Role of active bed width in bed load transport - Coarse bed rivers

The available models for bed load transport are based upon the assumption of mean surface now width parameter which may be correct for uniform cross-sectional rivers but for coarse bed rivers (steep gradient - commonly with non uniform cross-sections) is mostly untrue. As in coarse bed rivers (mostly) certain part (or parts) of channel plays active role (known as active bed width) in the transport of bed load whereas remaining part acts just as a water discharge passage. Partly because of this assumption bed load transport models rarely predict sediment loads correctly. This study was therefore designed to investigate the role of active bed width. And a model for the computation of active bed width was developed. The performance of this model was found encouraging when tested with Gardener and Sarcee gauges data. However, this performance test was based upon very limited data and further tests therefore are suggested before generalising the model for common use.