Extreme Rain & Flooding

Observation: After a couple of days of rain and then a hard down pour during the night, I went down to the Little Susitna River to check on accessibility to the other side of the river and observed the flooded roadways. There are a lot of folks that live near or next to the river and wanted to make sure things were okay. With the amount of rainfall, my concern is the debris and ground saturation occurring, making for the right conditions for erosion and the possible human health concerns.

Video: To view flood video, click here.

LEO says: A 2016 scientific investigations report (Estimating Flood Magnitude and Frequency at Gaged and Ungaged Sites on Streams in Alaska and Conterminous Basins in Canada, Based on Data through Water Year 2012) "provides methods for estimating streamflow statistics at gaged and ungaged sites in States across the United States, including Alaska. Methods for determining the magnitude of floods that have annual exceedance probabilities (AEP) of 50, 20, 10, 4, 2, 1, 0.5, and 0.2 percent, and presents discharge estimates for these AEP for 387 streamgages in the study area. The report describes methods for revising regional skew and presents an updated regional skew for selected areas in Alaska and a new regional skew exclusion area for sparsely gaged areas. For estimating flood magnitude and frequency at ungaged basins, the report presents methods for developing regional regression equations using AEP discharge estimates at 341 streamgages and updated basin characteristics and describes the accuracy and limitations of these equations." Source: U.S. Department of the Interior, U.S. Geological Survey (Scientific Investigations Report 2016-5024. Curran, J., et al.). M. Tcheripanoff

Resources:

U.S. Army Corps of Engineers, Alaska District – "USACE has conducted a Baseline Erosion Assessment (BEA) to coordinate, plan, and prioritize appropriate responses to erosion throughout Alaska; the study, begun in April 2005 and completed in March 2009. Through a process of stakeholder meetings, review of previous reports, and extensive correspondence with communities, 178 Alaska communities were found to have reported erosion problems. After subsequent investigation, the Corps designated 26 communities “Priority Action Communities”—indicating that they should be considered for immediate action by either initiating an evaluation of potential solutions or continuing with ongoing efforts to manage erosion. Sixty-nine communities where erosion problems are present but not significant enough to require immediate action were designated “Monitor Conditions Communities.” Eighty-three communities where minimal erosion-related damages were reported or would not be expected in the foreseeable future were designated “Minimal Erosion Communities.” Source: Alaska Baseline Erosion Assessment: Study Findings and Technical Report. March 2009