The hazard zone mapping of debris flows with different return period

• Main Authors: HUI-MIN FENG, 馮輝閔
• Other Authors: 陳春盛
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/80189608478530945453

碩士 === 健行科技大學 === 土木工程系空間資訊與防災科技碩士班 === 103 === In the past 20 years, debris flows caused great casualties and severe property losses in Taiwan. For disaster prevention, the hazard zone mapping of debris flow becomes more and more important. Although many empirical formulas has been proposed for engineering, but it seems to be not accurate enough. Therefore, we have developed a numerical model Debris-2D to simulate the in-situ debris flows. The boundary layer concept is used to simplify the governing equations(Huang,2003). This numerical model is verified with analytical solutions, laboratory flume tests and historical debris flow events. The simulated results show some good agreements with the measured data. However, rainfalls with different return periods will lead to different scales of debris flow, which will need different planning for evacuation and shelter. In this study, we first introduce the rainfall duration in a historical debris-flow disaster event into the empirical formula to compute the rainfall intensities and peak flows of different recurrence intervals. The rainfall duration means the time elapsed from start of the rainfall to the occurrence of debris flow. Next, the amount of water in debris flow for a certain return period can be estimated conservatively as the product of rainfall duration and the corresponding peak flow. Then the debris-flow volumes of different return periods can be obtained according to the concept of equilibrium concentration. A case study in Xin-Kai Tribe, where a severe debris flow occurred during Typhoon Morakot, shows how this approach can be applied in debris-flow hazard zone mapping.