Coastal flood, high surf advisories, as Sonoma County digs beach channel to stop Russian River floods

Coastal flood and high surf advisories will take effect in the North Bay Tuesday morning, as Sonoma County officials are set to dig a channel near the sand-blocked mouth of the Russian River to prevent water from spilling over the banks into the town of Jenner.

The advisories were triggered by extremely high king tides and expected large breaking waves of up to 30 feet, according to the National Weather Service.

The coastal flood advisory is set to last from 5 a.m. to 1 p.m. Tuesday. The high surf advisory, meanwhile, will be in effect from 10 a.m. Tuesday to 3 p.m. Wednesday.

As of Monday afternoon, the mouth of the Russian River remained sealed, shut by mounded sand piled across the outlet by treacherous surf over the weekend.

Sonoma Water, the county water agency, plans to send a heavy equipment operator Tuesday morning to dig a trench aimed at halting potential flooding by releasing water from the river estuary to the ocean.

Barry Dugan, a spokesman for the agency, said that while the water had not yet reached flood levels on Monday, the concern is that continued high tides and surf could spill over into the lagoon while at the same time pushing more sand to the mouth of the river, keeping it from breaching the beach damn.

By Monday morning, the river’s surface had swelled to a height of over 8 feet at the Jenner Visitor’s Center, a more than 2-foot increase from the day before, according to Sonoma Water.

“When that water gets between 7 and 9 feet is when we consider digging an artificial breach,” Dugan said.

In addition to the tides and surf, possible light rain was forecast to arrive in the area Monday night and into Tuesday.

Anna Schneider, a National Weather Service meteorologist, said a plume of moisture pushing toward the Pacific Northwest could brush Sonoma County, though it was not expected to bring enough rain to significantly contribute to any flooding along the coast.

“This is going to be a few hundredths of an inch, maybe a tenth of an inch,” Schneider said of the expected rainfall.

You can reach Staff Writer Ethan Varian at ethan.varian@pressdemocrat.com or 707-521-5412. On Twitter @ethanvarian