Channel-forming discharge and hydraulic geometry width predictors in meandering sand-bed rivers

This paper defines channel-forming discharge as a theoretical parameter commonly used to develop preliminary channel dimensions for natural channel design. The channel-forming discharge concept is based on the idea that for a given alluvial channel geometry there exists a single steady discharge that given enough time would produce channel dimensions equivalent to those shaped by the natural long-term hydrograph. This theoretical discharge therefore dominates channel form and process and may be used to make morphological inferences. Bankfull discharge, effective discharge and a designated flood peak frequency are three deterministic parameters commonly used to represent the channel-forming discharge. Using this concept of channel-forming discharge, data were collected from 57 meandering sand bed streams in the United States and the three deterministic discharges were compared. The estimated channel-forming discharge was then used to develop generalized hydraulic geometry relationships for bankfull width. Statistically significant differences in the regression of bankfull width and bankfull discharge were determined based on a simple classification of bank vegetation density. These relationships are presented with both single response and mean response confidence limits.