Lower Clark Fork Valley feels flood pressures

Posted at 5:21 PM, May 20, 2018
and last updated 2018-05-20 19:21:28-04

PLAINS – While Missoula is breathing a little bit easier with the flooding crisis this weekend, forecasters are turning a worried eye to the rest of the Clark Fork Valley and the increasing potential for flooding between here and Idaho.

The past two weeks, while most of Montana was focused on the record flooding in Missoula, residents in the Lower Clark Fork have been dealing with their own problems, as all that floodwater pushes downstream.

The high water had wiped out 18-feet of riverbank in a matter of days in Sanders County, putting the town of Plains’ wastewater treatment plant in jeopardy. The facility sets near the river just downstream from town, where the Clark Fork must detour around a point of land. But the US Army Corps of Engineers stepped in to wrap up emergency repairs this past week.

"One was bank stabilization in front of the Plains wastewater treatment plant. That has been completed. And as we were working on that we started work upstream of that just a little bit aways, stabilizing off of some work that we had done in 2012 to ensure that the Clark Fork didn’t cut through the field and make its way to the wastewater treatment plant," said Jess Jordan with the US Corps of Engineers.

Yet, everywhere in this part of the valley you can feel the river’s powerful presence. Water is filling side channels and some low-lying fields, surrounding some outbuildings, and completely filling the main channel to the brim. And that’s with the Lower Flathead River running full, but not flooding. Flood warnings are in place this weekend for the Lower Clark Fork, and may be just a foot below "moderate" flood stage by the end of this coming week…

"While much of our attention has been focused on the upper parts of the watershed forecasters are starting to look at the Lower Clark Fork, as all of this water begins to make its way to the Pacific.

"Exponentially bigger as you move downstream. As the Flathead has come up and really is putting a lot of water in it’s right there where the Clark Fork dumps in and it’s a fair bit of water," Jordan said.

"And then as we take this water and we route it downstream there’s a little bit longer attenuation time as we call it, as the water makes its way downstream. So the next place that will see a pretty good rise in the river just from all this water routing downstream from both the Clark Fork and the Bitterroot, and now the Flathead coming in is down towards Plains.," explained National Weather Service hydrologist Ray Nickless.

"They’re going to see the Clark Fork River rise there. And it’s going to be up to at least what it was the last time around, maybe even just a slight bit higher. So those areas downstream, as we push this water out towards the rest of the Columbia River Basin are going to have to keep an eye out," Nickless added.