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 Yukon River in Canada resulted in large volumes of ice and water to move down the Yukon River into Alaska.

Flood in YUKON FLATS NEARBY UPLANDS, ALASKA
From 13-MAY-23 18:30:00 to 14-MAY-23 12:00:00 (AKST-9)
Location: CIRCLE
Flood cause: Ice Jam
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Local Official

Record flooding occurred on the evening of May 13th at Circle. The Riverwatch team flew between Eagle and Circle on the afternoon of May 13th. During the day on May 13th, an observer 28 miles upriver of Circle reported the highest water he���d ever seen. The Riverwatch team observed widespread flooding (trees inundated, islands covered in ice, river well out of bank) upriver from Circle. Ice had degraded during the day in warm conditions and the Riverwatch team saw ice start to move while they were in Circle at 5 pm May 13th. Prior to landing, the Riverwatch team observed a roughly 90-mile-long run of ice behind the breakup front. For context, that is the longest run of ice that this Riverwatch team could remember ever seeing. The Riverwatch team circled above several times after takeoff and observed ice moving, and progressive disintegration of larger ice sheets (indicating weakness and that given the momentum of the river ice jams were unlikely). The flooding came on quickly; the water rose extremely fast and major flooding was first reported at around 8 pm. There was extensive damage, with flood waters estimated to be higher than the previous flood of record, 1945. The store had water up to the ceiling of the first floor. Ice moved into town and damaged homes with stranded ice throughout the community. Most structures in the town flooded and also flooded the airport apron and taxiway. The Riverwatch team flew over the next day and did not observe evidence of ice jamming but believe that the river simply slowed at the S-curves (where the Yukon becomes more braided) and compounded with historically high water levels. By the next morning, floodwaters had receded and had dropped below the airport access road by 3 pm May 14th.

Flood in YUKON FLATS NEARBY UPLANDS, ALASKA
From 14-MAY-23 17:21:00 to 15-MAY-23 16:18:00 (AKST-9)
Location: FT YUKON
Flood cause: Ice Jam
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Local Official

The breakup front progressed towards Fort Yukon on May 14th, finally stopping (jamming) just below Fort Yukon by late afternoon/evening. Water levels rose rapidly over bank and resulted in moderate flooding of the community. The river crested the night of the 14th. Several homes/structures were inundated with water. The tribal hall was flooded with water just up to the floor level with likely damage to the floor.  The road to the east of the Tribal Hall was breached to help reduce water levels with water flowing through the breach and back towards the Yukon River. The levee held well and prevented more significant damages. A local observer reported that water levels came to within one foot of overtopping the low spots along the levee, and estimated that the water level was similar to 1981. Water started receding early in the morning of May 15th when the ice jam released. The water took several days to fully drop back within bank.

Flood in UPR TANANA VLY FORTYMILE, ALASKA
From 12-MAY-23 17:37:00 to 13-MAY-23 18:19:00 (AKST-9)
Location: EAGLE
Flood cause: Ice Jam
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Local Official

Ice jam flooding started late at night on May 12th and when the Riverwatch team landed in Eagle on May 13th (early afternoon) flood waters had receded leaving stranded ice well above the bank. The USGS river gage had a preliminary crest of 42 feet at 5 AM ADT on May 13th. Moderate flood impacts included damage to the seawall with the guardrail along the seawall was destroyed, stranded ice, and flooding on the road between Eagle and Eagle Village leaving the road impassable for a week due to stranded ice. Several structures in town were damaged by ice and floodwaters, including the Falcon Inn which had a high water mark of almost 2 feet into the finished basement. Preceding the ice jam, the river was at or above bank full, with Mission Road beginning to flood late afternoon of May 12th.
Prior to the Eagle event, there were multiple significant ice jams in Canada, including a 30-mile-long jam with the toe of the ice jam located approximately 30 miles upriver from Eagle on May 12th. This jam caused major flooding in Canada. Downstream of Eagle was a mix of intact ice sheets, open water, and an ice jam 8 miles downriver from the month of the Tatonduk River. Thus, conditions were ripe for ice jams to impact Eagle once the Canadian ice jam released, which occurred late at night on May 12th.