A new study that used social media to measure the impact of tidal flooding along the US East and Gulf coasts suggests flooding happens more frequently in some areas than current flood monitoring technologies can detect.
The study, published Tuesday in the journal Nature Communications, also finds that data from social media can help coastal communities prepare for and respond to floods.
These findings come on the heels of another study showing that sea level rise accelerated nearly everywhere along the US coastline in 2019, one likely and expected consequence of a warming climate.
How tweeting can help study floods
Coastal flooding is monitored in part by gauge stations that measure changes in the sea level, but these stations are few and far between along much of the US coast. There are just 132 stations covering the 3,700 miles along the Eastern and Gulf coastlines, according to the study.
Most gauges have three tide heights to determine minor, moderate and major flooding.
But the researchers argue these standard measures often don’t reflect the real impact of tidal flooding, even within a small geographic area. What’s considered minor flooding in one location could have major consequences in another depending on what’s lying in the water’s path.
“The same degree of inundation could have substantively different social impacts, depending on the distribution of people, infrastructure and economic activity along the coast,” the study says.
That’s where the study says social media can fill in the gaps.
By analyzing data from 473,000 tweets sent by more than 5 million Twitter users covering some 237 counties, the researchers were able to identify 22 counties where flooding has happened at tide heights lower than the areas’ existing flood thresholds.
Boston, New York and Miami are among the big cities the study identified as locations that are seeing nuisance flooding that often goes undetected by tide gauges. The study also found that much of Texas’ Gulf Coast is flooding more frequently than local tide gauges reflect.
But the authors caution that Twitter users are a relatively small portion of the general population and that Twitter data may become a less effective way to monitor flooding in the future.
As sea levels continue to rise and floods become more common, the researchers say, it’s possible people will tweet about them less as they become more accustomed to living with flooding.
Accelerating sea level rise a ‘game changer’
Meanwhile, another study recently found that sea levels along much of the US coastline rose at higher rates in 2019 than the previous year – likely driven by increasing rates of melting ice sheets and warming oceans as a result of climate change.
Researchers at William & Mary’s Virginia Institute of Marine Science studied 32 gauge stations across the country’s coastline for its yearly “report card” on sea level rise.
Of the 32 stations studied, 25 of them saw levels rise at rates higher than in 2018. The station in Rockport, Texas, saw the greatest increase in the rate of local sea level rise at 0.26 millimeters per year in 2019. At this rate, sea levels in Rockport could be 2.69 feet higher in 2050 than they were in 1992, the report said.
“Acceleration can be a game changer in terms of impacts and planning, so we really need to pay heed to these patterns,” VIMS emeritus professor John Boon said.