Coastal and Shelf Processes

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Coastal and Shelf Processes
Hurricane Isabelle, Avalon, NJ 9/18/2003
December Noreaster, LBI, 12/1993

• Marine Geology

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Marine Environments Pelagic realm plankton
(floaters) and nekton (swimmers) Shelf (green),
oceanic (blue) zones epipelagic, meso-, and
bathy- don't worry about these benthic/benthos
bottom dwellers lifestyles suspension feeders,
grazer, deposit feeders depth zonation function
of light, pressure (bars), oceanography zones
supratidal, intertidal/littoral neritic (i, m,
o) shelf sublittoral (0-200 m) bathyal
200-2000 up 200-600, m 600-1000, lo.
1000-2000) Abyssal (2000-5000 m), hadyl
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Deltas
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regressive on 100 m scale due to progradation
(building out is not the same as regression
progradation happens during regressions, but also
during advances of alluvial fans and submarine
fans).
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Estuaries

• Definitions
• simplest flooded river valley not a broad
  enough definition since does not include Fjords
• inlet of the sea reaching into river valley
  influenced by tides
• semi-enclosed coastal body of water w/ free
  connection to open sea and in which sea water is
  diluted by fresh water
• includes
• drowned river valleys examples Raritan Bay, De
  Bay, Chesapeake Bay sea level rise 18 Ka to
  present
• tectonic estuaries
• Fjords drowned glacial estuaries (U-shaped)
• barrier estuary matter of definition vs. lagoon

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http//www.nasm.si.edu/research/ceps/rpif/landsat/
Viewing.html
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Estuaries

• loose less dense surface waters
• gain deeper waters.
• High productivity (gmCarbonm-2yr-1)
• sediment sinks
• important for navigation, food, recreation
• sinks for pollutants
• processes
• freshwater interaction with seawater
• tidal forces

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Estuaries

• type determined by flux of fresh (Qr) vs.
  seawater (f(tidal range))
• Stratifiedsalt wedge riverine dominated
• mostly in microtidal areas
• salt wedge extends upstream along bottom
• freshwater flows out without much mixing
• weak tidal currents, most transport by rivers
  out
• partially mixed river tidal effects
• typical of mesotidal areas
• salt water wedge has a strong current
• turbidity max in mix zone transport of
  sediment in during flood tide
• rivers may still transport out
• may vary seasonality with river discharge
• well mixed tidally dominated
• low vertical gradient in
• generally in macrotidal areas
• Fjord often dammed
• hypersaline lagoon (negative estuary)

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Estuaries Sedimentation

• salt water causes floculation
• increasing salinity causes "floculation" of
  clays
• group together fine sec. electrolytes in
  seawater neutralize - charge on clays
• turbidity max due to floc, diatom prod. in mixing
  zone

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Tides

• tidal curve height of water/time
• most tidal curves two high/low tides per tidal
  day (24 hr. 50 m) tidal day (24 hr. 50 m)
  successive passes of moon over 1 spot
• semidiurnal two occur 2 times a day more or
• less equal strength, e.g., most Atlantic ports
• diurnal one per day e.g., GOM
• mixed tides two times, but unequal strength
• e.g., Pacific ports
• HHW higher high water
• LHW lower high water
• tidal range high tide to low tide
• microtidal 0-2 m
• mesotidal 2-4 m
• macrotidal gt4 m
• spring tides full new moons tidal range is
  higher
• neap tides 1st and 3rd quarters tidal range is
  lowe

http//140.90.78.170/restles4.html,
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• http//www.crazyquest.net/trips_aerialops.htm

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Beaches and the nearshore zone A tour of the
shore
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Sandy Hook Oct. 1997 Honors Geology
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Beach Ridges, Sandy Hook
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1764 Light House, Sandy Hook 2008
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Sandy Hook toward Highlands
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Sandy Hook-Sea Bright
Courtesy of N. Psuty
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Sea Bright

• http//grothserver.princeton.edu/groth/random_pic
  s/bikerides/twin_sep2002/twin_sep2002.htmlx

http//3dparks.wr.usgs.gov/nyc/parks/loc67.htm
http//www.beachcomber.com/Njshore/Monmouth/Seabrg
ht/Graphics/seabrit.html
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The Wall at Sea Bright
Sea Bright before/after at right
http//gannet.stockton.edu/njbpn2004/

• http//3dparks.wr.usgs.gov/nyc/images/fig180.jpg

http//www.sptimes.com/2002/05/12/Worldandnation/Y
ou_bought_this_beach.shtml
had virtually no beach in the early 1990s. But
the federal nourishment in 1994-96 created a wide
expanse of sand. These aerial views show the area
before (top right) and after (below right) the
sand arrived
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Fight back with beach nourishment?
Nourishment lasts 0 to 7 years Generally 90 lt 5
yrs (Pilkey Dixon, 96) Future is now at Deal,
NJ 2007 overflight
Deal
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• Long Branch

http//photos10.flickr.com/13489597_994dbdde3e_m.j
pg
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Walls Exacerbate Erosion
http//gannet.stockton.edu/njbpn2004/2004/monmouth
/mchome.htm
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Normady, Silver, Ocean Beachs
How NOT to develop
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Gods Country Island Beach
http//www.amheli.com/
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LBI Long Beach Island
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Harvey Cedars, LBI
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Harvey Cedars, 3/62 Ash Wednesday Storm
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Surf City, LBI
http//www.longbeachisland.com/images/photos/Airvi
ew.jpg
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Holgate, LBI
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Holgate North to Beach Haven
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Long Beach Island, NJ
Human stabilized
400 m
Natural movement
Courtesy N. Psuty
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Marshes South of Holgate
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Barnegat (Tidal) Inlet
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Lagoons

• Lagoons shallow marine body (sound, channel, bay,
  saltwater lake), communicating with the sea, but
  partly separated by a strip of land examples LI
  Sound, Barnegat Bay, Little Egg
• lagoon generally behind barrier island
• barrier bears brunt of waves
• lagoons dominated by tides generally low E
• less affected by fresh water input
• circulation restricted by some barrier
• principle water movement through tidal inlets
• low E, not true near inlet
• "fine grained sediments" Muds?
• actually many exceptions
• washovers
• wind blown from dunes
• near tidal delta high energy
• barrier beach or shelf sands brought on flood
  tides

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Marshes

• very high productivity "3.5 x Iowa cornfield"
• gmCarbonm-2yr-1
• central ocean basins 50 coastal 100, upwelling
  300
• cornfield, lakes, gt500 marsh, gt1000
  gmCarbonm-2yr-1 "salt marshes" generally
  submerged at high tide, protected from wave
  attack
• supratidal flats (e.g., sabkahs in dry regions)
• (inter)tidal flats marsh grasses

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Marshes

• Wetlands are essential part of ecosystem
• Sustain wildlife by providing food, protection
  from predators, and spawning and nursery habitats
  for many fish and wildlife species?
• Improve water quality by filtering out
  pollutants,
• Prevent erosion by absorbing wave energy?
• Form buffer zones during storms that help protect
  lands from flooding,
• Provide recreational area

Spartina grass, intertidal marsh, near Tuckerton,
NJ
Phragmites australis, Navesink River, NJ
http//www.constantreader.org/v2/view43.html
http//www.williamburt.com/gallery/23lg.jpg
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Effects of Sea-Level Rise Coastal Flooding
Coastal marshes cannot retreat as they must to
survive sea-level rise
Increased effects of storm surges
Left 100 year storm October 12, 2005
http//hypercomp.net/personnel/cmr/gallery/campics
/NJ05/pageimg_9850.jpg.html
Ammerman McClennen 2000
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The Bayside is Vulnerable
My shore house is an island during three
100-year storms Hallloween 91, Dec. 92, Oct.
05
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Waves

• wavelength, period
• generated by wind stress on surface
• f(wind strength, fetch, duration
• orbital motion of water (e.g., "bobbing")
• threshold critical v f(orb. v, grain size and
  wave period )
• at ?/2, bottom effects result in elliptical
  orbits
• generates a "to-fro" motion
• Shoreface
• shoaling zone to-from low Tide-Mean Wave base
• breaking zone orbital Vgt wave v shoreface lt1.3 H
• (i.e., 3 ft wave breaks in 4 ' water)
• surf zone turbulence
• Foreshore
• swash zone up/down intertidal
• backshore-dune behind berm immediately above
  high tide

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Beach profile -- Backshore

• Dunes -- landward margin of many beaches
• Rest of backshore is dominated by aeolian
  processes

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backshore/dune storm "deposits" (largely
erosional) eolian dunes foreshore swash zone,
planar, seaward dipping fine-med sand poorly
preserved in record shoreface surf zone, breaker
zone, shoaling zone Proximal upper shoreface
(surf and breaker zones) Highest E, fine -
medium. clean sand, longshore bars,
multidirectional trough x-sets, low angle
bidirection x beds Distal upper shoreface
(shoaling zone) heavily bioturbated fine-medium
sand Lower shoreface (below fairweather wave
base) lower E, fine sand, some muds
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overstep-rapid facies shift transgression
movement of the strand line (beach)
landward regression movement of the beach
seaward
Waretown
Surf City Shipbottom
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Cross-bedded sands
Organic-rich muds
Shoreface sands fining offshore
Sandy muds to muddy sandy
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transgression movement of the shoreline
(strandline, beach) landward a deepening upward
sedimentary package may fine upward or coarsen
upward Transgression but on shelf transgressions
fine up, in lagoon they coarsen up. Regressions
coarsen up on shelf and nearshore
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transgression may fine upward or coarsen
upward Transgressions shelf transgressions fine
up, in lagoon they coarsen up. Regressions
coarsen up on shelf and nearshore
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neritic (shelf/sublittoral environments)
littoral mean high to lean low tide "old
fashioned concept of decrease of grain size of
modern sediments away from shore" Kennett, p 309
many cases untrue, yet generally seems to work
that coarsening upward shoaling upward shelf
facies model for NJ Cretaceous-Miocene sequences
Figure from NJ glauconite or shell beds deepest
water middle (30-100 m) to outer (100-200m)
neritic shallows upsection to silts (30 m
inner neritic) to sands (offshore bars)
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Geostrophic currents cause along-shelf transport
on storm-dominated continental shelves Geostrophi
c means it balances pressure and coriolis
effect The pressure gradient is set up during
storms (storm surge coastal set up) This is
the probable control on the distribution of
shore-attached ridges
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U.S. Geological Survey USGS Fact Sheet
FS13601 January 2002 shore-attached ridges of
Long Island. Probably cannibalized barrier
islands redistributed by storm geostrophic
current.
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Surf City, NJ 2006
http//loveladies.org/news.php
http//graphics8.nytimes.com/images/2007/05/15/nyr
egion/190-sand-03.jpg
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Sunset Oer Ol Barney, 1st Yr Flight 2007