- 期刊
一級溪流土石流危險因子及其與臨界降雨線之關係
Dangerous Factors of Debris Flow Occurrence of First Order Streams and Their Relationships with Critical Rainfall Lines
摘要
本文提出一級溪流土石流發生臨界降雨線之設定方法，並嘗試建立陳有蘭溪流域一級溪流土石流發生臨界降雨線推估公式，該公式亦可藉以推測未發生土石流集水區之臨界降雨線。研究方法係以陳有蘭溪流域中十七個一級溪流之資料爲樣本經由Mann-whitney-Wilcoxon檢定法進行統計分析，其結果顯示溪床平均坡度、土地利用因子，土壤內摩擦角正切值與土壤粒徑大於四號篩百分比值相乘積及集水區平均寬度値與溪床平均坡度值相乘積等因子及組合因子與土石流發生與否之關係較爲密切。再以流域中曾經發生土石流的九個一級溪流之資料爲樣本，取其於九二一集集大地震前之土石流發生紀錄資料，經由三維費雪區別函數分析其有效累積降雨量，有效降雨時間與上述因子及組合因子之關係，從而建立一級溪流土石流發生臨界降雨線預測公式。
並列摘要
In this study, a method to determine the critical rainfall lines of debris flow occurrence for first order streams was proposed. Using this method, the critical rainfall lines of debris flow occurrence for the first order streams in the basin of Chen- Yo-Lan stream were developed. Aside from these, for the watersheds in which debris flow has never occurred, the critical rainfall lines could be evaluated using this method. To achieve this goal, the basin of Chen-Yo-Lan stream was selected for investigation. In. this basin, 17 first order streams were chosen and their physiographic factors relevant to debris flow occurrence were analyzed by using the method of Mann-Whitney-Wilcoxon. The results showed that the average width of the watershed and the multiple of the internal friction angle of soil and percent of soil particle greater than sieve No.4 were relatively highly related to debris flow occurrence. In addition to this, a three dimensional Fisher's linear discriminant function was conducted by using the four dangerous factors (which passed the test of the Mann- Whitney-Wilcoxon method) of the nine first order streams in which the debris flows had occurred before the Chi-Chi Earthquake on September 21, 1999, effective accumulated rainfall and effective rainfall time. Then, the equations for evaluating the critical rainfall lines of debris flow occurrence for the first order streams were developed.