Marin Voice: Sea-level rise data shows the water is coming

By Gail Napell and Diana Benitez

PUBLISHED: September 7, 2025 at 12:57 PM PDT

It’s undeniable: The sea is rising. Property and infrastructure near and on the shoreline will be at risk of flooding.

In Marin, that means San Rafael’s Canal neighborhood, Marin City and low-lying neighborhoods along Highway 101 will see more frequent flooding in our lifetimes. Sea level along the coast and bay is predicted to rise 3 feet to 10 feet by 2100. The low estimate is based on immediately halting fossil fuel extraction and use. We’re not at that end of the trajectory.

Sea-level rise has an enormous impact on our ability to build the housing we need in Marin. and to protect the housing we already have. With 85% of our land constrained from development, available space for new housing is limited. Low-lying lands along the bay seem attractive – they’re less expensive to purchase than hillside or urban sites, have access to the highway and near bay views — but they are most at risk from sea-level rise.

Marin is already experiencing flooding related to sea-level rise, most noticeably in the Canal  and Marin City. Flood insurance – mandatory for financing development in flood zones designated by the Federal Emergency Management Agency – is increasingly expensive or difficult to get. This means developers will have to pay very high premiums, self-insure or go without.

In the immediate term, local agencies and community groups are training Marin County residents to prepare for a flood emergency, from assembling go-bags to seeking higher ground.

There are a number of long-term solutions being evaluated throughout Marin right now. These vary dramatically on price, environmental impact and extent of protection.

Some rely on massive engineered barriers like levees, seawalls and tidal gates as seen at Maeslantkering in the Netherlands, but these are enormously expensive, environmentally damaging and risk catastrophic failure.

Others create natural barriers by restoring wetlands and beaches, which absorb floodwaters and adapt as seas rise, though they take years and lots of horizontal space to establish.

Still others are “going up,” raising buildings and infrastructure or using floating buildings, like Sausalito’s houseboats. This allows housing and neighborhoods to remain in a flood zone and adapt to rising sea levels. But it requires a lot of coordination between individual property owners and the government. This is most practical on the bay, where wave action is negligible.

Managed retreat is moving away from the vulnerable area and working with local jurisdictions to “trade” vulnerable land for higher ground elsewhere. This is the most permanent solution for housing relative to sea-level rise and frees vulnerable areas for environmental wetland restoration and human recreation. Politically, this is extremely difficult. It needs to be managed on a neighborhood scale to preserve communities, and it requires a willingness to provide alternative land.

Of course, there is always the option of doing nothing. This saves money in the short term, but leads to unmanaged retreat in areas of rise. It also means communities are splintered as residents search for housing. Additionally, property owners suffer as their properties become losses and they become responsible for environmental clean up of contamination created by toxic materials.

The best outcomes will be achieved through a mix of strategies supported by the community. The most important aspect is to chart a path proactively, rather than reacting when disasters strike. This will require great political will by our residents. Most importantly, we need to acknowledge reality and start advocating for change now. This includes voting for elected officials who are honest about sea-level rise, and advocating for major reductions in fossil fuel extraction and emissions.

Many Californians believe that the federal government will come in and save our coastal communities. Unfortunately, the cost, controversy and current administration make this extremely unlikely. Find out what your town, city or county is doing to prepare for sea-level rise and get involved in the solution. The choices we make now in city council and county planning meetings, as well as at the ballot box, will determine whether Marin families can live safely here for generations to come.

San Rafael residents Gail Napell and Diana Benitez are board members for the Marin Environmental Housing Collaborative group.