Kolmakolfsky ice Jam Break - Kuskokwim River at Chuathbaluk

Observation by Patricia Yaska:

The Kuskokwim river ice jam was holding at the Kolmakolfsky River for many days, causing flooding at Napaimute, AK. On the evening of May 3rd, the ice jam broke free, and the ice reached Chuathbaluk around midnight on May 4th, 2020. It was the fastest, and loudest anyone has observed the ice flow in decades. We observed whole spruce trees standing tall, floating down the river. At 2am, we started seeing pieces of a cabin float by. Then we heard the gut wrenching noise of roof tin being warped by the ice coming at us. A few minutes later, we observed what was left of 2 pieces of roofing tin alone with more varnished, long, rectangular wood slabs float passed us. The water was significantly higher than it ever was in over a decade, and it reached Aniak in 30 minutes. Aniak is 10 miles away from Chuathbaluk, so the ice had to have been traveling at 20 miles per hour.

Comments from LEO Editors:

This observation as been shared with the National Weather Service, Alaska Pacific River Forecast Center.

Crane Johnson, hydrologist with the Alaska Pacific River Forecast Center, presented a forecast of spring 2020 break-up conditions in the April LEO Network webinar. Crane discussed snowpack and spring weather as two main contributors to ice thickness and break-up conditions. A cold winter contributed to thicker river ice than has been observed for a number of years, though in some places, freeze up was late. This year, warm May temperatures are expected to rapidly melt the above-average snowpack in much of the Interior. As snowmelt runs in to still-stable and relatively thick river ice, the risk of ice jams and flooding increases for many river communities.

On April 27th, the Alaska State Emergency Operations Center (SEOC) reported that the Yukon and Kuskokwim rivers were beginning to break up. On April 28th, a special weather statement warned that warm air temperatures and rapid snow melt were causing water levels to rise, initiating breakup. Thick river ice was leading to ice jams and flooding in the Interior. On Friday, May 1st, a flood warning was issued for the Kuskokwim river from Napaimute to Kalskag, and extended until the night of May 4th.