Author(s): Rod Boyce

New research shows flood risk for several Alaska communities

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Coastal Alaska communities from the Yukon-Kuskokwim Delta northward will see more of their buildings exposed to flooding by 2100 if they continue developing at the same location, according to new research.

University of Alaska Fairbanks graduate student Richard Buzard found that 22% of structures in 46 of 55 analyzed coastal communities are in flood plains. Sea level rise projections suggest the percentage will increase to 30--37% by 2100, he reported.

Western Alaska coastal communities currently have the greatest flood exposure and the most structures at risk, Buzard writes. Northern Alaska coastal communities will see similar flood exposure by 2100, he adds.

The research was published in April in Scientific Reports.

"Many communities and supporting organizations are actively planning how to reduce flood hazards," Buzard said. "This research is a stepping stone to map the current and potential future flood plain.

"Ideally, these groups can work toward safer coastal planning by using the results alongside local knowledge of infrastructure status, community development plans, subsistence use areas, culturally important sites and other relevant factors," he said.

Community planners commonly use the 100-year flood plain or record flood as benchmarks to guide community expansion. The term "100-year flood" refers to a statistical concept to describe a flood event that has a 1% probability of occurring in any given year.

Many remote Alaska communities don't have that information, however.

Buzard's research fills that gap.

The research paper's five co-authors include associate professor Chris Maio, director of the UAF Geophysical Institute's Arctic Coastal Geoscience Lab, and research associate professor Benjamin Jones of the UAF Institute of Northern Engineering. Researchers from the U.S. Geological Survey, National Oceanic and Atmospheric Administration and National Weather Service were also involved.

Buzard received his Ph.D. in geosciences from UAF in May and now works for the U.S. Geological Survey. The research was part of his doctoral work. Maio, who is also affiliated with the UAF College of Natural Science and Mathematics, was Buzard's adviser.

Buzard investigated flood risk for communities along the Bering, Chukchi and Beaufort sea coasts. He created a coastal flood database using written accounts and observations, identified record flood events, estimated current flood exposure and projected future flood exposure using global projections of relative sea level rise. 

The database as of June 2023 contained 448 entries for floods in 55 coastal communities. Records go back to 1887, but Buzard noted that recent decades have many more observations.

Of those entries, 382 are for storm-driven floods; 48 for ice jams; three for rainfall, snowmelt, spring runoff or a combination; and 15 are of unknown or unspecified cause. 

Of the 382 storm-driven floods, 46% are from storms large enough to affect multiple communities.

Overall, 76% of storm-driven floods occurred in the fall - September through November. 

Buzard writes that storms occurred more often in October but were more widespread and severe in November. The number of floods declined steeply into December and remained low until August, the research paper reads.

"The primary data source is direct observations from local residents," Buzard said. "Many communities and organizations have documented flood hazards over several decades and in some cases over a century. This is most often in the form of written observations made by residents of communities.

"We collected these observations and compared them to identify the highest-known flood," he said.

The research paper gives several instances of major flooding, among them the extensive flooding from a storm on Oct. 5, 1913. 

A New York Times headline of Oct. 7, 1913, proclaimed, "STORM SWEEPS AWAY 500 HOUSES AT NOME; Famous Alaskan Camp Nearly Destroyed - Damage Will Be $1,500,000."

That storm brought flooding 13 feet above the highest mean water level for that day at Koyuk, 12.5 feet at Nome and 9.5 feet at Teller, causing widespread damage. 

"The breadth of scientific data demonstrates sea level rise is an issue for coastal flooding and will affect future planning", Buzard said. "To plan for it, communities need numbers for how much of an issue it will be."

The research was funded by the North Slope Borough through the Arctic Strategic Transportation and Resources strategic plan, the Alaska Division of Geological and Geophysical Surveys Coastal Hazards Program, the National Science Foundation and the UAF Graduate School's Degree Completion Award.

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