Sometimes better flood protection comes from giving a river some space to roam. Hamilton City, 85 miles north of Sacramento, learned that lesson from a new levee project that both protects against flooding and restores wildlife habitat.
The levee will be set back from the Sacramento River for most of its 7 miles, allowing the river to spill over its banks and creating 1,400 acres of riparian forest and grassland. A model for flood-threatened areas nationwide, this project was the first designed by the U.S. Army Corps of Engineers to benefit both people and the environment.
The setback levee replaces one from 1906 mostly built right up against the river, where it was prone to erosion and water seepage. Since the 1980s, Hamilton City has been evacuated six times due to threats of inundation.
With the heavy rains of the past winter, the community nearly faced another evacuation.
“This year we had to make that decision, and it came down to minutes,” said Lee Ann Grigsby-Puente, a Hamilton City resident and president of Reclamation District 2140, the local project sponsor.
The first half of the setback levee is almost complete and the second half is scheduled to be finished by 2020, providing peace of mind for the 2,000-person community of Hamilton City and a refuge for birds, fish and mammals.
The setback levee allows the river to spill over its banks and nourish the restored floodplain. In some places, the levee will sit more than a mile away from the river. The area between the two will be planted with cottonwood, oak and sycamore trees and water-loving undergrowth.
With similar restoration projects, scientists have watched agricultural land successfully return to a nearly native wetland state within 10 years.
“In the big picture, it’s going to look like one of these great, big, glorious, riparian gallery forests with big cottonwood trees and nesting habitat for a lot of endangered birds and riparian birds in general,” said Jerry Dion, chief financial officer of River Partners, the contractor carrying out the ecological restoration.
Once an orchard, the area’s species diversity will increase drastically. Riparian forests are one of California’s most diverse habitat types. Such forests along the Sacramento River provide food and shelter for 250 species including deer, foxes, coyotes and rabbits that make their home there and hundreds of bird species that migrate through.
“There’s all these perfect conditions for growing this amazing habitat, and when you have that, you’re going to attract all these critters,” said Ryan Luster, a project director at the Nature Conservancy, which purchased and donated the land for the project. “That’s why the Sacramento River is still one of the most diverse and amazing rivers even though it’s been highly altered.”
Engineers didn’t foresee other ecological benefits 16 years ago when planning for the project began, Luster said. For one, water ponds in the floodplain and seeps into the ground to recharge the groundwater and ease the pain of droughts.
Reconnecting the river to the floodplain also allows Chinook salmon to spend their youth fattening up before they journey to the sea. Bugs and zooplankton that provide a feast for the young salmon feed on abundant algae there. A recent study by UC Davis researchers showed that salmon on fields flooded by the Yolo bypass grew much bigger than those in a fast-moving stream.
Once the restoration is finished, the land will be turned over to a state or local agency for public use. Grigsby-Puente said she hopes the restored area will provide opportunities for bird watching, fishing and hunting that the community never had access to before.
For Hamilton City, replacing the levee has been a long haul. Between 2000 and 2008, the Army Corps of Engineers scoped out the project, studied its feasibility and finished the planning. Then the economy tanked. Federal funds, accounting for 65 percent of the construction cost, weren’t approved until 2014.
Hamilton City remained committed to the project. It levied taxes to create Reclamation District 2140 to manage the completed levee and raised a 35 percent cost share from state grants. Their efforts over the past 35 years show how agricultural communities and environmentalists can come together to find solutions for flooding, said Grigsby-Puente.