Table 10. Description of the physiography, geomorphology, hydrology, permafrost and vegetation of ecodistricts

Figure 24. Map of ecotypes on the Tanana Flats, Ft. Wainwright , central Alaska, 1998

Table 10. Continued

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Table 10. Description of the physiography, geomorphology, hydrology, permafrost and vegetation of ecodistricts and

ecosubdistricts mapped within Fort Wainwright, central Alaska, 1998 (Fig 25).

A braided stretch of the Tanana River that includes braided-floodplain riverbed deposits, and active-

Floodplain

and inactive floodplain cover deposits. The lower perennial glacial river is turbid with glacial silt.

The area is subject to frequent flooding (every year on riverbed deposits), occasional flooding (every

25 years on active floodplain cover deposits) and infrequent flooding (about every 525 years on

inactive floodplain cover deposits. Groundwater is near (<23 m) the surface and permafrost is absent.

Vegetation includes partially vegetated river bars, riverine willow and alder tall scrub, and balsam

poplar and white spruce forests. Forest productivity is high.

Rosie Creek

A stretch of the Tanana Floodplain characterized by anastomosing channels, numerous stable islands

Tanana

and few braided river bars. Geomorphic units linked by fluvial processes include meander riverbed

Floodplain

deposits, active and inactive cover deposits, and the lower perennial glacial river. Meander scrolls and

backwater fens are common. The area has a similar flooding regime to that of the Eielson-Tanana

Floodplain. Permafrost is absent. Vegetation includes partially vegetated river barrens, riverine willow

and alder tall scrub, balsam poplar and white spruce forests, and wet sedge meadows. Forest productiv-

ity is high.

Chena

A meandering stretch of the lower Chena River that includes meander riverbed deposits, and active-

Floodplain

and inactive-floodplain cover deposits linked by surface and groundwater movement. The lower

perennial river has clear water and a flooding regime similar to that of the Eielson-Tanana Floodplain.

Permafrost is absent. Vegetation includes partially vegetated river barrens, riverine willow and alder tall

scrub, balsam poplar and white spruce forests, and wet sedge meadows. Forest productivity is high.

Chena Slough

A stretch of the Tanana floodplain that includes a large branch channel of the Tanana with numerous

Floodplain

meander point bars. Geomorphology includes meander riverbed deposits, and active- and inactive-

floodplain cover deposits linked by fluvial processes. The area has a similar flooding regime to that of

the Eielson-Tanana Floodplain. Permafrost is absent. Vegetation includes partially vegetated river bar-

rens, riverine willow and alder tall scrub, balsam poplar and white spruce forests, and wet sedge

meadows. Forest productivity is high.

Salchaket Slough

A stretch of the Tanana floodplain that includes a large channel of the Tanana River. Geomorphology

Floodplain

includes meander riverbed deposits, and active- and inactive-floodplain cover deposits linked by flu-

vial processes. The flooding regime is similar to that of the Eielson-Tanana Floodplain. Vegetation

includes partially vegetated river barrens, riverine willow and alder tall scrub, balsam poplar and

white spruce forests, and wet sedge meadows. Forest productivity is high.

Fairbanks

A flat area adjacent to the Tanana River that is dominated by abandoned-floodplain cover deposits

Lowlands

and occasional organic bogs. Due to thick (12 m) cover deposits, there is little surface expression of the

underlying fluvial morphology. The area is hydrologically linked to the Tanana Floodplain by ground

water movement and rare flooding events, but the lack of streams indicates little surface water move-

ment. Permafrost is nearly continuous; it is absent in occasional collapse scar bogs caused by perma-

frost degradation. Common vegetation include black spruce, tamarack, and birch forests and shrub

birchericaceous shrub.

Eielson Lowland

A flat area adjacent to the Tanana River that is dominated by abandoned floodplain riverbed deposits

with only thin cover deposits of overbank fines. Thermokarst features are rare and the surface is char-

acterized by the braided pattern of the old riverbed. The area is hydrologically linked to the Tanana

Floodplain by substantial groundwater movement and rare flooding events. Because of groundwater

movement, permafrost is difficult to predict but probably sporadic. Vegetation is dominated by black

spruce forest on interfluves and shrub birchericaceous shrub and willowsedge fens in abandoned

channels.

Salchaket Slough

A flat area adjacent to the Tanana River dominated by thick abandoned floodplain cover deposits and

Lowlands

occasional thermokarst features with organic bogs. The area is hydrologically linked to the Tanana

River by groundwater movement and rare flooding events, but there is little surface water movement

indicated by lack of streams. Permafrost is nearly continuous. Common vegetation types include black

spruce, tamarack, and birch forests and shrub birchericaceous low scrub.

Bear Creek

An area adjacent to the Tanana River that is dominated by abandoned-floodplain riverbed deposits with

Lowlands

only thin cover deposits of overbank fines. Thermokarst features are rare and the surface is characterized

by the braided pattern of the old riverbed. The area is hydrologically linked to the Tanana Floodplain by

substantial groundwater movement and rare flooding events. Due to groundwater movement perma-

frost is difficult to detect, but probably is sporadic. Vegetation is dominated by black spruce forests in

interfluves and shrub birchericaceous shrubs and willowsedge fens in former channels.

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