2004 Volume 48 Pages 1111-1116
Recently in Okinawa, red soil runoff becomes a remarkable problem, and sediment movements (erosion, transportation, and sedimentation) have to be grasped for assessments of new land development plans or sustainable managements of agriculture. A purpose of this study is to grasp the sediment movements at a watershed scalefrom the results of multi-point simultaneous observation in the small agricultural basin including the erosion observation. The time series of discharge, suspended sediment concentration were measured on several rainfall events andat proper intervals of time. The amount of sediment runoff from farm land and the sediment balance were calculated from observed data. It was substantiated that the low canopy covered farm lands and agricultural managements affect sediment yield, the structure and the arrangement of settling basins affect sedimentation. After the observation, USLE (Universal Soil Loss Equation) was applied and evaluated by the accuracy and the practicality as the first step to establish the prediction method of sediment runoff.
