GIS-USLEを用いたタイ北部, ナン県における土壌浸食量の推定

抄録

The Yao River basin, located in the Nan Province, north Thailand, is one of the most critical watersheds in terms of soil erosion. USLE method was combined with GIS technology so as to estimate the soil erosion volume in this basin. As a result, the total amount of 131, 500 ton/year for the whole basin was calculated. Based on the spatial distribution of USLE value, the most hazardous sub basin with 20, 075 ton/year was detected on the left side of the lower Yao River. Then, USLE analysis at larger scale was conducted for this sub-basin. By applying the higher resolution DEM and aerial photo interpretation, it became clear that the actual value was 8, 940 ton/year because the slopes were less steep and more vegetated. Although there is no land conservation practice, the supposed three conditions (contouring, stripping and terracing) were simulated in order to evaluate the effectiveness of each type of practice. The result shows that the erosion volume was reduced to less than half by constructing the stripping or terracing practice.