Relationships of dominant discharge and channel form to select watershed characteristics in snowmelt dominated streams

A primary assumption of the natural channel design method for stream restoration is that the bankfull design discharge is the channel forming or dominant discharge. Dominant discharge is defined as the theoretical discharge that if constantly maintained in an alluvial stream over a period of time will produce the same channel geometry that is produced by the long-term hydrograph. The dominant discharge appears in three different forms, effective discharge, bankfull discharge, and as a specified return period discharge. The selection of an appropriate design discharge that best approximates the dominant discharge is critical to natural channel design and dictates the success of restoration projects in improving stability and water quality. The objectives of this research are to: (1) compile existing methods of determining dominant discharge into a reference that compares each method and presents limitations, assumptions, data needed, and suggested use and (2) examine relationships between watershed and stream characteristics and bankfull and effective discharge magnitudes. The primary goal of this study is to provide guidance on selecting an appropriate design discharge for restoration projects within Wyoming and Colorado based on given watershed and stream conditions.