Risk Evaluation of Debris Flow Using a Digital Terrain Model

Abstract

In general, landslides of mountain areas have been occurred by typhoon and severe rain storm in Korea. The multiple landslides caused by heavy rain may lead to debris flow which is very rapid downslope movement of debris of a high water content along stream channels. Generally, a debris flow causes larger and severe damage. than a landslide. To protect and reduce the damage of debris flow, a reliable tool to predict potential damage area by drbris flow is needed. Since the water and moveable soils by landslide flow from high elevation to low elevation with additional erosion through the stream of valley, the magnitude of debris can subsequently amplified. Therefore any structures and people in the path of debris flow lies in great risk. Due to the chacteristics of debris flow which is delivered quite a long distance from the location of initiation (hundread meters-kilometers), the risk analysis of debris flow should consider larger area compared with landslide analysis and analysis unit need to be determined based a watershed. In this study, an anlysis tool for the evaluation of debris flow risk in a watershed incorperated with GIS system is proposed. The essence of system is a model to predict the risk of debris flow for any given location. The model is developed based on the statistical analysis of forty eight debris flow cases, which obtained from: field surveys, disaster reports on national roads of korea, and digital maps of the debris flow area. Each set of data in the database includes debris flow size, rainfall information, bedrock types, and run out distance of the debris. The comparison between predicted risk and actual occurrence of the debris flow hazard for forty eight site, showed accuracy of seventy seven percent based on accuracy-classification.

Risk-Level Assessment of Small-Scale Mountain Streams Using a Digital Elevation Model

“…Results of research on debris flow using DEMs have also been reported in the field of railways, and Nunokawa et al 17) proposed a method to evaluate the risk of debris flow using a DEM-based analytical model. 18),19) Hayashi et al 20) evaluated the risk of debris flow through simulations using DEM.…”

<b>Recent Research and Development on Disaster Prevention Technology</b>

“…In the case of operational management in case of rainfall, advanced methods are being developed that reflect changes slope stability due to rainfall after taking into account terrain and geology. This method involves using numerical terrain information and geological information in order to sequentially calculate changes in water content in the ground due to rainfall to obtain slope stability [3]. There are limitations on computational resources in implementing sequential computations of stability for the large number of slopes along a single railway line.…”

A Study on a Risk Assessment Method to Evaluate Small-Scale Sediment Inflows on Railroad Tracks

“…In recent years, methods have been developed to evaluate the risk of debris flows, using simulations that take into account slope geometry and debris flow mechanisms. Nunokawa et al 8) have introduced a method for assessing the risk of debris flow using an analytical model that calculates the stability of a slope by examining the groundwater level in the slope surface layer. Nakatani 9) has developed a versatile simulation that can be used easily by non-experts to evaluate the risk of debris flow.…”