Boosting Elkhorn Slough climate change plan – Monterey Herald - Monterey Herald

Boosting Elkhorn Slough climate change plan - Monterey Herald

MOSS LANDING — The Transportation Agency for Monterey County has received $1 million from the state to help plan for sea level rise in Elkhorn Slough, including raising a portion of Highway 1 that runs through the area.

The funding was announced earlier this week in a press conference led by Assemblymember Dawn Addis, D-Morro Bay, and State Senator John Laird, D-Santa Cruz.

“We have to do this in a thoughtful way,” said Addis at the Moss Landing press conference. “After the winter storms, when Monterey Peninsula almost became Monterey island (because of flooding), I knew that this project had to get started.”

The infrastructure updates will not only impact the sensitive habitat of Elkhorn Slough but also the everyday commuters, commercial freight, and tourism.

Highway 1, which was built in 1937, is the main road connecting Santa Cruz and Monterey counties. The frequently congested 8-mile stretch of the two-lane highway, which traverses the estuary, is an hourglass waist that is flanked by four-lane highway. Nearly 40,000 vehicles cross this portion of the road each day.

“The problem with the highway has been happening since the ‘50s. There were four lanes proposed back then but it never happened,” said Monterey County Supervisor Glenn Church, whose district encompasses the area. The only alternative to this route is the rural G-12 corridor that runs between Salinas and Pajaro Valley, which “can barely handle the traffic now, it won’t be able to handle it in the future,” said Church. The current planning committee will evaluate the widening of the two-lane section into a four-lane road.

The Elkhorn Slough is an estuary where salt and freshwater meet. It contains the third-largest tidal salt marsh in California and is a place with rich biological diversity, providing a habitat for over 20,000 migratory birds. It is the largest nesting area for the snowy plover, home to more than a hundred fish species, and a resting place for threatened southern sea otters.

The low-lying portion of this highway is vulnerable to regular storms and tidal flooding, which is occurring more frequently. Last March, the 120-foot-wide Pajaro River levee breach flooded the highway, forcing it to close for four days. The floodwater also spilled over to the Slough, bringing freshwater that harmed saltwater lives.

In 2020, the Association of Monterey Bay Area Governments (AMBAG) and The Nature Conservancy put together a report that evaluated options to elevate the highway while preserving the Elkhorn Slough ecosystem. The current funding will build on this report and create actionable plans for viable construction projects that consider the ecology and economy.

Healthy salt marshes are productive ecosystems for plants to grow and animals to shelter and feed. Salt marshes are also resilient to sea level changes. When the tides go in and out over the marsh, they leave sediment that accumulates on the marsh plane to form accretion – a buildup of trapped particles. This accretion helps move the marsh up and inland with the rising sea.

“Our issue is that sea level rise is happening at a faster rate and many of our marshes are not healthy,” said Dave Feliz, a senior environmental scientist at the Elkhorn Slough. Past land use practices that dried the marshes to build levees for farming purposes have lowered the marshland considerably to the point where it is no longer able to hold any soil in place to maintain accretion. During big tides, sea water often hauls up the Elkhorn Road and floods the 5-mile railway along the main stem of the Slough.

In April, The Elkhorn Slough received $2.2 million from the National Oceanic and Atmospheric Administration to restore salt marshes lost to diking. By taking about 600,000 cubic yards of dirt off the farmland, staff at the Slough added close to 7-feet of dirt pile onto the marsh plains.

Getting the right marsh height is challenging due to fluctuating tides but the water level is critical for plant survival. The highest tides of the month can go between 6 to 7 feet. “We want to be able to hit that ‘Goldilock Zone,’” said Feliz.

Over 110 acres of marsh restoration is completed, which according to Feliz will continue to be healthy for at least 50 years.

The current planning project could benefit the effort to restore marshland around the section of Highway 1 that crosses the Moss Landing Wildlife Area. One strategy to raise the highway is by packing a pile of dirt to create a long gentle slope on both sides of the road, creating a buffer zone between the salt marshes and the highway, called ecotone levee. The ecotone levee will protect the highway from flooding by providing more land space for the salt marsh to move inland during sea level rise and slow the storm and wave surges. Another strategy to raise the highway is by installing piles that will allow water movement beneath the road that does not interfere with animal migrations.

Over 700 acres of marsh restoration was proposed for the current project.

Leaving the highway as is is not an option. “A do-nothing scenario will impact critical transportation, linkages, connections between communities, and the quality of life in the region,” said Scott Eades, director of Caltrans District 5. “A do-nothing scenario also degrades the health of the salt marsh.”

According to Eades, the goal now is to come up with a fully informed, consensus-based plan that will set the stage for the project and bring in additional funding. One of the challenges is to come up with a strategy to keep the highway open while construction is underway. The planning itself can take a couple of years. “Finding the right solution will be difficult yet absolutely essential,” he said. Once the planning stage is complete, the committee will identify projects and secure more funding to meet budget needs. Eades speculated that it will be well over 5 years before the construction begins.

Creating a project initiation document concurs with the recent approval of California Senate Bill 272 proposed by Laird. The bill will require all coastal cities in California to come up with a sea level rise coastal resiliency plan by 2034. “With this planning in place, Monterey (County) will be ready when the coastal plan is required,” said Laird.

The project is a collaboration between multiple partners, including the California Department of Fish and Wildlife and the California Coastal Commission. “Planning together across sectors is no easy feat,” said Alyssa Mann, climate resilience project director at the Nature Conservancy. “We don’t always agree, but together using good science, we can co-design innovative multi-benefit solutions that result in better outcomes for the people and ecosystems.”