Abstract
Mega earthquakes or serious rainfall storms often cause crowded landslides in mountainous areas. A large part of these landslides are very likely blocking rivers and forming landslide dams in series along rivers. The risks of cascading failure of landslide dams are significantly different from that of a single dam. This paper presented the work on risk-based warning decision making on cascading breaching of the 2008 Tangjiashan landslide dam and two small downstream landslide dams in a series along Tongkou River. The optimal decision was made by achieving minimal expected total loss. Cascade breaching of a series of landslide dams is more likely to produce a multi-peak flood. When the coming of the breaching flood from the upstream dam perfectly overlaps with the dam breaching flood of the downstream dam, a higher overlapped peak flood would occur. When overlapped peak flood occurs, the flood risk would be larger and evacuation warning needs to be issued earlier to avoid serious life loss and flood damages. When multi-peak flood occurs, people may be misled by the warning of the previous peak flood and suddenly attacked by the peak flood thereafter, incurring catastrophic loss. Systematical decision making needs to be conducted to sufficiently concern the risk caused by each peak of the breaching flood. The dam failure probabilityPflinearly influences the expected life loss and flood damage but does not influence the evacuation cost. The expected total loss significantly decreases withPfwhen the warning time was insufficient. However, it would not change much withPfwhen warning time is sufficient.
Highlights
Mega earthquakes or serious rainfall storms often cause crowded landslides in mountainous areas
Many of these landslide dams were formed in series along rivers, including the Tangjiashan landslide dam, the largest one caused by the 2008 Wenchuan earthquake, and two relatively small landslide dams downstream along the Tongkou River (Cui et al, 2010; Liu et al, 2010; Shi et al, 2015)
In DABA 2.0, the inflow rates are set as a time-related variable instead of some piecewise constant values; the cross section was divided into three parts: left crest, breach, and right crest to simulate the overflow and erosion
Summary
Mega earthquakes or serious rainfall storms often cause crowded landslides in mountainous areas. Decision Making of Landslide Dams formed 45 landslide dams; the Typhoon Morakot in 2009 induced 19 landslide dams in Taiwan (Dong et al, 2011; Wang et al, 2016); and the 2008 Ms 7.9 Wenchuan earthquake triggered as large as 257 landslide dams (Cui et al, 2009) Many of these landslide dams were formed in series along rivers, including the Tangjiashan landslide dam, the largest one caused by the 2008 Wenchuan earthquake, and two relatively small landslide dams downstream along the Tongkou River (Cui et al, 2010; Liu et al, 2010; Shi et al, 2015). The two dams were assumed of the identical soil properties of the Tangjiashan landslide dam, and the soil properties were assumed to distribute proportionally to the dam height (Shi et al, 2015)
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