An application of the flo-2d model to debris-flow simulation - a case study of song-her district in taiwan

Abstract

Taiwan is an island located in the subtropical zone where typhoons often bring heavy rainfall. In addition, streams and geology results in a high susceptibility to debris flow. Especially after the Chi-Chi earthquake on September 21, 1999, the geological condition of the mountain area located in the central part of Taiwan has been more susceptible to natural disasters of debris flow. Fractured geological units and landslides caused by frequent earthquakes provide abundant source material for debris flow. Following a typhoon or heavy storms, debris mixed with water form debris flows. Many studies have examined the triggering criteria, flow routing and deposition of debris flow in order to reduce the impact and losses caused by debris flow.
In this research, parameters and processes needed for a numerical simulation method for debris flow routing and depositions are formulated to provide a reference for hazard zone mapping. A two-dimensional model (FLO-2D software) was used to simulate a debris flow and flood, and the accuracy of the simulation, including flow depth, velocity and volumetric sediment, was analyzed using data collected on the rainfall and terrain. The case study in this research consists of three phases. In the first phase, debris flow data, including information on topography and rainfall from typhoon Mindulle in 2004 collected from First River Basin of Song-Her District in Taiwan, were compiled to establish a database of factors that influence debris flow. For the second phase, a numerical
simulation was performed using FLO-2D with the results presented as area of debris-flow inundation, maximum deposit depth, and deposit volume. The simulation results were then compared with the aerial photos and the micro geomorphological study. Finally, suitable conditions for using this model, and the suggestions for future research are discussed.