South SFV Today

Rising seas and extreme storms fueled by climate change are generating more frequent and severe floods in cities along rivers and coasts. Aging infrastructure is often ill-equipped to handle these new realities, leading to uneven distribution of benefits when governments and planners attempt to improve flood resilience.

Researchers from Stanford University and the University of Florida have developed a new modeling approach that allows planners to simulate future flood risks at the neighborhood level under conditions expected with climate change, such as extreme rainstorms coinciding with high tides elevated by rising sea levels. This method, described on May 28 in Environmental Research Letters, identifies areas where elevated risk may be invisible using conventional models that assess future risks based on data from a single past flood event.

“Asking these models to quantify the distribution of risk along a river for different climate scenarios is kind of like asking a microwave to cook a sophisticated souffle. It’s just not going to go well,” said Jenny Suckale, an associate professor of geophysics at the Stanford Doerr School of Sustainability. “We don’t know how the risk is distributed, and we don’t look at who benefits, to which degree.”

The new approach aims to help city and regional planners create better flood risk assessments while avoiding new inequities. The algorithm is publicly available for other researchers to adapt.

This study was developed through collaboration with regional planners and residents in bayside cities including East Palo Alto, which faces rising flood risks from both the San Francisco Bay and an urban river known as San Francisquito Creek. The creek has a history of destructive floods; notably, a 1998 flood inundated 1,700 properties causing over $40 million in damages.

Suckale began considering how science could inform future flood mitigation efforts around urban rivers like San Francisquito when she taught a course focused on equity, resilience, and sustainability in urban areas. Around this time, the San Francisquito Creek Joint Powers Authority had plans to redesign a bridge to prevent flooding but faced concerns from East Palo Alto officials about potential downstream impacts.

Suckale realized that determining how proposed designs would affect flood risk distribution could guide decisions protecting all neighborhoods equitably. “It’s actionable science, not just science for science’s sake,” she said.

The Joint Powers Authority had used a commonly employed hydrological model but found it inadequate for addressing concerns about downstream risks raised by East Palo Alto staff. Katy Serafin created an algorithm simulating millions of combinations of factors contributing to flood risk over coming decades due to climate change.

Serafin's algorithm was incorporated into the standard model to compute statistical likelihoods of flooding at various locations along San Francisquito Creek. Results were overlaid with household income data and social vulnerability indices revealing that while upstream bridge redesign would protect against another 1998-like event, it left hundreds of low-income households exposed as severe weather becomes more common due to climate change.

Sharing their findings with community collaborators highlighted that conventional models weren’t wrong but weren't designed for equity considerations. The results informed expanded infrastructure plans including permanent floodwalls beside the creek in East Palo Alto.

Ruben Abrica emphasized collaboration among researchers, planners, city staff, and policymakers is essential: “carry out projects that don’t put some people in more danger than others.”

The research underscores mutual respect between scientists and communities as critical for creating transparent decisions fair across different communities involved.

Co-authors include Derek Ouyang from Stanford's RegLab; Jeffrey Koseff from Stanford's School of Engineering; supported by Stanford’s Bill Lane Center for the American West under the Future Bay Initiative aiming for equitable urban futures.