台灣地區地震及降雨引致崩塌形成堰塞湖之壩體形狀分析

Geometry Parameters for Earthquake-induced and Rainfall-induced Landslide Dams in Taiwan

郭玉樹(Yu-Shu Kuo) ； 邱盛彥(Sheng-Yen Chiu) ； 陳昆廷(Kun-Ting Chen) ； 謝正倫(Chjeng-Lun Shieh)

《中華防災學刊》 4卷2期 (2012/08) Pp. 143-152

https://doi.org/10.30052/JTDPS.201208.0002

摘要

台灣山區地質構造破碎且脆弱，易於地震及降雨時產生崩塌，若崩塌土體阻塞河道可能形成天然壩，並蓄水成為堰塞湖。當堰塞湖天然壩受上游水體作用導致失穩破壞，將造成下游淹水並威脅河道兩側居民安全。因此，評估堰塞湖天然壩穩定性為防救災最重要的工作之一。堰塞湖天然壩壩體幾何形狀為評估其穩定性之基本參數，惟堰塞湖多發生於人員機具無法快速抵達的偏遠山區，使得天然壩壩體形狀參數無法於短期內以現地調查方式取得。本研究對台灣歷年堰塞湖天然壩壩體進行現地測量並蒐集相關資料，考量河床坡度及崩塌土體材料堆積特性，分析地震及降雨引致崩塌所形成之堰塞湖天然壩幾何形狀，以統計方法建立堰塞湖天然壩壩體之幾何形狀快速評估方法。利用本研究建立之天然壩形狀評估法，可考量不同崩塌地誘發原因及崩積土體特性，將天然壩幾何形狀簡化為三角形或梯形，由河道坡度及崩塌地面積快速推求天然壩之壩高、壩長及壩面堆積角度，提供堰塞湖天然壩形成初期穩定性評估參數。

關鍵字

天然壩 ； 堰塞湖 ； 壩體形狀 ； 穩定性評估

並列摘要

Due to fragile geological conditions, earthquake and rainfall events frequently cause landslides and result in landslide dams and lakes. When the lake storage makes the landslide dam unstable and a dam failure occurs, the stored water may inundate the downstream area, threatening the local residents. The failure of landslide dams may lead to a massive dam-break flood downstream. Landslide dams triggered by earthquake and rainfall resulted in different types of geometries and failure mechanisms. Stability analysis of the dam is important for disaster prevention and reduction. The dam's geometry plays an important role in understanding its stability. However, the geometry is very difficult to obtain when a landslide dam is initially formed because of its remote and mountainous location. This study develops a rapid geometry analysis method for both earthquake-induced and rainfall-induced landslide dams based on the real cases collected in Taiwan. The effects of triggered factors of landslide dams as earthquake are considered in the model and the shape of natural dams can be presented as triangle and trapezoid. The proposed method uses only satellite maps and the topographic maps to analyze the dam geometry. These maps are used to evaluate the area of the landslide and the slope of the river bed. Based on the evaluated information, the proposed method can calculate dam height, the length of the dam, and the angles of the dam in both upstream and downstream directions. These geometry parameters of a landslide dam provide important information for further dam stability analysis.

並列關鍵字

landslide dam ； landslide-dammed lake ； geometries of landslide dam