Mary Callahan, THE PRESS DEMOCRAT
High waves and heavy surf that have battered the Sonoma Coast for days and sealed the Russian River mouth with a great mound of sand have raised the water high enough to threaten flooding in the town of Jenner over the next few days.
Water already surrounded the Jenner Visitor Center at the river’s edge by Thursday afternoon, rising over the back deck and flooding into the parking lot adjacent to the post office and Highway 1. Farther inland, the river’s surface swelled to a height of 10 feet at the Highway 1 bridge.
But because of continued wave action on the beach, it has not been safe for Sonoma Water, the county water agency, to send out a heavy equipment operator to breach the beach dam by digging a channel through from the river estuary to the ocean. And though there has been some recent rain, the river flow remains low enough that it’s not exerting sufficient pressure to break through the sand on its own.
That combination of factors has allowed the mouth to close a “crazy” number of times this winter, said Suki Waters, who grew up in the area and owns Water Treks EcoTours in town, running boat rentals and guided kayak tours in the estuary.
“There’s not enough pressure in the river, not enough current to keep the river open during these high waves, high sand-pushing events,” she said.
At various times, the waves have been high enough to wash over the sand berm, adding even more water to the estuary, Sonoma Water said.
This is the fifth time in two months that the mouth has closed, in large part due to a dearth of rainfall that this year is sitting at around 30% of normal in most of the North Bay and wider Bay Area, National Weather Service meteorologist Matt Mehle said. Santa Rosa, as of Thursday, had received 5.3 inches of rain since Oct. 1, compared to 15.5 inches in an average year, Mehle said.
The outlook is for dryer than normal weather through the end of the month, as well, Mehle said, and another high-surf advisory taking effect at 6 a.m. Friday, with waves up to 25 feet in the most exposed coastal areas.
Sonoma Water, the region’s drinking water supplier, and charged with managing conditions at the river mouth, normally would consider mechanical breaching of the sandbar once the water reaches between 7 and 9 feet high, said Barry Dugan, a community and government affairs specialist. It already has done so on three occasions over the past two months — Nov. 19, Dec. 10 and Dec. 30. One other time this winter, the mouth closed but the river breached on its own Dec. 24.
At more than 10 feet, the river “is pretty high,” said Waters, whose boats were moored near the visitor center, formerly the town’s boat house, and being monitored.
“Normally, it either breaks or, if the county can open the river mouth, it usually happens before it gets to 10 feet,” Waters said. “This is a rare event.”
The river usually runs at a rate of several thousand cubic feet per second at this point in the season, but even with the rainfall early this week, it flowed only at 459 cfs by 4 p.m. Thursday at the Hacienda Bridge in Forestville.
That’s at least high enough to allow sport fishing once again in the main stem, where between Oct. 1 and April 30 angling is shut down at 300 cfs under a 2015 regulation designed to reduce stress for imperiled fish species already challenged by drought.
Though the river rose to 300 cfs briefly Dec. 18 and again between Dec. 26-28, the river was not opened until Wednesday, when it peaked at 559 cfs before beginning to drop.
“Last year, it opened right before Thanksgiving. The year before that it opened in late October, closed, and then opened again in mid-November,” said Scott Heemstra, a longtime fishing guide and manager at King’s Sport & Tackle in Guerneville. “So this is pretty late for opening.”
With the river mouth closed, only smaller steelhead trout that came in early were available to be caught, however, and once the mouth is opened, the river flow could be too low to fish.
Whether the water in Jenner rises high enough in the meantime to mimic December 2015, when people were canoeing and kayaking through riverside parking lots, remains to be seen.
Dugan said the visitor center floods when the water reaches around 10.3 feet and the southbound lane of Highway 1 at 12.3 feet.
He said the CHP, Sonoma County Sheriff’s Office and public safety and park agencies had been notified of the situation.
But he said it remained difficult to predict what might happen.
“All I can say with any certainty is there continues to be the potential for localized flooding,” Dugan said.
Source: https://www.pressdemocrat.com/article/news/russian-river-backed-up-at-coastal-mouth-threatens-flooding-in-jenner/
Our worst fears were realized in the Feb 28th flood event. The largest gravel pit mine, Syar’s Basalt Pit, had a complete levee failure on a section that had failed in previous floods. The image at left shows the breach in center of picture, with river on the left and Syar Basalt Pit on right. Over 30 years of mining waste containing extremely high levels of toxic metals as well as Healdsburg’s treated wastewater discharges are now connected to our river – our drinking water supply.