Evaluation of Inhibitory Effect by Adaptation Measures for Red Soil Runoff from Farmland due to Heavy Rainfall

Abstract

As the climate begins changing due to global warming, heavy rainfalls have become more frequent. These are, in turn, increasing the red soil runoff that has increasingly damaged the marine products and tourist industries. Over 85% of all such runoff is from farmland. Working with local farmers, we conducted field experiments in Ginoza Village in Okinawa’s Matsuda district to better understand the inhibitory effects on red soil runoff of different potential adaptation measures. Effectiveness of the adaptation methods conducted are discussed based on the obtained results. Further, a physical model is presented for simply estimating the sediment volume due to soil erosion by using the grain size distribution. The model can give a good agreement with the measured maximum particle sizes of the red soils discharged from farmland.