Statistical analysis on the planimetry of debris flow fans

The planimetry of debris flow fans could be represented by the combination of geometric figures. Two planimetric models of debris flow fans are presen ted in this paper based on aerial photograph observation and statistical an alysis of 52 debris flow fans in Xiaojiang Valley of southwestern China and in Alpine valleys of northeastern Italy. The combination of an isosceles t riangle with a semicircle best fits the fans in Xiaojiang Valley and a circ ular sector is best for the fans in northeastern Italian Alps. By using sta tistical analysis, two groups of morphometric relationships between debris flow fans and debris flow basins are established. The basin area and basin relief are identified as the significant factors influencing the plan shape s and the dimensions of debris flow fans. The statistical analysis on geomo rphic parameters of debris flow drainage basin could provide an empirical m ethod to predict the debris flow depositional extent.