Study on the configurations of debris-flow fans

Abstract

Studies on debris-flow fan configurations are fundamental to map hazard zone of debris flow disasters. This study aims to identify the morphological similarity of debris-flow fans based on a series of laboratory experiments and field investigations. The maximum length Lc, width Bm and thickness Zo of debris-flow fans are adopted as the characteristic parameters for analyzing the morphological similarity. The analysis demonstrates that the non-dimensional longitudinal and transverse profiles of debris-flow fans are described by Gaussian curves, while the non-dimensional plan form is closely fitted using a circular curve. By combining the three non-dimensional curves, the three-dimensional topography of debris-flow fans are easily obtained based on the parameters Lc, Bm and Zo. The volume V are simply related to these maximum values via V=αLcBmZo with an empirically determined shape parameter α. From the result of verification with a debris flow fan in Foncho Village, Nan-tou County of central Taiwan, it shows that the 3D topography function makes a good hazard zone mapping of debris flow. Furthermore, the parameter α is approximately 0.28 for a natural stony debris-flow fan.