堰塞湖潰決機制與減災工法研究

Failure Mechanism and Disaster Mitigation on Landslide-Dammed Lakes

陳樹群(Su-Chin Chen)

《中華水土保持學報》 30卷4期 (1999/12) Pp. 299-311

https://doi.org/10.29417/JCSWC.199912_30(4).0007

摘要

自然形成的堰塞湖與其所造成之災害，常為全球各地所關注的焦點，甚至有些天然壩的規模遠超過人工壩。堰塞湖的形成多是因為山崩堵塞河道所致，因此天然壩的安全性遠不及以工程方法構築之人工壩，這也就是天然壩易產生潰決，以至於釀成巨災的原因。大多數的堰塞湖年限極短，主要潰決原因爲溢流溯源沖刷。堰塞湖的壽命及可能之潰決方式，受制於天然壩體大小、崩塌堵江之土砂材料特性、上游流量大小以及堰塞湖之蓄水容量等。當然天然壩形成之後的工程處理方式，如溢洪道及分水工等設置或是壩體清除等，也會影響堰塞湖的使用年限。921大地震造成全台地形景觀上之巨變，其中由於河道的變遷及兩側崩塌造成十餘座堰塞湖，天然壩可能發生的洪水等二次災害已成爲全民關注之焦點。因此本研究收集國內外歷年來堰塞湖發生之原因及其處置方式等文獻，將其分類統計，配合此次地震實地踏勘所收集之資料加以分析，歸納堰塞湖爲五大類型及若干減災安定工法。

關鍵字

堰塞湖 ； 溯源沖刷 ； 溢流侵蝕 ； 921地震

並列摘要

Landslide dams have proved to be both interesting natural phenomena and significant hazards in many areas of the world. A few of these blockages attain heights and volumes which are rival or exceed the world's largest man -made dams. Since landslide dams are natural phenomena and thus are not subjected to engineering design (although engineering methods can be utilized to alter their geometries or to add physical control measures), they are vulnerable to catastrophic failure by overtopping and beaching. Some of the world's largest and most catastrophic floods have occurred because of the failure of these natural dams. Most landslide dams are remarkably short-lived. Overtopping was by far the most frequent cause of landslide-dam failure. The timing of dam failure and the magnitude of the resulting floods are controlled by dam sizes and geometry; material characteristics of the blockage; rate of inflow to the impoundment; size and depth of the impoundment; bedrock control＂ of flow; and engineering controls, such as artificial spillways, diversions, and blasting. The Chichi earthquake of September 21 scared the Taiwanese landscape and caused more than ten landslide dams. Natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam. For this purpose, we collected and analyzed numerous kinds of natural dams from literature and field survey. Finally, landslide dams can be classified into five categories and some methods of disaster mitigation.

並列關鍵字

landslide-dammed lake ； headcutting ； overtopping ； Chichi earthquake