PORTLAND, Ore. (KOIN) — Following a week of heavy rain and snow, much of Oregon and Southwest Washington are expected to flood as high water is forcing several roadways to close Friday.
I-84 is completely reopened after a landslide closed almost 50 miles of the highway from Troutdale to Hood River Thursday. The Oregon Department of Transportation warns there may still be slides in the area on Friday, and crews are continuing to clean up.
Bridge Avenue is still closed in both directions at the intersection with Lower Columbia River Highway.
“Highway conditions remain volatile with precipitation continuing and temperatures dropping below freezing in many parts of the state,” said ODOT.
A landslide has all lanes of the Old Historic Highway closed 7 miles west of Ainsworth State Park.
The impacts of some of Oregon’s most extreme wildfires are being felt years after those fires were put out.
Falling debris and landslides were reported this week in areas burned by the Eagle Creek fire in 2017.
In areas where fire has killed the trees, the impacts could be felt for at least a decade. The timing depending, in part, on how mature the forest was when it burned.
Anytime there’s a lot of rainfall in Oregon and southwest Washington, Professor of Geology Scott Burns says there is potential for two different types of landslides on the steeper slopes.
“One is when the slope gets very, very wet and then slides down in mass,” Burns explained. He says that’s called an “earth flow”.
The second type of landslide caused the closure of I-84 in the gorge Thursday.
“Up in the gorge in Dodson where they had a huge one yesterday – that closed down I-84 – it’s what we call a debris flow,” Burns said. “That was the same place last year that a lady was killed, she was buried in the debris flow that came down.”
Burns says a landslide like that starts up in the upper headwaters of an area. The sediment then slides into a stream – eroding the stream bed.
“By the time it gets down to the major river, it is more of a slurry,” Burns said.
In places where there’s been significant wildfire, Burns says sometimes it takes four to five years before you will see the more significant debris flows because while the trees may have been killed by fire, it takes a while for the roots to break down – allowing the soil to potentially give way.
“If the roots are still there, it takes five to ten years for those to break down. Then, you get major rainfall events like we’ve been having, you will have those smaller landslides up above and create those debris flows,” Burns noted.
The magnitude of slides that could result from 2020’s historic fires remains to be seen. The Riverside fire which burned parts of Clackamas County and the Beachie Creek fire which burned in Santiam Canyon and beyond.
“The surface erosion occurred right after us, but the big landslides that we are concerned about, that will take a few years to form,” Burns said.
It all depends on how much burning went down into the roots systems and the maturity of the forest. The more root systems, the more stability and the longer it takes to decay.
“We can’t really give a timeframe, but definitely there is a delayed reaction,” Burns said.
Burns says the good news is the weather was dry today, giving the land time to drain. Even a half day of dry weather is beneficial for drainage, according to Burns.
Conditions aren’t any better in Washington county. One of its flood gates is closed on Southwest Fernhill Road by the wetland trailhead. This stretch of road typically floods with heavy rains.
A video shared to Twitter by Forest Grove Fire & Rescue shows SW Fernhill Road’s closure and where floodwaters have approached the road at SW Old Highway 47.
Washington County transportation officials want to remind travelers to obey these closures and if not expect hefty fines.
Officials say the Seaside area still has some water covering roadways. While out near Tillamook US 101 is closed where it intersects with Highway 6 due to high water; detours are in place.
There is a downed power line on Highway 34 in Waldport west of Nelson State Park.
Most of the water that slammed parts of Warrenton Thursday has dissipated. The town’s tide gates are struggling to keep up with water from the rain and snowmelt.
“I’ve never seen it this bad. There’s water coming out in places that we’ve never seen it before,” Warrenton mayor Henry Balensifer said.
Parts of Warrenton were under water Thursday night as the city’s drainage system and tide gates struggled to keep up with added water from rain and snow melt.
One of their two main storm water pumps overheated, so Mayor Balensifer says it was all hands on deck as he declared a state of emergency.
“Who would’ve guessed we were using fire trucks to pull water instead of just pump it out onto a building, right that was a novel use for flood recovery,” Balensifer said.
Friday, they’re still trying to assess the extent of the damage. Water remains, but he says all of the roads are now passable and back open.
“The drainage is not happening fast as we would like it to happen, but it’s manageable at this current moment. So, our emergency for now has been abated that doesn’t mean that we don’t have a lot of stuff to still do and we’re still doing it, working around the clock,” Balensifer explained.
A stretch of Highway 47 closed Friday morning in Columbia County after a chunk of the road near Mist Junction was washed away along with rushing water Thursday.
“We’ve got a lot of work right now to figure out just what went wrong and what we’re going to have to do to get that open again too,” Don Hamilton of ODOT said.
ODOT says they’re expecting wet roads to continue to dry out through the weekend on the coast, but they’re not in the clear just yet.
“The roads are still pretty wet and even though we’re seeing a drying out period over the next couple of days and through the weekend in there too, we still all got to look out for high water, we got to look out maybe for fallen trees, we got to look out for slides, we’re not out of this yet, we all have to still be very careful,” Hamilton said.
In Southwest Washington, I-5 Northbound to exit 77 at Main Street is closed due to high water. Officials advise drivers seek an alternate route. High water has also closed nearly a 20-mile stretch of Interstate 5 southbound in both directions from Chehalis to Grand Mound.
Highway 47 near the Mist Junction is closed after part of the road was washed out. WSDOT advised there’s a natural gas line in the area so Northwest Natural and ODOT crews are securing the area.
A landslide has closed SR 411 at milepost 11 in Cowlitz County, officials said. However, the National Weather Service in Portland said flooding at the nearby Cowlitz River has peaked, and they expect it to gradually recede Friday and through the weekend.
In a Facebook post, the Cowlitz County Department of Emergency Management compiled a full list of road closures in the area. The department said, “With the weather forecast, we suspect many of these issues will resolve themselves quickly unless there is extensive damage that will require repairs.”
Around 6:30 a.m., a crash shut down all lanes of State Route 14 eastbound near Washougal.