| Rock glaciers are critical suppliers of cold water in semi-arid mountainous regions.
Understanding their hydrologic contributions has become increasingly important for snow
dominated regions with increasingly common warm and dry years. However, rock glaciers often
lie in valley-head cirques and are difficult to study on a regional scale. Here we assess surface
velocities of seven rock glaciers, including their seasonal and longitudinal velocity variations,
using Interferometric Synthetic Aperture Radar (InSAR). One rock glacier was found to be
active (>10 cm/yr), four intermediate (2 to 10 cm/yr), and two inactive (<2 cm/yr). We assess the
relationship between InSAR surface velocity patterns and outflow stream conditions using
baseflow index as a proxy for stream outflow persistence. We determine that faster moving rock
glaciers supply more persistent baseflow and colder water than do slower moving rock glaciers.
Following spring snowmelt, the two inactive rock glacier outflow streams dropped to near zero
values, three of the four intermediate rock glaciers declined significantly, and the single active
rock glacier sustained a near constant baseflow. The exception is Dickey Peak rock glacier, an
intermediate rock glacier with near constant baseflow. It is the only valley filling, elongate rock
glacier and we infer that it may focus meltwater and possibly groundwater into a single pathway
near the terminus. This project suggests that InSAR-derived rock glacier velocities are useful
both for classifying rock glacier activity level and as a remote indicator of outflow stream
conditions.
Key Words: rock glaciers, alpine hydrology, water resources, remote sensing, climate change |