Why is this Important?

SMC’s location as a coastal county exposes it to high risk of inundation. The recent incidences of deadly wildfires that continue to grow in intensity and frequency have also impacted huge populations in SMC. The report highlights some of the key long-term climate-change risks as well as public agencies that have come together to respond to them.

Risks and exposures caused or aggravated by climate change

Wildfires: Factors that exacerbate the risk of wildfires include lower precipitation levels, high temperatures, drying out of vegetation, and anthropogenic factors such as construction near high-risk areas, negligent behavior during campfires, and ignorance of fire prevention and preparation measures.[1]. California Department of Forestry and Fire Protection (CAL FIRE) has created Fire Hazard Severity Zones (FHSZs) in San Mateo County to identify vulnerable areas based on factors such as terrain, weather, fuel (vegetation), and fire history and can be found here.


Flooding/ innundation in low-lying areas due to sea-level rise and storm surges/ extreme tides

The SMC bay shoreline comprises features such as natural tidal marshes, mudflats, a network of non-engineered berms, engineered flood protection structures (e.g., levees and floodwalls) and engineered shoreline protection features (e.g., bulkheads, revetments, and rip-rap). They all serve as the first line of defense to flooding risks and protect the densely built inland areas from coastal hazards. To read the full range of multiple sea-level-rise scenarios, inundation risks, and adaptation strategies, check here.


Figure: Shoreline cross-section showing permanent inundation and temporary flooding.

Source: Report on Sea Level Rise & Overtopping Analysis for San Mateo County’s Bayshore, accessed here.

Costal erosion due to water inundation and human activities will disrupt natural sediment deposits and disturb ecosystems that serve as a natural barrier to such erosion. Responses to coastal erosion vary from expensive and less sustainable hard structural protection measures like building seawalls and levees to natural and more sustainable habitat restoration measures, known as green infrastructure. Green infrastructure uses vegetation, soils, and other elements and practices to restore some of the natural processes required to manage water and create healthier urban environments. At the city or county level, green infrastructure is a patchwork of natural areas that provides habitat, flood protection, cleaner air, and cleaner water. To understand more about coastal changes due to sea level rise, please read here.

Saline water inundation due to sea level rise and groundwater over-exploitation may also result in saltwater intrusion contaminating the drinking-water sources and may threaten freshwater supplies in SMC, which relies on groundwater for about 40% of its total water supply. To know more about groundwater sources in SMC, please read here.

Stakeholders doing long-term planning for emergency preparedness should consider shifting demographics, the economic costs and response capacity associated with social inequities, health care affordability, and inflated food and water prices ensuing from extreme weather events. They should integrate focused risk-reduction strategies and resilience building efforts for socially vulnerable populations into comprehensive planned responses for a more equitable outcome. For more information on SMC’s hazard vulnerability assessment and emergency response plan, read here. An online and publicly available tool is Climate Central’s Surging Seas Risk Finder that provides downloadable tables and figures by zip codes/areas to map SLR and helps determine exposure along with providing insights on how to respond to risks.

In response to SMC’s exposure to SLR and its long term impacts, SMC and 20 cities are forming a Flood and Sea Level Rise Resiliency Agency to create multi-jurisdictional solutions, avoid duplication of efforts, and create a unified voice that will better position the county and its cities to obtain state and federal funds for shoreline protection from SLR. This new agency will consolidate the work of the SMC Flood Control District (FCD) and Flood Resiliency Program (FRP) through integrated regional planning, project implementation, and long-term maintenance. More information can be found here.

Exposure to hazards such as wildfires and sea level rise will greatly impact SMC’s infrastructure and built environment such as transportation networks, energy systems etc. Sea level rise will impact 6% of rail stations, 20% of highways and local roads, the SFO and San Carlos airports, and the Port of Redwood City in SMC.[2] Floods, landslides, and other natural disasters can lead to infrastructure damages that may result in loss of accessibility by communities that could become isolated. Emergency officials may find it difficult in these situations to reach out to help those in need. Along with emissions reduction, it is critical to fortify existing transportation infrastructure to adapt to these projected hazards. To know more about adaptation plans, refer to this report’s adaptation section. Read SMC’s full Hazard Mitigation Plan here.

Transportation also has significant impact on GHG emissions and air quality which is discussed in detail in the next section. Laying out infrastructure and incentives for renewable energy and energy efficiency and transitioning to clean energy can help mitigate GHG emissions.

[1] http://www.sanmateocourt.org/documents/grand_jury/2018/wildfire.pdf

[2]Sea Change San Mateo County (2019), A Prepared And Stronger Community (Vulnerability Assessment)

(jump to top of page)