Cosumnes River flows avoid flood stage as another wet, warm storm blasts region

Flows slowed on the fast-moving Cosumnes River, which will not reach flood stage overnight, state river watchers said Tuesday afternoon.

The forecast is a shift from earlier projections that had the Cosumnes at its 12-foot flood stage at 11 p.m. Tuesday at Michigan Bar near Rancho Murieta and 42 feet, the flood stage downstream at McConnell.

By 4:30 p.m., new projections from the California-Nevada River Forecast Center pegged Michigan Bar at 11.5 feet at its height at 2 a.m. Wednesday. McConnell was expected to register at 41.3 feet at crest at 1 p.m. Wednesday, according to the center.

The unregulated river that flows through Wilton — the south Sacramento County community hit hard hit during January’s powerful storms — had bobbed between monitor and flood stage throughout the latest atmospheric river wave. The river at Michigan Bar, seen as the warning bell for what happens downstream, had been expected to reach its 12-foot flood stage at 11 p.m., before cresting at 12.7 feet at 3 a.m. Wednesday, according to the California-Nevada River Forecast Center.

Minor flooding is forecast with the high water, according to the National Weather Service office in Sacramento. At 12 feet, water flows onto roads near Wilton. Water enters homes when the water rises above 13 feet.

Sacramento County has sandbag stations at Wilton Fire Station, 10661 Alta Mesa Road; and in Point Pleasant at Point Pleasant United Methodist Church, 3329 Point Pleasant Road.

Downstream at the McConnell station near Highway 99, flows have hovered between the river’s monitoring stage, from 38 to 40 feet, since late last week.

Levels at both spots had been expected to slide sharply Wednesday into Thursday and the end of the workweek as storms moved out of the region, according to forecasts by the California-Nevada River Forecast Center.

The concern for creeks, streams and smaller rivers across Northern California and the communities along their path: the warm atmospheric river storm known, as a Pineapple Express, drenching the heavy Sierra snowpack in the alpine watersheds and the rain-soaked ground downhill in the Valley.

Weather service forecasters say the dense snowpack will absorb much of the rainfall above 4,000 feet But, flooding of small creeks, streams and rivers, especially those coming out of the Sierra, is possible. Forecasters said residual flooding was possible Wednesday and into Thursday through area waterways as runoff makes its way downstream.

UCLA climate scientist Daniel Swain in a Monday video call said this latest warm wind-driven storm “may cause bigger problems” than the previous round late last week, not for the amount of rainfall, but for the conditions on the ground.

“That’s why I’m more concerned,” Swain said. “Soils are super-saturated. Rivers are running high, at or near flood stage. This storm is far from historic, but the watersheds are primed, grounds are saturated and rain is falling in the foothills.”

The prediction of lower flows on the Cosumnes came as fierce winds whipped through the Sacramento region. Gusts of 45 to 55 mph were expected to top out at 60 mph in some locations, forecasters said.

This story was originally published March 14, 2023 at 2:42 PM.

Darrell Smith

The Sacramento Bee

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Darrell Smith is a local reporter for The Sacramento Bee. He joined The Bee in 2006 and previously worked at newspapers in Palm Springs, Colorado Springs and Marysville. Smith was born and raised at Beale Air Force Base and lives in Elk Grove.