RELATIONSHIPS BETWEEN PARTICLE MOVEMENT AND CHANNEL MORPHOLOGY IN SOME NORTHERN IDAHO STREAMS1

Abstract

ABSTRACT: Data were collected in 1992 from 17 mountain streams located within fine‐ to coarse‐grained schist formations on the Idaho Panhandle National Forests. These were used to examine predictive relationships potentially useful in monitoring stream channel stability and fishery habitat. Channel morphology, sediment, and lithological data were obtained at 123 riffle sites. An analysis of materials deposited on gravel bars showed that at most sites, critical grain size, calculated using Duboy's tractive force equation, often does not provide accurate estimates of particle sizes moved at bankfull discharge. The tractive force equation gave reasonable estimates (± 10 mm) at 16 percent of the sites, but significantly over‐ or underestimated the sizes at the remaining sites. Regression and discriminant analysis showed that the relationship between critical grain size and the geometric mean diameter of material deposited on gravel bars was influenced most by the substrate size, slope, and width‐to‐depth ratio. Similarly, lithology was correlated with the size of particles moved. Particle sizes moved at bankfull discharge were not well correlated with residual pool depth or pool length.