Riparian Ecosystem Map Unit: RDA

Wetland Classification and Mapping of the Kenai Lowland, Alaska

Map Unit Descriptions

Ecosystem: Riparian

Map Unit: RDA

Extent: 10 wetland polygons; 145.9 ha; 0.10% of wetland area; 0.06% of wetland polygons.

Bluejoint grass and thinleaf alder on an RDA unit north of the village of Nikolaevsk (polygon 6968).

Wetland Indicators

Type: Stream

Average depth to water table: 5 cm at the single site measured.

Organic layer thickness: 66 cm at the single site measured.

Average depth to redoximorphic features: 135 cm at the single site measured.

Common Soils: STARICHKOF

Common Plant communities:

Barclay willow / Bluejoint / Marsh fivefinger

NWI: Stream: R2US3,4. Valley wetlands: PSS1Jg

HGM: Stream: Low Gradient Natural Stream-braided. Valley wetlands: Lotic Flat groundwater-dominated Throughflow/Bidirectional-nontidal.

Accuracy assessment: 2 polygons interpreted as RDA on aerial photographs were field checked. They both remained RDA.

RDA reaches are braided sluggish streams in Rosgen's (1996) 'DA' category. On the lowlands, RDA reaches form when a stream spreads onto a flat relict glacial lakebed terrace, forming multiple, more or less braided, channels. RDA is uncommon. The channel is often concealed beneath thick bluejoint grass (Calamagrostis canadensis) cover. Bed material is usually sand and gravel. The wetland fringe of these units is more extensive than other Riparian Ecosystem map units, and a thick organic mat is common.

Fourteen streams in the project area are covered under Kenai Peninsula Borough's Anadromous Streams Habitat Protection Ordinance. Many activities require a permit, or are prohibited within 50 feet of these streams. For a list of the streams, rationale for the ordinance, and details on obtaining a permit, visit the link highlighted above.

"The Kenai Peninsula Borough manages a Floodplain Ordinance that addresses proper development to reduce flood risks and lessen the economic losses caused by flood events. The ordinance provides building standards for construction projects within the floodplain to ensure the availability of flood insurance through the National Flood Insurance Program. These building requirements also are intended to minimize or prevent damage when flood events occur. The ordinance requires floodplain development permits for all projects in floodplains."