The County Sea Level Rise Vulnerability Assessment highlights San Mateo County as the most vulnerable county in California to sea level rise in terms of property value at risk. The assessment identified 43 County-owned facilities are at risk from 3.3 feet of sea level rise, projected to occur by 2070. Fifty facilities are at risk from 6.6 feet of sea level rise, projected to occur by 2100 under the medium-high risk projections.
Sea level rise impacts include flooding, stronger waves, rising groundwater tables and saltwater intrusion, and increased erosion of the shoreline; all of which are exacerbated by coastal storms. In addition, high water levels can prevent water from draining to the bay or ocean, which can cause flooding, further inland far from the shore.
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.
These projects must also consider local and regional sea level rise adaptation and flood mitigation projects that could reduce impacts on County-owned assets prior to developing plans to modify existing facilities.
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.
Sea Level Rise Policy Implementation Plan
In 2018 and 2019, the Office of Sustainability held focus groups meetings with County Departments to provide information on the science of sea level rise, discuss potential impacts to County assets, and to develop relevant policy language.
Implementation of this policy is expected to increase the useful life of County facilities; protect residents and staff today and assure County operations will be continuous; reduce the current and future risks from sea level rise and flooding; reduce liability; and reduce insurance premiums and impacts to property value. 
Based on this policy, all new facility projects funded by the County shall be sited, designed, constructed, and adaptively managed to minimize sea level rise risks over the life of the project. Following a baseline assessment of sea level rise vulnerability, existing facilities and properties will be subject to this policy during the Capital Improvement Planning or acquisition process, if major renovations or replacement of existing facilities and infrastructure are located in areas at risk from sea level rise beyond what will be protected through local or regional planned sea level rise adaptation projects.
Click here to download the San Mateo County Sea Level Rise Policy for County-Owned Assets and Implementation Plan.