Study on the roughness coefficient of mountain gravel-bed rivers

The bed slope of mountain river is relatively large, and the relationship between water depth and discharge is complex. Roughness coefficient is an important parameter in hydraulic calculations, how to choose the roughness coefficient is very important both in theoretical research and engineering calculations. Through flume experiments, we analyse the effects of hydraulic radius, water depth and discharge on the law of roughness coefficient. It is found that roughness coefficient is not a constant but changes with the water depth, we derive a new mountain gravel-bed river roughness coefficient formula according to the experiment results.