The Alaska Pacific River Forecast Center predicts the Kuskowkim will break up at Bethel between May 9th and May 15th. That range is right around the historical average of May 12th. But after a warm winter with little snow, the Forecast Center says this year’s breakup could happen in one of several ways.
Celine van Breukelen is a hydrologist with the National Weather Service. She says her team is looking at two different scenarios. The first is a traditional breakup based on snow melting upriver.
But the Kuskokwim snowpack is less than half of normal levels at this time. If the river breaks up in the traditional way with little snowmelt in the pipeline, the ice upriver could have trouble floating and lead to flooding.
“Because the water level is so low, there’s not enough depth to get the ice sheets down stream, they get caught in the bends of the river and they get caught on sandbars. That’s exactly what happened in Crooked Creek in 2011,” said van Breukelen.
Van Breukelen says, thanks to warmer than normal temperatures, that could lead to an earlier than normal breakup.
The second scenario is a thermal breakup – or mush out. That happens with the sun degrades the ice and there’s not enough water to push ice downriver.
“That could lead to a later than normal break up, in the sense that it just sits in the river and it takes time for the sun to work on it before it finally moves out,” said van Breukelen.
Ice thickness is currently a little below normal to normal. Measurements from earlier this month show ice 44 inches thick at Aniak, 34 inches at Napaimute, and 25 inches at McGrath.
In any case, the conditions over the next two weeks will in part determine what kind of flood risk residents of the Kuskokwim will face.
“It’s easy for people to say oh, there’s a very small snowpack, we can already see the ice beginning to deteriorate. But people just still be aware of the potential for breakup flooding, just for the reason that if there isn’t as much water to push on the ice sheets, they tend to ground and we could see some flooding from that. So still be aware and be prepared,” said van Breukelen.
Van Breukelen will be part of the 2014 River Watch program, a partnership between the state and National Weather Service to assess flood threats and navigational hazards. They plan to begin flying upriver around May 3rd, while a second team flying from Bethel could start around May 8th.