Wetland Classification and Mapping of Seward, Alaska



Map Unit Descriptions


Ecosystem: Tidal


Map Units: T67; T76


Seward Area Extent:

T67: 6 wetland polygons; 88.9 acres

T76: 3 wetland polygons; 48.4 acres

T6 is represented by the  uniform Lyngbye sedge stand in the foreground of this photo of a T67 wetland at the head of Resurrection bay.   T7 is represented by blue-green beachrye patches, one at center left, near the first stump.

Wetland Indicators

Type: Tidal

Average depth to water table: 8 cm on 20 June 2006 at the one site measured

Organic layer thickness: 9 cm

Average depth to redoximorphic features: 0 cm at the one site measured

Common Soils: Typic Cryaquents at the single site visited, but probably also Oxyaquic Cryofluvents

Common Plant communities:

Lyngbye's sedge (Carex lyngbyei)

Beachrye (Leymus mollis ssp. mollis)


These are the most common and extensive tidal wetland types around Seward.  They are a mix of the lower, wetter Lyngbye sedge (Carex lyngbyei) tidal marsh type (T6), and the higher beachrye (Leymus mollis ssp. mollis) type (T7).  when Lyngbye sedge dominates the wetland in named T67, and when beachrye is dominant, T76.


T6 corresponds with Vince and Snow's (1984) 'Inner Sedge Marsh Zone 7', estimated to be inundated on only the highest spring tides, or an average of 2 times per summer on the Susitna Flats (with a range of 0-5 times per summer), in upper Cook Inlet, Alaska.  Vince and Snow found that water was retained for greater than 5 days per inundation. 


T7 wetlands are found on coastal storm berms and higher riverbank levees.  Vince and Snow (1984) describe 'Riverbank Levees' dominated by other grasses, and that "Still higher levees featured [Beachrye] and large forbs..."  Their lower elevation riverbank levees flood an average of 1 time per summer; probably higher T7 beachrye berms or levees flood only when storms correspond with the highest spring tides.  Around Seward, T7 seems to occupy wetter areas than around Cook Inlet.



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Contact: Mike Gracz
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12 February 2007 15:31