Observation of Sediment Yield by Acoustic Bedload Sensor and Turbidity Meter in Agricultural and Forest Watershed

Abstract

Among the automatic measuring devices used for observing sediment flow in rivers, turbidity meter are commonly used for the observation of suspended sediments. However, no techniques have been established for the observation of bedload transport. In this study, suspended sediments and bedload transport were automatically observed by using turbidity meter and acoustic bedload sensor, respectively, at inlet of settling basin in the end of agricultural and forest watershed. As for this automatic observation data, it was shown that the observational error was small by comparing it with sediment deposit etc. by settling basin. The result of two-year observation showed bed load to account for 8% of the sediment flow in the river. While the relationship between the discharge and the suspended sediment load (L-Q) during floods varied depending on the amount of rainfall or snowmelt, the relationship between the discharge and the bedload transport was steady regardless of the cause of flooding.