Detection of snow avalanches using TerraSAR-X

Snow avalanches are natural hazards which cause damage to nature, persons, and property in mountainous terrain. But when and where happens avalanches and how large are they? A complete avalanche activity record over an entire winter season is important for the present avalanche research and forecasting which cannot be provided by traditional field measurements. Especially during strong snowfalls, like in January 2018 and 2019 in the Alps, information about avalanches is relevant in order to estimate the damage. Compared to optical satellite data, SAR satellite date with their weather independence can be used in such cases. Previous studies demonstrated the feasibility of avalanche detection using Sentinel-1 based on amplitude change detection. Due to its geometric resolution of 10 m, the Sentinel-1 sensor is not capable to detect small avalanches and small backscatter changes. In our study, TerraSAR-X StripMap single- and dual polarized data with a geometric resolution of 2.5 meter are used to analyze backscatter changes. We will focus on following questions: (1) How changes the backscatter in the avalanche zone compared to the surrounding area evoked by the change of surface roughness? (2) Which parameter plays an important role for avalanche detection? (3) Which polarization is better suited? The analysis are applied on different study sites in Austria and Switzerland during winter 2018/19. The avalanche archive of the Avalanche Warning Services in Austria (www.lawis.at) and the snow and avalanche research in Switzerland (www.slf.ch) is used as reference