Situk River Hydrology Following Closure of Russell Fiord by Hubbard Glacier

摘要

The impact on the hydrology of the Situk River of a sustained closure of Alaska's Russell Fiord by Hubbard Glacier is described. A hydrological model was developed and used to estimate the daily inflows into Russell Lake (created by the closure of Russell Fiord). These daily inflows, when routed through Russell Lake, determine the flow into the Old Situk River after the Russell Lake level has risen approximately 137.2 ft. A HEC-RAS one- dimensional flow model estimated the levels and flows of the Situk River system, including the Old Situk, Upper Situk, and Lower Situk rivers. The channel geometry was based on an extensive LiDAR survey conducted in 2005. The levels and flows in the Situk River system were simulated over 15 years using the estimated daily outflows from Russell Lake to determine the hydrology of the Situk River system. The flow percentiles, annual exceedance probabilities, and average daily flows were estimated. The flow profiles were used to develop inundation maps and investigate potential channel erosion, the impacts on the Old Situk River crossing and Situk Lake, and the potential influence of log jams and channel migration.