921地震後溪頭水文分佈特性與土石流防災相關之研究

Hydrologic Distribution Properties and Debris Flow Precaution in Chi-Tou after 921 Chi-Chi Earthquake

張振生(Cheng-Sheng Chang) ； 王志豪(Chih-Hao Wang) ； 劉維(Wei Liu) ； 廖禎茹(Chen-Ju Liao) ； 陳信雄(Hsin-Hsiung Chen)

《中華林學季刊》 37卷3期 (2004/09) Pp. 283-292

https://doi.org/10.30064/QJCF.200409.0004

摘要

台灣山坡地的災害多起因於集中豪雨，或颱風所帶來豐富的雨量所引起，然自1999年921集集大地震，所造成台灣山坡地的災害，無論在規模、形態以及機制上，均與過去坡地災害有顯著的差異。尤其對集水區地貌以及地下水文的演變，更有極為密切的關連。本論文就以921地震後溪頭集水區為對象，調查土石流坑溝之水文空間分佈特性，期能更瞭解震後溪頭地區的土石流災害演變並對防災工作有所幫助。
本研究利用溪頭集水區內各不同位置水位井監測地下水位變動資料發現，震後溪頭坑溝地表逕流在枯季有隱沒於地下的現象，其深度從上游地下2m到下游地下12m之處，且有逐漸加深的趨勢。對災害發生有直接關係的暴雨事件影響地下水位之起伏量，亦隨上游(1.09~1.43m)向下游(7.09~10.08m)有逐漸增加之趨勢。總之，暴雨促成不穩定土石方急速飽和的現象，對引發溪頭土石流堆積坑溝的擴張，將是研究溪頭土石流災害的重要關鍵。

關鍵字

921集集大地震 ； 土石流防災工程 ； 地下水文 ； 坡地災害

並列摘要

The main reason for slope damage in Taiwan is from heavy and intense rainfall. But the scales, forms and mechanisms of most slop failures in the affected area were changed after the 921 Earthquake. The effects of earthquake on slope stability were the most significant in watershed terrain formation and groundwater hydrology development. We investigated the hydrologic distribution of valleys in Chi-Tou, and tried to understand more about associated debris flow characteristics in order to provide information for designing disaster prevention engineering works.
In the study area, surface runoffs were replaced by subsurface flow during dry seasons. The depth of the subsurface flow decreasesd from 12 m to 2 m. Variations of the water levels also increased from 1.09~1.43 m to 7.12~11.14 m with the altitudes increased from 1,225 m to 1,425 m in the valley. In conclusion, heavy rainfalls over-saturated the unstable soils on the slope very soon and then debris flows occurring easily.

並列關鍵字

921 Chi-Chi Earthquake ； Debris flow prevention civil engineering ； Groundwater hydrology ； Slope failures