近年來臺灣極端降雨事件發生頻繁,有累積雨量變高、降雨延時更長及區域性降雨強度增強等情況發生,對於土壤沖蝕的影響甚鉅。目前臺灣多以通用土壤流失公式(Universal Soil Loss Equation, USLE)進行土壤流失量之估算,其中降雨沖蝕指數(Rainfall Erosivity, R)直接反映在降雨對土壤沖蝕的影響程度。因此,本文為了解降雨特性的改變對降雨沖蝕指數之影響,以臺灣地區為例,蒐集境內323個中央氣象局雨量站的降雨資料,利用降雨沖蝕指數(R=E×I30max)的計算方法,分析單場、月、季及年降雨量與降雨沖蝕指數的關係,探討臺灣地區降雨量與降雨沖蝕指數之時間及空間變化,有助於現今或未來對土壤沖蝕變化之了解。 結果顯示月、季及年之降雨量與降雨沖蝕指數的迴歸關係式其判定係數(R2)大致上均大於0.7以上,顯示迴歸式可以解釋資料的變異量相當好。北部地區之月平均降雨量及平均降雨沖蝕指數1月份、6~9月及11~12月Pm*與Rm*隨時間有逐年上升的趨勢;其餘月份Pm*與Rm*時間變化為持平或有下降趨勢;中部地區則是2~5月及10月有上升趨勢;南部地區為1月、7~12月份Pm*與Rm*的時間變化是有逐年上升的趨勢;最後東部地區是1月及7~12月份Pm*與Rm*的時間變化是有逐年上升的趨勢。季降雨量及降雨沖蝕指數於全臺灣地區之夏、秋季有逐年上升之趨勢,春季則相反。年平均降雨量(Py)及年平均降雨沖蝕指數(Ry)在23年(1993~2015年)期間有明顯上升趨勢。另外,本研究之降雨沖蝕指數分析結果與黃俊德(1979)、盧光輝(1994)及盧昭堯(2005)成果進行探討,得知近年來年平均降雨沖蝕指數有增大趨勢,其中大湖及月眉雨量站差異百分比高達238 %、234 %及272 %,整體來說,近年臺灣地區降雨沖蝕指數隨時間有逐漸增加之趨勢。
In recently years, trend of the rainfall characteristics have gradually changed due to extremely heavy rainfall event in the world. Rainfall is the major cause of soil erosion dynamic factor. Rainfall erosivity is a numerical description of the potential of rainfall to erode soil and is one of the key input parameter for USLE formula. The purpose of this study is estimating the rainfall erosivity based on diffirent rainfall events (single event, monthly, seasonal, and annual precipitation, respectively). In addition, this study explored the temporal and spatial variations for precipitation and rainfall erosivity by 323 rainfall stations (from 1993 to 2018) in Taiwan. In this reasarch results, precipitation and rainfall erosivity showed highly correlation in the relation formula, and monthly precipitation and rain erosivity concentrated in June to October. The analytical results of relationship between seasonal precipitation and rainfall erosivity corresponded with the result in monthly analysis, which also focused in summer and autumn. Moreover, results also showed an increasing trend for monthly, seasonal and annual precipitation, and the spatial variation also showed an increasing trend by altitude.