The Carmel River begins simply enough in the Santa Lucia Mountains. But 36 miles later, as it approaches the sea, it flows into an obstacle course of farms, neighborhoods, golf courses, shopping centers, gravel mines, levees and roads.

With nowhere else to flow, this lowest stretch of the river forms a lagoon in the winter, threatening to flood Highway 1 and nearby neighborhoods. That’s when the county public works department breaches the levees – a dicey process that harms the many plants and animals that depend on the seasonal lagoon, including wild steelhead.

Enter Big Sur Land Trust, which heads a multi-agency plan to restore the historic floodplain on the east side of the highway while reducing flood risk to developed areas.

In early October, BSLT Conservation Director Donna Meyers surveys the 90-acre property known as Odello East – a dry, flower-flecked basin owned by BSLT and Clint Eastwood’s family. “Imagine this as a giant bathtub,” she says, spreading her arms wide. “It’s just going to keep filling and filling, because the only plug is over by the [Carmel River] bridge. We want to put another plug in the bathtub.”

The restoration plan, like the river, has shape-shifted over time. The favored proposal involves hauling out 130,000 cubic yards of backfill, restoring 70 acres of estuary, installing a 500-foot causeway and removing a half-mile of earthen levee. The goal is to allow water to flow more easily between the east and west sides of the highway. With a little help from humans, the floodplain should restore itself over time.

If successful, the project will provide habitat for steelhead, pond turtles, red-legged frogs and massive flocks of migratory songbirds. It will recharge groundwater flows to the critically overdrawn Carmel River, improve lagoon water quality and reduce flood risk on the river’s developed north side. Serendipity Farms, which leases 30 acres from BSLT, will be moved to higher ground. A trail network connecting to neighboring Palo Corona Regional Park will allow hikers to access the river.

On the ocean side of the highway, a related restoration effort is underway at Carmel River State Beach, or Odello West. The properties are named after the Italian farming family that helped build the original levees along the river in the early 1900s. When floods threatened their crops, the farmers would breach the levees – a tradition the county public works department later adopted.

It’s a drastic measure, but locals have seen the consequences of inaction: The floods of the 1990s caused millions of dollars in damage and temporarily blocked access to Big Sur.

“It’s very important for us to allow a flood to flow more fully through a floodway rather than to flow into the developed side,” says Larry Levine, chair of County Service Area 50, an advisory committee of property owners formed after the 1995 flood. “We’ve been participating in the [restoration] process. But progress has been frustratingly slow, and of course every winter we’re vulnerable to being flooded all over again.”

About two dozen agencies, nonprofits and businesses are partnering on the restoration effort, which has been in the works for years and will take several more. BSLT heads the planning phase, a nearly $600,000 endeavor funded primarily by the California Coastal Conservancy and the U.S. Environmental Protection Agency. Construction could require up to $10 million more in state and federal grants.

But as Meyers point out, a big flood can cost a lot more than that.