The formation and evolution of a coastal alluvial fan in eastern Taiwan caused by rainfall-induced landslides
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- 作者：Hsien-Ter Chou ; Ching-Fang Lee ; Chia-Ming Lo
- 关键词：Landslides ; Debris flows ; Alluvial fans ; Rainfall threshold ; Morphology
- 刊名：Landslides
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：14
- 期：1
- 页码：109-122
- 全文大小：
- 刊物类别：Earth and Environmental Science
- 刊物主题：Natural Hazards; Geography, general; Agriculture; Civil Engineering;
- 出版者：Springer Berlin Heidelberg
- ISSN：1612-5118
- 卷排序：14
文摘
The formation and evolution of a coastal fan in eastern Taiwan associated with a sequence of rainfall-induced landslides during the 2009–2013 period are explored in this study. The evolution of these landslides is mainly attributed to the head-cutting process initiated by Typhoon Parma in October 2009. During the attack of Typhoon Megi in October, 2010, a subaerial coastal fan with a surface slope of 8.9° was formed after the mobilization of the rainfall-induced landslides. The geomorphic features both in the steep gully and on the coastal fan were categorized as the sequence of granular debris flows and sheet floods. Severe fan toe erosion occurred thereafter due to the wind-wave forcing. Even if the variations of both the cumulative rainfalls and the drainage areas are one or two orders of magnitude among devastating fan-forming landslides worldwide, the mean annual precipitation and the basin ruggedness index (Melton ratio) are effective indicators to normalize the rainfall threshold and to characterize the fan surface slope, respectively. Severe catastrophic landslides generally occur when the normalized cumulative rainfalls with respect to mean annual precipitation are greater than 0.1. The fan slope generally increases with the increasing Melton ratio for the catchment. Uchiogi’s empirical model is applicable for predicting the rainfall-induced area ratio of newly generated landslides. In this case study, the relationship of the fan area to the total landslide area follows a linear regressive curve when the ratio of landslide area with respect to the drainage area exceeds 0.0056.