Hawks Creek, Riverhead, New York management options

[From the U.S. Government Printing Office, www.gpo.gov]

New York State Department of State

awks CreekTON SC 29405-2413

July 1985

CMP/CPR/85-001

GB
454
.154 Property of C St Library
H39
1985
-1 985

I. Introduction

Tidal inlets are found at the mouths of tidal tributaries. Often,
these inlets possess important economic, environmental, and social,
values. They provide egress and ingress to and from protected
waters, thus serving as important boating access and commercial focal
points. Inlets also regulate the exchange of salt and freshwater,
thus balancing the unique and highly productive estuarine
environment. The littoral transport of sand along a beach is also
influenced by the opening, migration and closing of inlets. Finally,
inlets provide important social benefits associated with recreation
along the shorelines.

Natural inlets are self maintaining and self adjusting. T he
interaction of tides, freshwater inputs, littoral transport, and
coastal storms creates a natural balance of the economic, environmental
and social values described above. Often man will develop tidal inlets
to improve one or more of these benefits(e.g., dredging a channel
and stablizing the inlet shoreline). When such an action is taken, it
is imperative that the natural functions of the system are fully
understood before construction or other Improvements are begun. The
inlet must be continually monitored to verify that the original
assumptions are valid, and that a balance is still maintained.
Conflicts arise when one of the these values is desired to the
exclusion of one or more of the others(e.g., navigation for boat
access over beach erosion or water quality). These situations are
best resolved through negotiation.

In many instances, adequate analysis is not done prior to inlet
improvements, and problems may surface years later. It is imperative
therefore that these Inlets be examined when additional improvements
are proposed, or when the past maintenance activities are
re-authorized.

This paper synthesizes the available information on the tidal inlet
at Hawks Creek, and examines the management options. The option
which achieves the desired balance should be selected.

2. Study Area
Economic

Hawks Creek is a small tidal tributary of the Great Peconic Bay on
the north fork of Long Island. (Figure 1). Located at the South
Jamesport about 36 kilometers east of downtown Riverhead, it is an
important access point for about 200 recreational craft. The boat
basin is about 18,000 square meters and the throat of the inlet is
approximately 23 meters in width. The average depth of the basin is
2 meters below mean low water.

Geology

Geologically, Hawks Creeks flows through Holocene muds and sands,
less than 20,000 years old. This coastal area is undergoing a

Study Area>

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Figure 1: Location diagram of the study area in relation to Long Island.

gradual drowning of the shoreline due to the rise of sea level. The
rate of' sea level rise is approximately 0. 3 meters per century
(Disney, 1955 and Donn 'and Shaw, 1963). However, this rate of sea
level change is reportedly increasing (Hicks, 1972)

Tides and Tidal Currents

The tidal range of the semi-diurnal tides in Great Peconic Bay at South
Jamesport is 0.82 meters, with a spring range of 0.92 meters. The
highest tide of record at South Jamesport is 2.37 meters above mean low
water which occurred on September 21, 1938. The ebb current velocity
is significantly lower than the flood current in the area west of
Robins Island, making the South Jamesport area a zone of deposition
(Eisel, 1977). The tidal currents in and out of Hawks Creek run
perpendicular to the shoreline, and are probably ebb dominated due to
upland drainage. 'However, no specific information on tidal current
direction, velocity and duration is available.

Wind and Waves

The wind direction, velocity and duration are important factors in
Great Peconic Bay, since they significantly affect the direction and
magnitude of waves. The prevailing winds in this area are from the
west, but the strongest are from the -northeast, (Eisel, 1977). As
shown in Figure 1, the tidal inlet at Hawks Creek faces
south-southwest, into the prevailing winds. However, it is sheltered
from the more damaging northeast winds by Miamogue Point to the east.
The result is a sheltered cove like beach on either side of the
inlet.

Littoral Transport

Sand is transported parallel (longshore) to the beach by waves striking
the shoreline at an angle. Transport occurs from the zone of breaking
waves, to the inland extent of wave uprush on the beach. Littoral
transport is important, because it supplies sand to beaches from
adjacent sand sources. Obstructions on the beach, either natural or
man-made, can cause sand to be trapped on one side of the obstruction
and erode on the opposite side. The trapping or deposition side is
termed the up-drift side, and the eroding side is called the
downdrift side. In many instances, obstructions in the beach and surf
zone areas may be used to determine the direction of net littoral drift
(transport). Other indicators are sand waves and other natural sand
transport features.

The direction of net sand transport at the inlet of Hawks Creek
appears to be f rom east to west. This observation is based on
information provided in Eisel (1977), Figure 2, and an examination of
existing aerial photography (Figure 3). Miamogue Point is a source
area for sand that is transferred to the west by wave refraction
around the Point. Littoral transport can, however, be reversed
during specific meteorologic events. But, the major storms that
strike this area create waves from the east and thus move sand east
to west. This condition can cause beaches to widen as a result of
coastal storms from the northeast. The magnitude of net transport
can

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Figure 2: Littoral drift directions in the study area, from Eisel, 1977.

be related to the amounts periodically dredged from the inlet throat.
Examination of Suffolk County dredging records (see historical
analysis) suggests that the net littoral transport rate is about 800
cubic meters annually from east to west.

Storms

Storms are important to coastal areas, because they often cause
dramatic shoreline changes in short periods of time. Coastal storms
should not be thought of as "freak events" or "acts of God", but
rather as statistically predictable events.

Two principal storm types are pertinent to the study area, hurricanes
and extra-tropical storms. Both types have very strong winds from
the east and northeast, and can cause similar level of coastal
changes. Hurricanes have wind velocities in excess of 74 mph,but
occur infrequently. Extratropical storms or northeasters, have winds
usually less than 60 mph, but are quite common. Increasingly, storms
are being recognized as geologic agents that play an integral role in
shoreline development and change. Researchers often consider storm
intensity, sand supply and changes in sea level as the three
controlling influences in coastal processes.

Data on the coastal changes caused by storms is not available for
this area. However, Long Island experiences a storm which causes
moderate changes once every two years and a severe storm three times
a century (Davies, 1972). The last major storm to strike the study
area occurred in March, 1984. Considerable damage occurred in the
marina. The inlet channel shoaled, but the beaches appear to have
accreted as a result of sand being moved around Miamogue Point.

3. Historical Analysis
Initial Dredging and Jetty Construction

Prior to 1959, Hawks Creek was a more or less pristine wetland, inlet,
dune and beach system. Originally called King Creek, this area was
draglined to create a deep water boat basin (Rainey, 1985) and the
adjacent wetland area was filled to provide upland access. Probably at
the same time, or soon thereafter, a road was constructed north of
the boat basin. Conduits were placed beneath the road to allow fresh
water drainage to enter the basin. The original marina developer
also built a short jetty on the east side of the channel, presumably
to keep sand from filling in the channel.

Maintenance Dredging

The records of maintenance dredging for the Hawks Creek channel are
incomplete, but the following is a compilation of known information.
For a period of some twenty years following the original improvement,
the owner seasonally removed sand from the inlet channel caused by
natural shoaling (Rainey, 1985). The amount of material removed and
fate of the material is not known, but local sources estimate that
thousands of yards of sand where removed and carted away to an upland
site (Rainey, 1985). The

200 0 200 400 600 800 FEET

50 0 so 100 150 METERS

Figure 3z Tidal wetlands map, from NYS Department of Environmental Conservation, 1974.

original dredging permit was modified in 1981 to allow deposition of
sand removed from the channel on both the east and west sides of the
inlet. The process of alternating sides on a yearly basis continues
to the present.

In addition to private efforts, Suffolk County has dredged Hawks Creek
five times; 1966, 1975, and 1982, (SCDPW, 1984) in the following
amounts:

1966 - 23,586 cubic meters
1975 - 1,137 cubic meters
1982 - 956 cubic meters
1983 - 956 cubic meters
1984 - 1,916 cubic meters
28,551 cubic meters

This material was probably deposited on the beaches adjacent to the
inlet. The large amount of material dredged in 1966 is probably the
result of establishing the existing channel into Great Peconic Say.
Only small amounts where required to be removed thereafter to
maintain the channel at its authorized dimensions.

4. Impacts of Inlet Modification

The immediate impact of dredging and bulkheading the inlet area was
the loss of tidal wetlands and changes to the water circulation
conditions of the basin. However, other significant changes have
occurred over the almost thirty years since original construction of
the marina.

Shoreline Changes

The original shoreline of the Hawks Creek area, prior to dredging, was
a concentric beach with a small tidal inlet and shoal system in the
middle (see Figure 3). The present shoreline (Figures 4 and 5) shows
the eastern shore to be farther seaward than or offset from the
western shore. This condition could be the result of sand moving
east to west and preferentially depositing east of the constructed
jetty. The western shoreline also displays erosional indentations
that might be caused by waves refracting around the eastern jetty and
the loss of sand trapped by the eastern jetty (see Terchunian and
Fletcher, 1984). The dune area on the western shore is scarped, and
the beach in this area is narrow. All of these characteristics
indicate an erosional setting.

The shoreline east of the inlet is a broad arcuate shore which is
characteristic of areas up-drift of obstructions. The beach is wide,
and the dune slopes gently to meet the almost flat beach. These
characteristics indicate a depositional or stable environment. The
dune east of the Creek are generally sound. However, the area
immediately east of the jetty and the area in front of the residences
to the east is nearly void of vegetation. This is probably due to
human trafficing near the houses and improper dredge spoil
disposal near the jetty.

QUADRANGLE LOCATION

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SCALE 1:24000

1000 0 1000 2000 3000 4000 ~~5000 5000 7000 FEET

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UTM GRID AND 1956 MAGNETIC NORTH
DECLINATION AT CENTER OF SHEET

'Figure 4: The study area in 1956. Note the extensive tidal marsh
and the tidal shoal which protrudes from the shoreline. 'Hawks
Creek is now located in the location of the tidal delta.

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Hawks Creek,

QUADRANGLE LOCATIONns

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ow1000 0 1000 2000 3000 4000 5000 6000 7000 FEET
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Polyconic projection. 1927 North American datum.

MATTITUCK QUADRANGLE
1981 EDITION

Figure 5: The study area in 1981. Note the location of Hawks Creek relative
to the tidal delta. Also notice the offset between the east and west shore-
line.

Figure 6: Aerial photograph of the study area (April 21, 1983).
Littoral drift from east to west may be deduced from the sand at the tip of
Miamogue Point, the sand entering the channel of Hawks Creek and the sand
waves west of Hawks Creek.

Bathymetric Changes

The bathymetry of Hawks Creek has been radically altered by creating
the marina. Where once there was a small tidal delta seaward of the
Creek, there is now a six foot deep channel. The normal bypass of
sediment across the tidal delta is no longer possible. Therefore,
sand deposits in the channel. According to local sources and aerial
photographs, sand enters the channel from both the east and west
sides. On the east side, sand flows around the seaward end of the
jetty and deposits in the channel. This accounts for most of the
sand deposited in the channel and is the principal cause of
navigation problems. On the west side, where there is no jetty, sand
enters the waterway during littoral transport reversals. This
smaller shoal is less of a navigation hazard, but it can become a
problem after several years.

If no dredging were to occur, the inlet channel would eventually shoal
and a tidal delta would reform.

5. Conclusions

1. Net littoral drift at Hawks Creek is from east to west at a rate of
about 800 cubic meters annually.

2. The Creek mouth or inlet throat appears to shoal from both the
east and west sides.

3. The shoreline east of the Creek is stable.

4. The shoreline west of the Creek is eroding.

5. The dune east of Hawks Creek is depleted in areas due to human
trafficing and improper dredge spoil disposal.

6. Continued dredging is necessary to maintain a navigation channel.

6. Management Options

The following three options have been advanced by interested parties.
-- Option 1:

Under this option, the existing permits for dredging would remain in
effect, allowing material to be deposited on both the east and west
sides of Hawks Creek.

No additional erosion protection or navigation structures would be
built on either side of the inlet.

-- Option 2:

A new 200 foot jetty would be constructed on the western side of
Hawks Creek, and the eastern jetty would be extended 50' seaward.

Dredge material would be alternately deposited along the beaches on
the east and west sides of the inlet.

--Opitou 3:

The final option would be to construct a 100' long jetty on the western
shoreline and resheath the existing eastern jetty.

A deposition basin would be created on the updrift side.~of the east
jetty. Material initially removed from the depositon basin would be
used to rebuild the dunes to the east. Thereaf ter, the material
(sand) from the deposition basin would be bypassed to the west side
of the Creek. All material placed in the dune area will be planted
with American Beach Grass$ and access across the dune will be
provided by an approved walkway.

Sand dredged from the mouth of Hawks Creek would be placed on the west
side of 'Hawks Creek.

If a coastal storm destroys or significantly damages the protective
dune to the east, all deposition basin material and dredging material
will be used to rebuild the dune. Vegetation will be planted to
control eolian erosion, and walking or crossing the dune will be
controlled as above.

If an erosion rate of I foot, or-more, per year is documented on the
eastern shoreline, then deposition basin and dredging material will be
placed along the beach to ameliorate the observed erosion.

7. Option Evaluation and Selection

In considering which option is appropriate, one must strive for a
balance of economic, environmental and social values, through the
application of appropriate regulations. If option one is selected, the
beach and dune system to the west of Hawks Creek will continue to
erode. Eventually, the dune will be destroyed and the marsh behind
it adversely effected and probably destroyed. The channel to Hawks
Creek will have to be frequently dredged to allow boating access to
Great Peconic Bay. Sand placed on the beach east of the inlet would
re-enter the littoral transport system and shoal in the creek mouth.
The shoreline to the east would remain unaffected, since it cannot
accrete past the most seaward point of the eastern jetty.

The selection of option two would establish a fixed channel between
two jetties. The extension of the eastern jetty would cause sand to
deposit updrift (east) of the structure. This would eliminate
dredging until the 50' length of jetty had filled to impoundment
capacity. Thereafter, sand would spill around the east jetty and
into the channel in the same manner and magnitude as now. The
eastern shoreline would accrete to the seaward end of the jetty and
stabilize. The construction of the western 200' jetty would stop
sand that now enters the channel from the western side. However,
erosion on the west side would continue, since sand is being trapped
by the eastern jetty. The protrusion of the jetties into Great
Peconic Bay would also increase erosion an the western shoreline, due
wave induced swirling eddy currents.

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Prop'osed 100 Foot Jetty

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Figure 7: Summary of option three for Hawks Creek, Riverhead, New York

Option three entails reduced jetty construction and changing dredging
and disposal areas. The area to the east of the eastern jetty would be
regraded to form a deposition basin. Initially, the material would be
removed from the basin and used,,placed/to reinforce i~eakened dunes to
the east. This action will provide increased protection for the
structures east of the Creek. Since this material will be placed
above the zone of normal wave uprush, it will -not immediately
re-enter the littoral transport system and cause increased inlet
shoaling. After the initial regrading, deposited material rotath
basin would be bypassed to the west side of the inlet. This action
will have no effect on the eastern shoreline, since the sand has
already passed by the beach and would otherwise shoal in the inlet
throat. The establishment and maintenance of the deposition basin
will reduce shoaling in the inlet, and thus decrease dredging
frequency. The reinforced dune should provide appropriate flood
protection to upland properties. Construction of a 100 foot jetty on
the western side of the inlet will also prevent sand from entering
the channel on this side. However, the shorter jetty will lessen the
adverse erosion impacts caused by wave refraction creating swirling
eddies. The changing of dredge disposal to the west side of Hawks
Creek should stabilize, but not cause the shoreline to accrete, since
natural wave action will continue to move the sand further west. The
provisions for both catastrophic and chronic erosion conditions are
unique to this option and reflect the need to monitor changes to the
adjacent shorelines and the location of inlet shoaling. This
flexibility is necessary to maintain- the balance of economic,
environmental and social values.

Based upon the above evaluation of the recommended options, option 3
offers the best opportunity for:

1. Effective erosion control for the shorelines adjacent to Hawks
Creek.
2. Reduced inlet shoaling and subsequently inlet dredging.
3. Minimal adverse environmental impact.

Thus, it offers the best balance of economic, environmental and social
values unique to the South Jamesport area.

8. Future Actions

Coastal projects affecting tidal inlets are challenging because
conditions are always changing. Effective management must recognize,
understand and work with the changes. Otherwise, the uniqueness of
the inlets is lost to uniformity.

In reaching a management decision on Hawks Creek, all available
information should be reviewed. This existing documentation should
be made available to the proper reviewing agencies. The avilability
of this information should decrease the amount of time needed for
review, and improve the management decision. The following types of
information are important to the review of projects affecting tidal
inlets:

1. Historical maps and charts, including property surveys.
2. Historical aerial photographs.

3. Dredging and construction records.
4. Scientific and technical reports, including field surveys and
periodic observations.

After a project has been completed, it is important to observe the
actual effects upon the shoreline. The effective coastal manager
must determine these effects through on-site investigations and
discussions with field work, the people whose daily lives are
effected by the decision. Their observations should be recorded
so that the effects can be quantified and management decisions
modified to reflect actual conditions. For Hawks Creek, a series of
periodic observations should be established.

9. References Cited

Disney, L.P., 1955, Tide Heights Along the Coasts of the United States,
Proceedings ASCE., 81, Separate No. 666. 9.p.

Donn, W.L. and D.M. Shaw, 1963, Sea Level and Climate of the Past
Century, Science 142 - 1166-1167.

Davies, D., Axelrod, and O'Conner, 1972, Erosion of the North Shore
of Long Island, Tech Report #18, M.S.R.C., SUNY at Stony
Brook, NY, 11794.

Eisel, M.T., 1977, A Shoreline Survey: Great Peconic, Little Peconic,
Gardiners and Napeague Bays, SUNY @ Stony Brook, Marine Science
Research Center, Special Report 5, 77-1.

Hicks, S.D., 1972, On the Classification of Trends of Long Island
Period Sea Level Series, Shore and Beach, 40 (1): 20-23.

Rainey, W., 1985, Personal Communication.

Suffolk County, Department of Public Works, 1984, Dredging Summary,
County Center, Yapank Avenue, Yapank, New York, 11980.

Terchunian, A.T. and C.H. Fletcher III, 1984, Current and Shoreline
Effects of Shore Perindicular Structures, in Proceedings of the
9th Annual Coastal Society Conference.