I-DSTORIC COASTLINE CHANGES ON LONG ISLAND, NEW YORKPurposeTo purpose of this exercise is to document historic patterns of erosion and deposition along a section of the south shore of Long Island, and to investigate the causes of these patterns.
Barrier islands and beaches along the south shore of Long Island have changed in geometry and position through time as a result of beach erosion and deposition, migration of aeolian dunes, inlet expansion by erosion and closure by deposition, and deposition of overwash fans. These changes in the shore zone have had a major impact on human construction. An understanding of coastal erosion and deposition is essential before steps are taken to interfere further with these natural processes. We’ll concentrate on one area of the south shore that has seen both deposition and erosion, with impacts on access and development: Democrat Point and
Oak Beach. The area has been mapped since at least 1825, when the Fite Island Lighthouse was built at the western end of Fire Island at it existed then (see maps). In the 180 years since 1825, Fire Island has grown to the west by sediment deposition by at least 7.1 km. As a result, the west end of Fire Island (Democrat Point) overlaps the eastern end of Jones Island (Oak Beach). This deposition has threatened the access through Fire Island inlet into and out of Great South Bay. Furthermore, accretion at Democrat Point caused the tidai inlet to become narrower and deeper, leading to erosion of Jones Beach. The Army Corps of Engineers has attempted to deal with these problems by constructing a jetty at the end of Fire Island in 1940, dredging the western end of Fire Island back to the jetty about every 5 years since 1959, dumping sand on Oak Beach, and constructin8 a
dike at Oak Beach to reduce beach erosion. This process has continued to the present.
Exercise Analyze the
series of maps
from 1851 to 1964, the
map with superimposed shorelines,
and the
serial photographs
with respect to the morphological changes of the coastline, through 2012 (pre-Sandy). Explain the changes to the west end of Fire Island, Fire Island Inlet, and Oak Beach. In your write-up:
Describe qualitatively the sequence of changes imth ap d position of Fire Island, including hat has happened to Democrat Point Bach between buiiding the* jetty iñ 194 and just pnor to building tliediiie 195
Measure the amount of movement of the western tip of Fire Island to the west, and the migration of the northern and southern shorelines to the north or south, in the intervals between the maps. Plot the amounts of movement as a function of time, and calculate rates of movement.
Explain the changes to the Ape and qattemyof Democrat Point: what’s caused them?
Describe what has happened to the position of and what has happened to the iniets through Oak Beach. What caused them to form?
Make
a
simplified sketth
‹if the coastal system and include (1) arrows indicating the dominant sedipient transport direction.and (2) teâtboxes naming the processes that are the dominant cause of this sedirriént transport. Do riot hesitate te make this sketch big and Verifiable. Explain the sketch and discuss its implicâtions„./ This will be part of your Write a rep.ort i
:ién.tific
.ollo.w.in’.g .the,. ..
’ on*’
‘'.
o ’ on t'li:r,ough the
semester i.e. bstr ftgroducti including ,. . thod0 a d
zpretati 1S USSO onclus‘ ). -In answering thé. questions, explain the get›morphic c . ges of this area an t1ie.processes/ev9nts that caiised thém. .Clear,ly differentiate‘bétwgen tlie cauies
@râcesses )
ând‘the effects
{landforms).
in
your.discussi‹in;“irdicate how the foll‹iwiiig processes afféct what is happening along this part of Long Islaiid:
Long-shore currents and long-shore transport Tidal curre.fits and transport by tidal ciirrents Ebb tidal delta and Flood tidal delta Convergence and divergénce of currents Overwash fairs
Siorm event's / periods of calm weather Beach, bénn, %redunes
WaVe refraction; wave reflection Breaking waves, swell
i3reaker bars; sviâsh-backwash zone Human interference Write a rep.ort i
:ién.tific
.ollo.w.in’.g .the,. ..
’ on*’
‘'.
o ’ on t'li:r,ough the
semester i.e. bstr ftgroducti including ,. . thod0 a d
zpretati 1S USSO onclus‘ ). -In answering thé. questions, explain the get›morphic c . ges of this area an t1ie.processes/ev9nts that caiised thém. .Clear,ly differentiate‘bétwgen tlie cauies
@râcesses )
ând‘the effects
{landforms).
in
your.discussi‹in;“irdicate how the foll‹iwiiig processes afféct what is happening along this part of Long Islaiid:
Long-shore currents and long-shore transport Tidal curre.fits and transport by tidal ciirrents Ebb tidal delta and Flood tidal delta Convergence and divergénce of currents Overwash fairs
Siorm event's / periods of calm weather Beach, bénn, %redunes
WaVe refraction; wave reflection Breaking waves, swell
i3reaker bars; sviâsh-backwash zone Human interference