在台灣許多的水庫建造用來在旱季時能提供民生用水。為了增加水庫設計的壽命,必須了解每年水庫的淤砂量多寡。本研究的研究區域在台灣的石門水庫,利用萬用土壤沖蝕公式(Universal Soil Loss Equation, USLE)來估算水庫集水區周圍的土壤沖蝕量之多寡。在公式中有六個因子分別稱作降雨沖蝕因子Rm、土壤沖蝕性因子Km、坡長因子L、坡度因子S、植生覆蓋管理因子C以及水土保持因子P。在地形因子方面利用了ASTER以及行政院農業委員會林務局農林航空測量所製作的DEM進行坡度與坡長因子之計算。C值則是利用國土測繪中心之土地分類使用類別。 除了利用USLE公式外,本研究也結合ArcGIS之圖形介面分析模組,建置USLE圖形分析模組,可快速套疊不同年份的圖資,進行分時期水土保持分析。此外,可依據估算沖蝕量之多寡做為判定水庫壽命之一項依據。
Reservoirs not only built to retain water also for distribution during dry seasons. One of the most important influence the design life of reservoirs is the annual sediment input to reservoirs. The study area located in Shihmen reservoir, Taiwan. It is a important reservoir for distributing water in central Taiwan. To understand the amount of soil erosion of watershed, firstly we use Arc GIS graphic model to build USLE as the analysis tools, secondly we use one of the most important formula called Universal Soil Loss Equation, USLE as the caculating formula. There are six factors of USLE, namely the rainfall factor Rm, the soil erodibility factor Km, the topographic factors including the slope length factor L and slope degree factor S, the crop management factor C, and the erosion control practice factor P. Because of Arc GIS graphic model has its convenient, so we can analyze different years of sources to get the amount of soil loss of each year. Instead of using USLE formula, we also combine with GIS tools. Use GIS tools to build model, analyzing each factor of USLE. The result can be seen as judge the life of the reservoir.