(guest post by S.E. Darychuk) Flooding is a natural hazard that effects thousands of British Columbians - the provincial government spent over $162 million in flood response in 2018 alone. A heavy snowpack often contributes to flooding, as seasonal snow melt drives the flow of the majority of river systems in the province. Due to the heavy influence of snow melt on flow, snowpack monitoring is crucial for water management and flood prediction. Remotely sensed data can be a powerful tool for snow mapping as it is able to capture the entire extent of the snowpack. Recent advances in remote sensing technologies have been described as revolutionary, and researchers have greater access to data, and the ability to process that data, than ever before.
Sentinel-1, a satellite constellation that came into full effect in 2016, is one recent advancement that has offered new opportunities to monitor snow. Sentinel-1 is a radar satellite, an active remote sensing product that uses the return strength of a signal sent from the satellite to measure earth surface properties. As an active product, radar data offers some distinct advantages over traditional optical images, including the ability to detect water within a snowpack and the ability to see through clouds that often obscure the mountains. The presence of liquid water is important because it indicates that the snowpack is ready to melt.
In the animation below, I use radar imagery to detect wet snow for the upper Fraser River watershed. I combined this with maps of total snow cover created from optical imagery, which uses visible light reflected from the surface. This animation uses hundreds of Sentinel-1 radar images and optical satellite images to map the monthly progression of wet and dry snow for the 2019 melt season. Dry snow covers the entire basin in January and February, but wet snow starts to appear at lower elevations in March and April. By May, dry snow is found only at the higher elevations of the basin.
While these animations are still a work in progress, I am particularly interested in how these types of datasets could be used in flood prediction. Recent work with Sentinel-1 images has shown a strong link between radar data and the stages of snow melt. Future research will explore this link in mountain watersheds to see if radar data can be used in B.C. to improve snow melt and flood risk forecasts. \m/
