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The Coast temporary junctions between land and sea
are subject to change waves, currents, tides, biological processes,
tectonic activity position changes as sea-level does Sea level
18,000 years ago during last ice age If sea level rises 60cm (20ft)
Red areas will flood in about 100-200 years
Blue areas may flood over several centuries Red areas would flood
during spring high tides
Over the next century, sea level is most likely to rise cm along
most of the U.S. Atlantic Red areas would flood during spring high
tides Sea Level Rise Does Matter
Superstorm Sandy produced record storm surge levels for locations
in and around the NY City metropolitan region Sea levels have risen
more than a foot in the New York City region since the Industrial
Revolution. So what difference did this extra foot make for the
citizens of New York City? Quite a lot. 6,000 more people impacted
for each inch of rise! 70,929 more people and 30,551 more homes
flooded. According to Dr. Ben Strauss, Chief Operating Officer and
Director of the Program on Sea Level Rise at Climate Central
Beaches a zone of loose particles that covers part of the
shore
extends from a landward limit cliff, permanent dunes, seawall
extends to the seaward limit where movement of sediment on and
offshore ceases Figure 10.1 Beach Profiles Steepness of beaches
change with seasons and storms
Summer and calm periods build up beaches Swash dominates (soaks
into beach), less backwash Winter and storms erode and flatten
beaches Backwash dominates, very little swash soaks in because
beach is saturated) Figure 10.2a Wide berm Steep beach face Figure
10.2d Narrow berm Flatter beach face longshore bar Seasonal Changes
on a beach in California
Figure 11.13 As seasons change, sand moves on and off Boomer Beach
near La Jolla, California. Gentle summer waves move sand onshore
(a), but larger winter waves remove the sand to offshore bars,
exposing the basement rock (b). (c) The annual progression of sand
onshore and offshore for a typical year. East Coast beaches are
usually not as seasonally varied, but can change dramatically with
the advent of noreasters or tropical cyclones. Fig c, p. 254 Before
and After Sandy Long Branch, NJ Mantoloking, NJ Before and After
Sandy Cupsogue Beach, Westhampton, NY
Fire Island Natl Seashore Beaches exist in a delicate balance
between accumulation and destruction Waves can transport sand
onshore or offshore Longshore currents transport sand along the
coastline Figure 10.3b Barrier Islands Are essentially large sand
bars
Protect the coast behind them Very unstable themselves Figure 10.9
Toms River, NJ Heavily developed barrier island: Ocean City, MD
Barrier Island Migration
Figure 10.10 Figure 11.19 The migration of barrier islands. The
heavy black lines south of Ocean City represent jetties constructed
in the 1930s to protect the inlet. The jetties disrupt the
north-to-south longshore current. As a result, Assateague Island
has been starved of sediment and has migrated about 500 meters
(1,640 feet) westward. Fig , p. 258 Human Impact on Beaches
Attempts to save beaches or property often fail or make matters
worse Figure 10.18: Groins Figure 10.19 Shipbottom, NJ Groin Field
Cape May, NJ Figure 10.20: Jetties Figure 10.21 Santa Cruz Harbor,
CA Break water Santa Monica, CA Designed to protect harbors from
waves
Can cause excessive erosion, requiring dredging to keep area stable
Figure 10.24: Seawalls Alternative: Beach Replenishment Figure
10.26 Figure 10.B: Relocation