The regional sediment budget provides estimates of net LST rates, engineering activities
(beach fill placement and dredging), and sources and sinks representative of the Fire Island
to Montauk Point study area. These sediment budgets fall within accepted ranges of net
LST rates as derived by previous researchers and as calculated through independent
analyses herein. The lower magnitude in the net LST rate appears to better represent
processes for this study area for the 1979 to 1995 period.
Beach fill placement (and/or transfer of littoral material to adjacent beaches) is an
important mechanism in maintaining the study area beaches. The majority of the beach fill
placement most likely occurs through dredging of the inlets and bays, and placement on the
adjacent beaches, in effect, a mechanical bypassing (or backpassing) mechanism. From
1933 to 1979 and 1979 to 1995, the cumulative rate of beach fill placed from Montauk
Point to Fire Island was 295,000 and 309,000 m3/yr, respectively. Estimating that only 25-
percent of fills placed to close breaches reflects an alongshore movement of littoral material
reduced the 1979 to 1995 value to 208,000 m3/yr. Similar values for the 1979 to 1997 time
period are 468,000 (total fill) and 357,000 m3/yr (adjusted for breach fill). These rates of
beach fill placement are of the same order as estimates of the net LST rate at Fire Island
Inlet (compare Table 1 and Fig. 3). On a regional scale, future projects must maintain this
nourishment rate to preserve present-day beach conditions.
Shoals and the inner shelf offshore of central Fire Island have been postulated by other
researchers as a required source for solving the regional sediment budget. The sediment
budget formulated herein, and previous sediment budgets for this region do not require an
offshore source to formulate net LST rates within the accepted range. However,
incorporation of estimates ranging from 75,000 to 160,000 m3/yr for the offshore source
also agree with the accepted range for net LST at Fire Island Inlet. It is concluded that a
source of sediment offshore of central Fire Island may exist, although the forcing mechanism
Ms. Julie Rosati and Mr. Mark Gravens acknowledge permission granted by the
Headquarters, U.S. Army Corps of Engineers, to publish this paper developed under the
Fire Island to Montauk Point Reformulation Study, and the Coastal Inlets Research
Program, Inlet Channels and Adjacent Shorelines Work Unit. We are grateful for review
of this document by Mr. Keith Watson, U.S. Army Corps of Engineers, New York District,
and Mr. Bruce Ebersole, U.S. Army Corps of Engineers Coastal and Hydraulics Laboratory
(CHL). The kind assistance of Dr. Andrew Morang, CHL, in preparing Fig. 1 is appreciated.
Rosati et al.