Evaluation and calibration of bedload equation for the mountain ephemeral stream of Gujarat, India

Bedload is rarely measured in Indian rivers. It is recommended that 5% of suspended load can be taken as bedload in the absence of measured bedload. The present study validates this by direct physical measurement of bedload using the Helley–Smith sampler in an ephemeral mountain stream of Gujarat, India. It was observed that, on an average, the bedload formed 3.97% of the sus­pended load. The measured bedload flux was 1.02 tonnes/day. To overcome the need and dependability on actual physical bedload measurement, a bedload rating curve against specific discharge was developed to predict the bedload rate in the study reach. Few prominent existing bedload equations selec­ted from the literature were tested against the measured bedload, which over-predicted the bedload transport rate with a discrepancy ratio greater than 2 and RMSE 2.4–48. A calibration coefficient x = 0.00167 was introduced in the widely used Recking (2013) equation for the study reach resulting in an improvement of the coefficient of variation as 1.92 and RMSE as 1.35