Peak flows from Rhoads-Granite Creek (1987), Mt. Hayes Quadrangle, Alaska [report]

S. F. Mack
1988 unpublished
A large fire in late May in the Rhoads-Granite Creek drainage increased concerns of flooding across the Alaska Highway and sedimentation of Clearwater Creek. DGGS investigators and SCS cooperators installed recording equipment and measured flows at sites in upper Granite Creek and above the highway crossing on the 1408 Road. The equipment was in place when a mid July rainstorm produced flood flows across the Alaska Highway. The rainstorm was later estimated to have a 10 year return period. The
more » ... return period. The peak flow at the upper gage site was estimated to be 2850 cis which falls between the 10 and 25 year floods estimated for the upper gage site in a 1987 report using HEC-1 computer model to predict flood flows at the Alaska Highway Crossing. The peak flow at the highway site was estimated to be 340 cfs, much lower than what was predicted by the 1987 HEC-1 model. An explanation for this is that at very large flows excess water enters the old channel of Granite Creek and other distributary channels and is lost to the system. If this hypothesis is correct, the potential for sedimentation of Clearwater Creek is small. During the 1987 summer no noticeable impacts from the fire on flood levels or erosion occurred.
doi:10.14509/1359 fatcat:d3n37fqx7jh67hjazln326xipy