Unique Challenges and Potential Solutions for Surface Water Models in High Relief, Mountainous Catchments with Vulnerable Alpine Glaciers

Abstract Submission: Continental alpine glaciers are some of the most vulnerable ice formations on Earth. These glaciers are projected to drastically reduce in size, such as those in the Many Glacier Valley in Glacier National Park (GNP), Montana, creating drastic changes to alpine watersheds. Modeling glacial watersheds often proves difficult due to the high relief catchment and drop-pool style streamflow. Furthermore, data collection can be difficult due to the sensitivity of the watershed’s ecosystem. With the release of the Montana Statewide Phase 2 LIDAR dataset, we now can model surface water at resolutions appropriate for mountain stream systems. Using a Teledyne StreamPro acoustic doppler current profiler and small pressure transducers we were able to estimate stream depths to calibrate a 2D HEC-RAS model. 2D HEC-RAS has difficulty providing accurate depths in drop-pool style terrain such as those found in the watersheds of interest. Using terrain modifications, we adjusted for these features in the model to create more accurate upstream and downstream surface water levels. With aerial LIDAR data collection, stream obstructions, such as logs, are included in the digital elevation model. The obstructions incorrectly returned as ground create streamflow blockages rather than allowing water to flow under. These obstructions were corrected through alterations to the LIDAR data set and terrain modifications in HEC-RAS. These modifications allowed us to generate a more accurate surface water model for future use. This model will be used to address questions about the relationship between precipitation and surface water features in a vulnerable glaciated watershed.

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