Fs
Subtidal
Seaweed community
Coarse-grained subtidal flats and bedrock ledges which support seaweed growth.
Sz
Supratidal
Man-made land
Structures or fill emplaced by man in the nearshore environment.
Sm
Fresh-brackish marsh
Water-saturated, organic-rich sediments characterized by broad-leafed vegetation tolerant of constant submergence in fresh water.  Salinity of interstitial water < 5 ppt.
M1
Intertidal
High salt marsh
Organic-rich sediments densely vegetated primarily with the salt marsh grass Spartina patens (salt-meadow grass). High salt marshes are at the same level as mean high water.
C4
Estuarine channel
Tidal channels where ocean and river waters mix.  Estuarine water salinities range 0.5 - 30 ppt.
Fm
Mud flat
Fine-grained subtidal flats.
M2
Low salt marsh
Mud or muddy sand embankments sparsely to densely vegetated by the salt marsh grass Spartina alterniflora (salt cord-grass). Low salt marsh exists between mean tide level and mean high water.
F
Mud flats
Flats comprised of sediment finer than sand.
M
Ledge
Subaerially or subaqueously exposed bedrock.
B5
Low-energy beach
Beaches consisting of a wide variety of sediment sizes which are protected from high wave energy.  Sediment characteristics are dependent upon sediment source, which is usually from upland scarps immediately shoreward of the beach.  Low-energy beaches ma
exhibit growth of salt marsh grass when there is little sediment movement.
C2
Medium-velocity tidal channel (1-2 mps)
Tidal channels where maximum flow velocities probably attain values between 1 and 2 meters/sec. (mps).
Bw
Washover fan
Fan-shaped deposits of gravel located behind gravel beach ridges and covering portions of marshes.  Few washovers have been recognized as mappable units on sand beaches.  Washover fans are deposited by storm waves.  Fan sediment is derived from the beach
itself.
Sd
Dunes and vegetated beach ridges
Unconsolidated sand or gravel deposits capping beach environments.  Dunes are subject to storm waves and winds, while gravel beach ridges are subject only to storm wash.  Each may be vegetated with salt-tolerant vegetation.
C1
High-velocity tidal channel (> 2mps)
Tidal channels where maximum flow velocities probably exceed 2 meters/sec. (mps).
F2
Seaweed-covered coarse flat
Coarse-grained, shallow subtidal and low intertidal flats which act as a stable substrate for seaweed such as Ulva, Enteromorpha, Ascophyllum, and Laminaria.
F1
Coarse-grained flat
Intertidal flats where sand or larger-size material comprises most of the sediments.  Coarse-grained flats are subject to higher tidal-current veolocities than mud flats.
B3
Gravel beach
Beaches consisting of gravel-size sediment which are subject to high or moderate wave energy.
Br
Boulder ramp
Sloping surfaces in the lower intertidal zone veneered by large boulders.  This environment is seaward of gravel or boulder beaches on high wave energy shorelines.  Boulders are remnant lag deposits of eroded glacial tills.  Boulder movement is limited t
periods of intense storm wave activity.
Sw
Fresh-brackish water
Ponded water behind beach ridges, man-made constrictions on former tidal embayments, or on marsh surfaces transitional between upland and salt marsh enivronments.  Salinity of the water is < 5 ppt.
Mb
Fan delta
Coarse-grained, fan-shaped deposits which accumulate on intertidal flats where upland streams drain onto high tidal-range shorelines.
B2
Mixed sand and gravel beach
Beaches consisting of sand and gravel-size sediment which are subject to high or moderate wave energy.
Fb
Upper shoreface
The innter subtidal slope which extends seaward from large exposed sand beaches where sediments are actively transported by bottom currents generated by storm waves.  The upper shoreface is a sandy environment of constant wave shoaling under normal wave
conditions.
Fp
Lower shoreface
The outer subtidal slope which extends seaward from the upper shoreface.  The lower shoreface is affected only by currents generated by storm waves.  Lower shoreface sediments grade from sand to mud in a seaward direction.
Mc
Fluvial-estuarine channel
Transitional channel between river and estuarine channels. The fluvial, tidal fluvial, or estuarine state depends upon the volume of river discharge entering the estuarine basin.
Mp
Point or lateral bars
Accumulations of sediment adjacent to intertidal channel margins at channel bends (point bars) or along straight segments (lateral bars).
C5
Estuarine flood channel
Estuarine tidal channels where floodtide current velocities greatly exceed velocities attained during ebb tide.
Fe
Eelgrass flat
Fine-grained and coarse-grained, shallow subtidal (low intertidal) flats which support dense stands of eelgrass (Zostera marina).
C6
Estuarine ebb channel
Estuarine tidal channels where ebb-tide current velocities greatly exceed velocities attained during flood tide.
F6
Veneered ramp
Former boulder ramps presently covered by fine-grained sediment settling out of the water column.
F3
Mussel bar
Low mounds of living mussels, Mytilus edulis, and/or disarticulated and broken mussel shells accumulated by wave shoaling.  Mussel bars generally occur at the mouths of estuaries or embayments at tidal channel margins where nutrient-laden oceanic waters
first flood flat environments.  Mussel bars accumulate on intertidal flats.