UC Santa Cruz researchers value salt marsh restoration as a crucial tool in flood risk reduction and climate resilience in the San Francisco Bay

UNIVERSITY OF CALIFORNIA - SANTA CRUZ

Salt marsh restoration can mitigate flood risk and bolster community resilience to climate change in our local waterways, according to a recent study published in Nature by a postdoctoral fellow with UC Santa Cruz’s Center for Coastal Climate Resilience (CCCR). 

The study, titled “The value of marsh restoration for flood risk reduction in an urban estuary,” explores the social and economic advantages of marsh restoration amidst the growing threats of sea level rise and storm-driven flooding. Climate change will put many communities at risk. In California, some of the study co-authors from the U.S. Geological Survey (USGS) have shown that 675,000 people and $250 billion in property are at risk of flooding in a scenario with 2 m of sea level rise combined with a 100-year storm. Flooding due to sea-level rise is amplified by storms, which drive higher coastal water levels via surges, waves, and increased river discharge, along with increasing coastal population density. 

To simulate marsh restoration, the research team used a hydrodynamic model of San Francisco Bay, focusing on San Mateo County, the county most vulnerable to future flooding in California. The team ran computer simulations of the county’s shoreline during storms, with and without marsh restoration, and worked closely with local flood managers and planners to incorporate their input into the model. 

“The Bay Area is low-lying and densely populated, thus at significant risk for future climate change impacts, and home to really large areas of degraded habitat. We have found compelling evidence that marsh restoration can reduce flood risk to people and property locally, providing both community and ecosystem co-benefits,” said CCCR fellow Rae Taylor-Burns, whose research also appears in a Springer Nature blog. 

Key findings from the study include:

• Identification of priority areas in San Mateo County for salt marsh restoration to maximize socio-economic impacts in reducing flood risk. 
• Development of a detailed flood model to evaluate the risk of flooding with and without salt marshes locally, aiding in the planning and design of restoration projects.
• The monetization of flood risk reduction benefits to identify cost-effective investments in marsh restoration, potentially attracting public and private funding.

The study underscores the broader implications of wetland restoration beyond flood protection, including carbon sequestration, habitat preservation, and recreational opportunities. It also makes the case for investments in nature-based solutions and community resilience that can help lessen future climate change impacts. 

Researchers show the benefits of integrating salt marsh restoration into comprehensive climate resilience strategies in San Mateo County and estuaries worldwide that are facing similar threats. This could include funding from FEMA grant programs or Regional Measure AA, which provides approximately $500 million for marsh restoration throughout the San Francisco Bay. This work also supports identifying CA coastal wetlands as critical national infrastructure, as the Center has helped support coral reefs in Guam, Hawai’i, Puerto Rico, and the U.S. Virgin Islands.

“As we confront the escalating challenges posed by climate change, it is imperative that we explore innovative solutions to enhance community resilience," said Michael W. Beck, director of the Center for Coastal Climate Resilience and a co-author of the study. “Salt marsh restoration represents a nature-based approach that can complement traditional infrastructure and safeguard our coastal communities."

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JOURNAL

Nature

METHOD OF RESEARCH

Meta-analysis

ARTICLE TITLE

The value of marsh restoration for flood risk reduction in an urban estuary

 

NSF grant awarded to manage salt contamination of tidal river water supplies

PENN STATE

UNIVERSITY PARK, Pa. — Salt contamination of water supplies in tidal rivers is a growing problem around the world, threatening the safe drinking water of billions of people, according to researchers at Penn State. Those researchers are part of a multi-institution team of scientists and engineers who were recently awarded $650,000 in funding from the U.S. National Science Foundation (NSF) to develop tools to help monitor and manage decision-making to address this critical issue.

Raymond Najjar, professor of oceanography and one of the co-principal investigators, said the team will develop a new coupled watershed-estuary model that simulates the transport and fate of major salt ions by leveraging recent advances in hydrological and estuarine modeling. They plan to use the Chesapeake Bay and its tidal rivers as a pilot study site to better understand the saltwater intrusion process.

“It's unusual to have watershed and estuary models coupled in real time,” Najjar said. “It's not unusual to simulate the conditions of the estuary, given the output of a hydrological model or using observed data like streamflow, but it is unusual to link and run the models together.”

The project was one of 15 multidisciplinary teams selected for Phase 1 of the NSF Convergence Accelerator program's Track K: Equitable Water Solutions. The Convergence Accelerator program builds upon NSF's investment in basic research and discovery to accelerate solutions toward societal and economic impact. The Penn State team also includes Alfonso Mejia, associate professor of civil and environmental engineering and co-principal investigator, and Antonia Hadjimichael, assistant professor of geosciences.

About 70% of the U.S. drinking water supply comes from surface waters, including tidal rivers, which are the tidal fresh region of estuaries. Drought and sea level rise, which lead to saltwater intrusion from the ocean, and changes in land-use, which lead to freshwater salinization, are putting water resources at risk. The risk extends to water uses for thermoelectric power, irrigation and industrial production, according to the researchers.

“Saltwater contamination has been discussed a lot in regard to groundwater but what’s novel about this project is that it is addressing surface water contamination,” Najjar said. “It is an issue that’s coming from two different directions. It can come from ocean saltwater making its way up the estuary, like it does under drought conditions when freshwater flow is low or from predicted sea level rise. It can also come from freshwater sources, like when road salt makes its way into streams and rivers. That is the reason for trying to couple these two modeling systems.”

Many water suppliers do not have the necessary planning and technical capacity to prepare for these changes. This project proposes to develop and prototype decision support and monitoring tools for salinity management through co-production with water resource managers, under-resourced rural communities and water suppliers.

“Both developed and developing countries are struggling with salt contamination of tidal river waters, and many rely on numerical models to manage salinity,” said Ming Li, project lead and professor at University of Maryland’s Center for Environmental Science. “These new tools will be applicable to numerous systems around the globe.”

The model will be used in combination with artificial intelligence algorithms to quantify the tradeoffs between competing needs for freshwater resources. This approach will also be used to search for long-term planning strategies to help communities adapt to increased salinization.

Najjar said another novelty is that the team is going to simulate individual ions as opposed to only bulk salinity.

“In ocean models, the salinity is just predicted as the total amount of dissolved ions,” Najjar said. “The model doesn't distinguish whether the ions are sodium, chlorine, potassium, sulfate and so forth. The mix of ions in seawater is relatively constant but those ratios are different than they are in the rivers. So, we're going to be looking at trying to model individual ions and that's something new as well.”

Other co-principal investigators are Sujay Kaushal from the University of Maryland and Allison Lassiter from the University of Pennsylvania. Additional institutions contributing to this effort include the Salisbury University, Rutgers University, Izaak Walton League of America, Maryland Department of the Environment, Maryland Department of Planning, Maryland Geological Survey, Metropolitan Washington Council, Interstate Commission on the Potomac River Basin, Susquehanna River Basin Commission, Delaware River Basin Commission, EPA Chesapeake Bay Program and Maryland Sea Grant.