Flood in Lower Yukon Valley, Alaska

On the lower Yukon River at Russian Mission, an ice jam formed downriver from Russian Mission near Marshall on May 21st. Major flooding began May 22nd with complete submersion of the airport runway, inundating 2-3 homes, and other miscellaneous structures. Additional homes and structures were completely surrounded by flood water for four days. The ice jam released on May 24th, which resulted in a gradual drop in water levels as the large volume of impounded water from the extensive lowland flooding between Holy Cross and Russian Mission drained. An ice jam flood warning was issued on May 22nd and was canceled on May 27th. Flood advisory products were continued until June 2nd.

A prolonged period of well-below-average spring temperatures combined with an above-average winter snowpack created a dynamic breakup of the Yukon River. This resulted in numerous ice jams and snowmelt flooding on the Yukon River. Breakup flooding began on May 12th in eastern Alaska in Eagle and ended on June 3rd in the Yukon River delta at the Bering Sea coast at the community of Emmonak. The primary cause of this active flood year was a 1-2 week delay in breakup when compared to typical timing. April temperatures were well below normal, and when temperatures began to warm in early May, it melted the low-elevation snowpack quickly. Because of the relatively quick addition of snowmelt onto strong ice, the ice was more susceptible to jamming and floods. In addition to the late breakup, the snowpack this winter was 1 to 1.5 times greater than the climatological normal for interior and western Alaska. Significant ice jams and associated flooding on the Upper Yukon River resulted in large volumes of ice and water to move down into the Lower Yukon River.