment budget. The inlet has become less tide-
dominated and more wave-dominated throughout this period. Hurricane
Elena destroyed the remaining portion of this ebb-tidal delta and
thereby enabled the inlet to close due to littoral drift. This
occurred in 1986 and although there are plans to open it, Dunedin Pass
is no longer an active tidal inlet.

Figure 21 DUNEDIN PASS


m0 1
0 1000









DUNEDIN PASS
Diurnal Tide Range: ocean: 87cm bay: 85cm
Net Littoral Drift: 76,400 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRISSP PRISON MAXFL MAXEB MIG


500 5.8


1300 520

1904 396

396

427

305


1873

1880-85

1926

1941

1949

1950

1951

1956

1957

1958

1959

1962

1970

1972

1973

1974

1975

1976

1977

1977-79

1980

1984

1986


460 125


373

200

137.

1337* 563* 2.40

80

84

137

170

75

160 110 1.5

70

169 107 1.6


10.641


3.2 2.100


51.5 51.5


68.0 79.3 240N

70S


4.1


55.8 53.9

300N

36.0 40.0 80S


1.869


0.362

0.917 0.262


330 61

200 67


1.8 2.349


* NOT AT THROAT, AT MOUTH


2 6.713


1.835


6.499


740 135





630 134

400 98


1.248


0.821

0.606


0.821


0.654

0.969


1.835









Clearwater Pass -
The origin of Clearwater Pass is not known. However, it has
changed greatly over the past several decades. A century ago it was
called Little Pass and although it was only about 100 m wide, it was
over 8 m deep. The pass carried a large tidal prism and was pressured
by converging littoral drift from Sand Key on the south and Clearwater
Beach Island on the north. A thorough discussion on Clearwater Pass is
available in the report by Newman (1983).

This inlet did not have a clearly defined natural flood-tidal
delta about 100 years ago. At the present time there is a shallow
shoal landward of the inlet that appears to represent a flood-tidal
delta in its location and form. Its origin is primarily the result of
northerly transport of sediment by longshore currents on Sand Key which
were then entrained by tidal currents and deposited in the form of a
tidal delta. The supply of sediment to this flood delta has largely
been cut off by the construction of the long jetty on the south side of
the inlet in 1975.

The inlet channel of Clearwater Pass has been problematical
throughout much of recent history. Continual influx of sediment by
littoral drift caused persistence of a narrow but deep channel until
the turn of the century when the width increased nearly an order of
magnitude (University of Florida, 1973; Lynch-Blosse, 1977). After
construction of the causeway between Clearwater and the island, this
trend of widening was reversed due to reduction in tidal prism.
Eventually the combination of littoral drift from the south and reduced
tidal prism resulted in the need for a jetty to stabilize the inlet.

The ebb-tidal delta at Clearwater Pass was prominent in the late
1800s. It extended about 500 m into the Gulf and had a shape of a
mixed-energy ebb delta. As the tidal prism was reduced, the relative
impact of waves increased and the ebb-tidal delta was greatly reduced
in size. At the present time, small shoals at each side of the inlet
on the Gulf side (Fig. 22) are forming a vestigal ebb delta.

Figure 22 CLEARWATER PASS


SAND KEYV'C




1000
0 100o


CLEARWATER
BEACH
ISLAND


I







CLEARWATER PASS
Diurnal Tide Range: ocean: 86cm bay: 79cm
Net Littoral Drift: 76,400 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRISSP PRISON MAXFL MAXEB MIG


1873 140

1880-85 2 1.552 0.688 106

1926 1410

1941 914

1949 1853 926 2.0 3.2

1950 2.294 3.892 747

1951 2071 1075 1.9 19.244 67.0 56.7

1956 745

1957 2 2.053 880 96 670 2.8 0

1959

1962 2 1.678 930 102 520 50N

1965 373

1968 343

1972 274

1973 2 335 200NW

1977 411

1984 5.367 0.688 411 2.6 25.753 45.7 50.3

1986 1133








Indian Pass -
Indian Pass was a small, wave-dominated inlet located south of
Indian Rocks on Sand Key (Fig. 23). It was closed in 1929 by the U. S.
Army, Corps of Engineers. This inlet was a wild pass because it
migrated rapidly over long distances and had the associated spit
breached on numerous occasions. Indian Pass was <2 m deep and <100 m
wide throughout its historical existence. No tidal deltas are apparent
on old charts and no residual sediment bodies remain.
Figure 23 INDIAN
I INDIAN PASS














1873 1883 1 1926

I 0 m 500 IDIA, PISS





















THIS PAGE LEFT BLANK

INTENTIONALLY









John's Pass -
An intense hurricane in 1848 created Johns Pass by breaching the
barrier that is now called Sand Key to the north and Treasure Island to
the south. This primary inlet serving Boca Ciega Bay has remained
fairly stable over the past century.

The flood tidal delta is large and consists of multiple sediment
lobes which have apparently not changed significantly since their
formation. These sediment bodies, which are in part intertidal and
supratidal, have been vegetated for decades. As a result, the flood
delta is completely stable.

The inlet channel has also been stable with a migration of only
100 m or so to the south during the past century (Mehta et al., 1976).
The primary reason for the relative stability of this pass is its
tide-dominated nature although some structuring has also facilitated
its position. The tidal prism is large because most of Boca Ciega Bay
is serviced by this single tidal inlet.

The present ebb-tidal delta at Johns Pass is large and typical of
a tide-dominated inlet. This situation has not prevailed throughout
the past century. In the late 1800s the ebb delta extended several
hundred meters into the Gulf but its shape was that of a mixed inlet
with a downdrift offset. There was an arcuate terminal lobe (Fig. 24)
indicating significant wave effect on the morphology. Over the next
several decades the inlet had an increase in the tidal prism as Blind
Pass, the next inlet to the south, decreased in size (Mehta et al.,
1976). This resulted in a more tide-dominated ebb delta although it
became assymetrical and there was some influence by man. The north or
updrift side of the ebb-tidal delta became quite elongate parallel to
the channel and extended over a kilometer into the Gulf. This was in
response to the increased tidal prism and tidal current strength
redistributing the sediment being provided by the southerly littoral
drift along Sand Key. The south or downdrift side of the ebb delta
showed less change from its earlier shape (Fig. 24).

Figure 24 JOHN'S PASS _


m0
0 1000








JOHN'S PASS
Diurnal Tide Range: ocean: 81cm bay: 70cm
Net Littoral Drift: 38,200 cubic meters per year, soutn,

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRISSP PRISON MAXFL MAXEB KIG


4.0 14.037


103.0 77.0


4.817


1.588

1.328


1.029


1 3.838
1

1 3.838


880 57

750 42


710 64


0.382


190

882 180

200

190

180


0

220SW



30SE


4.9 7.6


48.5 65.5








Blind Pass (Pinellas County) -
Blind Pass has undergone considerable change during the past 150
years. These changes were initially due to the formation of John's
Pass by the hurricane in 1848 and more recently as the result of
man-related activities. In the late 19th century Blind Pass was a
large, mixed-energy inlet with a pronounced downdrift offset. In 1873
Blind Pass was larger than John's Pass, by 1925 it had become smaller
and by the 1970s Blind Pass had only 5% of the cross sectional area as
John's Pass (Mehta et al., 1976).

There is a large flood-tidal delta associated with Blind Pass,
however, it is far north of the inlet mouth (Fig. 25). During the
latter part of the 19th century, the inlet channel trended to the
southwest and the flood delta was in a position similar to that of
Dunedin Pass (see Fig. 21). Since that time the inlet has migrated
over a kilometer to the south and the flood delta has been greatly
modified by man's activities.

The inlet channel of Blind Pass was greatly reduced in size and
migrated rapidly to the south as John's Pass increased in size and
tidal prism. The decrease in tidal prism changed Blind Pass from a
typical mixed-energy offset inlet to a distinctly wave-dominated inlet.
By the 1920s it had been reduced to about 100 m in width and a depth of
<2 m (Mehta et al., 1976). Eventually its position was stabilized by
hardening the south (downdrift) side in 1938.

A similar trend has taken place in the ebb-tidal delta of Blind
Pass over the past century. Initially, it was well-developed and
typical of a mixed energy inlet. It extended > 500 m into the Gulf in
the 1880s. The advent of wave-dominated conditions resulted in the
nearly total destruction of the ebb delta. Jetties have permitted some
accumulation of sediment however the present inlet has no significant
ebb shoal at its mouth.

Figure 25
BLIND PASS TREASURE
IPINELLAS C01 ISLAND


S LONG KEY


0 500 1000








BLIND PASS (Pinellas County)
Diurnal Tide Range: ocean: 80cm bay: 69cm
Net Littoral Drift: 38,200 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDH PRIS.SP PRIS.MN MAXFL MAXEB MIG


1873 538 155 3.5 0

1883 496 165 3.0

1885 0.872 0.000

1926 209 108 1.9 1190S

1936 225 155 1.4

1939 670S

1952 0.328 157 59 2.7

1974 4 40 25 1.6 0.990 80.2 114.6

1984 1.262 0.000 182 1.2









Pass-a-Grille -
The inlet at the south end of Long Key is rather unconfined and
has historically included two main channels that bifurcate in the
Gulfward direction. It was quite large a century ago with an ebb delta
that extended 1.5 km into the Gulf. There was little definition to the
inlet throat due to the lack of a confining barrier island to the
south, however, that has been changed with accretion on the mangroves
to the south where islands know as The Reefs have developed. A
distinct ebb-tidal delta was not present and has not developed since.
The primary changes in this inlet during the past century have been in
the size and position of the two channels, North Channel and South
Channel, and Shell Key, which is the mobile island that separates these
channels.

Both channels were about the same width (100 m) and depth (6-9 m)
during the 1880s but South Channel extended about 0.5 km further into
the Gulf. During the next few decades the north channel widened
greatly. In the 1960s North Bunces Key developed across the mouth of
South Channel (Fig. 26) and stopped tidal flow (Davis et al., 1985).
The channel has not been filled in but has become relict in nature.
North Channel currently carries a large tidal prism and has been
somewhat stabilized by the construction of a jetty at the south end of
Long Key.

The ebb-tidal delta at Pass-a-Grille has maintained a rather large
and tide-dominated accumulation throughout recent history. The
cessation of flow through South Channel had little apparent effect on
the overall inlet morphology. The ebb delta protrudes nearly two
kilometers into the Gulf and has been the source of borrow material for
recent beach nourishment projects in southern Pinellas County.

Figure 26 PASS-A-GRILLE AND BUNCES PASS


- 6


m
0 1000 2000








PASS-A-GRILLE PASS
Diurnal Tide Range: ocean: 79cm bay: 64cm
Net Littoral Drift: 76,400 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS.SP PRIS.MN HAXFL HAXEB HIG


1926 3762 1447 2.6 7.2

1950 3251 604 5.4 40.186 61.9 71,9

1952 17.967

1957 1 2.112 830 77 750 0

1962 1 2.205 850 72 800 40SW

1964

1973 1 2.164 780 79 930 120E

1976 1 2.759 930 81 820 70NW








Bunces Pass -
The inlet at Bunces Pass remains one of the few totally pristine
tidal inlets along the west-penisular coast of Florida. This inlet,
along with Pass-a-Grille, are actually part of the huge tidal delta
complex associated with the mouth of Tampa Bay even though each is a
distinct system. The type and configuration of Bunces Pass have not
changed significantly over the past century, however, it has enlarged
somewhat in the past few decades. There has been a southerly migration
of the seaward part of the channel over the past 100 years.

This inlet has no flood tidal delta. The channel retains its
definition several kilometers eastward across the shallow grass flats
of the margin of Tampa Bay. The throat of the channel is 6-7 m deep
and has been stable for the past few decades. This stability is made
possible by the large tidal prism and the large sediment accumulations
which have recently emerged into small barrier islands on each side of
the seaward inlet channel.

The ebb-tidal delta is distinctly tide-dominated with elongate
shoals extending nearly 2 km into the Gulf (Fig. 27). This tidal delta
has increased in size during the past few decades, probably in response
to the closure of South Channel of Pass-a-Grille. It rests on the
north side of the Egmont tidal delta system at the mouth of Tampa Bay
and is, thereby, sheltered from some wave energy by the shallow waters
in the Gulfward direction. All indications are that this inlet is
stable and no significant changes are forecast.

Figure 27 PASS-A-GRILLE AND BUNCES PASS


0 m .
0 1000 2000








BUNCES PASS
Diurnal Tide Range: ocean: 79cm bay: 66cm
Net Littoral Drift: 76,400 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA COM PRIS.SP PRIS MN MAXFL MAXEB HIG


1150 86

930 72

990 74

800 97

910 94


0

120NW


510

580

500

1490 428 3.5 5.9 11.478


60.0 80.0


3.926

2.994

3.816

1.361

1.753








Ecmont/Southwest Channels -
The largest tidal delta complex in the Gulf of Mexico is located
at the mouth of Tampa Bay. This huge channel complex and sediment body
system serves a tremendous body of water and carries an enormous tidal
prism (Fig. 28). There has been little natural change in the overall
system over the past century due to its size and tide- dominated
nature. Locally some channels have shoaled and required maintainance.
Considerable dredging has been completed to remedy this problem and to
deepen channels for larger ship traffic.

There is no flood tidal delta associated with this tidal system.
The three channels decrease in size and depth from north to south.
Egmont (North) Channel was up to 28 m deep a century ago and is the
same now with the deepest natural area just to the north of Egmont Key.
Southwest Channel is considerably smaller with a maximum depth of
about 10 m and Passage Key Inlet is only a few meters deep except just
off the north end of Anna Maria Island. These deep locations are the
result of extreme tidal scour at the ends of islands, which is a common
phenomenon in most barrier/inlet systems.

The ebb-tidal delta system associated with this tidal environment
is distinctly tide-dominated but is broad on the Gulf side. It extends
9 km into the Gulf at present and has done so without major change for
at least the past century. The linear shoals that border the channels,
especially along the north side of Egmont Channel are quite shallow at
the crest; only a meter or so. Southwest Channel is less defined and
Passage Key Inlet is diminishing in size due to the pressures of
littoral drift.

Figure 28 EGMONT CHANNEL, SOUTHWEST CHANNEL,

AND PASSAGE KEY INLET


ANNA MARIA
ISLAND


1000 4000
370 1008OOO








EGMONT CHANNEL, SOUTHWEST CHANNEL, AND PASSAGE KEY INLET
Diurnal Tide Range: ocean: 76cm bay: 73cm
Net Littoral Drift: 84,040 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDO PRIS SP PRISON MAXFL MAXEB WIG


1885 1 267.594


0,000


61.0 137.2


1984 1 267.594


0.000


1280 6.4









Longboat Pass -
The vicinity of the present Longboat Pass has experienced major
changes over the past 100 plus years. There have been some breaches in
the narrow portion of Anna Maria Key on the north and there were some
major changes to the north end of Longboat Key about 100 years ago.
The inlet had a wave-dominated to mixed- energy (straight)
configuration during the latter part of the 19th century but changed to
a mixed-energy (offset) type. At present, the inlet is tide-dominated
(Fig. 29).

There appears to be multiple flood-tidal deltas associated with
this inlet. These evidently were formed by storm activity associated
with the known and the apparent breaks in southern Anna Maria Island
and northern Longboat Key. There are no indications that these multi-
lobate sediment accumulations have been active during the past 100
years. Some vegetation has developed on the higher elevations.

The inlet channel at Longboat Pass has maintained a fairly similar
size and shape over the past several decades. It is about six to seven
m deep at the throat and has been 100-200 m wide. The channel was
deflected to the south up until the 1970s. It is now nearly
perpendicular to the shore and retains its definition over a kilometer
from the coast.

Currently, the ebb-tidal delta at Longboat Pass shows a tide-
dominated morphology with the north side distinctly linear and shore-
normal, whereas, the south side is more arcuate. A comparison with
John's Pass (see Fig. 24) shows a very similar morphology. The gradual
trend from a mixed-energy to a tide-dominated ebb-tidal delta is a
response to an increase in tidal prism or a decrease in wave energy and
sediment supply. There is no apparent reason for an increased prism at
Longboat Pass based on activities of man or natural changes.


Figure 29 LONGBOAT PASS








LONGBOAT PASS
Diurnal Tide Range: ocean: 77cm bay: 67cm
Net Littoral Drift: 45,840 cubic meters per year, south,

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS SP PRISON MAXFL MAXEB MIG


12.386


1.217


1.147


710 85


130

1059 241


4,3 8.8 13.867


92.6 82.3


5.948


1.297

1.454


91.4 82.3


1.605

1.555


4.3 8.7 8.426


1.885

1.908


6.216


1.806


1.147


790 64


230

170

228

210

833 194


65,0 118.0








New Pass (Sarasota County) -
This inlet was quite deep and well developed in the late 19th
century. There has been little change in the overall morphology during
the past 100 years, except that the ebb-tidal delta has become larger.
Dredging of the inlet has taken place since 1926 (Hine et al., 1986),
thus imprinting man's activities on the morphology.

In the late 19th century a prominent flood-tidal delta was marked
on coastal charts with "soft sand" and "quick sand" which is suggestive
of mobile sediment at that time. During the past half- century there
has been some benthic vegetation and its abundance is increasing.

The inlet channel is narrow and deep and has been since the
surveys of the 1880s. At that time the channel was <100 m wide and the
maximum depth was 7 m. The channel was deflected slightly to the south
as it entered the Gulf. Shoaling became a problem in the early 1900s
and the inlet has been regularly dredged for the past 60 years.
Present channel depth is four to five m and the width is about 125-150
m.

The ebb-tidal delta at New Pass was essentially absent during the
latter 19th century. At that time the inlet was in the wave-dominated
category however it has become a mixed-energy (straight) inlet during
the past half-century. A small but prominent ebb delta with distinct
channel margin shoals now persists (Fig. 30). Wave energy is not
sufficient to close off the Gulfward. end of the main channel.
Undoubtedly, the repeated dredging during the last several decades has
contributed to this morphology by keeping the channel area rather large
and thereby encouraging tidal flow.

Figure 30 NEW PASS

(SARASOTA COI 6





... LONGBOAT


L KE100



m ^~









NEW PASS (Sarasota County)
Diurnal Tide Range: ocean: 77cm bay: 64cm
Net Littoral Drift: 45,840 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS.SP PRISON MAXFL MAXEB MIG


0.994


4.740


90 7.0


3.5 11.320


82.3 51.5


170SW

130S

90N

50SW

30NE


160

592 170



160

170

170

130

170

137

170

447 156


1.006


680 68


5.046


1.016


620 66


0.908

1.204

0.992


2.9 6.1 4.292


3.364


0.965


4,740


*530 '78


60.0 65.0









Big Sarasota Pass -
Most of the tidal prism of Sarasota Bay flows through Big Sarasota
Pass and it probably carried more tidal flow in the past. This large
inlet is a classic example of a mixed-energy (offset) type and it has
shown little change in morphology over the historical past. This has
been aided by the hardening of the south side (downdrift) of the
channel which has stabilized the position of the inlet.

Big Sarasota Pass has a very large flood-tidal delta which is
located more than a kilometer north of the inlet channel due to early
migration. The general situation is similar to that at Dunedin Pass
(compare Figs. 31 and 21) but is more extreme at Big Sarasota Pass.
This flood-tidal delta was inactive and stabilized by vegetation in the
early 1900s and then became the site of residential development in the
1960s. Dredge and fill activities have completely converted the flood
delta into a finger canal housing development.

The main inlet channel trends in a southerly and arcuate course
into the Gulf (Fig. 31). It is asymmetric with the deep side against
the north end of Siesta Key to the south. The channel is wider at the
landward end than where it enters the Gulf. This is due to the
pressures of southerly littoral drift of the shoals in the ebb- tidal
delta. The inlet has narrowed a bit over the past 100 years in
response to dredge and fill activity in Sarasota Bay and the contiuned
maintenance of New Pass.

The ebb-tidal delta at Big Sarasota Pass is large and
asymmetrical; the latter being partly related to the large offset (Fig.
31). Tides are the primary controlling process with wave modification
being secondary. There are small and shallow channels that cut through
the ebb shoal on the updrift side similar to flood channels. Only a
small sand body is present on the downdrift or south side. There has
been a decrease in the Gulfward extent of this ebb delta during the
past several decades, which also reflects the loss of prism mentioned
above.

Figure 31 BIG SARASOTA PASS








BIG SARASOTA PASS
Diurnal Tide Range: ocean: 77cm bay: 64cm
Net Littoral Drift: 45,840 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS_SP PRISON MAXFL MAXEB MIG


6,850


3.226


14,297


3,640

3.700

4.098

4.417

3.782


10.367


5.428


1610 60





1620 56

1840 51

1810 52

1850 52

1810 54


570

2845 889

2146 573

540

560


3.2 6.3

3.7


21.508


77.1 51.5


5.428


1620 55 2223 574 3.9


22.806


93.0 93.0 30S


3.105









Midnight Pass -
The tidal inlet recently called Midnight Pass was preceded by an
inlet in the same location called Little Sarasota Pass. This inlet was
wave dominated in the late 19th century. It had the configuration of a
wild inlet, with channel migration in excess of four kilometers toward
the north. Further northward migration was prohibited by the lithified
sediment at Point of Rocks. The narrow spit produced by this migration
was breached on multiple occasions. Typically, this occurred in the
area of the original inlet and the associated flood-tidal delta. In
the 1950s, Midnight Pass was a healthy mixed-energy inlet, but it
became unstable and wave-dominated in the late 1960s and is closed at
present. There are proposals to open it and structure it for
stability.

The flood-tidal delta at Midnight Pass is quite large and has been
stable for at least the past century. Vegetation has persisted for
several decades. The addition of spoil from the dredging of the
Intracoastal Waterway has enabled upland vegetation to become
established.

The inlet channel has experienced extreme variation over the past
century, both in terms of location and size. The distinct wave-
domination and channel migration persisted until the breaching of the
spit by the 1921 hurricane. From that time until the 1970s, Midnight
Pass displayed a fair amount of stability and increased in size (Davis
et al., 1987). Several reversals in dominant littoral drift direction
took place during this time. By 1955 the channel had reached its
maximum size and stability; it was 140 m wide and 4.5 m deep at the
throat (Vincent & Corson, 1980). Instability of the channel began in
the late 1960s and by 1982 the channel had narrowed to 15 m with a
depth of about 1 m (Fig. 32). It was closed in 1984 with the
assistance of man.

There was no ebb-tidal delta throughout the time that Midnight
Pass was distinctly wave-dominated. During the period of relative
stability, this situation changed and a prominent but small ebb-tidal
delta was developed in the 1950s. It was a mixed-energy (straight)
type inlet at that time but this morphology was short-lived.
Diminution of the tidal prism by the dredging of the Intracoastal
Waterway, 1963-1964, resulted in the return to wave-domination and the
eventual closure of the inlet.

Figure 32 MIDNIGHT PASS



2


mo 10
0 500 1000








MIDNIGHT PASS
Diurnal Tide Range: ocean: 78cm bay: ?
Net Littoral Drift: 53,480 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS SP PRIS MN MAXFL MAXEB MIG


230 117


270 53

210 96

270 107

210 53

160 63



130 35


299 140

70

100

190

80

70

15 15.4

35


2.1 4.5 7.900 7,650 96.0 72.0


350SE

80NW

30NE

100W

120NW


1.2 0.150


28.0 21.0


280NW


0.345


0.482


0.254

0.156

0.356

0.369

0.172


0.122


0.994


0.056









Stump Pass -
There have been numerous changes in the location of what is now
called Stump Pass. In the late 19th century there was a tidal inlet
located 1.5 km north of the present Stump Pass. This unnamed inlet was
7 m deep and had a reasonably well-developed flood-tidal delta. There
was also what appears to be a flood-tidal delta at the present site of
Stump Pass behind a narrow barrier. The opening of the present inlet
took place during the hurricane in 1910 which had landfall near the
present inlet (Reynolds, 1976). The flood-tidal delta associated with
Stump Pass is typical of this coast. It is primarily intertidal and
vegetated with mangroves. The two channels that pass on either side
have remained stable since the last opening of the inlet.

The channel of Stump Pass has remained stable in its location
during the period that it has been opened. There has been a modest
shift in orientation from southwest to northwest and back. The channel
has shallowed from five m in 1955 (Vincent & Corson, 1980) to less than
three m in 1980 when initial dredging took place.

The ebb-tidal delta at Stump Pass has exhibited modest change over
the past 60 years with a general shape of a mixed-energy inlet.
Whereas the initial configuration was straight, there has been
development of a modest downdrift offset since the mid 1970s. This
shape of the ebb delta and the southwesterly orientation of the channel
(Fig, 33) are the result of a significant southerly net littoral drift.

Figure 33


STUMP PASS








STUMP PASS
Diurnal Tide Range: ocean: 78cm bay: 49cm
Net Littoral Drift: 30,560 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA COM PRIS.SP PRIS.HN MAXFL HAXEB MIG


1952 2 250

1955 548 226 2.4 5.4

1955-56 10,216

1970 2 0.487 430 45 160 0

1972 459

1973 2 1.068 460 47 130 20NE

1974 2 1.043 430 41 130 50SW

1977 2 1.293 600 42 110 11ONE

1979 2 0.771 540 34 130 100S

1981 3 0.983 530 42 150 50E

1983 494 195 2.5 6.943 115.8 149.4

1987 413 180 2.3 3.6









Bocilla and Boca Nueva Passes -
Two tidal inlets were present during the latter part of the 19th
century in Charlotte County on what are now Don Pedro Island and Little
Gasparilla Island. Bocilla Pass on the north was distinctly
wave-dominated with a marked southerly overlap of the ebb shoal. Depth
in the channel throat was 2.2 m which shallowed to 0.5 m over the ebb
shoal. There is indication that a flood- tidal delta was present. The
actual date of closure is not known.

Boca Neuva inlet was only about 1.5 km south of Bocilla Pass in
the 1880s. This inlet later became known as Little Gasparilla Pass.
The inlet appears to be about three to four m deep with an ebb shoal
depth of 0.5 m on the 1895 coastal chart (U.S.C. & G.S. #175). There
is no indication of a flood tidal delta. The spit at the mouth of the
inlet indicates a northward net littoral drift; opposite of that at
Bocilla Pass. By 1950 this inlet had developed a distinct flood-tidal
delta and a slight downdrift (south) offset. The inlet, which was
quite narrow and shallow, was closed naturally by 1957.

Although the former locations of these two inlets are quite
apparent on maps and aerial photographs, neither is active today.





















THIS PAGE LEFT BLANK

INTENTIONALLY









Gasparilla Pass -
This is the largest inlet between Sarasota Pass and Boca Grande.
It has been rather stable over the past century with the primary change
being an increase in the downdrift offset. The inlet is natural with
the exception of two causeways that traverse the flood-tidal delta.

The flood-tidal delta is large and is dissected by several
channels. There is considerable vegetation throughout most of its
extent. Undoubtedly, the construction of the causeways from Gasparilla
Island to the mainland caused modification to the flood delta. The
apparent activity of the most distal lobes in the 1940s was probably
associated with the causeways.

The channel of Gasparilla Pass has been stable over the past
century although the depth has varied. In the 1880s the channel was
about 5 m deep but that increased to a maximum of 8 m in 1955 (Vincent
& Corson, 1980). The present depth is 4 m. The orientation of the
channel has persisted as essentially perpendicular with a southwesterly
turn in the ebb-tidal delta.

The ebb-tidal delta of Gasparilla Pass exhibits a typical
downdrift offset (mixed) configuration (Fig. 34). The offset has
increased from about 100 m or so in the latter 19th century to nearly a
kilometer at present. The channel width is presently 600 m. The
ebb-tidal delta at Gasparilla Pass is well-developed and strongly
resembles Sarasota Pass (compare Figures 31 and 34). The typical
asymmetry of a mixed energy-offset inlet is displayed with the updrift
ebb-delta shoal extending at least a kilometer beyond the coastline of
the downdrift island (Fig. 34). The only pronounced change over
historical time is the increase in the downdrift offset.

Figure 34 GASPARILLA PASS







ASPARILLA ISLAND ..L




I. .LITTLE GASPAR.LLA
.--m ISLAND









GASPARILLA PASS
Diurnal Tide Range: ocean: 78cm bay: 49cm
Net Littoral Drift: 76,400 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA COM PRIS SP PRIS.MN MAXFL MAXEB MIG


1883 3.456 1.835


5,275


2.659


1.602





1.369

1 .796

1.166

1.492


760 62





820 63

660 73

740 67

820 64


1.835


330

1177 406

1235 479

570

560

560

550

548

1240 626


2.9 8.4

2.6


13.300


51.5 56.7


120NW

30S

50E

20W


4.0

2.0 8.6 9.571


71.0 93.0









Boca Grande Pass -
Boca Grande Pass is the second largest inlet along the west-
peninsular coast of Florida, trailing only the Egmont Channel complex
at the mouth of Tampa Bay. Boca Grande has been quite stable over time
due to its size and its extreme tidal prism. It is the primary inlet
serving Charlotte Harbor. There has been significant maintenance since
the early 1900s which has resulted in some morphologic changes to the
inlet and to the adjacent islands.

Like the Egmont area, Boca Grande has no flood-tidal delta due to
its broad width. A distinct channel extends several kilometers into
Charlotte Harbor and has done so for at least a century.

The main inlet channel at Boca Grande had a maximum depth of 13 m
in the 1880s. This increased slightly to 17 m in 1956 (Vincent &
Corson, 1980). Because of the abrupt shallowing both seaward and
landward of the throat, dredging has taken place in order to maintain a
channel of 10 m for shipping. The channel has not changed position and
has increased in width from 1.2 km to about 1.5 km from 1930 to 1970,
largely at the expense of the south end of Gasparilla Island (Dean &
O,Brien, 1987).

The ebb-tidal delta at Boca Grande is extremely large and has been
tide-dominated at least throughout the past century. There is a
distinct asymmetry to the ebb delta, similar to, but more extreme than
at Johns Pass (compare Fig. 24 and 35). The north or updrift lobe is
long and narrow extending about 4 km into the Gulf whereas the southern
lobe is broad and extends into the Gulf a bit less than its north
counterpart. There has been a tendency for the inlet to try to become
a downdrift offset by accreting beach ridges on the north end of Cayo
Costa Island. Numerous supratidal bars have developed on a nearly
continuous basis with some migrating shoreward and welding to the
island and others being destroyed. Cayo Costa has also displayed
alternations of cuspate foreland development with erosion of beach
ridge systems (Herwitz, 1977). The main ebb channel, which bends
toward the southwest, has changed position depending upon the presence
and position of these ephemeral sand bars.

Figure 35 BOCA GRANDE PASS



.12



0 isl iurin
O 1~0 :sf r.~:Z~s12


CAYO








BOCA GRANDE PASS
Diurnal Tide Range: ocean: 79cm bay: 56cm
Net Littoral Drift: 84,040 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA COM PRIS SP PRIS HN MAXFL MAXEB HIG


1883 1 86.089 0.000 5.8

1956 1 133,797

1959 1 15421 1589 9.7 356.580 113.4 92.6

1970 1 10854 1447 7.5 17.9

1985 1 122.099 0.000 914 9.8

1988 1 15.3









Captiva Pass -
Captiva Pass is a good example of a mixed energy inlet with a
pronounced downdrift offset (Fig. 36) and has remained so throughout at
least the last 100 years. It has a flood-tidal delta and a distinctly
asymmetric ebb-tidal delta, which is somewhat like that at Sarasota
Pass (see Fig. 36). Captiva Pass has been quite stable throughout
recent history and is a pristine inlet system.

The flood-tidal delta has a multilobate morphology similar to most
of those along this barrier coast. However, unlike most others, it is
totally subtidal. Shallowest depths are about one m and do show
stabilization by sea grasses. The relatively deep surface of this
flood delta is probably related to the large size of the inlet.

The main inlet channel has been stable in position and size over
the past century. It was about 600-700 m wide at the throat with a
maximum depth of 12 m in 1960 (Vincent & Corson, 1980). There is an
abrupt shallowing landward onto the flood ramp of the flood delta. The
ebb channel retains its definition for about three km and curves
distinctly toward the south producing an accurate ebb delta shoal on the
updrift or north side.

The ebb delta is pronounced and large with a volume of about 10
million cubic meters. It is quite asymmetric with a large and accurate
north or updrift lobe, and a much smaller southern lobe which is
limited by the southerly and nearshore location of the main ebb channel
(Fig. 36). There has been some progradation of beach ridges on the
North Captiva Island side over the past several years thus increasing
the downdrift offset which is presently about 0.5 km.

Figure 36 CAPTIVA PASS







S5




NORTH CAPTIVA
4 ISLAND .CAYO COSTA
m
0 1000








CAPTIVA PASS
Diurnal Tide Range: ocean: 79cm bay: 58cm
Net Littoral Drift: 76,400 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRISSP PRISON MAXFL MAXEB HIG


1883 3 6.269 2.064

1956 9.435

1958 3 3.849 1540 37 520 0

1960 2666 579 4.6 12.7 53.770 92.6 97.8

1970 3 3.796 1460 42 550 90NE

1975 3 3.718 1360 45 580 60SE

1982 9.152 2.064 548 4.6

1988 2811 540 5.2 10.6








Redfish Pass -
The hurricane of 1921 separated Captiva Island from North Captiva
Island by forming Redfish Pass. However, maps from the 19th century,
indicate that a channel was present at this site, but was closed by a
narrow barrier. It is probable that Redfish Pass occupies the position
of a former tidal inlet. This inlet has been relatively stable
throughout its short history and has developed a tide-dominated
morphology, although there has been some recent tendency toward a
downdrift offset.

The flood-tidal delta at Redfish Pass is very distinct and
multi-lobate (Fig. 37). All data indicate that there have been no
significant changes in its configuration or size since its formation.
The flood delta is completely subtidal and has been stabilized by sea
grasses since shortly after its formation.

The main channel at Redfish Pass has been stable since its
development by the 1921 hurricane. The channel has maintained a
minimum width of 200-300 m and it achieved a maximum depth of 12 m in
1955 (Vincent & Corson, 1980) since shortly after its formation without
benefit of any dredging.

The rather large tidal prism of Redfish Pass has not only
maintained a stable channel but has produced a tide-dominated ebb delta
morphology. The channel-margin linear bars are nearly perpendicular to
the shore and rather symmetrical although the southern lobe is
typically broader. No substantial change has taken place on the ebb
delta except the removal of borrow material for beach nourishment in
the late 1970s. The tendency for downdrift offset has varied through
time with the present situation tending toward a straight coast on
either side of Redfish Pass. Maximum offset occurred about 1960.


Figure 37 REDFISH PASS


5


ISLAND


I LANL


0 1000
0 1000








REDFISH PASS
Diurnal Tide Range: ocean: 79cm bay: 64cm
Net Littoral Drift: 76,400 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRISSP PRISON MAXFL HAXEB MIG


1926 1257

1944 201

1953 1 0.629 600 87 230 0

1956 2.867

1958 1 0.871 660 79 180 80W

1960 3.249 1249 208 6.0 11.8

1970 1 0.784 690 90 180 120E

1972 1 0.965 730 84 170 20N

1975 1 1.208 760 86 200 40NE

1979 1 1.221 750 82 190 40SW

1982 2.141 1.988 182 4.6

1988 1 1002 180 5.6 7.6









Blind Pass (Lee County) -
Blind Pass, which separates Captiva Island from Sanibel Island,
has experienced a varied history. Surveys from the late 19th century
show this inlet with a mixed-energy offset morphology. There are
suggestions from the 1895 chart (U.S.C. & G.S. #175) that there was at
least one relict channel which indicated a wave-dominated inlet
morphology. Since the formation and development of Redfish Pass, Blind
Pass has been distinctly wave-dominated and has been closed for
extended periods.

The flood-tidal delta at Blind Pass is large and well-defined. It
is intertidal to subtidal and has an extensive sea grass community on
it. There is no indication that the size or shape of the flood delta
has changed in the past century.

The inlet channel at Blind Pass has experienced much change in
both size and configuration during recent history. About 100 years ago
the inlet was 200 m wide and five m deep at the throat. There was a
distinct offset of 250 m. By the mid-20th century the inlet channel
had migrated over two km to the south but remained open. Closure took
place in the 1960s. Blind Pass opened again in the mid-1970s as the
result of erosion of the long spit across its mouth. This was short-
lived however, as closure again took place by 1979. It was opened
again in 1986 (Dean & O'Brien, 1987) and remains so at the present
time, 1988.

A century ago Blind Pass had a mixed-energy downdrift offset
morphology. The formation of Redfish Pass and the capture of most of
the tidal prism from Blind Pass led to its becoming a wave-dominated,
"wild pass" type of inlet. There has not been an appreciable ebb-
tidal delta for about 50 years. Closure is the typical situation due
to the combination of significant littoral drift and small tidal prism.
The present open channel has a small ebb shoal but it is unlikely to
maintain this configuration (Fig 38).

Figure 38 BLIND PASS
ILEE CO1 m
0 1000








BLIND PASS (Lee County)
Diurnal Tide Range: ocean: 79cm bay: 64cm
Net Littoral Drift: 84,040 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDH PRISSP PRISON MAXFL MAXEB HIG


1889 3

1953 4 0.244 350 11 60 0

1958 4 0.135 210 40 20 660S









Big Carlos Pass -
Although good survey data are more limited for this inlet in
comparison to those to the north, there appears to have been overall
stability of Big Carlos Pass over the past 100 years. Its size and
position have remained essentially the same over that period.

There is a large, distinct, multi-lobate flood-tidal delta at Big
Carlos Pass. It is almost entirely intratidal to supratidal and is
covered with a dense mangrove community.- All indications are that the
flood delta has been stable over at least the past century.

The channel has maintained a width of 300-400 m and a depth of
about four m over the past century. It extends well landward into the
flood delta area and is nearly perpendicular in the Gulfward direction.
Some stabilization has been provided by the causeway which was
completed in the mid-1960s and the increased tidal prism due to the
closure of small inlets to the south (Hine et al., 1986).

The ebb-tidal delta at Big Carlos Pass has a mixed-energy.
(straight) coast shape. Although the surveys of the 1880s showed a
northward deflection of the main ebb channel (U.S.C. & G.S. #174),
there is a general symmetry to the ebb delta. This plus the absence of
a distinct outer wave-modified lobe gives some cause to consider a
tide-dominated classification. The tide-domination is due to the
fairly large prism and the very low wave energy along this reach of
coast which is sheltered from northerly storm waves by the offset in
the coast at Sanibel Island (see Fig. 39). There has been significant
accretion of spits and beach ridges on both sides of the inlet. This
appears to have ceased on the south but continues on the north (Dean &
O'Brien, 1987). The general pattern indicates lack of significant net
littoral drift.

Figure 39 BIG CARLOS PASS











LOVERS- .. .
KEY









BIG CARLOS PASS
Diurnal Tide Range: ocean: 82cm bay: 82cm
Net Littoral Drift: 42,020 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA COM PRIS.SP PRIS MN HAXFL MAXEB HIG


2 3.578

2 3.970

2

2


3.211


3.875

3.454


1030 104

1100 102


1908. 435

500

410


19.737


2

2 6.147


1889

1960

1970

1975

1978

1978-80

1982


75.0 81.1


1933 487 3.9 6.1

410 3.4


3.211








New Pass (Lee County) -
There is no real documentation on the origin of New Pass. The
surveys of the 1880s show an inlet, Little Carlos Pass, between Big
Carlos and Big Hickory Passes. However, the location is not coincident
with New Pass and there are no indications of migration of this pass.
The barrier through which Little Carlos Pass flowed was removed through
persistent erosion. The definition and development of New Pass seems
to have arisen from increasing tidal flow through a tidal channel
coupled with accretion on adjacent mangrove islands forming a precursor
barrier island to the north. The aerial photos of the early 1950s show
several tidal channels just north of the present New Pass that have
subsequently been closed with New Pass gaining their tidal prisms.

The flood-tidal delta at New Pass appears to be unlike most in
that it represents scour and channelization of a bifurcating system
through the previously existing and vegetated shallow bay environment.
Aerial photos indicate some sediment movement in the area but primarily
of an erosive nature.

The main channel at New Pass has become more defined and deeper
over the past few decades. The channel width has increased from 300 m
to over 400 m since 1953 and the cross-section area increased from 470
to 680 square meters between 1960 and 1978 (Jones, 1980). Maximum
depth increased from about 3.5 m to five m over the same time period.
The position of the inlet channel has been fairly stable although the
thalweg has moved toward the north since the late 1970s.

Initially there was no ebb-tidal delta at New Pass. This has
changed greatly to the point that now there is a rather substantial ebb
delta which extends nearly 600 m into the Gulf (Fig. 40). The lobes of
this ebb delta display little wave influence and, like Big Carlos Pass
to the north, could be considered tide-dominated due to the absence of
waves. During the past few years, there has been some ridge accretion
on the north side of the inlet and there are indications of an offset
developing to the north, the direction of net littoral drift.


Figure 40 NEW PASS
ILEE CO1








NEW PASS (Lee County)
Diurnal Tide Range: ocean: 82cm bay: 82cm
Net Littoral Drift: 42,020 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRISSP PRIS MN MAXFL MAXEB HIG


0.215


270 143


180

466 238 3.1


0.410


0.515

0.500

0.512


250N

90E

S160S


6.697 0.000 78.3 64.6


0.454

0.321 0.592 0.229


2.7 5.5

2.1









Big Hickory Pass -
This inlet has been small or closed for the periods of record.
One hundred years ago Big Hickory Pass was about 300 m wide with a
maximum depth of less than 3 m. None of the historical records show a
larger inlet at this location and it is likely that the name came from
the adjacent Big Hickory Island rather than from the size of the inlet.

Old surveys show a mangrove island just landward of the inlet in
1869 (Jones, 1980). It is likely that this represents the original
flood-tidal delta. There are no indications of mobility or
modification since that survey.

During most of historical time, the inlet channel at Big Hickory
Pass has been a "wild inlet". It migrated in a northerly direction
continuously throughout the past century. It migrated 400 m from 1885
to 1927, 150 m between 1944 and 1953 and continued in this path until
it was closed in 1976, 1.8 km north of its location in 1885 (Jones,
1980). The increase in size of New Pass to'the north captured much of
the tidal prism of Big Hickory Pass and eventually led to closure.
Although it was opened by dredging in 1976 (Fig. 41), it closed again
in 1979, 300 m north of the position of 1976 (Hine et al., 1986).

Little or no ebb-tidal delta has been present at this inlet since
the original surveys of the Corps of Engineers in 1869. At that time
there was a small, shore-attached and northwest oriented shoal on the
south side of the inlet channel (U.S.C. & G. S. #174). Subsequent
charts and photos show significant spit platform development and lack
of ebb shoals as the inlet migrated northward. There have, however,
been short periods of southwesterly channel orientation such as shown
on the aerial photos of 1953.

Figure 41 BIG HICKORY PASS


LITTLE
HICKORY
ISLAND


HICKORY ISLAND




m
0 560 1000









BIG HICKORY PASS
Diurnal Tide Range: ocean: 82cm bay: 76cm
Net Littoral Drift: 42,020 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS.SP PRIS MN MAXFL MAXEB MIG


214 106 2.0


0.535


270 37 167

204

190 155 111


23

56 38


1944

1953

1958

1965

1970

1975

1976

1978

1978-80


0.000


0.126


0.133

0.036


3 6 0.3 0.9


160 162


0.034


152.4









Wiqqins Pass -
This inlet has been small throughout the historical record and
closed multiple times prior to 1952 (Hine et al., 1986). No
measurements on size are available prior to 1952 and the chart of the
late 19th century shows no depths. Channels through the wetlands
landward of the barrier islands were dredged in 1952 and caused an
increase in the tidal prism of 50 percent (Hine et al, 1986).

Aerial photos and topographic maps indicate that there are
presently some partly vegetated, shallow subtidal to intertidal
sediment bodies landward of the inlet channel which may represent a
flood-tidal delta (Fig. 42). Historical information on the size and
tidal prism suggest, however, that they may simply be recently modified
but previously existing shallow banks in the lagoon landward of the
inlet/barrier complex. The increase in tidal prism that took place in
1952 could be responsible for the relatively recent modification of
these sediment accumulations.

The inlet channel has shown significant stability since 1952 with
depth increased from about 1 m to nearly 2 m in 1982. Recent dredging
in 1983 increased the cross-section to a width of 60 m and 2.5 m in
depth. It has been partially reduced since that time (Dean & O'Brien,
1987).

No prominent ebb-tidal delta has existed at Wiggins Pass
throughout the period of record. The aerial photo of 1981 does show a
small yet distinct ebb shoal that extends a few hundred meters into the
Gulf. During most of the time, there is an indication of modest
accretion on both sides of the inlet channel in the Gulfward direction
in the form of prograding beach ridges.

Figure 42 WIGGINS PASS


m
0 560 1000








WIGGINS PASS
Diurnal Tide Range: ocean: 83cm bay: 65cm
Net Littoral Drift= 64,940 cubic meters per year, south,

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS SP PRIS HN HAXFL MAXEB MIG


0.090

0.069

0.104

0.196

0.076

0.064

0.152


0,107


0.136


150 108


50

40

70

70

70

70

50

61 44

80

90

46 91

87 64


0.9 1.8 0.787 0.787 79.0 89.0


1.8

1.3 2.6


0.708









Clam Pass -
This inlet has been quite small throughout the period of record.
There is no early map of the entire inlet. Only a map of the outer
coast which shows no bulge in contours or soundings that indicate the
presence of an ebb-tidal delta. No early data on the inlet channel or
flood-tidal delta are available.

The morphology of the inlet as it appeared on 1952 photos
indicates a small and active flood-tidal delta. Active sand
accumulation landward of the inlet channel was primarily subtidal and
intertidal with very little stabilizing vegetation at that time.
Recent photos indicate that most of this apparent flood delta has been
vegetated, primarily with mangroves and is, therefore, stable.

The inlet channel at Clam Pass is small but has been reasonably
stable in its position considering the small tidal prism that it
serves. Channel width has been 30-40 m with a depth of 1.0-1.5 m.
Seasonal shifting of the inlet mouth has been common (Hine et al.,
1986) and there was a northward migration of 30 m from 1952 to .1973.
The inlet closed due to natural processes in 1976 and again in 1981.
It was open by dredging each time and remains open at the present time.

There has been no sediment accumulation on the Gulf side of Clam
Pass that is worthy of the ebb-tidal delta designation. Very small
sand shoals appear on some aerial photos but they are ephemeral. The
present situation consists of a small spit and spit platform on the
south side of the inlet (Fig. 43).

Figure 43 CLAM PASS


2




.. ... --" VANDERBILT BEACH




-- 0 500 1000








CLAM PASS
Diurnal Tide Range: ocean: 84cm bay: ?
Net Littoral Drift: 64,940 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS.SP PRIS MN MAXFL MAXEB HIG


1952 4 0.027 80 127 8 0

1972 11 15 0.8 1.8

1973 4 0.012 50 129 16 30NE

1979 4 0.005 0.031 50 24 13 1.2 10NW








Gordon Pass -
This inlet is the largest between New Pass and Big Marco Pass on
the southwest Florida coast. Like most of the inlets in Collier
County, there is not an accurate chart or map from the 19th century.
Available data indicate that there have not been major changes in the
size and location of Gordon Pass since the 1880s. However, development
on the north side of the inlet since the 1960s has resulted in
considerable structuring in order to attempt to maintain stability.

There is no good information to support the presence of a flood-
tidal delta at this inlet. There are vegetated uplands and mangrove
communities landward of the inlet throat that may include relict flood
deltas, but the morphology is not at all distinct. Spoil disposal
areas have also acted to mask the origin of these intertidal and
supratidal environments landward of the north tip of Keewaydin Island.

The inlet channel has been narrow throughout its natural history
with a minimum of 30 m in the early 1950s. Depth was only a meter or
so at that time. Dredging of the channel began in 1962 and has
continued to the present with a width of 160 m and depth of 2.5 m (Hine
et al., 1986). Structuring of the inlet with groins on the north and a
jetty on the south took place at the same time as initial dredging.

Gordon Pass has always maintained a distinct ebb-tidal delta. In
the late 19th century, it was small but distinct as shown by the
Gulfward protuberance of the six and 12 foot contours on the coastal
chart (#174). The aerial photos and maps beginning in the early 1950s
show a more pronounced ebb delta (Fig. 44) extending 400-500 m into the
Gulf and having a rather broad shape indicative of mixed energy
conditions. Although the dredging has resulted in a straight and
perpendicular channel, the ebb delta has not shown significant change
since dredging was initiated.

Figure 44 GORDON PASS








KEEWAYDIN Ir
ISLAND "
m 0 PORT ROYAL
0 1000

^'I:h'.*.'.


I








GORDON PASS
Diurnal Tide Range: ocean: 87cm bay: ?
Net Littoral Drift: 53,480 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA COM PRIS.SP PRISON MAXFL MAXEB MIG


1952 3 0.533 390 79 45

1970 366 182 2.0 3.9

1982 0.443 0.092 164 2.4

1987 936 298 3.1 7.3 11.976 103.5 123.9









Little Marco Pass -
This inlet has shown tremendous change in both morphology and
location since the late 19th century. In the 1880s Little Marco Pass
had a distinct downdrift offset and was in the mixed energy category.
During most of this century it has been distinctly wave-dominated and
has migrated nearly 5 km to the south.

The present position of the inlet mouth and channel are far
removed from their original location. Based upon the location on chart
#174 and the morphology landward of the barrier at that latitude, there
appears to be a relict flood-tidal delta associated with the ancestral
Little Marco Pass. A somewhat lobate and currently vegetated
intertidal and supratidal environment is located landward of the former
position of the inlet.

The inlet channel was 4.5 m deep at the throat and about 200-250 m
wide in the 1880s. An apparent decrease in tidal prism permitted the
strong southerly littoral drift to dominate and cause a rapid and
extreme shift in the channel position to the south. By 1952 the "wild
inlet" had migrated 3.5 km and this increased to over 5 km at the
present time. The channel is presently about 100 m wide and 1.5 m
deep.

About a century ago there was a small but distinct ebb-tidal delta
at Little Marco Pass. As the inlet became wave-dominated and migrated
to the south (Fig. 45) this was removed by waves and currents. The
present inlet mouth has a small and undoubtedly ephemeral sand shoal at
its mouth.

Figure 45 LITTLE MARCO PASS








LITTLE MARCO PASS
Diurnal Tide Range: ocean: 95cm bay: ?
Net Littoral Drift: 53,480 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDH PRISSP PRIS MN MAXFL MAXEB MIG


0.597

0.549

0,482

0.639


430 77

480 28

400 59

510 56


225 4.5

70

80

80

240


465 183 2.5 3.3 6.066


580SE

500SE


101.6 123.4


1885

1952

1962

1973

1981

1987









Big Marco Pass -
This has been one of the largest and most stable inlets along the
southern part of the west-peninsular barrier system of Florida. Its
overall size and morphology are quite comparable to that of Big
Sarasota Pass (compare Figs. 31 and 46). Even though development on
Marco Island on the south side of the inlet is extensive, the inlet
itself is pristine.

The survey of the late 19th century shows what is probably a
relict flood-tidal delta with lobes between two rather large channels
on the landward side of the inlet. These have been vegetated
throughout the period of record and in the 1960s were extensively
developed including dredge and fill with the usual finger canals. This
development does not seem to have affected the stability of the inlet
itself.

The inlet channel has had a similar size and shape for at least
the past 100 years. In the late 1880s, the inlet channel was about 300
m wide with a maximum depth of nearly 10 m. Nearly 100 years later,
1970, the inlet was 280 m wide and 7.5 m deep (Vincent & Corson, 1980).
A complicating factor in the tidal prism of Big Marco Pass developed
when the narrow barrier to the north was breached sometime between 1962
and 1973, and Capri Pass was formed. This inlet has not only captured
a significant portion of the prism formerly carrier by Big Marco Pass,
but it left a small vegetated island which has separated the two inlets
(Fig. 46). Both of these inlets are about 300 m wide at the present
time (Dean & O'Brien, 1987).

The ebb-tidal delta at Big Marco Pass is a classic example of a
mixed energy offset morphology. This general morphology has persisted
for at least the past century. The large shallow to intertidal shoal
on the north (updrift) side extends about 500 m Gulfward of the
downdrift offset which itself is quite pronounced. There has been a
relatively continuous appearance of shoreward-migrating sand bars on
the south (downdrift) side. The accretion of these bars has produced
the beach ridge and catseye-pond complex at the north end of Marco
Island.

Figure 46 BIG MARCO PASS


m
0 1000 2000
0 1000 2000


i.
..
..








BIG MARCO PASS
Diurnal Tide Range: ocean= 95cm bay: 79cm
Net Littoral Drift: 53,480 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS.SP PRIS HN MAXFL HAXEB MIG


1889 3 15.673 2.599

1952 3 2.832 1370 66 230 0

1962 3 2.900 1320 65 270 190S

1970 1600 266 6.0 7.8

1981 3 2.937 1670 47 270 300N

1982 11.698 2.599 347 3.0

1987 2685 610 4.4 5.6 19.133 33.5 103;9









Caxambas Pass -
This inlet presents problems for the inlet classification
presented earlier in this report. The morphology is, and has been, one
of mixed energy offset with the distinct offset on the north side of
the inlet making it an updrift offset. The island to the south shows
what appears to be a spit-like configuration however there is little
evidence of northerly growth that would indicate a local reversal in
littoral drift. The construction of a major seawall at the south end
of Marco Island in 1958 has caused major changes in the inlet (Stephen,
1981).

There is a large flood-tidal delta with multiple lobes associated
with Caxambas Pass (Fig. 47). Most of it has been stabilized
throughout the period of record by mangroves, although there is
indication of subtidal sediment movement on several sets of aerial
photos.

The inlet channel has shown significant change during the last 60
years especially after the construction of the seawall in 1958. The
coastal chart of 1924 (U.S.C. & G.S. #12564) shows a channel oriented
somewhat to the northwest. By 1952 the orientation was essentially
east to west and than persisted until severe erosion on the south end
of Marco Island produced a southerly growing spit which deflected the
channel to the south. The spit was eventually breached and the inlet
developed two distinct channels, the situation that prevails now. The
inlet was 500 m wide with a maximum depth of 8 m in 1924. The change
in inlet morphology has not significantly altered the cross section
area; it was 1850 square meters in 1978 (Stephen, 1981).

The ebb-tidal delta was very large and well developed prior to and
shortly after construction of the seawall. It had a relatively
tide-influenced morphology in 1924 when the north side extended nearly
a kilometer Gulfward of Marco Island and the south side extended over
1.5 km out from Dickman's Point on Kice Island. By the 1950s the ebb
delta was a bit more wave-influenced, but was still quite large and
well-developed. By the late 1960s, the ebb delta was quite reduced in
size and the ephemeral shoal was in the outer part of the inlet
channel. Although a distinct ebb-tidal delta persists, it shifts
markedly over just a few years. At the present time, there is little
of the ebb delta that protrudes Gulfward of the south end of Marco
Island.
Figure 47 CAXAMBAS PASS
Figure 47


KICE
ISLAND /









CAXAMBAS PASS
Diurnal Tide Range: ocean: 102cm bay: 71cm
Net Littoral Drift: 42,020 cubic meters per year, south.

YEAR TYPE ETDV ETDA FTDV CEND CENA CXSA CW CDA CDM PRIS.SP PRIS MN MAXFL MAXEB MIG


1952 3 1.562 2,141 860 110 460

1978 1854 600 3.0 5.6 25.410 170.0 155.0









EXPLANATION OF SYMBOLS IN DATA TABLES


Tide Range These data are from NOAA tide and tidal current tables.
Net Littoral Drift These data are derived using the technique of
Walton (1973) as compiled by Dean and O'Brien (1987).
TYPE Morphological classification of the inlet.
1= tide dominated
2= mixed energy straight
3= mixed energy offset
4= wave dominated
EDTV Ebb-tidal delta volume in cubic meters xl06
ETDA Ebb-tidal delta area in square meters xl06
FTDV Flood-tidal delta volume in cubic meters x106
CEND Distance in meters from the center of the inlet throat to the
centroid of the ebb delta. The centroid is the geometric
center or "center of gravity" of the outline of the ebb delta.
CENA Angle in degrees formed between the vector extending from the
center of the inlet throat to the ebb delta centroid and the
general shoreline trend. This angle is measured clockwise from
the shoreline. -Thus, a CENA value of 90 would indicate the ebb
delta is oriented perpendicular to shore, a value of 45 would
indicate the ebb delta is slanted to the southeast, and a value
of 135 would indicate a slant to the north or west.
CXSA Cross sectional area in square meters of the channel at the
inlet throat (measured below msl).
CW Channel width in meters at the inlet throat.
CDA Channel depth (average) in meters at the inlet throat (measured
below msl).
CDM Channel depth (maximum) in meters at the inlet throat (measured
below msl).
PRIS SP Tidal prism (spring) in cubic meters xl06
PRIS_MN Tidal prism (mean) in cubic meters x 106.
MAXFL Maximum flood current velocity in cm/s.
MAXEB Maximum ebb current velocity in cm/s.
MIG Migration in meters and direction (N= north, S= south etc.) of
the center of the inlet throat. The value shows the amount and
direction of migration since the date of the previous value.
The data begin with the year marked with a MIG value of 0.









REFERENCES CITED


Davis, R. A., Jr. (1988). "Morphodynamics of the west-central Florida
barrier system: the delicate balance between wave- and
tide-domination." Geologie en Mijnbouw, 67.

Davis, R. A., Jr., and Fox, W. T. (1981). "Interaction between wave-
and tide-generated processes at the mouth of a microtidal estuary:
Matanzas River, Florida (U.S.A)." Marine Geology, 40, 49-68.

Davis, R. A., Jr., and Hayes, M. O. (1984). "What is a wave-dominated
coast?" Marine Geology, 60, 313-329.

Davis, R. A., Jr., and Kuhn, B. J. (1985). "Origin and development of
Anclote Key, west-peninsular Florida." Marine Geology, 63, 153-171.

Davis, R. A., Jr., Hine, A. C., and Belknap, D. F., eds. (1985).
"Geology of the barrier island and marsh-dominated coast, west-central
Florida." Field Trip Guide Book, Geological Society of America, Annual
Meeting, Orlando, Florida.

Davis, R. A., Jr., and Andronaco, M. (1987). "Hurricane effects and
post-storm recovery, Pinellas County, Florida (1985-1986)." Coastal
Sediments '87, Proctocols of a meeting of the ASCE, New Orleans, N. C.
Kraus, ed., 1023-1036.

Davis, R. A., Jr., Hine, A. C., and Bland, M. J. (1987). "Midnight
Pass, Florida: inlet instability due to man-related activities in
Little Sarasota Bay." Coastal Sediments '87, Proc. of a meeting of the
ASCE, New Orleans, N. C. Kraus, ed., 2062-2077.

Davis, R. A., Jr., Andronaco, M. and Gibeaut, J. C. (in review).
"Formation and development of a tidal inlet from a washover fan, west-
central Florida." Sedimentary Geology.

Dean, R. G. and O'Brien, M. P. (1987). "Florida's west coast inlets;
shoreline effects and recommended action." Univ. Florida, Coastal and
Ocean. Engr. Dept. Rept. 87/016, 100 p.

Evans, M. W., Hine, A. C., Belknap, D. F., and Davis, R. A., Jr.
(1985). "Bedrock controls on barrier island development: west-central
Florida coast." Marine Geology, 63, 263-283.

Evans, M. W., and Hine, A. C. (1986). "Quaternary infilling of the
Charlotte Harbor estuarine/lagoonal system, southwest Florida:
implications of structural control." SEPM Annual Midyear Meeting
Abstracts, Raleigh, North Carolina, 3, 34.

FitzGerald, D. M. (1982). "Sediment bypassing at mixed energy tidal
inlets." Proc. of the 18th Coastal Engineering Conference, ASCE, Cape
Town, South Africa, 1094-1118.









FitzGerald, D. M., and Hayes, M. 0. (1980). "Tidal inlet effects on
barrier island management." Proc. of Coastal Zone '80, ASCE, Hollywood,
Florida, 2355-2379.

Hayes, M. 0. (1975). "Morphology of sand accumulation in estuaries."
Estuarine Research, v. 2, L. E. Cronin, ed., Academic Press, New York,
3-22.

Hayes, M. 0. (1979). "Barrier island morphology as a function of tidal
and wave regime." Barrier islands from the Gulf of St. Lawrence to the
Gulf of Mexico, S. P. Leatherman, ed., Academic Press, New York, 1-27.

Hayes, M. O., Goldsmith, V., and Hobbs, C. H. (1970). "Offset coastal
inlets." Proc. of the 12th Coastal Engineering Conference, ASCE, 1187-
1200.

Herwitz, S. (1977). "The natural history of Cayo-Costa Island."
Sarasota, Florida, New College Environmental Studies Program, ESP Publ.
No. 14, 118 p.

Hine, A. C., Davis, R. A., Mearns, D. L., and Bland, M. (1986). "Impact
of Florida's Gulf Coast inlets on the coastal sand budget." Univ. South
Florida, Rept. to Florida Dept. Nat. Res., 128 p.

Jones, C. P. (1980). "Big Hickory Pass, New Pass, and Big Carlos Pass;
glossary of inlets report no. 8." Florida Sea Grant College, Rept. No.
37, 46 p.

Lynch-Blosse, M. A. (1977). "Inlet sedimentation at Dunedin and
Hurricane Passes, Pinellas County, Florida." unpubl. M.S. thesis,
Geology Department, University of South Florida.

Mehta, A. J., Jones, C. P., and Adams, W. D. (1976). "John's Pass and
Blind Pass; glossary of inlets report no. 4." Florida Sea Grant
Program, Rept. No. 18, 66 p.

Nummedal, D., and Fischer, I. A. (1978). "Process-response models for
depositional shorelines: the German and the Georgia Bights." Proc. of
the 16th Coastal Engineering Conference, ASCE, Hamburg, West Germany,
1215-1231.

Oertel, G. F. (1977). "Geomorphic cycles in ebb deltas and related
patterns of shore erosion and accretion." Jour. of Sedimentary
Petrology, 47(3), 1121-1131.

Reynolds, W. J. (1976). "Botanical, geological, and sociological
factors affecting the management of the barrier islands adjacent to
Stump Pass." Sarasota, Florida, New College Environmental Studies
Program, Rept. No. 12, 69 p.

Smith, D. (1984). "The hydrology and geomorphology of tidal basins."
The Closure of Tidal Basins, W. van Aslst, ed., Delft University Press,
85-109.









Stephen, M. F. (1981). "Effects of seawall construction on beach and
inlet morphology and dynamics at Caxambas Pass, Florida." Ph. D.
dissertation, Univ. South Carolina, Columbia.

Tanner, W. F. (1960). "Florida coastal classification." Trans. of the
Gulf Coast Assoc. of Geological Sciences, 10, 259-266.

University of Florida, Coastal Engineering Laboratory. (1973).
"Coastal engineering study of Clearwater Pass and Sand Key."
UFL/COEL/70/011, Gainesville, Florida.

Vincent, C. L. and Corson, W. D. (1980). "The geometry of selected U.
S. tidal inlets." U. S. Army, Corps of Engineers, General Inv. of Tidal
Inlets, Rept. No. 20, 163 p.

Walton, T. L., and Adams, W. D. (1976). "Capacity of inlet outer bars
to store sand." Coastal Engineering, Ch. 112, 1919-1937.




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