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REPORT DOCUMENTATION PAGE
1. Report No. 2. 3. Recipient's Accession No.
4. Title aod Subtitle 5. Report Date
5. Report Date
Florida's East Coast Inlets December, 1987
Shoreline Effects and Recommended Action 6.
7. Author(s) 8. Performing Organization Report No.
R. G. Dean
M. P. O'Brien UFL/COEL-87/017
9. Performing Organization Name and Address 10. Project/Task/Work Unit No.
Coastal and Oceanographic Engineering Department
University of Florida 11. Contract or Grant No.
336 Weil Hall C4348
Gainesville, FL 32611 13. Type of Report
12. Sponsoring Organization Name and Address
Division of Beaches and Shores
Department of Natural Resources Final
3900 Commonwealth Boulevard
Tallahassee, FL 32399 14.
15. Supplementary Notes
16. Abstract
This report responds to the 1986 Beaches Bill which, in recognition of the
deleterious impact on Florida's beaches of inlets modified for navigation, mandated
a study of those inlets with identification of recommended action to reduce the
impacts. This report addresses East Coast inlets; West Coast inlets are the subject
of a companion report.
There are 19 inlets along that portion of Florida's East Coast commencing from
St. Marys Entrance at the Georgia border to Government Cut at the south end of Miami
Beach. Six inlets are constructed inlets and were cut for navigational and/or water
quality purposes. Of the 19 total, all but two have been modified for navigational
purposes.
A review of inlets in their natural condition demonstrates the presence of a
shallow broad outer bar across which the longshore transport occurred. These
shallow and shifting bar features were unsuitable for navigation which led to the
deepening of the channels and training with jetties. Inlets in this modified state
along with inappropriate maintenance practices have placed great erosional stress
along most of Florida's East Coast beaches. The ultimate in poor sand management
practice is the placement of good quality beach sand in water depths too great for
Over -
17. Originator's Key Words 18. Availability Statement
Bypassing
Entrances
Inlets
19. U. S. Security Classif. of the Report 20. U. S. Security Classif. of This Page 21. No. of Pages 22. Price
UNCLASSIFIED UNCLASSIFIED 65
the sand to reenter the longshore system under natural forces; placement depths of
12 ft or less are considered appropriate for Florida in order to maintain the sand
in the system.
With the interruption of the longshore sediment transport by inlets modified
for navigation, if the downdrift beaches are to be stabilized, there must be an
effective sand transfer program. Several East Coast inlets have such transfer
facilities; however, there is a need to increase substantially the quantities of
sand transferred. Although an evolution and improvement in the technical capability
to transfer sand around entrances is expected, a capability exists today and a
concerted program should be made to commence a scheduled implementation of this
capability at those entrances causing greatest erosional stress on the downdrift
shorelines.
A brief summary review for each of the 19 inlets is presented including: a
scaled aerial photograph, brief historical information, several items related to
sediment losses at each inlet and special characteristics relevant to State
responsibilities. For each inlet the above information is utilized to develop a
recommended action, usually in the form of periodic sand transfer quantities.
UFL/COEL-87/017
FLORIDA'S
SHORELINE
EAST COAST
EFFECTS AN
INLETS:
D RECOMMENDED ACTION
R.G. Dean
and
M.P. O'Brien
Sponsor:
Division of Beaches and Shores
Department of Natural Resources
Tallahassee, Florida 32399
UFL/COEL-87/017
FLORIDA'S EAST COAST INLETS
SHORELINE EFFECTS AND RECOMMENDED ACTION
R. G. Dean
M. P. O'Brien
December, 1987
Submitted To:
Division of Beaches and Shores
Department of Natural Resources
Tallahassee, Florida 32399
Prepared By:
Coastal and Oceanographic Engineering Department
University of Florida
Gainesville, Florida 32611
TABLE OF CONTENTS
PAGE
LIST OF TABLES........................................................... 4
LIST OF FIGURES....................... .................................. 5
EXECUTIVE SUMMARY .... .......................... ..... .................... 6
ACKNOWLEDGEMENTS ............... ................................ ....... 8
INTRODUCTION... ................. ............................. .......... 9
EAST COAST INLETS IN THEIR NATURAL STATE................................ 9
EAST COAST INLETS IN THEIR MODIFIED STATE................................ 12
Deeper Entrance Channel............................................ 12
Effects of Jetties.......................................... .. 14
Channel Maintenance Dredging........................................ 14
Fixed Channel Alignment............................................ 15
Summary of Modified Channel Effects............................... 15
METHOD OF BYPASSING SAND AND EXISTING EFFORTS............................ 17
Sebastian Inlet..................................................... 17
Jupiter Inlet............................... ................ ........ 17
Port of ralm Beach Entrance....................................... 17
South Lake Worth Inlet.............................................. 18
Boca Raton Inlet..................................................... 18
Hillsboro Inlet............................ ......................... 19
A CASE STUDY PORT CANAVERAL ENTRANCE................................... 19
INFORMATION AND RECOMMENDATION SUMMARY................................... 22
Photograph........................................................... 22
Brief Historical Information......................................... 22
Sediment Balance...... ............................................. 22
Brief Dredging History............................................ 23
Special Characteristics Relevant to the State Responsibilities ....... 23
Recommended Action..................... ............................ 23
ST. MARYS ENTRANCE................. ...... ....................... 24
NASSAU SOUND.................................................... 26
FT. GEORGE INLET............................................... 28
ST. JOHNS RIVER ENTRANCE (JACKSONVILLE HARBOR).................. 30
ST. AUGUSTINE INLET............................................. 32
MATANZAS INLET................................................ .. 34
PONCE DE LEON INLET..................................... ...... 36
PORT CANAVERAL ENTRANCE..................................... 38
SEBASTIAN INLET................................................. 40
FT. PIERCE INLET................................................ 42
ST. LUCIE INLET................................................. 44
JUPITER INLET.................................................. 46
LAKE WORTH INLET (PORT OF PALM BEACH ENTRANCE)................... 48
SOUTH LAKE WORTH INLET......................................... 50
BOCA RATON INLET.............................................. 52
HILLSBORO INLET............................................. 54
PORT EVERGLADES ENTRANCE.......................... ............ .. 56
BAKER'S HAULOVER INLET.......................................... 58
GOVERNMENT CUT (MIAMI HARBOR) ................................... 60
REFERENCES.................................................... ......... 62
LIST OF TABLES
TABLE PAGE
I. NATURAL DEPTHS IN CHANNELS AND ON BARS, Florida's East Coast
Entrances (From Fineren, 1938)..................................... 11
II. SUMMARY OF ANNUALIZED (1980-1985) QUANTITIES AND PERCENTAGES
FOR PLACEMENT OF BEACH QUALITY SAND (Federally Maintained East
Coast Inlets)....... ......... ...... ........................... 16
LIST OF FIGURES
FIGURE PAGE
1. Estimates of Net Annual Longshore Sediment Transport Along
Florida's East Coast .......................................... 10
2. Natural and Modified Bar Depths Along Florida's East Coast
Inlets and Jurisdiction of Channel Maintenance.................. 13
3. Effects of Establishment of Cape Canaveral Entrance and
Subsequent Nourishment Project on Downdrift Beaches (Shoreline
Change Results Provided by J. H. Balsillie)...................... 21
EXECUTIVE SUMMARY
This report responds to the 1986 Beaches Bill which, in recognition of
the deleterious impact on Florida's beaches of inlets modified for navigation,
mandated a study of those inlets with identification of recommended action to
reduce the impacts. This report addresses East Coast inlets; West Coast
inlets are the subject of a companion report.
There are 19 inlets along that portion of Florida's East Coast commencing
from St. Marys Entrance at the Georgia border to Government Cut at the south
end of Miami Beach. Six inlets are constructed inlets and were cut for
navigational and/or water quality purposes. Of the 19 total, all but two have
been modified for navigational purposes.
A review of inlets in their natural condition demonstrates the presence
of a shallow broad outer bar across which the longshore transport occurred.
These shallow and shifting bar features were unsuitable for navigation which
led to the deepening of the channels and training with jetties. Inlets in
this modified state along with inappropriate maintenance practices have placed
great erosional stress along most of Florida's East Coast beaches. The
ultimate in poor sand management practice is the placement of good quality
beach sand in water depths too great for the sand to reenter the longshore
system under natural forces; placement depths of 12 ft or less are considered
appropriate for Florida in order to maintain the sand in the system.
With the interruption of the longshore sediment transport by inlets
modified for navigation, if the downdrift beaches are to be stabilized, there
must be an effective sand transfer program. Several East Coast inlets have
such transfer facilities; however, there is a need to increase substantially
the quantities of sand transferred. Although an evolution and improvement in
the technical capability to transfer sand around entrances is expected, a
capability exists today and a concerted program should be made to commence a
scheduled implementation of this capability at those entrances causing
greatest erosional stress on the downdrift shorelines.
A brief summary review for each of the 19 inlets is presented including:
a scaled aerial photograph, brief historical information, several items
related to sediment losses at each inlet and special characteristics relevant
to State responsibilities. For each inlet the above information is utilized
to develop a recommended action, usually in the form of periodic sand transfer
quantities.
ACKNOWLEDGEMENTS
Much of the data presented in this report were assembled by Professor
A. J. Mehta and Captain J. N. Marino under contract with the Division of
Beaches and Shores. This contract resulted in the University of Florida
report "Sediment Volumes Around Florida's East Coast Tidal Inlets". Captain
Marino participated in the early stages of the present study in organizing
much of the data contained in the inlet summary forms. The contributions of
Ms. Lethie Penquite in assembling and preparing the photographs for the inlet
summary forms is greatly appreciated. Ms. Cynthia Vey provided her usual
expert manuscript preparation including typing and checking.
FLORIDA'S EAST COAST INLETS
SHORELINE EFFECTS AND RECOMMENDED ACTION
INTRODUCTION
At present, the nineteen inlets and channel entrances between the
Florida-Georgia border to Government Cut at the southern terminus of Miami
Beach serve as navigational entrances and passageways for renewal of water to
the bays and lagoons behind the barrier islands. All but two of these
entrances have been modified for navigational purposes or were artificially
created for navigation or water quality purposes. In their natural state,
these entrances were generally unsuited for navigation of commercial size
vessels. The deepening of these channels, the construction of jetties for
reduced channel maintenance and the dredging to maintain channel depth and
alignment have caused severe deleterious effects on the adjacent shorelines.
The effects are due primarily to the deprivation of the downdrift shorelines
of the supply of sand received in their natural conditions. Clearly, if these
entrances are to serve navigation without causing severe downdrift effects,
the transport of sand that has been interrupted by these entrances must be
reinstated. The purpose of this report is to provide a very brief historical
review and assessment of the effects of East Coast entrances on the adjacent
shorelines and,based on the available information, to develop recommendations
for remedial measures. This report is a companion document to the report
"FLORIDA'S WEST COAST INLETS SHORELINE EFFECTS AND RECOMMENDED ACTION".
EAST COAST INLETS IN THEIR NATURAL STATE
Under natural conditions, the East Coast inlets differed both in number
and in character from those currently present. These entrances and their
associated shoals achieved long-term equilibrium with the sand transport
processes. Due to the predominant northeast direction of wave approach, the
net longshore transport of sand is from north to south at the estimated rates
presented in Figure 1.
Typically, as demonstrated by Fineren (1938), the characteristics of
these inlets included a broad shallow ocean bar; perhaps with a channel
incised through the bar. Table I, from Fineren, demonstrates that the bar
depth was typically 3 to 6 ft, much too shallow for navigational purposes.
FLORIDA'S EAST COAST INLETS
SHORELINE EFFECTS AND RECOMMENDED ACTION
INTRODUCTION
At present, the nineteen inlets and channel entrances between the
Florida-Georgia border to Government Cut at the southern terminus of Miami
Beach serve as navigational entrances and passageways for renewal of water to
the bays and lagoons behind the barrier islands. All but two of these
entrances have been modified for navigational purposes or were artificially
created for navigation or water quality purposes. In their natural state,
these entrances were generally unsuited for navigation of commercial size
vessels. The deepening of these channels, the construction of jetties for
reduced channel maintenance and the dredging to maintain channel depth and
alignment have caused severe deleterious effects on the adjacent shorelines.
The effects are due primarily to the deprivation of the downdrift shorelines
of the supply of sand received in their natural conditions. Clearly, if these
entrances are to serve navigation without causing severe downdrift effects,
the transport of sand that has been interrupted by these entrances must be
reinstated. The purpose of this report is to provide a very brief historical
review and assessment of the effects of East Coast entrances on the adjacent
shorelines and,based on the available information, to develop recommendations
for remedial measures. This report is a companion document to the report
"FLORIDA'S WEST COAST INLETS SHORELINE EFFECTS AND RECOMMENDED ACTION".
EAST COAST INLETS IN THEIR NATURAL STATE
Under natural conditions, the East Coast inlets differed both in number
and in character from those currently present. These entrances and their
associated shoals achieved long-term equilibrium with the sand transport
processes. Due to the predominant northeast direction of wave approach, the
net longshore transport of sand is from north to south at the estimated rates
presented in Figure 1.
Typically, as demonstrated by Fineren (1938), the characteristics of
these inlets included a broad shallow ocean bar; perhaps with a channel
incised through the bar. Table I, from Fineren, demonstrates that the bar
depth was typically 3 to 6 ft, much too shallow for navigational purposes.
'I
APALACMICOLA
' 350,000 yd3/yr
PE CAkAVENUAL
0
MADEIRA &EACH ,
0 PASS-A-GRILLE
n^
.M BEACl ;.
CVERGLADES
NAPLtS
ER Oy yr
10=,0 yd /yr
KEY WEST04%
Estimates of Net Annual Longshore Sediment Transport Along
Florida's East Coast.
C.
r
ENGL WOOO D
CAPTIVA
KD
Figure 1.
TABLE I
NATURAL DEPTHS IN CHANNELS AND ON BARS
Florida's East Coast Entrances
(From Fineren, 1938)
Entrance Depth on Bar Channel Depth
(ft) (ft)
Nassau Sound 4 21-27
Fort George Inlet 4 11-26
St. Augustine Inlet 6 10-30
Matanzas Inlet Nearly Blocked 12-18
Mosquito Inlet Nearly Blocked 9-26
Canaveral Bight 6 to 18 30-40
Indian River Inlet Blocked 7-8
St. Lucie Inlet 4 8-12
Jupiter Inlet Blocked 3-5
Lake Worth Inlet 3 3-9
New River Inlet 8 10-15
Hillsboro Inlet 2.5 3-4
Norris Cut Not Affected Shoal
by Sand
Bear Cut 4 7-17
Cape Florida Channel Not Affected Coral Reefs
by Sand
Although the channels incised through the bar were considerably deeper, they
were still too shallow for modern commercial purposes. Additional serious
navigational disadvantages of these natural channels were their tortuous
alignments and migrational tendencies.
Although their number varied with time and storm history, in their
natural condition, there were usually only 13 inlets present in the shoreline
segment where there are now 19. Figure 2 presents a breakdown of the origin
of the 19 inlets currently present.
In their natural state, inlets will achieve an equilibrium with the
natural sand supply and processes. This "equilibrium" may include fairly
severe fluctuations of the shoreline as the channel migrates through the bar
to achieve transfer of the longshore transport. The ocean bar, its connection
to the adjacent shorelines and the adjacent shorelines have been termed by
coastal geologists as a "sand sharing system". It is important to recognize
that the form and geometry of this sand sharing system play a vital role in
maintaining the continuity of longshore sand transport processes along the
East Coast. In particular, the broad shallow ocean bars functioned as "sand
bri6-as" across which the sediment transport occurred from the updrift (north)
t'. downdrift (south) beaches. The interference with or geometric modification
of this sand sharing system, particularly the ocean bar, could cause
substantial interruption of the sediment supply to the downdrift shoreline.
EAST COAST INLETS IN THEIR MODIFIED STATE
Entrances, constructed or modified for navigational purposes, differ from
natural inlets in four respects: (1) the entrance channels are deeper,
(2) jetties are generally present, (3) periodic dredging may be required to
maintain the design channel depth, and (4) the channel alignment is fixed.
The effects of each of these differences are discussed below. Dean (in press)
presents a more detailed discussion of the effects of modified inlets on
adjacent shorelines and recommends measures for improvement.
Deeper Entrance Channel
As noted previously, to accommodate the longshore sediment transport,
inlets in their natural state include shallow broad ocean bars which function
as sand "bridges" across which the net longshore sediment transport occurs
.'-u. _-- St. Marys Entrance (N:?,M:40",F)
i---- ) Nassau Sound (N:4,M:No,NF)
S- ,- Ft. George Inlet (N:4',M:No,NF)
S""-"'" ---. St. Johns Entrance (N:?,M:42',F)
umm^, 0J ,' --St. Augustine Inlet (N:6',M:16',F)
Nm ;T""" -mill, Matanzas Inlet (N:-0,M:No,NF)
P"di-"-.I, I l- ,.t \
SIInlet (N:,M:15,F)
F- "ai Ponce de Leon Inlet (N:?,M:15',F)
S Port Canaveral (N:6',M:43',F)
S Sebastian Inlet (N: ,M:13',NF)
s. e T T-'-- Ft. Pierce Inlet (N: ,M27',F)
\-l --_--t j "IX lUWim
1 S1 r St. Lucle Inlet (N:4.5',M:10',F)
- 1--'--- -<-- Jupiter Inlet (N: ,M:8',NF)
moum ium
... 4-- -Lake Worth Inlet (N:3',M:35',F)
s ..._ south Lake Worth Inlet (N:O,M:8',NF)
S. r -. i-4-Boca Raton Inlet (N:?,M:10',NF)
-'--Hillsboro Inlet (N:?,M:10',NF)
a. Port Everglades (N:8,M:45',F)
S<-Bakers Haulover (N:0,M:11',F)
s-- it ..Government Cut (N:O,M:38',F)
LEGEND
'" N: Natural Bar Depth
S -: M: Maintained Channel Depth
j F: Federal Maintained
^ - NF: Non-Federally Maintained
Figure 2. Natural and Modified Bar Depths Along Florida's East Coast
Inlets and Jurisdiction of Channel Maintenance.
around the inlets. A channel deeper than the natural shallow depth over the
bar interrupts this transport. The system responds by attempting to rebuild
the bridge through deposition commencing on the updrift side of the channel, a
well-known phenomenon. If no attempts are made to maintain the channel depth,
the channel will fill, approaching the natural depth after which the full
transport processes will resume. It is important to recognize that if a
quantity of sediment is removed from the sand sharing system by dredging the
navigational channel; and if the channel is allowed to fill, the fill volume
will result in the downdrift system suffering that volumetric deficit required
to fill the channel. In a more likely case, dredging is carried out to
maintain the channel at the desired depth. If this dredged sediment is not
reintroduced into the system at the proper locationss, erosion will occur at
these locations) and farther downdrift.
Effects of Jetties
There are several purposes of jetties at navigational entrances. In
addition to providing wave sheltering to vessels entering the channel, jetties
are designed to prevent or reduce the amount of sand which would enter a
channel, primarily in the more active nearshore region. Also, as the term
suggests, jetties are intended to "jet" sand that would otherwise tend to be
deposited within the region of natural sediment motion including the outer bar
to water depths in excess of that desired for navigation. This explains the
rule of thumb that jetties should be constructed out to the desired
navigational depth. Olsen (1977) has determined that the St. Marys Entrance
jetties, constructed in the late 1800's and early 1900's, have caused the
seaward displacement of 120 million cubic yards an additional 2 miles
offshore. Jetties can cause adverse effects to the downdrift beaches simply
by impounding sand which must be manifested as downdrift erosion. The
aforementioned jetting of material an additional distance offshore such that
it no longer is part of the sand sharing system results in a loss to the
nearshore system in general and adjacent shorelines in particular.
Channel Maintenance Dredging
Sand dredged from navigational channels to maintain their depths, if not
placed at the appropriate locations on the adjacent beaches, will cause a
Although the channels incised through the bar were considerably deeper, they
were still too shallow for modern commercial purposes. Additional serious
navigational disadvantages of these natural channels were their tortuous
alignments and migrational tendencies.
Although their number varied with time and storm history, in their
natural condition, there were usually only 13 inlets present in the shoreline
segment where there are now 19. Figure 2 presents a breakdown of the origin
of the 19 inlets currently present.
In their natural state, inlets will achieve an equilibrium with the
natural sand supply and processes. This "equilibrium" may include fairly
severe fluctuations of the shoreline as the channel migrates through the bar
to achieve transfer of the longshore transport. The ocean bar, its connection
to the adjacent shorelines and the adjacent shorelines have been termed by
coastal geologists as a "sand sharing system". It is important to recognize
that the form and geometry of this sand sharing system play a vital role in
maintaining the continuity of longshore sand transport processes along the
East Coast. In particular, the broad shallow ocean bars functioned as "sand
bri6-as" across which the sediment transport occurred from the updrift (north)
t'. downdrift (south) beaches. The interference with or geometric modification
of this sand sharing system, particularly the ocean bar, could cause
substantial interruption of the sediment supply to the downdrift shoreline.
EAST COAST INLETS IN THEIR MODIFIED STATE
Entrances, constructed or modified for navigational purposes, differ from
natural inlets in four respects: (1) the entrance channels are deeper,
(2) jetties are generally present, (3) periodic dredging may be required to
maintain the design channel depth, and (4) the channel alignment is fixed.
The effects of each of these differences are discussed below. Dean (in press)
presents a more detailed discussion of the effects of modified inlets on
adjacent shorelines and recommends measures for improvement.
Deeper Entrance Channel
As noted previously, to accommodate the longshore sediment transport,
inlets in their natural state include shallow broad ocean bars which function
as sand "bridges" across which the net longshore sediment transport occurs
deficit of sediment to be manifested as erosion. In the simplest case of a
unidirectional sediment transport and in which only the net transport enters
the channel, obviously placement of the dredged material on the downdrift
beaches is appropriate. In more realistic cases, the proper placement
location may be best determined by monitoring the adjacent shorelines to
determine need. A modified inlet may result in the transport and deposition
in an inlet channel of substantially greater quantities than the net longshore
sediment transport. The legacy of offshore placement in deep water of large
quantities of beach quality sand dredged from inlets has caused a serious
erosional stress on Florida's East Coast beaches. As shown in Table II, as
recently as during the 1980-1985 period, almost half (47%) of beach quality
material dredged from the Federally-maintained East Coast inlets was placed in
water depths too great to return to and benefit the beach system.
Fixed Channel Alignment
Although the character of channel alignment differs for modified and
natural channels, the fixed alignment per se is not necessarily responsible
for adverse effects to adjacent shorelines. It is the previously discussed
measure, that are taken to maintain the alignment that cause these adverse
shoreline effects.
Summary of Modified Channel Effects
In summary, there are two types of potential adverse effects that a
modified channel entrance can have on adjacent beaches: (1) a distribution
effect, i.e. accretion in one location and corresponding erosion in another,
and (2) a net erosion. Jetty impoundment is an example of the former in which
the volumetric increase of sand on the updrift side of the inlet is balanced
(in volume) by a corresponding erosion on the downdrift side. In this case,
there is no net loss of sand to the system. The offshore deposition of
dredged sand or the jetting of sand to water depths greater than those of the
sand sharing system will result in a net and permanent loss to the nearshore
system. Although both of these types of effects are serious, the net loss of
sand to the nearshore system is more detrimental and will appear as a net
erosion of the shoreline.
TABLE II
SUMMARY OF ANNUALIZED (1980 1985) QUANTITIES AND PERCENTAGES
FOR PLACEMENT OF BEACH QUALITY SAND
(Federally Maintained East Coast Inlets)
Amount Amount Amount Offshore
Dredged Placed Placed Depth of
Beach on Beach Offshore Placement
Entrance (yd3/yr) (yd3/yr) (yd3/yr) (ft.)
St. Marys Entrance
(Fernandina Harbor) 60,000 60,000 0
St. Johns Inlet
(Jacksonville Harbor/
Mayport) 644,530 214,070 430,460 41-50
(33%) (67%)
St. Augustine Inlet 20,210 0 20,210 17
(0%) (100%)
Ponce de Leon Inlet 163,700 163,700 0
(100%)
Port Canaveral Harbor 0 0 0 44-48
Ft. Pierce Harbor 4,260 0 4,260 50
(0%) (100%)
St. Lucie Inlet 76,800 76,800 0
(100%) (0%)
Lake Worth Inlet
(Palm Beach Harbor) 82,640 40,270 42,370 40-50
(49%) (51%)
Totals 1,052,140 554,840 497,300
(53%) (47%)
METHOD OF BYPASSING SAND AND EXISTING EFFORTS
From the preceding discussion, it is clear that generally improved sand
management practices will be required at entrances if the adverse effects on
adjacent shorelines are to be reduced. Undoubtedly, considerable innovation
will be required to minimize future costs and maximize efficiency.
Perhaps somewhat surprisingly, responsible entities at some East Coast
entrances have been bypassing sand for several decades. Jones and Mehta
(1980) have summarized the bypassing efforts in Florida. In most cases, the
bypassing and funding are accomplished by an "inlet district", a taxing
district authorized by the Florida Legislature. To provide perspective, the
six entrances at which bypassing is being carried out are discussed below.
Sebastian Inlet
Sand transfer at this inlet is managed by the Sebastian Inlet Commission,
a taxing authority which encompasses portions of Brevard and Indian River
counties. Transfer is accomplished from a depositional basin located 2,500 ft
inside (west) of the inlet throat. Recent transfer efforts have been hampered
by environmental concerns over the amounts of fines present and the presence
of Sabellariid (worm) rock reefs immediately south of the south jetty.
Jupiter Inlet
This entrance is managed by the Jupiter Inlet Authority and bypasses sand
on a biennial basis with the material obtained predominantly from a deposition
basin located 1,000 ft west of the inlet throat.
Port of Palm Beach Entrance
This entrance, also known as Lake Worth Entrance, was cut in 1917 as a
replacement for a natural shallow inlet located to the north. The fixed
bypassing plant was installed on the north jetty in 1958. Currently, the
county is responsible for bypassing. Records indicate an average annual
bypassing of approximately 70,000 cubic yards per year compared with the
estimated net longshore sediment transport of 250,000 yd3 per year. One
shortcoming of the bypassing plant is that interests on the updrift (north)
Singer Island were effective in requiring the installation of a low submerged
"coffer dam" around the sand intake point to limit the amount of sand which
can flow to the bypassing plant. The limited effectiveness of the bypassing
plant is reinforced by the annual dredging to maintain the channel depth of 35
ft. Records available over the six year period, 1980-1985, indicate that an
average annual amount of 42,370 cubic yards was dredged from the channel and
placed offshore.
Over the history of this entrance, 2.8 million cubic yards of dredged
material have been lost due to deep water disposal. In addition to placing
large quantities of sand offshore, earlier disposal practices included
placement in an interior shoal called "Peanut Island" which has been built to
approximately 25 ft in elevation and contains an estimated 1.2 million cubic
yards. Much of the 20 mile segment forming Palm Beach Island is in an
advanced degree of erosion.
South Lake Worth Inlet
This entrance, also known as Boynton Inlet, is located approximately 20
miles south of Lake Worth Inlet and was cut in 1927 to provide additional
flushing to impro a the water quality of Lake Worth. Upon completion of
cutting the int:t and installation of short jetties, downdrift erosion was
swift and dramatic. Recognizing the need to replace the interrupted longshore
transport, in 1937 local interests installed the first (in the world) fixed
sand bypassing plant. This plant has undergone modifications and relocations,
but in principle is the same as initially installed in 1937. The bypassing
history at this entrance indicates recent average annual transfer rates of
60,000 cubic yards per year compared with the estimated net longshore sediment
transport of 220,000 cubic yards per year. The fact that the bypassing is
inadequate is evident by the large offset at the entrance and the eroded
conditions of the downdrift shoreline as compared to that updrift.
Boca Raton Inlet
This inlet is maintained by the City of Boca Raton utilizing a small
dedicated floating dredge to bypass sand flowing through a fairly small (60 ft
wide) low weir section in the updrift jetty. The weir feature was added
fairly recently (1980) and appears to be functioning reasonably well. In
addition to bypassing material settling in the deposition basin, approximately
750,000 cubic yards were removed from the ebb tidal shoal in 1985 and placed
on the downdrift beaches. This placement widened these beaches substantially;
however a visit in November 1987 showed that these beaches were returning to
an eroded condition.
Hillsboro Inlet
Inlet modifications in 1966 incorporated a weir section into the updrift
(north) jetty. The base of this weir section is a natural rock reef. A
deposition or settling basin is located immediately inside the weir section.
This entrance is managed by the Hillsboro Inlet District and has been
bypassing sand for the past 25 years.
Bypassed quantities, averaged over 1952 to 1976, are 70,000 cubic yards
per year and are to be compared with the estimated annual net longshore
sediment transport of approximately 200,000 cubic yards per year.
A CASE STUDY PORT CANAVERAL ENTRANCE
Although, because of the complexity and diversity of East Coast
entrances, no particular entrance can be representative, Port Canaveral
Entrance is selected here as an example for more detailed discussion as it is
fairly young and documentation in terms of shoreline effects is relatively
good.
Port Canaveral is an artificial entrance which was cut in 1951 in the
Canaveral Bight, a location sheltered from the northeast waves by Cape
Canaveral and the associated offshore shoals. Jetties were not constructed
prior to excavation of the channel and erosion of the adjacent shorelines with
deposition in the channel occurred so rapidly during construction that it was
not possible for the dredge to excavate the channel to the desired depth.
Jetty construction was carried out in 1953-1954.
Prior to the channel construction, it was estimated by the U.S. Army
Corps of Engineers that the net longshore sediment transport was 350,000 cubic
yards per year to the south, and that erosion would occur at this rate in the
downdrift located cities of Port Canaveral, Cocoa Beach, Satellite Beach,
etc. In recognition of this potential for downdrift erosion, in 1967 the
Corps of Engineers studied the possibility of installing a sand transfer
system and concluded that it was practical. This possibility is again
currently (1987) under study. None of the study efforts to date has resulted
in a sand bypassing installation, even though the need for such a facility was
recognized in the initial (1950) report and a sand transfer facility was
authorized in 1967.
It is enlightening to examine pre- and post-entrance downdrift shoreline
changes. Figure 3a presents the shoreline changes from 1877 to 1951, prior to
entrance construction for the 41 mile segment downdrift of Port Canaveral
Entrance. It is clear that in its natural condition, although there were
areas of erosion and accretion, on the average this 41 mile shoreline segment
was accreting at a rate of approximately 1 ft per year. Figure 3a also
documents the erosion over the 23 year period 1951 to 1974. Immediately
downdrift (south) of the entrance, erosion rates were up to 16 ft per year
with a maximum localized erosion extent of nearly 400 ft in the 23 year
period. Interpretation of these data indicated that the volumetric rate of
erosion is approximately 200,000 cubic yards per year rather than the 350,000
cubic yards per year originally estimated,
By the early 1970's, the downdrift erosion had become so acute that local
interests initiated legal action to r-medy the erosion conditions caused by
the entrance. The legal settlement included the placement, in 1974, of
approximately 2.5 million cubic yards of sand on the 2.1 mile segment
immediately south of the south jetty. The shoreline over this segment was
advanced seaward an approximate distance of 400 ft which more-or-less
reestablished the pre-entrance shoreline. Figure 3b presents the shoreline
changes between 1974 and 1986. Several features are noteworthy. First by
1986, the erosion that was formerly located within 4 miles south of the south
jetty had by 1986 spread out to a distance of 14 miles south of the
entrance. Secondly by 1986, the nourishment placed within 2.1 miles of the
south jetty had benefitted the beach system up to 4 miles south. Finally,
even though the 12 year period (1974-1986) is not long compared to shoreline
changes, it is of interest to note that by-and-large the shoreline changes
outside the limit of influence of the entrance exhibit strong similarities to
those based on the longer term changes (1877-1951).
750,000 cubic yards were removed from the ebb tidal shoal in 1985 and placed
on the downdrift beaches. This placement widened these beaches substantially;
however a visit in November 1987 showed that these beaches were returning to
an eroded condition.
Hillsboro Inlet
Inlet modifications in 1966 incorporated a weir section into the updrift
(north) jetty. The base of this weir section is a natural rock reef. A
deposition or settling basin is located immediately inside the weir section.
This entrance is managed by the Hillsboro Inlet District and has been
bypassing sand for the past 25 years.
Bypassed quantities, averaged over 1952 to 1976, are 70,000 cubic yards
per year and are to be compared with the estimated annual net longshore
sediment transport of approximately 200,000 cubic yards per year.
A CASE STUDY PORT CANAVERAL ENTRANCE
Although, because of the complexity and diversity of East Coast
entrances, no particular entrance can be representative, Port Canaveral
Entrance is selected here as an example for more detailed discussion as it is
fairly young and documentation in terms of shoreline effects is relatively
good.
Port Canaveral is an artificial entrance which was cut in 1951 in the
Canaveral Bight, a location sheltered from the northeast waves by Cape
Canaveral and the associated offshore shoals. Jetties were not constructed
prior to excavation of the channel and erosion of the adjacent shorelines with
deposition in the channel occurred so rapidly during construction that it was
not possible for the dredge to excavate the channel to the desired depth.
Jetty construction was carried out in 1953-1954.
Prior to the channel construction, it was estimated by the U.S. Army
Corps of Engineers that the net longshore sediment transport was 350,000 cubic
yards per year to the south, and that erosion would occur at this rate in the
downdrift located cities of Port Canaveral, Cocoa Beach, Satellite Beach,
etc. In recognition of this potential for downdrift erosion, in 1967 the
Corps of Engineers studied the possibility of installing a sand transfer
ui
Ul
0.I
Figure 3.
0 10 20 30 40
DISTANCE SOUTH FROM PORT CANAVERAL
ENTRANCE (miles)
m) Effects of Channel Entrance on Downdrift Beach Stability,
Compared to Pre-Entrance Condition.
t Port Canaveral Entrance
Sebastian Inlet Entrance
0 10 20 30 40
DISTANCE SOUTH FROM PORT CANAVERAL
ENTRANCE (miles)
b) Shoreline Changes Following 1974 Nourishment Project.
Effects of Establishment of Cape Canaveral Entrance and Subsequent
Nourishment Project on Downdrift Beaches (Shoreline Change Results
Provided by J. H. Basillie).
INFORMATION AND RECOMMENDATION SUMMARY
This section presents, for each inlet, information and recommendations in
a two-page summary form. The order of presentation of the inlets is from
north to south, commencing with St. Marys Entrance at the Florida-Georgia
border and concluding with Government Cut at the south end of Miami Beach.
The items presented and some background as to their relevance are discussed
briefly below.
Photograph A scaled aerial photograph is presented to illustrate the
character of the inlet including modifications if present. In
many cases, qualitative effects of the entrance on the downdrift
and updrift shorelines are evident.
Brief Historical Information Provides background, including whether inlet is
natural or constructed and the timing of modifications.
Sediment Balance Addresses several items relevant to adjacent shoreline
stability. Increases in volumes of sard in the ebb tidal shoal
generally represent good quality sand removed from the beach
system and in most cases sand suitable for shoreline nourishment.
Net littoral transport rates provide a measure of the net
amount of sand moving under natural forces along the shoreline.
Where inlet modifications have altered the system through channel
deepening, jetty construction, etc. to a degree that natural
transport is interrupted, it is this quantity that must be
transferred by engineering measures to ensure stability of the
downdrift shoreline. Two estimates of the net longshore sediment
transport are presented. The first denoted USAE is as presented
by the U.S. Army Corps of Engineers and is generally based in
part on the rate of updrift sediment accumulation against newly
constructed jetties. The second estimates were developed by
Walton (1976) based on observations of wave characteristics made
by ships at sea.
Shoreline volume changes provide a measure of the impact of
the entrance on the adjacent shoreline. The usual pattern is
accretion updrift of the entrance and erosion of the downdrift
shoreline. However, if the updrift jetties allow sand to drift
through them, it is possible that the updrift shorelines will
accrete at lower rates than the net longshore transport, or in
the limiting case, erosion of the updrift shoreline can occur.
Brief Dredging History Provides information relevant to adjacent shoreline
impact. In particular good quality sand disposed in deep water
usually represents sand from the longshore transport system and
therefore will result, on a per unit volume basis, in erosion of
the adjacent shoreline(s).
Special Characteristics Relevant to the State Responsibilities Identifies
those operational or jurisdictional features that are relevant to
the State's responsibility to providing maximum stability of the
beach resource.
Recommended Action All available information is synthesized into concise
recommendations which are in accordance with the requirements of
the 1986 Beaches Bill. Because of the importance of these
recommendations, they are highlighted inside a rectangular
enclosure.
ST. MARYS ENTRANCE
(Date of Photography: December 17, 1985)
Brief Historical Information
First survey of the natural inlet in 1875.
Construction started on north jetty in 1881.
South and north jetties completed in 1904.
In connection with the King's Bay Terminal project, depth became 36-40
ft. and channel width 375 ft. in 1978.
Present plans include a project depth of 46 ft.
ST. MARY'S ENTRANCE
Sediment Balance
Ebb shoal:
1870 118.2 million cubic yards
1974 126.0 million cubic yards
Net littoral transport rate:
550,000 cubic yards per year (Southward-USAE)
200,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1857-1975:
+11.6 million cubic yards over 14,600 ft. south of south jetty
+10.5 million cubic yards over 5,000 ft. north of north jetty
-12.2 million cubic yards (erosion) over 25,000 ft. of shore
north of the 5,000 foot fillet north of north jetty
Brief Dredging History
From 1903-1985, 12.9 million cubic yards was dredged from the entrance
channel; 400,000 cubic yards was placed on the south beach; the
remainder has been disposed of at sea.
Special Characteristics Relevant to State Responsibilities
St. Mary's Entrance is part of the King's Bay Trident project.
There is erosion in the City of Fernandina and along the southerly
portions of Amelia Island.
Recommended Action
The net littoral transport (between 200,000 and 550,000
cubic yards per year) should be by-passed to Fernandina
Beach. The Navy and the State of Florida have signed a
Memorandum of Understanding calling for all maintenance
dredging to be placed on Amelia Island, as required to
maintain stability of this shoreline.
NASSAU SOUND
(Date of Photography: December 27, 1985)
Brief Historical Information
* Natural inlet without dredging or jetties.
Over the past century, the major changes have been the recession of the
southern portion of Amelia Island to the north, the accretion of Little
Talbot Island to the south, and the emergence of Bird Island.
* Entrance 5,600 ft. wide with quite variable depth, up to 20 ft.
NASSAU SOUND
Sediment Balance
Ebb shoal:
1871 -
1954 -
1973 -
49.4 million cubic yards
53.7 million cubic yards
40.5 million cubic yards
Recommended Action
S As this is a natural entrance, no action is recommended.
FT. GEORGE INLET
1 \ 500
__3X 0 15000 2000 3000 &00
I'." """SCRLE IN FEET
(Date of Photography: January 5, 1982)
Brief Historical Information
In 1881, construction of the north jetty at St. John's River partially
stabilized the position of Ft. George Inlet.
In 1934, the north jetty at St. John's Entrance was sand-tightened with
a concrete cap.
In 1937, jetties at St. John's River were extended: north jetty, 14,300
ft. long; south jetty, 11,200 ft. long.
S In 1949, bridge of 30 bents constructed across Ft. George channel near
mouth.
FT. GEORGE INLET
Special Characteristics Relevant to State Responsibilities
The Ft. George ebb shoal coalesces with St. John's shoal and is
reported with St. John's data.
Spit growing northward from St. John's River north jetty towards
Ft. George Entrance. Substantial erosion of Little Talbot Island has
resulted.
Recommended Action
Consideration should be given to relocating the channel to
the south, thereby reducing the erosion on the south end of
Little Talbot Island.
ST. JOHNS RIVER ENTRANCE (JACKSONVILLE HARBOR)
(Date of Photography: January 5, 1987)
Brief Historical Information
Federal navigation project.
St. Johns River mouth stabilized by jetties in period 1881-1890.
North jetty sand-tightened with concrete cap in 1934.
In 1937, north jetty lengthened to 14,300 ft. and south jetty
lengthened to 10,600 ft.
Channel deepened to 42 ft. in 1965.
ST. JOHNS RIVER ENTRANCE (JACKSONVILLE HARBOR)
Sediment Balance
Ebb shoal:
1874 -
1967 -
1978 -
Flood shoal:
1970 -
52.7 million cubic yards
90.2 million cubic yards
174.0 million cubic yards
1.0 million cubic yards
Net littoral transport rate:
480,000 cubic
250,000 cubic
Shoreline volume changes, 1924-1970:
31.0 million cubic yards
+ 13.0 million cubic yards
yards per year (Southward-USAE)
yards per year (Southward-Walton)
over 59,000 ft. south of entrance
over 21,000 ft. north of entrance
Brief Dredging History
From 1925-1985, 26.4 million cubic yards were dredged. Of that total
20.8 million cubic yards were disposed at sea, 4.1 million cubic yards
were placed inland, and 1.5 million cubic yards were placed on the
south beach.
Special Characteristics Relevant to State Responsibilities
Channel maintenance by Corps of Engineers.
Beach south of entrance must be replenished at frequent intervals.
Over the period 1980-1985, an average of 214,070 cubic yards per year
or 33% of the beach quality sand dredged for maintenance was placed on
the downdrift shoreline.
Recommended Action
Place all beach quality dredged material from the channel
on the beach south of the entrance in a "feeder beach".
Similar previous placements have proven effective.
ST. AUGUSTINE INLET
(Date of Photography: December 31, 1985)
Brief Historical Information
Two natural inlets existed before construction of the north jetty and
excavation of the channel at a third location in 1941. South jetty
constructed in 1957.
S Authorized channel width 200 ft.; depth 16 ft.
S Maintenance by Corps of Engineers.
Connected to Intracoastal Waterway.
ST. AUGUSTINE INLET
Sediment Balance
Ebb shoal:
1924 -
1955 -
1979 -
Flood shoal:
1970 -
76.7 million cubic yards
106.0 million cubic yards
110.4 million cubic yards
0.7 million cubic yards
Net littoral transport rate:
440,000 cubic yards per year (Southward-USAE)
380,000 cubic yards per year (Southward-Walton)
Reversal of direction frequent in summer months. Shoreline has changed
markedly since opening the new channel.
Shoreline volume change, 1924-1976:
+1.5 million cubic yards over 13,000 ft. north of inlet
+7.3 million cubic yards over 30,000 ft. south of inlet
No erosion occurring over 4 mile segment south of inlet, but severe
erosion occurs south of this point.
Brief Dredging History
From 1940-1985, a total of 1.6 million cubic yards of material has been
dredged. All but 120,000 cubic yards of this material has been placed
on the beach or within the littoral zone (greater than 12 ft. depth).
Special Characteristics Relevant to State Responsibilities
The littoral transport does not appear to be passing around this
entrance.
S Anastasia State Park is located south of entrance.
Severe erosion of shore evident beyond 4 miles south of entrance, near
the City of St. Augustine Beach.
Recommended Action
Continue to place all sand dredged on downdrift shoreline.
Placement should occur at sufficient distances south
(approximately 30,000 ft) to reduce the severe erosion
there.
MATANZAS INLET
SCAIIFIN ???TO
(Date of Photography: December 31, 1985)
Brief Historical Information
S A natural inlet without dredging or jetties, Matanzas Inlet has been
affected by bridge and abutment construction.
* In 1925, highway bridge constructed parallel to the shore and near the
throat of this inlet. Replaced in 1956.
* In 1972, breakthrough in Rattlesnake Island from Intracoastal Waterway
to Matanzas tidal area.
S Breakthrough was closed by dike construction in 1976.
MATANZAS INLET
Sediment Balance
Ebb shoal:
1964 4.4 million cubic yards
1978 6.3 million cubic yards
Flood shoal: 400,000 cubic yards
Net littoral transport rate:
440,000 cubic yards per year (Southward-USAE)
290,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1923-1978:
+400,000 cubic yards over 4000 ft. north of inlet
-300,000 cubic yards over 2900 ft. south of inlet
The tendency for the inlet to migrate southward is prevented by the
presence of the concrete bridge abutments.
There is severe erosion immediately south of Matanzas Inlet,
undoubtedly due to the storage of large quantities of beach quality
sand as an emergent flood tidal shoal.
Recommended Action
SBypass sand so that there is no additional storage inside
the flood tidal shoal.
PONCE DE LEON INLET
500
0 1000 2000 3D0D 0
SCALE IN F
(Date of Photography: March 8, 1984)
Brief Historical Information
A natural inlet, surveyed by U.S. Coast and Geodetic Survey in 1851.
S Lighthouse constructed in 1883.
S First dredging of inlet channel in 1943.
Construction of north and south jetties completed in 1971. Weir
section 1,800 ft long in inshore portion of north jetty.
S Weir section of north jetty closed by addition of rock in 1984.
PONCE DE LEON INLET
Sediment Balance
Ebb shoal:
1925 -
1974 -
21.8 million cubic yards
22.5 million cubic yards
Net littoral transport rate:
500,000 cubic yards per year (Southward-USAE)
180,000 cubic yards per year (Southward-Walton)
Strong transport reversals may occur in summer months.
Severe erosion occurs at Bethune Beach, some 8 miles south of inlet.
Shoreline volume changes, 1936-1977:
1936-1962: -3.7 million cubic yards (erosion) over a distance of
12,000 ft. north of inlet
1971-1976: -300,000 cubic yards (erosion) over 3,600 ft. north
of inlet
1936-1962: -1.2 million cubic yards (erosion) over 19,500 ft.
south of inlet
1971-1977: +2.3 million cubic yards (accretion) over 4,500 ft.
south of inlet
Brief Dredging History
Total of 3.6 million cubic yards dredged from channel and all placed on
north beach.
Recommended Action
By-pass to the south the normal rate of littoral transport
(180,000 to 500,000 cubic yards per year) at sufficient
distances southward to reduce erosion in vicinity of
Bethune Beach.
PORT CANAVERAL ENTRANCE
(Date of Photography: April 18, 1986)
Brief Historical Information
Entrance cut in 1951.
Port depth 43 ft.
Twin jetties 1,150 ft. long built in 1953-1954.
S Surveys of this shore available back to 1855.
Sediment Balance
Ebb shoal:
1979 -
5.6 million cubic yards
Net littoral transport rate:
360,000 cubic yards per year (Southward-USAE)
250,000 cubic yards per year (Southward-Walton)
Transport direction usually reversed (northward) in summer months.
PORT CANAVERAL.ENTRANCE
Sediment Balance (Continued)
Shoreline volume changes, 1928-1971:
1928-1958: +10.8 million cubic yards over 22,000 ft. north of entrance
+2.0 million cubic yards over 24,000 ft. south of entrance
1956-1965: -0.5 million cubic yards over 22,000 ft. north of entrance
-0.9 million cubic yards over 24,000 ft. south of entrance
1965-1971: -1.1 million cubic yards over 12,700 ft. south of entrance
Brief Dredging History
From 1877-1951, average change in width of 40 mile-long south beach:
+ 1 ft. per year.
In 1955, average erosion rate immediately south of south jetty: 16 ft.
per year.
In 1974, erosion not evident beyond 3.4 miles south. Two and one-half
million cubic yards of sand were placed on 11,000 feet of beach south
of south jetty.
In 1986, 1974 replenishment wave had advanced 4 miles south, and
preceding erosion wave 14 miles, south of entrance.
From 1953-1985, entrance channel and harbor excavated by dredging;
volume, 31.1 million cubic yards. Ten million cubic yards of this
total was for maintenance of the channel. 2.5 million cubic yards has
been placed on the adjacent beaches.
Special Characteristics Relevant to State Responsibilities
S Harbor is a Federal navigation project. Maintenance by U.S. Army Corps
of Engineers.
South beach responds quickly to change in sediment supply. Frequent
replenishment required.
S Ebb shoal contains only 5.6 million cubic yards, however, Cape
Canaveral shoal contains in excess of 100 million cubic yards of good
quality sand.
S Interception of transport on north side and bypassing planned by Corps
of Engineers but not yet constructed.
Recommended Action
Federal government construct and operate system to by-pass
the volume of the net longshore transport (250,000 to
360,000 cubic yards per year).
SEBASTIAN INLET
N ? 00
(Date of Photography: April 18, 1986)
Brief Historical Information
Many early attempts to maintain a navigable inlet, starting in 1886.
Inlet opened on present alignment in 1948.
Jetties constructed and modified from 1950's to 1970.
Interior sand trap located 2,500 ft. west of inlet throat.
Inlet under the jurisdiction of the Sebastian Inlet Commission.
Sediment Balance
Ebb shoal:
Contains less than 100,000 cubic yards as estimated in 1974
Net littoral transport:
300,000 cubic yards per year (Southward-USAE)
160,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1948-1974:
+100,000 cubic yards over 2,000 ft. north of the inlet
-200.000 cubic varda nvr 9 nn f-_ cnt-h nf t-h 41in1
SEBASTIAN INLET
Brief Dredging History
A total of 1.8 million cubic yards of sediment generated by
construction dredging has been placed offshore.
At present, an attempt is made by the Sebastian Inlet Commission to
place all beach compatible sand on the downdrift shorelines.
Special Characteristics Relevant to State Responsibilities
This inlet places significant erosional stress on the downdrift
shoreline.
There is no substantial ebb tidal shoal from which to borrow material
to establish a feeder beach.
Present bypassing procedure has been hampered by considerable
environmental concerns over turtle nesting, tern habitat and worm
rocks.
Recommended Action
Cooperate with the Sebastian Inlet Commission to:
1. Continue to bypass the sand collecting in the interior
sand-trap.
2. Evaluate alternate bypassing systems that would result
in less environmental constraints.
3. Augment the by-passed volumes with material from an
alternate (as yet unidentified) source to ensure the
flow to the downdrift beaches of the net transport
amount (approximately 200,000 cubic yards annually).
FT. PIERCE INLET
(Date of Photography: April 11, 1986)
Brief Historical Information
* Artificial entrance constructed in 1920 to replace smaller inlet to
north.
* Harbor construction started in 1925.
* In 1926, harbor structures rebuilt with jetties 1,800 ft. and 1,200 ft.
long north and south respectively, spaced 900 ft. apart. Project depth
27 ft.
* Federal navigation project since 1935.
* Sabellariid (worm) reefs in channel.
FT. PIERCE INLET
Sediment Balance
Ebb shoal:
1975 -
Flood shoal:
1930 -
Net littoral transport rate:
29.4 million cubic yards
7.9 million cubic yards
225,000 cubic yards per year (Southward-USAE)
140,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1882-1975:
+ 55.2 million cubic yards over 40,000 ft. north of inlet
47.6 million cubic yards over 32,000 ft. south of inlet
Brief Dredging History
From 1930-1985, total volume dredged: 3.2 million cubic yards, dumped
at sea: 2.7 million cubic yards, placed inland: 0.5 million cubic yards
and placed on beach: 0 cubic yards.
Recommended Action
Place all compatible dredged material on the beach south of
entrance.
S Restore the normal littoral transport rate south of
entrance by by-passing the net longshore sediment transport
(140,000 to 225,000 cubic yards per year) with a target
value of 200,000 cubic yards per year.
ST. LUCIE INLET
0 1000 2000 3000 400
SCALE IN FEET
-......
(Date of Photography: April 17, 1986)
Brief Historical Information
Inlet cut in 1892, 30 ft. wide by 5 ft. deep.
North jetty constructed 3,325 ft. long.
S From 1980-1982, "Dog-leg" extension added to north jetty (900 ft.
long), detached breakwater added south of channel (500 ft. long) and
south jetty constructed (1,500 ft. long).
Inlet is a Federally maintained navigation project.
Authorized channel dimensions 6 ft. deep by 100 ft. wide.
ST. LUCIE INLET
Sediment Balance
Ebb shoal:
1964 -
Flood shoal:
1977 -
21.7 million cubic yards
3.0 million cubic yards
Net littoral transport rate:
230,000 cubic
200,000 cubic
Shoreline volume changes, 1888-1964:
1888-1929: -0.2 million cubic yards
-23.0 million cubic yards
1929-1964: +2.4 million cubic yards
-23.0 million cubic yards
yards per year (Southward-USAE)
yards per year (Southward-Walton)
over 9,250 ft. north of inlet
over 35,000 ft. south of inlet
over 9,250 ft. north of inlet
over 35,000 ft. south of inlet
Brief Dredging History
There has been no deep water disposal.
A total of 3 million cubic yards is reported to have been placed on the
south beach.
Special Characteristics Relevant to State Responsibilities
Inlet has accumulated a total of approximately 25 million cubic yards
in the adjacent shoals and updrift of the north jetty.
Inlet has resulted in severe erosion to the north beaches of Jupiter
Island. For many years, this erosion was the most rapid in the state.
Until approximately 1980 the sand drifting through and depositing
inside the porous south jetty appeared to be equal to the net longshore
sediment transport. Since 1980, erosion has been acute north of the
north jetty. If sand deposited inside the north jetty is not bypassed,
the currents and waves redistribute the sand so that it is less
available for bypassing.
Recommended Action
S Short-Term: Conduct a one-time by-passing of approximately
3 million cubic yards to the downdrift beaches. Source of
material is sand inside inlet.
S Long-Term: Implement a periodic (annual or biennial)
bypassing from the shoal inside the north jetty. The
target bypassing quantities on an annual basis should be on
the order of 200,000 cubic yards.
JUPITER INLET
(Date of Photography: April 23, 1986)
Brief Historical Information
Natural inlet, relocated approximately 1,200 ft. north to present
position, in 1913-1922.
Jetties, 400 ft. long and 300 ft. apart, constructed in 1922.
In 1929 north and south jetties extended 200 ft. and 75 ft.,
respectively.
Inlet requires regular bypassing from a trap located 1,000 ft. west of
inlet throat.
Inlet is under the jurisdiction of the Jupiter Inlet District.
JUPITER INLET
Sediment Balance
Ebb Shoal:
1883 -
1967 -
1978 -
0.9 million cubic yards
1.0 million cubic yards
0.4 million cubic yards
Net littoral transport rate:
230,000 cubic yards per year (Southward-USAE)
240,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1913-1975:
-3.5 million cubic yards over 32,500 ft. north of inlet
-3.2 million cubic yards over 10,000 ft. south of inlet
Brief Dredging History
From 1952-1977, a total of 1.1 million cubic yards has been dredged.
All of the material dredged has been placed on the south beach.
On an average annual basis, the amount of bypassed sand is 44,000 cubic
yards.
Special Characteristics Relevant to State Responsibilities
S The bypassing program at this inlet appears to be functioning well and
is a "near model" program.
Some material may be bypassed naturally along the outer bar.
Recommended Action
Encourage the Jupiter Inlet District in its program of
inlet maintenance.
S An attempt should be made to increase the bypassing to the
net longshore transport rate of approximately 200,000 cubic
yards per year.
LAKE WORTH INLET (PORT OF PALM BEACH ENTRANCE)
SCALEIN EET
(Date of Photography: April 23, 1986)
Brief Historical Information
Inlet cut in 1917 to width of 750 ft. and depth of 15-18 ft.
Jetty construction completed in 1925.
Channel dredged to 35 ft. in 1967.
Since 1936, maintained by Corps of Engineers.
Sand transfer plant installed in 1958.
LAKE WORTH INLET (PALM BEACH HARBOR)
Sediment Balance
Ebb shoal:
1929 8.5 million cubic yards
1967 3.9 million cubic yards
Net littoral transport rate:
230,000 cubic yards per year (Southward-USAE)
380,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1883-1957:
+6.3 million over 7,500 ft. north of inlet
-0.9 million over 3,000 ft. south of inlet
Brief Dredging History
Total dredged volume, 1929-1986: 5.2 million cubic yards, placed at
sea: 2.8 million cubic yards, placed inland: 1.2 million cubic yards,
placed on beach: 0.7 million cubic yards, bypassed to south beach: 1.5
million cubic yards. Current average amounts bypassed by sand transfer
plant: 70,000 cubic yards per year.
Special Characteristics Relevant to State Responsibilities
South beach is badly eroded.
Restrictions on operation of sand by-passing plant have reduced volume
of sand by-passed below natural rate here.
Recommended Action
Eliminate restrictions on by-passing plant operation
imposed by coffer dam around pumping plant intake.
Attempt to increase bypassing to estimated net longshore
transport rate (approximately 200,000 cubic yards per
year).
SOUTH LAKE WORTH INLET
500
0 1000 2000 3000
SCALE IN FEET
-j..
(Date of Photography: April 23, 1986)
Brief Historical Information
An artificial inlet dredged through the beach in 1927 to improve water
quality in Lake Worth.
Jetties constructed in 1936.
First sand transfer plant installed in 1937, and discontinued in 1942
due to war-time fuel shortage.
Operation of sand transfer plant resumed in 1945.
Sand transfer plant replaced in 1948; new plant capacity of 73 cubic
yards per hour.
Jetties extended seaward in 1967.
Larger sand transfer plant installed 118 ft. seaward of earlier plant
in 1967.
Sand production monitor installed in sand transfer plant in 1984.
SOUTH LAKE WORTH INLET
Sediment Balance
Ebb shoal:
1967 -
1968 -
1969 -
Net littoral transport rate:
700,000 cubic yards
1,000,000 cubic yards
1,400,000 cubic yards
230,000 cubic yards per year (Southward-USAE)
280,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1927-1979:
+450,000 cubic yards over 2,400 ft. north of inlet
-400,000 cubic yards over 3,500 ft. south of inlet
Brief Dredging History
S The average annual bypassing by the sand transfer facility is
approximately 60,000 cubic yards per year.
Recommended Action
It may be necessary to augment the bypassing system.
By-pass an annual volume equal to the natural rate of
transport (approximately 200,000 cubic yards per year).
BOCA RATON INLET
I 1000 2000 3000 4000
SCALE IN FEET
(Date of Photography: April 23, 1986)
Brief Historical Information
Although this inlet was not opened artificially, it was open only after
heavy rainfalls, was very shallow and only marginally navigable by
small craft.
Dredged but continued to shoal, in 1925.
Two jetties constructed, in 1930.
North jetty extended 180 ft. and south jetty reinforced, in 1975.
Weir section installed in north jetty, in 1980.
City of Boca Raton currently operates a dedicated dredge in channel to
move sand to south beach.
BOCA RATON.INLET
Sediment Balance
Ebb shoal:
1981 1.1 million cubic yards
Net littoral transport rate:
150,000 cubic yards per year (Southward-USAE)
280,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1927-1971:
+600,000 cubic yards over 3,500 ft. north of inlet
-100,000 cubic yards over 5,200 ft. south of inlet
Brief Dredging History
S From 1940-1985, a total of 1.1 million cubic yards of material has been
dredged. It has all been placed on the south beach.
Recommended Action
Encourage City of Boca Raton to continue by-passing sand to
beach south.
Attempt to increase bypassing rates to approximately
200,000 cubic yards per year.
HILLSBORO INLET
500
0 1000 2000 3000 4000
SCALE IN FEET
(Date of Photography: February 4, 1981)
Brief Historical Information
Surveys of shore in this area date back to 1855. Natural depth on bar
2.5 ft.
Natural inlet, with rock structure built in 1930 to protect lighthouse.
North jetty constructed of rock on natural reef in 1966, gap in north
jetty functions as a sand weir with deposition basin inside.
Inlet maintained by dedicated pipeline dredge pumping from deposition
basin since 1959.
Outer channel dimensions are 10 ft. deep by 150 ft. wide.
S Inlet has been under the jurisdiction of the Hillsboro Inlet District
since 1957.
Inlet connected to Intracoastal Waterway.
HILLSBORO INLET
Sediment Balance
Ebb shoal:
1883 -
1961 -
2.7 million cubic yards
-0.3 million cubic yards
Net littoral transport rate:
100,000 cubic yards per year (Southward-USAE)
280,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1927-1967:
+0.2 million cubic yards over 1,700 ft. north of inlet
-0.7 million cubic yards over 2,500 ft. south of inlet
Brief Dredging History
In addition to the bypassed maintenance material, a total of 2.2
million cubic yards has been dredged.
Of the above, all but 0.6 million cubic yards has been placed on the
south beach.
Currently, on an average annual basis, approximately 70,000 cubic yards
per year is bypassed with the small dredge.
Special Characteristics Relevant to State Responsibilities
S The bypassing program at this inlet appears to be functioning well and
is a "near model" program.
Recommended Action
S Encourage and support the Hillsboro Inlet District in its
program of inlet maintenance.
S Attempt to increase amount of sand bypassed to the
magnitude of the net longshore sediment transport
(approximately 150,000 cubic yards per year).
PORT EVERGLADES ENTRANCE
14
k
JJ
(Date of Photography: February 4, 1981)
Brief Historical Information
Inlet opened through barrier island, in 1928. Earlier, a smaller
entrance, New River Inlet, had been located some 1,000 ft. to the
north.
Initial plan completed in 1931, including: north jetty 1,450 ft. long;
south jetty 1,250 ft. long; entrance channel 35 ft. deep by 210 ft.
wide.
Current project depth is 45 ft.
Entrance is a Federal navigation project. Connected to Intracoastal
Waterway.
PORT EVERGLADES ENTRANCE
Sediment Balance
Ebb shoal: 1978 negligible
Net littoral transport rate:
50,000 cubic yards per year (Southward-USAE)
270,000 cubic yards per year (Southward-Walton)
Apparently some transport reversal during summer months.
Shoreline volume changes, 1928-1981:
+2.1 million cubic yards over 4,800 ft. north of inlet
-0.6 million cubic yards over 15,000 south of inlet
Brief Dredging History
SFrom 1934-1984, of the 8 million cubic yards dredged, only 3.2 million
cubic yards has been placed on the south beach.
Special Characteristics Relevant to State Responsibilities
This entrance has caused substantial downdrift (south) erosion.
There does not appear to be as much maintenance dredging required as
the downdrift erosion experienced.
S Shore northward is highly developed.
No ebb shoal.
Recommended Action
Implement a program of placing on the south beach on an
average annual basis, the net longshore sediment transport
(50,000 to 270,000 yd3/yr). A minimum of 100,000 yd3/yr is
recommended.
S The source of this material could be bypassing from the
north beach or elsewhere.
BAKER'S HAULOVER INLET
0 2000 3000 4000
SCRLE IN FEET
(Date of Photography: February 14, 1985)
Brief Historical Information
Baker's Haulover was cut through
by two jetties.
South jetty extended in 1975.
North jetty extended in 1986.
Sediment Balance
Ebb shoal:
1928 -
1969 -
the barrier beach in 1925; stabilized
0.3 million cubic yards
0.6 million cubic yards
Net littoral transport rate:
20,000 cubic yards per year (Southward-USAE)
270,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1919-1961:
-0.4 million cubic yards over 250 ft. north of inlet
-0.6 million cubic yards over 2,000 ft. south of inlet
BAKER'S HAULOVER INLET
Brief Dredging History
S From 1937-1978, a total of 2.7 million cubic yards of material has been
dredged. Most of this, 2.5 million cubic yards, has been dredged since
1960 and it has all been placed on the adjacent beaches.
Special Characteristics Relevant to State Responsibilies
Baker's Haulover is the north limit of the Miami Beach Restoration
Project. Since extension of the south jetty (1975), the area
immediately to the south has stabilized substantially.
Recommended Action
Place any material dredged from the channel on the south
beach.
GOVERNMENT CUT (MIAMI HARBOR)
(Date of Photography: February 14, 1985)
Brief Historical Information
Entrance cut across southern end of Miami Beach in 1902.
North and south jetties stablized a channel 500 ft. wide and 38 ft.
deep.
North jetty 3,000 ft., south jetty 2,000 ft. in length.
Maintenance by Corps of Engineers.
GOVERNMENT CUT (MIAMI HARBOR)
Sediment Balance
Ebb shoal:
Small and difficult to identify because of presence of reefs
Net littoral transport rate:
20,000 cubic yards per year (Southward-USAE)
270,000 cubic yards per year (Southward-Walton)
Shoreline volume changes, 1867-1961:
+1.3 million cubic yards over 2,500 ft. north of inlet
Brief Dredging History
From 1957-1982, total volume dredged: 7.4 million cubic yards, placed
inland: 3.3 million cubic yards, placed on north beach: 4.1 million
cubic yards.
Recommended Action
* Continue to place compatible dredged material on north
beach.
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