Stream Surface Area Research Articles

Changes in Instream Habitat, Large Woody Debris, and Salmon Habitat after the Restructuring of a Coastal Oregon Stream

Abstract Elk Creek, a drainage of 26.6 km2 that historically has been severely degraded by logging, floods, and stream cleaning, was restructured in 1986, 1987, and 1989. In all, 106 full-spanning and 94 partial-spanning structures were installed along 4.2 km of stream. An upstream reach of 0.5 km was left untreated. Inventories of stream habitat conditions and large woody debris conducted in 1985 and 1990 (i.e., before and after restructuring), showed that restructuring caused substantial changes favoring suitable habitat for coho salmon Oncorhynchus kisutch; meanwhile, the untreated reach became less favorable for rearing coho salmon. Stream surface area and water volume, respectively, increased 74 and 168% in the treated reach, and 8 and 37% in the untreated reach. Surface area of pool and suitable of channel habitat, the most important summer and winter rearing components for coho salmon juveniles, increased nearly fivefold in the treated reach at summer low flow. In the treated reach, which had a mat...

Computer Analysis of Fish Populations in Fluctuating Streams

POPULATION ESTIMATES, a computer program designed to analyse fish populations in fluctuating streams, is described. Its special feature is to calculate population density (number and g m−2) as a dynamic function of variable stream area. Other output includes estimated population size, mean length, mean weight and mean condition factor. Simulated flow changes of 12.5–400% changed stream surface area 6–37% for straight channels, 11–80% for meandering channels and 18–182% for braided channels. Fish population density, however, may not change inversely proportional to stream size. The main use of POPULATION ESTIMATES is to evaluate the effects of fluctuating flows on fish populations.