  Current climate shift has significant impacts on both quality and quantity of
snow precipitation. This directly influences spatial variability of the
snowpack as well as cumulative snow height. Contemporary glacier retreat
reorganizes periglacial morphology: while the glacier area decreases, the
moraine area increases. The latter is becoming a new water storage potential
almost as important as the glacier itself, but with a much more complex
topography. This work hence fills one of the missing variables of the
hydrological budget equation of an arctic glacier basin by providing an
estimate of the snow water equivalent (SWE) of the moraine contribution. Such a
result is achieved by investigating Structure from Motion (SfM) image
processing applied to pictures collected from an Unmanned Aerial Vehicle (UAV)
as a method to produce snow depth maps over the proglacial moraine area.
Several UAV campaigns were carried out on a small glacial basin in Spitsbergen
(Arctic): measurements were made at the maximum snow accumulation season (late
April) while reference topography maps were acquired at the end of hydrological
year (late September) when the moraine is mostly free of snow. Snow depth is
determined from Digital Surface Model (DSM) subtraction. Using dedicated and
natural ground control points for relative positioning of the DSMs, the
relative DSM georeferencing with sub-meter accuracy removes the main source of
uncertainty when assessing snow depth. For areas where snow is deposited on
bare rock surfaces, the correlation between avalanche probe in-situ snow depth
measurements and DSM differences is excellent. Differences in ice covered areas
between the two measurement techniques are attributed to the different
quantities measured.
