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Modeling Physical Habitat Parameters

Robert K. Hall 1, Daniel T. Heggem 2, Anne C. Neale 2, Rick Van Remortel 3, Phil Kaufmann 4, Daniel Hagans 5 and Janet Y. Hashimoto 1

1 USEPA Region IX, WTR2, 75 Hawthorne St., San Francisco, CA 94105
2 USEPA ORD Environmental Sciences Division, Landscape Ecology Branch, Las Vegas, NV 89119
3 Lockheed Martin Environmental Services, Las Vegas, NV, 89119.
4 USEPA ORD Western Ecology Division, NHEERL, Corvallis, OR. 97333
5 Pacific Watershed Associates, PO Box 4433, Arcata, CA 95518

Salmonid populations can be affected by alterations in stream physical habitat. Fish productivity is determined by the stream's physical habitat structure (channel form, substrate distribution, riparian vegetation), water quality, flow regime and inputs from the watershed (sediments, nutrients, and organic matter). The interaction of these components influences primary production, and fish population and community structure within the stream. Physical habitat is an important and often overlooked ingredient for good stream condition. The objective of this paper is to predict, on a watershed scale, the characteristics of stream physical habitat structure in the Eel River Basin. Geology in the basin is dominated by the Franciscan formation, a complex assemblage of shales, sandstones and conglomerates of marine origin intermixed with igneous extrusives. These lithologies in combination with regional tectonic activity, steep terrain and climatic factors have rendered the Eel River Basin geologically unstable. Net result is high sediment loads to the streams. Terrestrial and riparian habitat consist of low elevation oak woodlands with valley oak grading to pines and fir at higher elevations. Canopy conditions range from closed, or nearly closed to open depending on the level of human disturbance. The metric of riparian habitat quality is calculated by using the National Land Cover Data along with the National Hydrological Data to determine the percentage of riparian vegetation cover. Per cent riparian forest correlated with channel alteration and bank stability. Sediment distribution, as tons per year for subwatersheds using the RUSLE model, correlated with the EMAP and Rapid Habitat Assessment sediment parameters.

Keywords: Salmonid, physical habitat, riparian, sediment

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