Mapping How Sea-Level Rise Adaptation Strategies Impact Economies, Floodwaters

“You may be protecting your immediate community, but you may be creating serious costs and damages for your neighbors,” said Robert Griffin, an economist at the Natural Capital Project and co-author on the paper. “When it comes to current sea-level rise planning, there’s some incomplete cost-benefit accounting going on.”

Griffin is also a Research Assistant Professor at the University of Massachusetts Dartmouth.

Guiding the Flood
The researchers identified places where Bay Area communities could strategically choose to guide floodwaters, rather than holding them back with walls. These strategic flood areas would act as overflow zones, absorbing the increased water and avoiding damage to communities.

One example is along the Napa-Sonoma shoreline, where Highway 37 is under threat of impending sea-level rise. Decision-makers are trying to decide how to adapt the road to prevent flooding in the future: either by building a taller embankment to raise the road or by rebuilding it as a causeway that allows water to flow between the bay and marshlands on the other side. The researchers modeled what would happen if the Napa-Sonoma shoreline were blocked by a concrete embankment and found that it would worsen flooding for almost all the Bay Area communities studied, from Martinez to San Jose. Building a causeway, on the other hand, would provide a natural absorption area for extra water to flow.

A Bay-Wide Strategy
“It’s critical to consider the regional impacts of local actions,” said Michelle Hummel, assistant professor at the University of Texas at Arlington and lead author on the paper. “Studies like ours can identify actions that will have large impacts, either positive or negative, on the rest of the bay and help to inform decisions about how to manage the shoreline.”

Not every city or county has a landscape suitable for strategic flooding, which requires wide plains or valleys where water will naturally flow. Therefore, the researchers say, it’s crucial that Bay Area communities work together to identify the places where nature-based solutions like flooding make the most sense.

The researchers also looked at demographic information in their models to better understand who would be affected by possible strategic flooding plans. They say avoiding adaptation plans that add more pressure to poor or otherwise overburdened communities – by forcing them to move or creating increased economic stress – is key.

To understand the broader impacts of climate resilience decisions, including investments in nature, the researchers plan to model how sea-level rise adaptation strategies are connected with infrastructure, employment, community dynamics and more.

“Our plans should be as interconnected as our ecosystems,” said Guerry.