Friday, April 24, 2009, 2 PM
Olsson Hall 120

Coupling Hydrodynamic Modeling and Empirical Measures of Bed Mobility
to Predict the Risk of Scour and Fill of Salmon Redds in a Large Regulated River

Dr. Christine l. May

Abstract

In order to assess the risk of scour and fill of spawning redds during floods, an understanding of the relations among river discharge, bed mobility, and scour and fill depths in areas of the streambed heavily utilized by spawning salmon is needed. Our approach coupled numerical flow modeling and empirical data from the Trinity River, California, to quantify spatially explicit zones of differential bed mobility and identify specific areas where scour and fill is deep enough to impact redd viability. Spatial patterns of bed mobility, based on model-predicted Shields stress, indicate that a zone of full mobility was limited to a central core that expanded with increasing flow strength. The likelihood and maximum depth of measured scour increased with increasing modeled Shields stress. Because redds were preferentially located in coarse substrate in shallow areas with close proximity to the streambanks, they were less likely to become mobilized or risk deep scour during high flow events but were more susceptible to sediment deposition.

Biography

Faculty Research Associate, Stream Ecology
Department of Geology & Environmental Science
James Madison University

The Civil Engineering seminar series is open to the University community.
Civil Engineering undergraduate students are especially invited to attend.