The Use of Sediment Rating Curve under its Limitations to Estimate the Suspended Load

The suspended sediment load in river water is an important index for the soil erosion rate in the watersheds of designated rivers. Amongst the various methods for estimating the suspended sediment load, the most frequently used one is the sediment rating curve. The sediment rating curve can aid in the understanding of the relationship between the behaviour of the suspended sediment transport and the discharge flow for estimating soil erosion. However, the rating curve tends to underestimate the actual values of both the suspended sediment load and the suspended sediment concentration during high discharge and to overestimate them during low discharge. The aim of the present paper is to confirm how to use the sediment rating curve to estimate soil erosion under its limitations and benefits. The accuracy of sediment rating curve is affected by various factors, including seasons, discharge stages, catchment area, and sampling frequency. In many cases, it cannot be concluded easily that sediment rating curve is the best method to estimate suspended sediment load. At the same time, there is no other method that is simple and commonly used for the estimation of suspended sediment load, as the sediment rating curve. Efforts on the improvement of the sediment rating curve, such as data separation among the seasons and the increasing of sampling frequency, are needed for the better estimation as well as the accuracy of suspended sediment load.