With more rain in store for North Coast, dam managers weigh releases from Lake Mendocino

Deadly storms that have landed repeated blows on the North Coast over the past two weeks are forecast to hit again over the weekend and into next week, raising a persistent threat of creek and river flooding, mudslides and falling trees.

The Russian River is projected to climb back toward flood stage in Guerneville on Thursday and Sunday, though predictions eased Wednesday, suggesting a slightly lower risk than was indicated at the start of the day.

The raised river level still means fast-flowing creeks will be likely to back up as they reach confluences, potentially causing the kind of flooding that this week spread into Guerneville from Fife Creek.

Further east, along River Road east of Forestville, the body of a Ukiah woman was recovered Wednesday from her submerged car, which had been overtaken Tuesday by floodwaters from Mark West Creek.

It was one of at least four storm-related deaths in Sonoma and Mendocino counties since Jan. 4. Statewide, the death toll rose to at least 18 on Wednesday.

Heavy rain expected Friday and Saturday likely means six-day rainfall totals by early Tuesday should be in the 4-to-6 inch range for inland valleys and 7-to-10 inches in the coastal mountains, National Weather Service meteorologist Valerie Thaler said.

Already, remote communities in the western hills of Sonoma County have seen in some cases feet of rain since a series of moisture-heavy atmospheric rivers took aim at the region two days after Christmas.

The tiny road stop known as Venado in the Mill Creek watershed west of Healdsburg received almost 28 inches between Dec. 26 and Tuesday, according to Sonoma Water.

Cazadero has received something closer to 18 inches, while about 13.74 inches have fallen at the Charles M. Schulz-Sonoma County Airport during the same time frame.

The U.S. Army Corps of Engineers, meanwhile, is looking for a break in which some water might be let go from Lake Mendocino near Ukiah without swamping Highway 175 downstream in Hopland.

It would be the first flood releases for Coyote Dam since 2019, the last wet year before three years of intense drought during which the lake reached its second-lowest level in history.

The reservoir by Tuesday held 78,985 acre feet of water, more than 10,000 acre feet above the threshold at which the Army Corps takes over management from Sonoma Water.

The Corps has discretion to hold back extra water in the reservoir as long as it still has ample space behind the dam to absorb incoming storms. Under an operational model developed in partnership with Sonoma Water and the Center for Western Water and Weather Extremes at the Scripps Institute of Oceanography, the Corps can base its decision on the presence or lack of storms in the forecast.

Nick Malasavage, chief of operations and readiness for the Corps’ Golden Gate District, said a release from Coyote Dam would mostly be undetectable given the vast amount of water in the drainage at present. But he said there was concern about ensuring it didn’t contribute to flooding in Hopland, about 50 miles to the south.

The river at Hopland has surged above its 15-foot flood stage at least three times since last week and was forecast to crest above flood level again early Thursday and early Saturday.

Malasavage said the operations team has continued to assess potential windows in the weather for releasing a pulse of water from the dam or beginning a smaller but longer term release.

If forecasts for flooding on the river stabilize, rather than continuing to oscillate, as they have been, an earlier release could be considered, but a weekend release is more likely, Malasavage said.

“There’s a lot of water in the system. The watershed is saturated,” he said. “Since we do have quite a big space left in Lake Mendocino, we’re going to do a wait and see.”

“We always want to be mindful of the resource that has been delivered to us,” he added, “while still being prepared for more storms.”

You can reach Staff Writer Mary Callahan (she/her) at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.