Chapter 8: Barrier Systems Physical Description •General Description of Morphology •Wave built accumulations of sand •Distribution & Coastal Setting •Waves and Winds sustain their evolution •Barrier Types •Linear features, parallel to coast •Evolution (Prograding, Retrograding, or Aggrading) •Occur in groups or chains •Barrier Stratigraphy •LI Barrier System

Barrier Systems Barrier Interior Beach Beach: dynamic, evolution dependant on winds, waves and tides Barrier Interior: sand dunes, dune lines, vegetated beach ridges, brackish ponds. Landward Margin: intertidal sand/mud flats, salt marsh, overwash splays, transitions into bay, lagoon or tidal creek

Landward Margin

Barrier Distribution Distribution and Coastal Setting •Comprise ~15% of the worlds coastline •Found on every continent (except Antarctica), geologic- climatologic setting •Amero-trailing edge coasts •Mid-low latitudes, micro-meso tidal environments

Microtidal: < 2 m Mesotidal: 2 – 4 m Macrotidal: > 4 m

1 Amero-Trailing Edge Coasts Marginal Sea & Collision Coasts Sediment supply Sediment supply is low (short steep rivers) Shelf width Shelves tend to be narrow (high wave energy) US east coast Sediment is often transported to ocean basins barrier chains extend 3100 km

Slow erosion Appalachian Mnts Afro-Neo Trailing Edge Coasts Lack of sediment Gulf coast (1600 km) Lack of organized drainage

Types of Barriers

Barrier Spits

Stony Brook Harbor, Long Beach

Recurved spits

2 Spit Formation

Tombolos

Georgica Pond, NY

Welded Barriers

•Barrier chains are aligned parallel to the coast •Most have formed in a regime of slow eustatic sea-level rise NOTES •They are separated from the mainland by shallow lagoons, marshes, and/or tidal flats •Tidal inlets separate individual barriers along a chain •They formed during periods of sand abundance

3 Barrier Island Formation Spit Accretion Theory

Offshore bar theory (de Beaumont, Johnson)

Spit accretion theory (Gilbert, Fisher)

Submergence theory (McGee, Hoyt)

Shinnecock Inlet, 1938

Spit Accretion Theory Spit Accretion

Prograding Barriers: building/migrating seaward Retrograding Barriers - bar island rollover

Any mechanism that forms a continuous feature along the barrier that acts as a nucleus for dune ridge development

4 Dauphin Island Hurricane Ivan, September 2004

Aggrading Barriers: Barrier systems is stationary, keeps up with rising sea level Barrier Stratigraphy Layering or sequencing of sedimentary deposits

Sources of Sand For Littoral Transport

Bluff Erosion Offshore Glacially Deposited Sand Ridges, Relict Ebb Shoals

Cliff or Bluff Coast Tide Dominated & Riverine

2 m Gravel

Wave Dominated

Sand

Barrier Island Mixed Energy

5 Maximum Amount of Material Derived From Bluff Erosion

•Historic estimates 81,100 yd3/yr to 132,100 yd3/yr •The bluffs at Montauk Point are receding at 1 ft/yr •This recession rate has been well documented due to endangerment of the historic Montauk Light House constructed in 1796.

•Analysis of the bluff composition and historic rates of recession have determined Montauk (Ronkonkoma •Littoral Transport reaches a maximum rate of 463,015 to Moraine) bluffs could not account for all of the 601,657 yd3/yr at Democrat Point (Fire Island Inlet) material contained within the littoral system. •Based on sieve analysis data •63-percent of the size fraction (by weight) is similar in composition (fine to medium sand) to the barrier beaches to the west

6 Calculated Recession Rates for Montauk Bluffs Atlantic Coast of Monitoring Program

SA Lit. Cont. Years Reference Recession Rate m2/yr ft3/yr yd2 yd3/yr 0.29 0.95 253,550 81,100 1979 – 1995 Rosati et al, 1999 0.31 1.02 253,550 86,600 1983 – 1995 Rosati et al, 1999 0.14 0.46 253,550 39,000 1995 USACE, 0.47 1.56 253,550 132,100 1955 – 1979 Kana, 1995 0.30 1.00 253,550 76,065 1796 – 1996 McCormic & Pilkey

Seasonal Profiles 1995 through 2004

Measured Recession Rates and Littoral Drift 6 to 29 % of Longshore transport at Fire Island Inlet. Contribution for Montauk Bluffs

ACNYMP Recession Rate Vol. Change Integrated Littoral Volume Station ft/yr yd3/ft/yr Volume yd3/yr yd3/yr M35 0.32 3.20 9725 6127 M37 0.83 1.20 2640 1663 M38 1.90 7.80 17514 11034 M39 2.00 0.40 1150 725 M40 0.20 1.20 3015 1900 M41 0.31 0.62 1453 916 M42 1.30 4.45 9000 5670 M43 0.91 0.81 9654 6082 Average 0.97 Total 54151 34117

The Flandrian Transgression Shoreline Retreat During The Flandrian Transgression

•Current sea level rise which began approximately 18-19,000 years ago (during latest Pleistocene time and continuing progressively during Holocene time to the present).

•This rise in sea level is directly related to the melting of continental polar and mountain piedmont glaciers. -50 m -40 m -30 m •During the "climax" of the Wisconsin glacial advance (lowstand) sea level was anywhere between 70 to 150 meters below its current level

•Shelf Break = the outer edge of the continental shelf

-20 m -10 m 0 m

7 •30 kilometer wide band of sand ridges on the middle continental shelf represent a broad band of degraded and submerged barrier islands formed between 14,000 and 8,000 years before present (Stubblefield, et al. 1983)

•Shelf currents are actively reworking the barrier sands into ridges

•It has been in the last 4000-6000 years that the majority of modern coastal barrier islands and tidal wetlands have developed.

109,868 to 517,948 yd3/yr of sediment may be coming from offshore, however the exact mechanism for the material transport into the littoral zone has not been determined (Schwab et al., 1999)

Additional Metropolitan Beach Composition

River and Raritan Bay Sediments Wave driven transport and winnowing

Raritan Bay Sediments

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