A study on snow depth distribution in mountainous regions at peak based on multiple measurements by airborne laser scanning

In cold and snowy regions, snow melt water is essential to meet water demands. Therefore it is very important to estimate snow depth distribution in mountain regions as accurately as possible at its peak. Recently airborne laser scanning has made it possible to acquire high-density three-dimensional spatial data for wide areas and the number of measurements of snow depth distribution by airborne laser scanning has been increasing. In our research airborne laser scannings were conducted four times to measure snow depth distribution in the same range in mountainous regions at peak of snow accumulation period and the patterns of snow depth distribution were analyzed.

The target range for airborne laser scanning is located in the northern part of Japan, central Hokkaido Island. It ranges of altitude between 1100 m and 2300 m and includes the highest peak in Hokkaido, Mt. Asahidake (2291 m). The forest line is in the target range at the elevation of about 1450 m. The airborne laser scannings to measure ground surface were conducted from 22/Sep./2009 to 25/Sep./2009, and the ones to measure snow surface were conducted on 10/Mar./2012, 27/Mar./2015, 13/Mar./2017 and 21/Mar./2018. The snow depths were calculated as the difference between the elevation of snow surface and that of ground surface.

As a result, the similar patterns of snow depth distribution were found. We calculated the coefficient of determination, R², of the linear regression, which determine the degree of similarity between snow depths of two measurements and coefficient of determination ranged between 0.75 and 0.84 in forests, 0.76 to 0.86 in alpine zone. It suggest that the ranges with deep (shallow) snow depth at peak are almost same every year. For all four snow depth distributions, in forests linear relationships between elevation and snow depth were found and in alpine zone linear relationships between overground-openness of ground surface and snow depth were found. Compared to snow depths at the Asahidake Onsen observation point in the lower part of target range on the days when airborne laser scannings were conducted, linear relationship between snow depth and total snow volume in the target range was found.

We believe these characteristics of snow depth distributions at peak might lead to develop a simple method to estimate snow depth distribution at peak.