Hydrologist explains rise in local river levels

WASILLA — The Matanuska and Yentna are among Valley rivers running high this month.

A video uploaded to Facebook on Tuesday has nearly 10,000 views, showing the flood damage around the Yetna River, features images of numerous houses and cabins on the river surrounded by water.

High temperatures last week followed by rain created a perfect storm of sorts for flood conditions. Not only the Valley, but areas in Cordova and Seward also saw flood conditions, and the National Weather Service is monitoring the Mendenhall Glacier area in Juneau for a possibly imminent flood. Scott Lindsey, hydrologist in charge of the Alaska Pacific River Forecast Center, said that 2018 is not unusual as compared to other years.

“It’s not any more dangerous than normal years. What we’re seeing is a week of really warm temps followed by some rain. The glacial streams, the Talkeetna, Yentna and Matanuska got primed really well by a lot of glacial and snowmelt and we had rain right on top of that. Most of those streams have crested and are falling very quickly now,” Lindsey said.

Lindsey did not have a prediction as to when the water may return to normal levels. Flooding often occurs in the late summer and early fall months as tropical precipitation systems cause excessive rain, which raises river levels.

Lindsey’s office works in collaboration with the Division of Homeland Security Emergency Management to inform them if they see flooding that overwhelms the boroughs resources, so that the borough can request state assistance.

“In the event that something turns into the 1995 Kenai flood, they’re prepared to step in and apply their resources,” Lindsey said.

Lindsey’s office works with different information sources around the state, primarily the US Geological Survey river gauges, satellite information, and Bureau of Land Management fire weather sites in the bush for data. They review weather models to see what is predicted and perform hydraulic modeling to determine if a flood occurs, where would it have it’s more severe effect and how far it would reach outside the banks.

“Most deaths related to flooding occur when people drive into flooded roadways,” Lindsey said.

Lindsey said that doesn’t necessarily occur much in Alaska, but primarily in the lower 48. “

Contact Frontiersman reporter Tim Rockey at tim.rockey@frontiersman.com.