莫拉克颱風引致堰塞湖之案例分析

Case Analysis of Landslide Dam Formation by Typhoon Morakot

陳昆廷(Kun-Ting Chen) ； 臧運忠(Yun-Chung Tsang) ； 郭玉樹(Yu-Shu Kuo) ； 呂明鴻(Ming-Hung Lu) ； 謝正倫(Chjeng-Lun Shieh)

《中華防災學刊》 2卷1期 (2010/02) Pp. 43-50

https://doi.org/10.30052/JTDPS.201002.0006

摘要

莫拉克颱風於民國98年8月襲台，造成台灣南部豪大雨，引發台灣多處大規模崩塌，崩塌之土石阻塞河道，形成多處堰塞湖。根據現場調查及衛星影像判釋結果發現，莫拉克颱風生成之堰塞湖共計形成16處，目前尚存在者共計7處。降雨生成之堰塞湖不論在型態、形成雨量或空間分佈上都具有不同特性。顯示莫拉克颱風挾帶之高強度、長延時、大範圍降雨不只為誘發堰塞湖之主要原因，更直接影響堰塞湖之形成與潰壩型態。本文根據調查結果，將莫拉克颱風期間之堰塞湖狀況概略分為：(A)未潰壩(B)部分潰壩，仍存在(C)已潰壩，不存在等三種堰塞湖。同一主流上易形成多個堰塞湖，因天然壩壩體本身含水量高，滲透係數小，加上上游水量來得大且快，天然壩體蓄水時間相對短，故易造成部分潰壩或已潰壩之情況產生。此外，當主流生成多處堰塞湖時，易發生連續性之潰壩，最上游堰塞湖潰壩時所帶來之潰壩尖峰流量，極易衝擊下一處堰塞湖，造成下一處堰塞湖更大之尖峰流量，此乃為致使主流下游堰塞湖存在時間短暫之原因。

關鍵字

莫拉克颱風 ； 堰塞湖

並列摘要

In August 2009, Typhoon Morakot raided Taiwan, including heavy rain in southern Taiwan. Stones from large-scale landslides blocked river bed and forming many landslide dams. According to field investigation and satellite imagery analysis, a total of 16 landslide dams were formed as a result of Typhoon Morakot's passing and 7 still exist at present. Because landslide dams are characterized by differences in formation, rainfall, and spatial distribution, it shows that the high rainfall intensity, long storm duration, and large areas by Typhoon Morakot not only to induce landslide dams but also influence its formation and collapse styles.
Base on the investigation, this study categorized the Typhoon Morakot landslide dams by means of following conditions：(A) not collapsed, (B) partially collapsed, but still exists and (C) collapsed and no longer exists. It is easy to form many landslide dams in the same mainstream due to the natural dams contain high water content and low coefficient of permeability. Besides, the upstream flow come fast and big, so that the timing of storage is relatively short and easy to induce partially break or broke. When many landslide dams formed in one mainstream that cause continuous dams collapse. When the most upstream landslide dam collapses, the peak flow it brings impacts the next one, and the next one combined with the first impact that will produce a bigger peak flow. That is why the downstream landslide dams exit only for a short period of time.

並列關鍵字

Typhoon Morakot ； landslide dam ； dam break