An Assessment Method for Debris Flow Dam Formation in Taiwan

Kun-Ting Chen,Chia-Hsing Lin,Chjeng-Lun Shieh,Xiao-Qing Chen,Gui-Sheng Hu,Xiao-Jun Guo

doi:10.15446/esrj.v22n1.62389

Kun-Ting Chen, Chia-Hsing Lin + Show 4 more

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https://doi.org/10.15446/esrj.v22n1.62389

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Abstract

Debris flows in tributaries rush into and block the main branches of rivers and often result in serious hazards. Dam failures cause large floods in the downstream area and can lead to fatalities and property damage. This study proposes an assessment method to evaluate the formation of a debris flow dam, which includes two conditions: (1) the sediment transported by the debris flow must reach across the river; and (2) the thickness of the deposit by the debris flow must be higher than the in situ water depth. This methodology was used to study the case of a debris flow dam caused by debris flow across the Er River in Taiwan, which blocked the Chishan River and led to the formation of the Namasha debris flow dam. This methodology can also be applied to identify the formation of debris flow dams.

Highlights

Fragile geological conditions, frequent and intensive typhoon attacks and heavy rainfall can cause debris flows to transport large amounts of sediment, which can lead to the formation of dams on rivers in Taiwan (Chen, 1999; Kuo et al 2011; Zhou, et al 2012; Dong et al 2014)
This study aimed to develop an assessment method to evaluate debris flow dam formation considering the debris flow volume, velocity, deposition slope angle, possible run-out distance, and deposition depth
Where Lc is run-out distance of the debris flow in Typhoon Morakot event; Lci is run-out distance of the debris flow at changed value; Lm is average between Lc and Lci; Pc is parameter’s base value; Pci is parameter’s changed value; Pm is average between Pc and Pci

Summary

Introduction

Frequent and intensive typhoon attacks and heavy rainfall can cause debris flows to transport large amounts of sediment, which can lead to the formation of dams on rivers in Taiwan (Chen, 1999; Kuo et al 2011; Zhou, et al 2012; Dong et al 2014). The materials of the dam are rapidly transported by the river flow to the downstream area and can cause serious debris flow, river bank erosion and flooding hazards downstream of the catchment (Ermini and Casagli, 2003; Korup, 2004; Dong et al 2011; Li et al 2011; Peng and Zhang, 2012; Chen et al 2014; Shrestha and Nakagawa, 2016). A theoretical method to evaluate dam formation is important for disaster prevention

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