臺灣本土降雨動能及降雨沖蝕指數推估公式之評估-以臺灣北部為例

Abstract

通用土壤流失公式(USLE)，為目前最廣為使用之土壤流失量估算方法，也是臺灣水土保持手冊中明定計算土壤沖蝕量之方法。公式中的降雨沖蝕指數，係為黃俊德(1979)利用美國華盛頓地區之降雨動能公式(Wischmeier and Smith, 1958)，並輔以臺灣地區200個雨量站約20年的年平均雨量，建立目前水土保持手冊中所使用之年平均等降雨沖蝕指數圖。然而，此年平均等降雨沖蝕指數等值圖，因採用的雨量資料較為久遠、未使用本土化之降雨動能公式及參考有限的雨量站等因素，其是否能代表現況、臺灣地區之特性、或空間分布精度是否足夠、甚至僅以歷年平均值作為設計值代表等，皆仍有相當之探討空間。 爰此，本研究採用自動化雨滴譜儀，蒐集臺灣北部地區(中央站、翡翠站、霞雲站及寒溪站)之雨滴粒徑資料，建立臺灣北部地區本土化之降雨動能推估公式。其後，結合各雨量站點的10分鐘降雨資料，進行臺灣北部地區年降雨沖蝕指數之計算與修訂。最後，考量到雨量觀測網之空間分布精度尚嫌不足的情況，利用空間統計方法進行年降雨沖蝕指數於臺灣北部地區之空間分布推估。

The universal soil loss equation (USLE) has been the most widely used in the world and adopted as the method in the handbook of soil and water conservation in Taiwan for evaluating soil loss. The rainfall erosion index(the R factor) in the handbook was proposed by Huang(1979) using the rainfall kinetic energy equation(Wischmeier and Smith, 1958) derived from the measured data in Washington D.C., U.S., and the average R value of 20-year period using the rainfall data obtained from 200 rainfall observation stations to establish the iso-erodent map. However, the rainfall data used for establishing the map was relatively too long ago; the rainfall kinetic energy equation was not derived from the local data; the rainfall observation stations were limited; therefore, the representativity of situation, the characteristics of Taiwan, the precision of spatial distribution, and whether the annual average R value could be used for design, need to be further studied. Accordingly, in the study, disdrometers were adopted, drop size distribution of the rainfall in northern Taiwan were measured and collected to derive the kinetic rainfall energy equation for northern Taiwan. Then, the rainfall data collected from stations at every 10 minutes were used to compute and revise the annual R factor of northern Taiwan. Finally, spatial statistical methods were applied to improve the precision of the spatial distribution of the R factor in northern Taiwan.