Seas are rising around us. Where should we build housing?
SHOULD WE BUILD HOUSING ON UNDERUTILIZED, LOW-LYING SITES NEAR THE COAST The issue, potential solutions, what we can do now. — Written by MEHC Board Members Diana Benitez and Gail Napell.
THE ISSUE: Sea level is rising
It’s undeniable: the sea is rising around us. Every property near and on the shoreline — private or public, every development, our public infrastructure and utilities (think landfill, sanitation plant, roadway, water or electricity facility of any kind) — is under threat. So is the housing that we have built along our shores or in low-lying areas. And of course, the people who live in that housing are vulnerable too.
Sea level rise has an enormous impact on our ability to build more housing in Marin – and to protect the housing we already have. Available space for new housing in Marin is notably constrained. Almost 85% of our land area is protected from development as designated open space, federal parkland or protected watershed, or is limited to agricultural use. And, as to the remaining 15%, our County has a long history of residents opposing multi-unit and affordable housing. We’ve recently begun to understand that if we can’t provide housing for the lower- and middle-income residents who work here, they will eventually move – and work – somewhere else. These are the mechanics who repair our cars, the teachers who educate our children, the caregivers who assist our elderly residents, the medical technicians who support our doctors, the chefs and servers and dishwashers who make it possible for us to dine out.
Sea level along the Pacific Ocean Coast and Bay is predicted to rise between 3 and 10 feet by 2100. The wide range is based on a variety of climate change scenarios, from the optimistic (i.e., the world immediately stops producing fossil fuels and emitting greenhouse gases – 3 feet) to the pessimistic (i.e., we continue on our current emissions trajectory – 10 feet or more). There’s still low-lying land and marshland in Marin County, primarily on the Bay side, that’s undeveloped or previously developed with former uses no longer in play. These low-lying sites are attractive as they’re often less expensive than hillside / urban sites, have access to 101, and are near the water with Bay views.
HOWEVER – Existing housing along the Bay is already experiencing sea level rise, most noticeably in San Rafael’s Canal District and Marin City. Low-lying areas present challenges to any building development and housing is no exception.
- Areas within 100 feet of the Bay Shoreline are under the jurisdiction of the San Francisco Bay Conservation and Development Commission (BCDC). New development and renovations within this band are limited, when permitted at all. And, the shoreline is increasingly moving as mean sea level rises. Flood insurance is increasingly expensive or nearly impossible to get, especially in these /areas that are clearly at risk from sea level rise. This means that builders and owners will have to pay very high premiums, self-insure or go without. Flood insurance is mandatory if a structure to be financed is located in a FEMA-designated flood hazard area. Banks and mortgage lenders require insurance before issuing loans, and may call a loan if a property becomes uninsured.
- Check sea level rise in your community! The State of California has an excellent, science-based, free sea level rise viewer with which anyone can establish the likelihood and approximate amount of sea level rise at any site along the Bay and Pacific Ocean coast.
Possible solutions
There are several ways to respond to sea level rise at existing housing or to build housing in flood-prone areas. They all come with trade-offs, and none of them are free. The National Institute of Building Science has collected data which shows that each dollar spent on anticipatory disaster mitigation (such as flood) saves $6 — $31 dollars in recovery cost. This is an impressive return on investment.
IMMEDIATE | Emergency Preparedness
Multiple local agencies and residents are training Marin County residents how to prepare for a flood emergency, from preparing go-bags to seeking higher ground.
There is still more work to be done as can be seen in the Canal, where residents would like more detailed evacuation plans, training and materials in multiple languages to be prepared for the next big flood.
LONG TERM | Hard engineered barriers
1. Berms and levees (often built at the individual property scale).
2. Sea walls (typically built for multiple properties, neighborhoods, even cities)
3. Tidal gates
PROS AND CONS
Pros: These barriers can protect entire neighborhoods or even regions, as in the Maeslantkering storm surge barrier in the Netherlands.
Cons: Extremely expensive to build. Planning approvals can take years (even decades) if they touch private property. Effective levees and sea walls obstruct water views, which are often treasured by property owners. And these barriers do not adapt easily if the sea level rises beyond the fixed level used for design and construction. Failures are often catastrophic.
NATURAL BARRIERS
1. Wetlands, wetlands restoration
2. Horizontal levees, South Bay
3. Oyster beds, Billion Oyster Project (New York)
4. Beach nourishment, Ocean Beach, Army Corps of Engineers
PROS AND CONS
Pros: These barriers can protect entire neighborhoods or regions. They buffer wave action. They are adaptable to continued sea level rise, and are environmentally restorative.
Cons: Expensive, take up a lot of horizontal space, and can take many years to build.
ELEVATING THE HOUSING, or elevating the housing and the infrastructure around it.
This can be fixed height elevation (pilings and columns sunk into the water and down to rock), floating buildings and/or infrastructure, or amphibiation.
PROS AND CONS
Pros: Allows housing and neighborhoods to remain in a flood zone; floating and amphibiated housing adapts virtually infinitely to sea level rise, can be done by individual property owners; acknowledges that the water will do what it’s going to do anyway
Cons: Challenging on the ocean coast where wave action is intense; to keep neighborhoods intact, infrastructure must also be elevated or floated. Expensive and requires individual property owners to raise funds.
MANAGED RETREAT
This means planning to move away from the vulnerable area and working with local jurisdictions to ‘trade’ vulnerable land for higher ground elsewhere in the jurisdiction.
PROS AND CONS
Pros: Safest, most permanent solution for housing relative to sea level rise; acknowledges that the water will do what it’s going to do anyway; can free up wetland area for environmental restoration and human recreation.
Cons: Politically this is wildly unpopular; needs to be done on a neighborhood scale to preserve community integrity; requires significant jurisdictional resources to provide the alternate land to address displacement and deconstruct structures that will cause contamination when the water reaches them. This impacts social cohesion and sense of community when communities need to leave.
DO-NOTHING OPTION: PROS AND CONS
Pros: Little immediate costs while there is no flooding.
Cons: This will lead to unmanaged retreat (abandonment) for most structures in sea level rise areas. Renters will be severely impacted first, as they search for alternate housing in an already limited, expensive market. Property owners will be severely impacted as their properties become losses and they will be responsible for environmental clean up of contamination created by toxic materials in the rising water. This creates trauma for residents and the jurisdictions.
MOST REALISTIC APPROACH — A MIX OF STRATEGIES
Example: Provide immediate short-term protection such as sandbags, build out coastal wetlands to buffer storm surge, and plan for long-term more costly solutions such as managed retreat or a seawall.
Pros: Mixed strategies meet us where we are. They engage us in the actions we can take immediately, and bring communities together to dialogue and plan for the long term.
Cons: Our society is notoriously reluctant to plan for the long term. Community cooperation and action are essential. Rugged individualism doesn’t work for this issue.
WHAT CAN YOU DO?
AS AN INDIVIDUAL – Take action where you have agency.
- Find out if your apartment / home is in an area threatened by sea level rise within the timeframe you expect to live there. (Our Coast Our Future Hazard Map)
- Find out what your town, city or county is doing to prepare for sea level rise and get involved. Comment on your local government’s plans – or lack of plans – and share ideas with your elected officials. It will take all of us to figure this out.
- Advocate for reductions in fossil fuel use and greenhouse gas emissions at all levels – locally, regionally, nationally, globally, at governmental, commercial, and personal levels.
- Vote for elected officials who are honest about sea level rise and its impacts on our community: who seek out and support science-based information with voice, vote and budget; and who don’t attempt to placate voters with false promises and distractions. Listen to them when they share hard truths; don’t shout them down for being honest.
AS A PROPERTY OWNER
- Talk with your insurance agent about flood insurance. There may be improvements you can make to your building that will reduce premiums or make it insurable if it isn’t currently. Make any flood-resistance improvements you can afford, now, to your property.
- Talk with your neighbors. You may be able to work with them to adapt your neighborhood together.
- Be involved with your local Chamber of Commerce and government.
- Advocate for reductions in fossil fuel use and greenhouse gas emissions at all levels – governmental, commercial, and personal.
- Periodically check on potential grants or loans for sea level rise adaptation.
All of us need to acknowledge the reality — and the immediacy — of our situation.
A common misconception is that the State of California and/or the Federal Government will build sea walls to protect all the low-lying areas in Marin County. However, the price tag for sea walls is extremely high ($1.2 billion is estimated for Stinson Beach alone). The current federal administration is cutting unspent funds, even those already committed, from the Inflation Reduction Act, which had millions of dollars earmarked for resilience measures such as sea level rise adaptation. Our State has a serious budget shortfall.
Kicking the can down the road is only making the problem worse, and could lead to catastrophic damage and loss of life.
| E N D N OT E S |
| visitmarin.org Intergovernmental Government Panel on Climate Change Summary for Policymakers, p.13 Knee Deep Times KQED BCDC FEMA maps do not take sea level rise into account, and may not show these sites as being in flood zones. Also, flood insurance is mandatory if a structure to be financed is located in a FEMA-designated flood hazard area. Our Coast Our Future Hazard Map US Army Corps of Engineers UN Environment Program Holland.com Coastal Care |
You can be a part of MEHC’s important work by reading & sharing our monthly PERSPECTIVE newsletters, joining our weekly COMING UP IN HOUSING email list (signup here>>), participating in our advocacy campaigns, and also, if you can, by donating >> to help defray our expenses. Thank you.
