HYDRAULIC GEOMETRY AND, STREAM CHANNEL BEHAVIOR - AN UNCERTAIN LINK

The at-a-station hydraulic geometry of stream channels can serve as a predictor of alluvial stream channel behavior. This geometry is the em pirical relations describing changes in water surface width, mean dept h, and mean velocity with changing discharge. The exponent values are correlated with channel morphology and behavior such as scour and fill , flow resistance, bank resistance, and competence. Channel behavior a nd morphology are apparently related, but some causes for effects are uncertain. Several studies, using empirical and theoretical bases, are reviewed here to illustrate the relation between hydraulic geometry a nd channel behavior, but the relations are not always consistent. Hydr aulic geometry variables are easy to measure and readily available, bu t they do not always reflect what may be more important ones such as t urbulence, the velocity distribution profile, and distribution and coh esion of sediment particles. This paper illustrates some of these prob lems, provides some solutions, arid addresses need for more work to be tter predict stream channel behavior from hydraulic geometry.