Sea Level Rise

In addition to the flooding risk to many of our communities, our networked infrastructure is also at risk. Sea level rise is expected to affect us all through impacts to roads and highways, electric substations, and wastewater treatment plants that are essential to day-to-day community and economic functions. For example, a flooded highway, wastewater treatment plant or electrical substation could temporarily shut-down businesses, close roads and lead to many community-wide disruptions. By working together, we can protect our communities’ many assets, including neighborhoods, businesses, parks and beaches – places we all love.

STUDY AREA: from the southern edge of Half Moon Bay to the county line south of Pescadero

The SMC South Coast is known for its iconic beaches, agricultural areas, and small coastal communities. Many of these areas, including Coastside beaches and bluffs, roads, agricultural land, businesses and residences are already at risk from flooding and erosion, and these impacts will get worse as sea level continues to rise. Our communities need to know what to expect and what we need to start doing today to protect ourselves from these impacts.

This study evaluates the impacts of sea level rise on the South Coast right now, at .8 feet, at 1.4 feet and at 4.9 feet. The vulnerability assessment provides projections of the extent of coastal hazards and of the physical and economic impacts to community assets like buildings, roads, farmland, and coastal access infrastructure. Learn more in the Executive Summary (PDF) and the full report (PDF) or browse our interactive maps in English and Spanish to learn more about the study findings.

• Protecting the South Coast from Sea Level Rise Story Map
• Protegiendo La Costa Sur del Aumento del Nivel del Mar

STUDY AREA: the San Mateo County coast and bay shorelines except for the south coast

Understanding how sea level rise will affect San Mateo County residents, businesses, and the services and infrastructure we all rely on is a crucial step in building prepared, healthy and safe communities. Sea level rise could affect a wide array of communities, critical facilities, energy networks, transportation systems, flood protection infrastructure, natural and recreational areas, wastewater and stormwater systems, and solid waste facilities. While the changing climate and rising seas pose many risks to people and places in San Mateo County, we can plan ahead to create resilient communities and ecosystems. 

Learn more in the 2018 San Mateo County Sea Level Rise Vulnerability Assessment (PDF) full report (appendices below) or browse the Highlights Brochure (PDF).

There are many strategies available to address the challenges of sea level rise. San Mateo County Sea Level Rise Vulnerability Assessments have identified three key categories of adaptation strategies: (1) emergency preparedness and resilience efforts, (2) shoreline and site-specific strategies, and (3) policies, plans and procedure updates to address sea level rise. 

• Adopt new development standards and ordinances for at risk areas.
• Utilize nature-based solutions, including vegetated, permeable, and tree-covered surfaces, water detention systems and habitat restoration.
• Update building design standards and codes to incorporate flood risk best practices.
• Implement protection or accommodation approaches that attempt to stop erosion or flooding.
• Consider managed retreat or hazard avoidance, which relocates or realigns potentially vulnerable infrastructure.

The San Mateo County Flood and Sea Level Rise Resiliency District (“OneShoreline”) began operating in 2020 to coordinate countywide efforts to combat the harms of sea level rise caused by climate change. OneShoreline provides expertise in the complex process of designing and building for sea level rise, working with cities and developers to build resilience through planning and coordinating multi-jurisdictional flood mitigation projects. Learn more about OneShoreline.

In 2019, the Board of Supervisors approved a Sea Level Rise Policy for County-Owned Assets. The Policy requires that sea level rise is considered in all County-owned and operated assets, design and construction projects, leases, and property acquisitions and dispositions. The intent of this policy is to understand the vulnerability of County-owned property and assets over their life cycle; develop an incremental approach to adaptation based on the current and future level of risk; and coordinate with other communities on developing regional solutions.

Learn more through the 2019 San Mateo County Sea Level Rise Policy for County-Owned Assets (PDF) and Implementation Plan (PDF).