PARENT SESSION
Poster Session #23: Fish, Lakes, Streams, and Wetlands.
Wednesday, August 8, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Relationships between land use, geology and in-stream physical habitat in small northern Oregon coastal streams.

SCOTT, LARA¹, FORD, JESSE¹, ¹

ABSTRACT- Salmonid populations in the Pacific Northwest are at historic lows and continue to decline. Previous studies have linked declines in salmonid populations to land use through degradation of in-stream physical habitat. This study focuses on relating land use and geology patterns to habitat parameters known to be important to salmonids. We have not focused on local scale (riparian zone) influences, but are interested in the relationships between basin scale land use patterns and the in-stream condition. Unlike most land use studies, this study covers a broad region. The North Coast Gene Conservation Area is a region of heavy logging activity with dairy farming at the outlets of most lowland basins. During the 2000 low-flow season we collected data on 48 first and second order reaches distributed among 9 combinations of land use and geology. Preliminary regression analyses of the resistant geology basins indicate that logging is related to elevated percent fine sediments, increased percent of the reach in slow water and pools, and more wood in the channel. Unconsolidated basins with agriculture tend to have an increased percent of the reach in slow water and pools, elevated percent fine sediments, and decreased width to depth ratios. Preliminary analyses of the weak geology basins reveal few relationships between logging patterns and habitat parameters. Further work will use two-way analysis of variance to relate the land use in the basin to an array of in-stream variables.

KEY WORDS: land use, physical habitat, streams, Oregon coast