Image credit: Matt Rath/Chesapeake Bay Program
For all the headlines it generates, climate change can still feel to many like a vague and distant threat, if not an outright straw man. Coastal communities, however, rarely enjoy such an advantage.
A new study published Feb. 15 in the journal Science Advances, measures the financial cost of sea level rise for businesses in coastal communities. Stanford graduate student Miyuki Hino and her colleagues found that downtown Annapolis, Maryland’s state capital, suffered a loss of 3,000 visits in 2017 due to high-tide flooding, which equates to a loss of somewhere between $86,000 and $172,000 in revenue.
Also known as nuisance, or sunny day flooding, high-tide flooding occurs when tidal waters rise above the levels that coastal infrastructure was designed for. Far from the extreme events that win screen time during hurricane season, high-tide flooding does its damage by filling streets and parking lots, preventing normal foot and vehicle traffic.
Previously uncommon, high-tide flooding has become an increasingly costly nuisance as sea levels continue their slow rise. A previous study, which the Stanford group used as a reference in their own, showed that the amount of time that water spends at nuisance flood levels has increased substantially over time. Measuring 27 locations across the U.S., the number of high-tide flooding days rose from an average of 2.1 days per year in the late 1950s to 11.8 during 2006–10.
The Stanford study focused on Annapolis, which had exceeded its own high-tide threshold 63 times in 2017. The group estimated the lost revenue from flooding using data from parking meters, satellite imagery, interviews, dated photographs and social media. Critically, they found no evidence to suggest that would-be customers returned to businesses after the floods subsided.
The group found that losses to the City Dock area businesses due to flooding in 2017 amounted to slightly less than 2% of annual visitors, but warn that things could get much worse as sea levels continue to rise. The study projects that a further 3 inches (7-8cm) of sea level rise would mean an estimated 4% loss of visitors and that a 1ft/30cm rise would reduce visits by a further 24%, translating to hundreds of thousands of dollars of lost revenue.
The authors point out that lost revenue from disrupted business visits is only one measure of the impact of high-tide flooding. This study did not take into account increased travel time due to road closures, missed work hours, or damage to cars, roadways, or other infrastructure.
In the words of Katharine Mach, the director of the Stanford Environment Assessment Facility and a co-author on the study: “What we’re finding is something many local leaders in coastal cities already know: the waters are rising up and surging into daily life. So are the costs,” Mach said. “Understanding the impacts for people today – at large and small scale – is an essential starting point for making smart adjustments to the risks.”