Discharge of landslide-induced debris flows: case studies of Typhoon Morakot in southern Taiwan

• Main Authors: J.-C. Chen, M.-R. Chuang
• Format: Article
• Language: English
• Published: Copernicus Publications 2014-07-01
• Series: Natural Hazards and Earth System Sciences
• Online Access: http://www.nat-hazards-earth-syst-sci.net/14/1719/2014/nhess-14-1719-2014.pdf
• ISSN: 1561-8633; 1684-9981

Three debris-flow gullies, the Hong-Shui-Xian (HSX), Sha-Xin-Kai (SXK), and Xin-Kai-Dafo (XKD) gullies, located in the Shinfa area of southern Taiwan, were selected as case studies on the discharge of landslide-induced debris flows caused by Typhoon Morakot in 2009. The inundation characteristics of the three debris flows, such as the debris-flow volume <i>V</i>, deposition area <i>A</i>_d, and maximum flow depth, were collected by field investigations and simulated using the numerical modeling software FLO-2D. The discharge coefficient <i>c</i>_b, defined as the ratio of the debris-flow discharge <i>Q</i>_dp to the water-flow discharge <i>Q</i>_wp, was proposed to determine <i>Q</i>_dp, and <i>Q</i>_wp was estimated by a rational equation. Then, <i>c</i>_b was calibrated by a comparison between the field investigation and the numerical simulation of the inundation characteristics of debris flows. Our results showed that the values of <i>c</i>_b range from 6 to 18, and their values are affected by the landslide ratio <i>R</i>_L. Empirical relationships for <i>c</i>_b versus <i>R</i>_L, <i>Q</i>_dp versus <i>Q</i>_wp, <i>Q</i>_dp versus <i>V</i>, and <i>A</i>_d versus <i>V</i> are also presented.