This study applies the Universal Soil Loss Equation (USLE) and a spatial analysis to assess the amount of soil loss in the Wangthong Watershed in the lower northern part of Thailand. The USLE requires several input parameters (e.g., rainfall; soil; topography, including slope length and steepness; and land use/land cover). The distribution of these parameters was identified by a geographic analysis. The simulation was conducted over the entire watershed on a cell-by-cell basis. The relationship between the input parameters and the soil loss rate was calculated to identify the significant causes and factors. The second assessment in this study involved the regular analysis and monitoring of the risk of soil erosion (e.g., possibly daily). The proposed technique was based on daily rainfall that was derived from the Tropical Rainfall Measuring Mission (TRMM)-based satellite rainfall estimates. The graphics of soil erosion susceptibility were then distributed in a geo-spatial, web-based system.
The simulated results from the USLE indicate that the agricultural areas of the watershed significantly impact the soil loss rate, which makes the watershed more vulnerable to erosion. Others factors (e.g., slope steepness, slope aspects and elevation) also considerably affected the rate of soil loss.
Land management practices, such as shifting cultivation and the generation of areas that are susceptible to soil erosion, are one of the main problems in Thailand. Evaluation of the factors involved allowed the areas prone to erosion, and the cause of the erosion, to be identified. This information enables planners and/or decision makers to target problem areas for best management practices.

特集 気候変動と環境の新しいパラダイム
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