Sea Levels Rise and Shallow Groundwater Flooding

The San Mateo County Sea Level Rise Vulnerability Assessment identified Shallow Groundwater flooding as a critical information gap in understanding flood risk and adaptation planning. SeaChange SMC is working with scientists and Bay area municipalities to address this gap.

Coastal communities throughout California are actively planning for coastal impacts from climate change. Many impacts, such as sea level rise, storm surges, shoreline change and bluff erosion, have a comprehensive suite of scientific information that can help communities plan. Accordingly, many communities have completed vulnerability assessments and have begun identifying adaptation strategies to plan for this overland flooding. However, emerging research indicates that sea level rise, in addition to its potential to increase overland flooding, can also lead to rising shallow groundwater tables and lead to flooding hazards where we might not expect them.

Bay Area Groundwater and Sea Level Rise Workshop

In recognition of the growing body of scientific study and interest by coastal communities, the County of San Mateo (SMC), the US Geological Survey (USGS), Silvestrum, and the SF Bay Conservation and Development Commission (BCDC) convened a workshop on November 13, 2019 in Oakland, CA, to discuss the importance of considering the influence of sea level rise on the shallow groundwater table, and how some Bay Area stakeholders are planning for and adapting to this threat.

Shallow Groundwater Workshop Summary

• Technical Memo – The Shallow Groundwater Layer and Sea Level Rise: Description of Approaches

Developing a Baywide Groundwater and Sea Level Rise Map and Tool

SeaChange SMC is part of a grant awarded to the San Francisco Estuary Institute by the Bay Area Council’s Climate Resilience Challenge, a new grant opportunity designed to address unmet climate change-related needs facing communities across the state.

The project will develop a series of shallow groundwater maps that consider the response to eight sea level rise scenarios (e.g., 12”, 24”, 36”, 48”, 52”, 66”, 84”, and 108”) for four of the nine Bay Area counties.

The sea level rise scenarios build upon and integrate with maps presented within the Adapting to Rising Tides (ART) Bay Shoreline Flood Explorer, which have been used extensively in the Bay Area to support local and regional adaptation planning. The sea level rise scenarios also pair with the current State guidance on sea level rise for the Bay Area.

The project will also develop guidance for how to use the future-condition shallow groundwater mapping, addressing questions such as: how to use and understand the various data layers; how to consider the uncertainties within the data layers; how to update a sea level rise vulnerability and risk assessment to consider rising groundwater levels; and how to communicate this new potential flood risk to stakeholders.

This project will enhance, advance, and support existing efforts, including the ART Program’s Regional Bay Area Vulnerability Assessment, SFEI’s Adaptation Atlas, the University of Berkeley’s rapid regional groundwater assessment, and the University of Wyoming and the USGS’s modeling and research of the response of the shallow coastal groundwater layer to sea level rise.