南投地區土石流發生臨界降雨線之設定及其於集集大地震後之修正

Determination of Critical Rainfall Lines of Debris Flow Occurrence in Nan-Tou Area and Their Revision After the Chi-Chi Earthquake

范正成(Jen-Chen Fan) ； 劉哲欣(Che-Hsin Liu) ； 吳明峰(Min-Fon Wu)

《中華水土保持學報》 33卷1期 (2002/03) Pp. 31-38

https://doi.org/10.29417/JCSWC.200203_33(1).0004

摘要

本研究以集集大地震前南投地區28條一級溪流爲樣本，分析得到與土石流發生較爲相關的五個影響因子，並經由三維費雪區別函數分析而得此地區之土石流發生臨界降雨線預測公式。為了反應集集大地震對土石流發生的影響，乃對上述臨界降雨線預測公式做若干的修正。修正的因素包括地震時當地之地表最大加速度和地震後隨時間增加而恢復的影響。此外，本研究亦將90年7月30日之桃芝颱風和90年9月16日之納莉颱風雨量資料加以分析和驗證。從整個研究結果，略可推論新興橋當地之土石流發生臨界降雨線已因集集大地震之發生而大幅下降，且隨著大地震後時間之增加而逐漸提升；另外，本研究所提出之土石流發生臨界降雨線和有效雨量路徑可作爲對土石流發生與否及發生時間之預測，且其預測結果與事實相近。

關鍵字

土石流 ； 一級溪流 ； 地表最大加速度 ； 臨界降雨線 ； 有效雨量路徑

並列摘要

In this study, 28 first-order streams in the Nan-Tou area were chosen as samples. After analyses, five factors of the stream samples were found to be more related to the occurrence of debris flow. Using the analysis of the three-dimensional Fisher's linear discriminant function, we obtained the predicting equations for the critical rainfall lines of debris flow occurrence in this area. To reflect the effect of the Chi-Chi earthquake on the occurrence of debris flow, some modifications were made for the aforementioned predicting equations. These modifications included the peak ground acceleration (PGA) during earthquake and the effect of time increase after the Chi-Chi earthquake on the thixotropy. In addition, the rainfall data of the Toraji typhoon on July 30, 2001, and the Nari typhoon on September 16, 2001 were used for analyses and tests. The results showed that the critical rainfall line of debris flow occurrence at the Hsin-Hsin bridge dropped noticeably right after the Chi-Chi earthquake, and rose gradually thereafter. The critical rainfall lines of debris flow occurrence and the effective rainfall path proposed in this study were employed to predict the occurrence of debris flow and its time of occurrence. The predictions were found to be very close to the facts.

並列關鍵字

debris flow ； first order stream ； peak ground acceleration ； critical rainfall line ； effective rainfall path