Unusually warm temperatures contribute to swollen rivers
Unusually warm weather for early May, a healthy snowpack, and a heavy thunderstorm caused flooding and mudslides near Mazama last week, where a creek carried water and debris down a steep slope burned in the 2021 Cedar Creek Fire.
Further south, the swollen Twisp River broke a record midday Friday (May 5), rising to 12.34 feet at the Poorman Creek Bridge gauge, about 1.5 miles west of Twisp, according to Twisp Public Works Director Andrew Denham. The previous record was set in 2017, when the river reached 12.06 feet.
The temperature in Mazama reached 86 degrees on Wednesday (May 3) and 85 on Friday, before dropping more than 30 degrees to a high of 51 on Saturday. Winthrop was even warmer, reaching 87 degrees every day last Tuesday through Friday. A powerful thunderstorm pelted Mazama with 0.58 inches of rain on Friday.
“It’s awfully early in the season for our region to be experiencing temperatures in the 80s,” which is about 20 degrees above average, said Greg Koch, a forecaster with the National Weather Service in Spokane. People in flood-prone areas should take that seriously, he said.
While there is still a lot of snow in the mountains at higher elevations, in the past week, almost all the snow from 3,000 to 5,000 feet melted, Koch said.
The convergence of events sent water coursing into neighborhoods and onto private roads on the south side of Highway 20 near the Mazama junction last week. Flooded areas were visible over several miles east and west of the junction.
Although the dike at the River’s Edge Mobile Home Park in Twisp is 3 1/2 feet above that record for the Twisp River, Denham and Okanogan County Emergency Manager Maurice Goodall were carefully monitoring water levels through the weekend.
The river held steady at its record height for a few hours before it began a slow decline Friday afternoon. The level dropped considerably over the weekend and was just 10.42 feet on Monday, Denham said.
The Methow River was also full of snowmelt. The gauge in Winthrop registered the river’s fourth-highest flow ever, at 18.92 feet on Friday, eclipsing readings from 2017 and 2018, Denham said. By Monday, the Methow River had dropped to 15.91 feet.
Davelaar Drive, across from the Mazama junction, was one of the hardest-hit areas, according to area residents. During the worst of the flooding, deep mud and fast-flowing water rendered the road impassable. Some residents had to dig a trench to divert water from their homes, and others built walls of sandbags.
Looney Creek, which flows down Sandy Butte to the south of the houses, typically fills the Early Winters irrigation ditch every spring as the snow melts, but this year, “the amount of water has been unbelievable,” said one resident.
Looney Creek has been changing on a daily basis as it seeks out new channels, resident Andrew Gastineau said. At one point, the water was flowing so swiftly that crossing the road was dangerous, with the ominous sound of rocks moving through water so murky that you couldn’t tell how deep it was, he said.
Although the flows had subsided on Monday after cooler weather over the weekend, parts of Davelaar Drive remained inaccessible.
Other roads in the area became conduits for a steady surge of water that carved deep fissures in the road bed. There were large, muddy ponds alongside Highway 20, but in most areas, the water didn’t go onto the highway. Late last week, the Washington State Department of Transportation posted warnings about water over the roadway east and west of the Weeman Bridge, several miles east of Mazama, but traffic could still pass at reduced speeds, Goodall said.
Water flows in the Davelaar Drive area have changed since the Cedar Creek Fire. A massive rainstorm last August sent a tidal wave of mud and boulders into the area as Looney Creek surged down the burnt slopes of Sandy Butte. The mud scoured vegetation and affected many homesites, leaving marks 10 feet high on trees, resident Dan Norton said.
This spring, the creek spread out again, blocking neighboring roads and encroaching on Highway 20. When the water undercut the foundation of his home last week, Norton hired an excavator to repair the road. The big machine got stuck, he said.
There’s evidence of many creek beds that have formed over the last hundred years, Davelaar Drive resident Pete Fisch said. As mud fills the channels, the water seeks out new routes and goes everywhere. It’s been changing day to day, he said.
The irrigation ditch, which is at the base of Sandy Butte, caught a lot of debris that could have created problems elsewhere, but the silt must be cleaned out before the ditch can be opened, delaying the usual irrigation schedule, Early Winters ditch president Frank Kline said.
Goodall visited the area and met with residents last week. The water flowing out of Looney Creek and across the burn scar carried silt and trees and overflowed several roads, Goodall told the Methow Valley News. Driveways have been eroded, but there were no reports of damage to homes, he said.
After a wildfire, this is part of a natural process, and state and federal land-management agencies aren’t going to go into the mountains to try to redirect the water, he said.
Although the water and damage this spring have been worse than last fall, there are ways to mitigate problems in the future. Possibilities include new culverts or adding hoses along the length of the irrigation ditch to distribute the water, Goodall said.
Fisch and some of his neighbors met with Okanogan County Engineer Josh Thomson last week. Thomson provided information about liability and potential recommendations for addressing the problem, such as channelizing the water to direct it away from homes or creating dips in the road that would allow water to flow, Fisch said.
Warm weather problems
While river levels had dropped considerably after cooler temperatures, the forecast calls for very warm weather by the end of the week, potentially causing another round of flooding, Goodall said.
The cooler weather helped reduce the rate of snowmelt and, with no heavy rain or warm temperatures in the forecast until late this week, the weather service discontinued flood warnings in the Methow and Okanogan valleys on Monday, Koch said.
While that’s good news in the short term, temperatures are expected to reach the upper 70s on Friday (May 12) and to climb into the 80s over the weekend, Koch said.
In Twisp, the River’s Edge Mobile Home Park is prepped with sand bags, and town and county officials are prepared to marshal volunteers to fill the bags to protect structures so people don’t need to be evacuated, Denham said.
“There’s still a lot of snow, so we’ll keep it staged and we’ll monitor it. We’re ready if we need it,” he said.
A 3-mile stretch of Wolf Creek Road affected by the Cedar Creek Fire has been closed by flooding and debris slides. The same area had to be closed last year, Goodall said. There are no residences on that part of the road.
Roads are also closed in other parts of the county, including near Tonasket and Loomis. In Conconully, water rose about 5 inches over the bridge on Main Street and, while the water has receded, the bridge is still closed. Goodall said. Conconully regularly sees high water during spring runoff, but things are worse since the Muckamuck Fire burned the mountains above town.
Plentiful mountain snowpack
With cooler than normal temperatures in April, the mountain snowpack initially increased, but by the end of the month most of those gains had vanished, according to the May Washington Water Supply Outlook Report from the Natural Resources Conservation Service.
The cool temperatures extended the peak snowpack by a couple of weeks in many parts of the state, which could benefit irrigation and fish passage by shifting peak flows to later in the spring, according to the report.
But as the warm weather in early May showed, that snowpack can melt rapidly. The weather forecast through the end of May shows a probability of above-normal temperatures, but no conclusive prediction for precipitation. Heading into summer, the forecast is for above-normal temperatures and below-normal precipitation.
As of May 1, in the Upper Columbia basin snow cover was 121% of normal, and April precipitation was 131% of normal. But precipitation for the entire water year, which starts in October, was just 91% of normal. Snow cover in the Methow basin was 107% of normal, compared with 128% of normal last year.
• Sandbags are available in Twisp, and at the fire stations in Winthrop and Mazama. People will need to provide their own sand.
• The Okanogan Conservation District has resources at www.okanogancd.org/wildfire.