Building loss ratio comparison based on physical vulnerability and event-based data in Taiwan

In this study, several debris flow physical vulnerability curves and the even-based inundation depth were applied to a mountainous community hit by debris flow in 2015 to estimate the various possible loss ratio of each building. Then the comparison between estimated possible loss ratio and loss ratio determined by expert in the field is made to map out the distribution and deviation.

Vulnerability is commonly related to the consequences of natural hazard. For debris flow hazard these consequences are generally measured in terms of losses (Fuchs et al., 2007). In risk management vulnerability is an essential component for analyzing natural hazard risks (Lo et al., 2012). It is expressed on a scale from 0 (no damage) to 1 (total loss) and increasing with the intensity of hazard.

The Taoyuan DF034 debris flow potential torrent is located in northern Taiwan. In 2015, during Typhoon Soudelor the rainfall caused a shallow landslide which was transformed instantly into a debris flow. 13,000 cubic-meter of debris were washed out and deposited in 5,200 sq-meter area. Because of the evacuation before debris flow event, only 15 residential houses were inundated and no one was injured fortunately. In order to understand the inundation depth, the field investigation was executed shortly after the event. The building dimension, floor, structure type, location, and inundation depth were well documented and the loss ratio of each building was determined by expert as well.

The comparison of loss ratio based on inundation depth and impact pressure between Kang and Kim (2016), Papathoma-Köhle et al. (2015) and Lo et al. (2012) is made. The result shows building characters and debris flow velocity affect the loss ratio significantly.

Key Words: Debris flow, Vulnerability, Loss ratio, Taiwan