Estimation of Snow Water Equivalent Distribution Outside Forests Using Airborne Laser Scanning

In cold and snowy regions, multi-purpose dams cover water use in summer by storing influent water generated in spring with melting of snow accumulated on mountains in winter. Therefore it is necessary to estimate snow water equivalents in a dam basin as exactly as possible. In this study, for better estimation of snow water equivalents in a dam basin in cold and snowy regions, a relationship between snow depth distribution outside forests in mountain region and topography was investigated using a high-resolution digital elevation model (DEM) created from airborne laser scanning. Linear relationships between snow depth and overground-openness and between snow water equivalents and overground-openness were clarified. Over-ground is an index to describe sky extent over the point within a certain distance and takes large values for convex terrain like ridge and small values for concave terrain like valley. Characteristics of snow depth distribution are different in forests and outside forests. Thus we developed a method to estimate snow water equivalents in a dam basin divided into forests and outside forests. A method to estimate snow water equivalents outside forests was based on the linear relationship between snow water equivalents and overground-openness above mentioned. Using the method, snow water equivalents in the Chubetsu Dam basin was estimated and resulted in estimates with a higher level of accuracy than those based on existing methods.