DETERMINING TOPOGRAPHY CHANGE OVER 50 YEARS IN TWO ALASKAN NATIONAL PARKS USING REMOTE SENSING

The topography of many Alaskan national parks has changed greatly over the last 50 years because of high relief and associated deglaciation and mass wasting. Glaciers have downwasted as much as 640 m and retreated up to 17 km. Large landslides, often associated with ground-rupturing earthquakes, have transported tens of millions of cubic meters of material from mountain sides and in-filled valleys.

Previous researchers developed a technique that determined glacier volume changes in southeast Alaska by subtracting the 1948 National Elevation Dataset (NED) Digital Elevation Model (DEM) and the 2000 Shuttle Radar Topography Mission (SRTM) DEM. Because Denali National Park and Preserve (DENA) and the vast majority of Wrangell-St. Elias National Park and Preserve (WRST) lie above 60°N latitude, the SRTM DEM is not available and the technique was not applicable.

DENA and WRST were the first national parks in Alaska to obtain a new 5 m spatial resolution, airborne interferometric synthetic aperture radar (IFSAR) DEM in June 2012. The new DEM covers approximately 98% of DENA and 30% of WRST, or the northern 1/3 of the park. With the acquisition of the IFSAR DEM, we used the proven technique to determine topography change over the last 50 plus years due to glacier change, mass wasting, and other processes.

This study quantifies the volume change of all glaciers in the study area and includes topography changes in non-glaciated areas. Large mass wasting events are common in the high mountains of the parks, yet very few are identified, much less quantified. This project also establishes baseline data for program managers so that they can make informed decisions on resource stewardship and science communication.