Estimation of 1 km Grid-based WATEM/SEDEM Sediment Transport Capacity Using 1 Minute Rainfall Data and SWAT Semi-distributed Sediment Transport Capacity Results for Han River Basin of South Korea

Abstract. When assessing the total sediment yield of a watershed through sediment transport from soil erosion process, the ratio of sediment delivery is a critical and uncertain factor during modelling. This study is to estimate watershed scale sediment yield distribution of 1 km by 1 km spatial resolution with the evaluation of RUSLE (Revised Universal Soil Loss Equation) rain erosivity (R factor) for 14 years (2000–2013) using 1 minute data from 16 rainfall gauging stations in Han River basin (34,148 km²) of South Korea. The WATEM/SEDEM sediment delivery algorithm based on RUSLE R, soil erodibility K, length-slope LS factors was adopted. The average R factor values of 1 minute for the basin were evaluated as 3,812 MJ/ha mm/year. To determine the 1 km grid-based KTC (transport capacity coefficient generally given as 100) for the WATEM/SEDEM sediment transport estimation, the SWAT (Soil Water Assessment Tool) MUSLE (Modified USLE) results from 181 sub-watersheds (from 50 km² to 300 km²) were used. The SWAT simulated suspended solids versus observed ones at 7 locations showed average R² (determination of coefficient) of 0.72. Using the SWAT sediment yields, the spatial KTC based on 60 minutes R factor was determined at each sub-watershed from 0.16 to 142.6 with average value of 12.7 for the whole basin.