Quantifying the resistance of woody debris in natural streams

Discharge is one of the most important natural stream variables affecting a system's ecology, water quality, hydroelectric power, and navigation. Hydrologists commonly use the friction factor equation to estimate water discharge in ungaged streams. In natural streams the equation does not accurately predict discharge in streams with woody debris and vegetation. The objective of this project is to develop a refined method of incorporating woody debris components, commonly found in natural streams, into the friction factor equation, resulting in a more accurate discharge estimation. Ten gaged gravel bed streams with 30% woody debris were surveyed. Discharge was measured and compared to values given by the friction factor. By incorporating a woody debris factor into the equation, discharge estimates match measured values closer by over twenty percent.