Glacier Outburst Flood Modeling

Location: 
Juneau, Alaska
Duration: 
Aug 2018
aerial image of a glacier flowing into a basin

Information need

Emergency managers for the City and Borough of Juneau, AK and hydrologists at the National Weather Service - Alaska-Pacific River Forecast Center need a glacier-based hydrologic model that can forecast the timing and size of outburst floods released from Suicide Basin, an ice-marginal basin on the lower Mendenhall Glacier near Juneau.

End products

A physically-based glacier hydrologic model will be developed that can be used to project the magnitude and timing of peak streamflow on the Mendenhall River during glacier lake outburst flood events.

Why are we doing this?

  • Floods from glacier dammed lakes cannot be reliably estimated using standard statistical techniques in hydrology.
  • Suicide Basinhas experienced annual glacier outburst floods since 2011.
  • Recent flood events have resulted in the evacuation and inundation of the USFS Mendenhall Glacier Campground, closure of several residential streets in the Mendenhall Valley, and flooding of homes along the river.
  • Accurate forecasts will improve the process of initiating and implementing closures and evacuations within the Mendenhall Valley, particularly given the lag (6-18 hours) associated with the onset of glacier outburst floods.
  • The development of a glacier-based flood model will benefit other Alaskan communities that are subject to glacier lake outburst floods.

Approach

Existing monitoring equipment will be used, including a webcam and lake level gage in Suicide Basin that was recently installed by the USGS Alaska Science Center to provide real-time data on the rate at which the basin fills; and a streamflow gage, operated by the USGS Juneau Office, on the Mendenhall River immediately downstream of the glacier. These data, plus, new data collected on ice thickness in Suicide Basin and the Mendenhall Glacier, will be used to develop a glacier hydrologic model that produces flood forecasts for the National Weather Service and the City and Borough of Juneau.

Partners

City and Borough of Juneau, USGS Alaska Science Center, University of Alaska Southeast, NOAA National Weather Service Office, Juneau