Three-Dimensional Topography of Debris-Flow Fan

Study on debris-flow fan configurations lays the groundwork for hazard zone mappings of debris flow disasters. This paper 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 in the analysis of morphological similarity of debris-flow fans. This analysis demonstrates that the nondimensional longitudinal and transverse profiles of debris-flow fans can be described by Gaussian curves, while a circular curve can be used to fit the nondimensional plan form of the debris-flow fans. By combining the three nondimensional curves mentioned above, the volume (for all) of a debris-flow fan can be related to the maximum length Lc, maximum width Bm, and maximum thickness Z0 by (for all) (alpha) LcBmZo, via an empirical coefficient (alpha) . The parameter (alpha) is approximately 0.275 for a natural stony debris-flow fan and greater than 0.275 for a natural mud debris-flow fan. In addition, the three-dimensional topography of debris-flow fans can be easily derived based on the parameters Lc, Bm, and Zo using three morphological similarity formulae.