Closing of MVID irrigation ditch changed runoff’s course
By Ann McCreary
Although spring floodwaters may seem like a distant concern right now, Twisp town officials are looking for ways to avoid a repeat of flooding that has occurred in the Painter’s Addition neighborhood during the past two springs, resulting from the closure of an open irrigation ditch above the neighborhood.
Twisp officials recently toured the Painter’s Addition area with state Department of Ecology officials to consider ways to prevent spring runoff from collecting in streets and yards of the Painter’s Addition neighborhood, located on a hillside above Twisp.
The flooding was especially problematic during heavy runoff in March of 2016, when town public works crews had to build diversions with gravel and dirt to prevent the water from damaging streets and homes.
Andrew Denham, Twisp public works director, said the flooding began after the Methow Valley Irrigation District (MVID) closed an open irrigation ditch that ran along a hillside above the residential area. The ditch was filled in and irrigation water is now piped as part of a larger project conducted by MVID and Ecology, designed to reduce the amount of water diverted from the Twisp and Methow rivers and improve habitat for endangered fish.
“The project originated with the Department of Ecology. It’s always trying to put more water back in the river,” Denham said.
Spring runoff flows toward Twisp from the Alder Creek and Lookout Mountain areas above town, Denham said. For the past 107 years, much of the runoff was captured by the open MVID ditch and diverted away from the homes and streets that were built over time in the neighborhood that is commonly known as the Painter’s Addition.
“For the last 100-plus years there was basically a gutter around it,” Denham said. The water entered the ditch on property owned by Bill White on Lookout Mountain Road west of the Painter’s Addition, Denham said. “At White’s property it got diverted into the ditch. It no longer went down the historical path,” he said.
A pressurized pipe system replaced the gravity-fed ditch two years ago as part of the project carried out by Ecology and MVID. After the ditch was shut down, the spring runoff began following a path that carried it down a ravine between Lookout Mountain Road and the Painter’s Addition neighborhood, Denham said.
During the walk-through of the area, the Ecology representatives “identified that this was the natural path for drainage,” Denham said.
“We’re talking about very significant flow coming down the mountain from the Alder Creek area,” Denham said. The likelihood of runoff water returning to its original path “was overlooked in the design and engineering of the project,” Denham said.
During March of 2016, the first spring after MVID filled in the ditch, “we experienced extraordinary flow” due to a rapid snowmelt, Denham said. Water collected on May, Harrison and June streets, flowing into yards and threatening homes in the area. Water collected and remained for several weeks in a yard with a depression that acted as a retention pond, Denham said.
“Last spring was a less-significant event, the warm-up period was longer. We experienced localized flooding in the same area,” he said.
The threat of future flooding “is a major concern for us,” said Denham. He said Twisp officials are looking to Ecology for help in correcting the problem because the town doesn’t have the infrastructure or funding in place to deal with it on its own.
“We don’t have a stormwater utility. We have no funding within the town to collect and treat stormwater,” Denham said. “If we don’t come up with a resolution, this is something the town will have to deal with every spring on an emergency basis.”
“We are waiting to hear back from Ecology now that the ground troops have been here,” Denham said. “It’s my opinion they are taking it very seriously to mitigate this.”
Ecology “is exploring the concerns brought forward. What the outcomes will be has not yet been determined,” said Joye Redfield-Wilder, a spokesperson for Ecology.
In addition to two Ecology representatives and Denham, the tour of the Painter’s Addition area included Twisp Mayor Soo Ing-Moody and representatives of MVID, Trout Unlimited and the Bureau of Reclamation. Trout Unlimited and Reclamation were also involved planning and implementing MVID’s Instream Flow Improvement Project.
Ecology’s Office of Columbia River “oversaw with the local entities improvements in the basin to assure long-term water for the town, fish and irrigators,” Redfield-Wilder said. “Stormwater management is an important aspect that will need additional study … we, with the town, will help explore what other solutions are out there and what other entities may need to be involved.”
The $10 million “Instream Flow Improvement Project” installed pipes to replace most of MVID’s two open canals that ran along the west and east sides of the Methow River, and ended the district’s diversion of water from the Twisp River.
The project also provided for the sale of water by MVID to Twisp, to alleviate the town’s longstanding shortage of municipal water. The project was funded through $6 million from Ecology’s Office of Columbia River and about $4 million from habitat mitigation funding from the Chelan-Douglas County and Grant County Public Utility Districts.