降雨沖蝕指數是通用土壤流失公式(Universal Soil Loss Equation, USLE)重要的參數之一,它的大小表示降雨對土壤沖蝕能力的高低。分析降雨沖蝕指數的變化有助於了解降雨對土壤沖蝕的影響及變遷。計算降雨沖蝕指數需要30分鐘或更短延時的雨量資料,然而許多地區歷史的雨量記錄資料,往往缺乏短延時(如十分鐘)雨量資料,只有時雨量資料,甚至只有日雨量資料。因此如何使用較方便取得的雨量資料來推估降雨沖蝕指數,是一個非常值得探討的課題。本文首先收集會文水庫集水區十分鐘雨量資料及時雨量資料,將十分鐘雨量資料計算所得之降雨沖蝕指數和以時雨量資料計算所得的擬似降雨沖蝕指數(R60)進行比較,結果顯示兩者之間有非常密切之關係,前者約爲後者的1.52倍,因此未來可以利用R60來推估降雨沖蝕指數。此外,本研究結果也顯示會文水庫集水區歷年降雨沖蝕指數有顯著增大的趨勢。
The paper proposes a new method to estimate the rainfall erosivity index using hourly rainfall dada. A pseudo rainfall erosivity index R60 is proposed and computed using hourly rainfall data obtained from six rainfall stations at the Watershed of Tseng-Wen Reservoir, and compared with the rainfall erosivity index calculated with the 10-mm rainfall data. Regression analysis shows the rainfall erosivity index is closely and linearly correlated to the pseudo rainfall erosivity index, and the former is about 1.52 times larger than the latter. This study also reveals the annual rainfall erosivity index has an increasing tendency in the Watershed of Tseng-Wen Reservoir.