台灣降雨沖蝕指數之研究

Studies on the Rainfall Erosion Index in Taiwan

黃俊德(Chung-Teh Huang)

《中華水土保持學報》 10卷1期 (1979/07) Pp. 127-144

https://doi.org/10.29417/JCSWC.197907_10(1).0008

摘要

土壤冲蝕係降雨冲蝕土壤之能力(erosivity) 與土壤受蝕性( erodibility)之函數。自從W. H. Wischmeier發現EI_(30)。index 與土壤沖蝕量有密切關係後，EI_(30) - index 就被公認為衡量降雨對土壤能力之最佳尺度。隨即被改寫R- index並直接代入土壤冲蝕萬用公（A =R.K.LS.C.P )，以估計農地之土壤沖蝕量或未選擇水土保持方法之用。本研究保以基隆、新竹、台中、日月潭、高雄、恆春、花蓮及台東8個測候所之自記雨量記錄為基礎，推測全台灣各地之R-index，並劃成如圖1之等降雨冲蝕指數圖。從圖1可知台灣各地之R-index遠比美國南部雨量較多地區之R-index (表四)高出甚多。山坡地之R - index一般均在1,000以上，最高竟達3,000，此種現象充分顯示台灣降雨之特性與山坡地土壤冲蝕之嚴重性。八個測候所之50 %, 20 %, 5 %及1 %機率年R-index如表5，最大一次暴雨冲蝕指數之期望值如表6，按各地之降兩冲蝕指數特性，即可將全台灣分為如圖2之12區，而各區R-index月百分率之分配如圖3 - 8。

並列摘要

Soil erosion is a function of the erosivity of the rain and the erodivility of the soil. Since W. H. Wischmeier found that there existed the high correlation between EI_(30)-index and son erosion, later EI_(30)-index transformed into R-index was recongnized as a suitable scale for measuring the power of the rain which caused erosion. This R-index can be substituted directly for the universal son erosion equation (A=R.K.L.S.C.P.) for the prediction of soil erosion or used as a criterion for the choices of son and water conservation methods. The propose of this study is to predict R-index in Taiwan and then to prepare a rainfall iso-irodent map shown in figure 1. From figure 1. it is found that the values of R-index in Taiwan are higher than those of the southern United Stated where rainfall is considered heavy (Table 4.). Generally, the values of R-index in Taiwan are over 1000 on slopeland, in some places even 3000. This fact clearly shows that the rainfall characteristics which causes the son erosion of slopeland is really a major problem in the island. Table S shows the occurred probabilities of R-index in eight meteorological stations. Table 6. lists the expected maximum rainfall erosion index of a single storm. Figure 2 indicates the classification of 12 groups according to the similarities of the rainfall erosion index over the island. Figure 3. to Figure 8. show the percent of distribution of distribution of the monthly R-index.