Hubbard Glacier, Russell Fiord and Situk River – A Landscape in Motion

• Main Authors: Robert Gubernick, Steven Paustian
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: glaciers; LIDAR; flood modeling; geophysical survey; floods; ice dam stability; jokulhlaups; glacial outburst; Hubbard Glacier; Tidewater
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.159.8778; http://stream.fs.fed.us/afsc/pdfs/Gubernick.pdf

in a constant state of motion. The area is an extremely active and dynamic landscape with an advancing tidewater glacier (10 km wide at tidewater), two major seismic faults, and a maximum net isostatic uplift rate of 0.44 cm/yr. The southern end of Russell Fiord is confined by a terminal moraine whereas the northern end of the fiord flows into Yakutat Bay. In 1986 and 2002, the advance of the Hubbard Glacier blocked the northern of the Russell Fiord from Yakutat Bay, temporarily creating Russell Lake. Subsequent failure of the ice or moraine dams in 1986 and 2002, respectively, produced the two largest glacial outburst floods in historic times. Both of these dams failed before the lake had risen to an elevation that would have caused it to spill over the terminal moraine at the southern end of Russell Fiord into the Situk River drainage. In 2002 the Tongass National Forest commissioned an interagency technical team to investigate the implications of the Hubbard Glacier completely closing Russell Fiord and rising lake levels overtopping the moraine at the southern end of Russell Fiord, forcing flow into the historic Situk River channel. Complete closure of Russell Fiord has major economic and safety issues affecting the City of Yakutat. The Situk River provides world class sport, subsistence and commercial fishing, which drives and supports the majority of the Yakutat economy. A sustained closure of the Hubbard-Russell ice dam will increase average daily flows in the Situk River from the current 3 to 11 cubic meters per second (cms) to over 566 cms if Lake Russell overtops the moraine, resulting in significant short and long-term changes to the river ecosystem. Hydrologic and geomorphic analyses of potential overflow scenarios were performed using data obtained from field and remote sensing technologies. The results and methods used to perform the analyses are discussed.