Integration of terrain and AVHRR-derived multi-temporal snow cover data for statistical assessment of avalanches: case study of a part of NW Himalaya

Abstract

In this paper, the data of Advanced Very High Resolution Radiometer (AVHRR) 1 km resolution of daily time series is used to extract the distribution of seasonal snow in the Chowkibal-Tangdhar (CT) area. Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) at 90-m resolution has been used to delineate the terrain characteristics such as aspect, slope, and altitude. The study is focused on two major objectives, first is to assess the snow cover variation with a time series analysis and second one is the snow cover changes with respect to the changes in terrain parameters mainly at avalanche prone regions. Study area has 60 registered avalanche sites; most of these avalanches trigger during the winter months when snow deposition takes place in the steep slopes due to successive snowfall spells. Normalized Difference Snow Index (NDSI) method is used to monitor the snow cover of the study area from the satellite image. The multi-temporal analysis of the snow cover derived from the AVHRR data shows that the binary snow cover in the study area increases with time from November to March due to successive snowfalls. After that, the snow cover starts to deplete from the mid-March onwards due to rise in temperature. Maximum snow cover area (SCA) has been found 85.67% and minimum is at 14.33% respectively. An attempt has been made to understand the influence of terrain parameters by extracting the major terrain and snow parameters for each of the avalanche site and correlating it with occurrences of the avalanches. The study suggests that the sites having terrain characteristics of slope 25–45°, aspect 26.45%, and altitude 2500–3500 m has more occurrences of avalanches.