Hazard Assessment of Debris Flows by Statistical Analysis and GIS in Central Taiwan

This paper aims to build an analytical process of assessing debris-flow hazards using multivariate analysis and geographic information system (GIS) techniques. The watershed of the Chen-Yu-Lan River is investigated in this study. Factors that are believed to be critical in the occurrence of debris flow are identified and considered in the assessment of debris-flow hazards. These factors used for assessing the debris-flow hazard are: (1) rock formation, (2) fault length, (3) naked-land area, (4) slope angle, (5) slope aspect, (6) stream slope, (7) watershed area, (8) form factor, and (9) cover and management factor. Using the spatial analysis feature of GIS, the indexes of these factors are calculated. By using principal component analysis (PCA) and discriminant analysis (DA) of all indexes according to each factor, the discriminant function of overall debris-flow hazard at any particular creek in the Chen-Yu-Lan River may be assessed. The applicability of the proposed approach for hazard assessment of debris-flow in the watershed of the Chen-Yu-Lan River has been confirmed with other researches and field observations in recent debris-flow events.