Modeling of Aufeis-Induced Flooding

Jarvis Creek flows as a wide braided channel in glacial moraine deposits through the Donnelly Training Area (DTA) of the U.S. Army's Fort Wainwright near Delta Junction, Alaska. The U.S. Army Alaska is in the process of designing a $55 million Battle Area Complex (BAX) and Combined Arms Collective Training Facility (CACTF) within the DTA for increasing training opportunities for infantry and mechanized troops. While open water flooding events are easily contained within the channel corridor, massive accumulations of aufeis generated during severely cold winters result in almost total channel blockage at several locations. Spring snowmelt events send water out of the channel and into the floodplain, eventually passing out of the Jarvis Creek basin. The U.S. Army Alaska contracted the Engineering Research and Development Center - Cold Regions Research and Engineering Laboratory (ERDC-CRREL) to determine whether these floodplain flows would effect the proposed locations for the BAX and CACTF within the DTA. HEC-RAS modeling was used to simulate aufeis blockage of the channel and floodplain water elevations at the proposed site locations. While the Eddy Drop Zone site was initially thought to be an optimal site due to the absence of permafrost and sensitive wetlands areas, the modeling has shown that significant overbank flow passes through the area. This paper describes Jarvis Creek, its flooding history, HEC-RAS modeling and the impacts of spring snowmelt flooding events on the proposed BAX/CACTF location at the Eddy Drop Zone site within the DTA.