Study finds Sergeant Creek Road at high risk of overtopping; recommends raising alignment and increasing flood conveyance

Summary

A hydrology and hydraulic study for Russian River and Sergeant Creek found frequent overtopping and high velocities at Sergeant Creek Road and recommended raising the road alignment, adding floodplain culverts or increasing bridge conveyance to reduce risk. The study was funded by a FEMA-related grant and produced by River Focus, Inc.

River Focus, Inc. presented the final hydrology and hydraulic (H&H) study for Russian River and Sergeant Creek to the Kodiak Island Borough Assembly on Sept. 25, finding that Sergeant Creek Road is overtopped frequently and carries high-velocity flows that threaten access and public safety.

The study — funded by an Advanced Assistance Hazard Mitigation grant awarded by the Alaska Division of Homeland Security and Emergency Management and originating from a FEMA program — modeled 5-year through 500-year flood events and used a mixture of newly collected terrain survey data, 5-meter IFSAR data, USGS regression estimates and NOAA tidal controls. For the model tailwater the team used mean higher high water from NOAA and noted local uplift reduces the sea-level-rise effect at the site.

River restoration engineer Jess Robb, lead for River Focus, told the assembly the modeling shows Surgeon/Sergeant Creek Road begins to overtop in a 5-year event with depths and velocities that exceed safe-driving thresholds and produce a few feet of inundation in a 100-year event. Robb…

Study finds Sergeant Creek Road at high risk of overtopping; recommends raising alignment and increasing flood conveyance

Summary

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