Sea-level rise threatens to produce more frequent and severe flooding in coastal regions and is expected to cause trillions of dollars in damages globally if no action is taken to mitigate the issue. However, communities trying to fight sea-level rise could inadvertently make flooding worse for their neighbors, according to a new study from researchers at The University of Texas at Arlington and the Stanford Natural Capital Project published in Proceedings of the National Academy of Sciences.
Michelle Hummel, an assistant professor of civil engineering at UTA, was lead author of the report, which shows how seawalls constructed along the San Francisco Bay shoreline in California could increase flooding and incur hundreds of millions of dollars in damages for communities throughout the region. The team's findings could also be applied to other coastal regions, such as Texas' Galveston Bay and Chesapeake Bay on the East Coast.
The researchers used complex mathematical models to map how floodwaters--and the economic damages related to floods--would flow depending on where new seawalls were built. They found that blocking certain areas of the bay's shoreline would be particularly damaging to communities throughout the region.
"It's critical to consider the regional impacts of local actions," Hummel said. "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, including coordination on a regional level."
Damages to buildings and homes aren't the only losses that could result from walling shorelines--it also could cut off habitats for important bird and fish species, limit the natural area available to store carbon and create water quality issues by destroying wetlands that naturally provide water treatment.
The researchers emphasized how non-traditional approaches, like choosing to flood certain areas of land rather than build walls, can provide more sustainable solutions for the Bay Area and similar coastal bay communities.
"It's not practical to keep building taller and taller seawalls to hold back the ocean," said study co-author Anne Guerry, chief strategy officer and lead scientist at the Stanford Natural Capital Project. "Our goal was to show how the threat of sea-level rise is interconnected with the whole social-ecological system of the Bay Area. Communities need to coordinate their approaches to sea-level rise adaptation so we can find solutions that are best for the whole bay."
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 study notes that it's crucial that coastal communities work together to identify 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 that 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.
"Regional planning approaches that account for the interconnectedness of our coastal systems can improve the resilience of our communities, now and into the future," Hummel said.
- Written by Jeremy Agor, College of Engineering
Proceedings of the National Academy of Sciences