農業流域における土砂動態の現地観測およびUSLE・WEPPによる評価

抄録

In these years, red-soil erosion and runoff have led to agricultural and environmental problems in Okinawa, and sediment movements (erosion, transportation, and sedimentation) have to be grasped and its analysis models are demanded. In this study the sediment movements were grasped at a watershed scale from the results of multi-point simultaneous observation in the small agricultural basin including erosion observation. 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, the Universal Soil Loss Equation (USLE) and the Water Erosion Prediction Project (WEPP) were tested to verify their applicability in predicting sediment runoff at rainfall event. In case of the field level application, WEPP was more accurate and practical than USLE. These models were expanded to the watershed level; WEPP was more accurate and practical than USLE. This result was due to appropriate representation of suspended sediment movements at channels and impoundments.