A grassroots campaign to reduce flood risk in Nicasio has led to some significant victories, including the scrapping of a plan to dramatically expand the reservoir.
But even as they celebrate some wins, residents are bracing for the looming super El Niño—and for more activism.
Over the last month, Marin Municipal Water District crews have cut back the thick canopy of willows whose branches crisscross Nicasio and Halleck Creeks, dropping debris during dry seasons and obstructing water flows in heavy rains. It’s a welcome, if short-term, measure.
“The work that’s being done by Marin Water right now is exactly what we’ve been asking for,” said Martha Davis, who sits on the Nicasio Landowners Association board. “It’s an emergency. Winter is coming, and we need a place for the water to go.”
For the long term, the district is developing a creek management plan ordered by the San Francisco Bay Regional Water Quality Control Board. Public comment on an environmental assessment to inform that plan is being collected through Oct. 18.
A central part of the long-term plan is the removal of 50,000 cubic yards of sediment from Nicasio and Halleck Creeks, which converge just behind Nicasio School. Sediment would be dredged from a 3,150-foot stretch of upper Nicasio Creek and a 1,200-foot stretch of Halleck Creek.
Fifty thousand cubic yards of sediment is enough to pile the height of a two-story building across an entire football field.
The work would be done over two construction seasons and involve widening the delta where Nicasio Creek approaches the reservoir. The plan calls for ongoing maintenance, with the removal of up to 10,000 cubic yards of sediment and vegetation thinning once every five to 10 years.
Residents had hoped that some excavation could occur before this year’s rains commence. But the environmental report, a requirement of the California Environmental Quality Act, will push that work back at least another year.
Sediment began building up in the creeks after Seeger Dam was built to create the reservoir in 1960. Until 1998, the water district performed regular maintenance, but since then, sand and gravel have accumulated six or seven feet deep in some sections, making the creek far more likely to breach its banks during storms.
“We’re very grateful that they’re finally doing something, because we’ve been trying to get them to do this for way over 20 years,” said Kasey Briare, whose property abuts Nicasio Creek. “It looks cleaner and will probably flow better, but until the sediment is removed, it’s not going to prevent flooding.”
Ms. Briare and her neighbor, Monica Seybold, designed the “Don’t Flood Nicasio” and “Restore Our Creeks” yard signs that have proliferated around Nicasio over the last year.
They mobilized two years ago, when the district announced plans to raise the dam’s spillway and increase the reservoir’s capacity by 17 percent. Marin Water abandoned the plan last year after residents discovered that it had considered a similar plan in 1980 but dropped it, finding it would have inundated homes, roads, and the school.
The last serious flooding of Nicasio Creek occurred during an atmospheric river just last year.
“It became a raging river,” Ms. Briare said. “It moves very forcefully and very fast.”
Once, the water in Ms. Seybold’s backyard became so deep that her husband, Mike, had to swim across to rescue his goats. “They had crawled up on top of their metal cages, and then their feet fell through, and they couldn’t get themselves out,” she said. “He had to swim out there, at night, where there shouldn’t be any water.”
Marin Water has folded its environmental assessment of the creek management plan into an environmental impact report already underway for a pipeline project that would funnel surplus Russian River water to Nicasio Reservoir during big winter storms and store it there for use in droughts.
But residents fear that combining the projects could slow or derail the creek work, which they believe warrants a separate review from the pipeline project, known as the Atmospheric River Capture project, or ARC.
“The creek management project is really completely independent of the ARC project,” said Matthew Pickett, who sits on the Nicasio Landowners Association board. “It needs to happen as soon as possible, regardless of whether the ARC project actually gets constructed.”
Marin Water has hired an engineering firm, Environmental Science Associates, to develop a model that can predict where and how much flooding is likely to occur depending on rainfall and how much sediment is removed from different areas.
Last month, Andy Collison, a consultant with E.S.A., told the district board that it would make sense to remove more sediment further upstream, away from the reservoir, and less near the mouth of the creek. The firm anticipates the removal of no more than two feet near the reservoir, two to four feet behind the school, and as much as six feet closer to town.
But that’s not the only work needed.
“From the school and from Halleck Creek down to the back end of the reservoir, the most effective thing you can do is widen the creek rather than deepen the creek,” Mr. Collision said.
Digging deeper into the creek bed can provide diminishing returns. “At a certain point, you’re making a hole that’s filled with water and that water won’t flow very fast and it will actually encourage more sedimentation,” he said.
Although the reservoir is in their village, Nicasio residents rely on wells and are not among Marin Water’s 196,000 customers. Residents along the creek fear that flooding could eventually damage their wells.
Last year, the landowners’ association hired an engineering firm to shore up an eroding section of bank behind the school with boulders. The area is directly behind the playground and the school’s well.
On Monday, Ms. Davis walked along the creek bed, a meandering path of sand, gravel, and tree roots. Since the landscapers began their work a few weeks ago, they have cleared a path that had been largely impassable due to a thicket of branches.
“This is a good news story,” Ms. Davis said. “But there’s more to be done.”
For more information or to comment on the environmental review, go to https://tinyurl.com/CreekManagementPlan