The San Mateo County Flood and Sea Level Rise Resiliency District, known as OneShoreline, is an independent government agency working throughout the county to make our communities more resilient to the climate change-related impacts of sea level rise, flooding, and coastal erosion. With start-up funding from the County and 20 incorporated cities within it, OneShoreline provides a unified vision and voice to plan for the future. And OneShoreline goes beyond planning; it is securing funding for and will build projects that protect us, enhance our environment, and create recreational opportunities.

San Mateo County includes urban, suburban, and rural areas within its approximately 750 square miles on the San Francisco Peninsula. Due to the intensity of development in low-lying areas close to (or in some cases, below) sea level, the county faces serious flood risk from storm events and high tides — a problem that is accelerating with sea level rise.  According to the County’s Sea Level Rise Vulnerability Assessment, located within the current FEMA 100-year floodplain (i.e. without future sea level rise) are over 4,200 acres of urbanized or industrial lands and 4,800 acres of natural lands; with 3 meters of future sea level rise, the number of urban acres increases by a factor of ten. 

In terms of financial losses along the shoreline due to climate change, San Mateo County is the most vulnerable county in California — by 2100, it is estimated that over 40% of our land could be adversely affected by these issues. This challenge acts irrespective of jurisdictional boundaries, and far exceeds the capabilities of a single agency to face alone. By working together through OneShoreline, local governments, residents, and businesses can integrate their planning, design, permitting, and project implementation to create a resilient San Mateo County to head off the increasing impacts of climate change.

The work to plan, design, permit, fund, and construct complex cross-jurisdictional projects that protect and enhance our communities takes years.  Climate change is not waiting for our local, state, or federal governments to take these actions, and experience has shown that the cost of these projects increases beyond the rate of inflation. Plus, we know that when it comes to disasters, a proactive approach saves lives and money – every $1 spent on mitigation saves an average of $6 in future disaster costs. Thus, the time to move forward with building resilience is now. 

OneShoreline is engaged in various types of projects:  projects resulting from MOU’s involving cities and San Mateo County, new projects with these types of entities that are being developed right now, and long-standing efforts related to the flood zones established by the County that are now the responsibility of the District. You can learn more about our work on our Current Projects page.

Only stormwater is allowed to enter the storm drain system. Potential pollutants and other materials such as washwaters, sewage, automotive fluids, construction materials, paint, sediment, silt, and food wastes are not allowed to enter the storm drain system. Reporting incidents of water pollution problems such as illegal dumping, spills or illicit discharges helps keep our local creeks, San Francisco Bay, and the Pacific Ocean clean.

When to make a report:

• When you find dumped waste in or near the storm drain
• When you notice unusual odors in or near the storm drain
• When the drainage system has unusually large flows during dry periods
• When you see someone illegally dumping anything into a storm drain

How to make a report:

• For direct discharges to Colma Creek, San Bruno Creek, or San Francisquito Creek: OneShoreline, info@oneshoreline.org, 650-844-8310
• In unincorporated areas of San Mateo County: Sustainability Department, sustainability@smcgov.org, 1-888-442-2666
• In cities or towns in San Mateo County, contact the appropriate illicit discharge coordinator from the list found here: flowstobay.org/reportpollution