When water levels start to rise in Miami, pictures and videos quickly pop up on social media of cars fording deep puddles, and tourists trying to keep their luggage dry.
A new study suggests that those posts — specifically, the tweets — could be an effective method for measuring the real-life impact of floods. It also highlights the gaps in the official government measurements for flooding, an issue that has already prompted the city of Miami to find new ways to measure flooding in the city.
The University of California Davis study found that Miami residents start to ramp up their Twitter posts about flooding long before the city hits the official measure for minor flooding, which suggests that even low levels of flooding affect day-to-day life in the city.
The analysis considered much of the U.S. coastline and found that some places, like Miami and Texas’ Gulf Coast, reacted to lower levels of flooding by tweeting more about it. In Miami, NOAA’s official standard for minor flooding is 1.3meters. This study found that Miamians start to talk much more about floods on Twitter around one meter of flooding.
Fran Moore, a professor of environmental science and policy at UCDavis and co-author of the study, said using social media gets at something that a tidal gauge doesn’t — the broader human impact of a flood.
“There may be a certain amount of inundation, but how important is that inundation? That depends on a lot of things. Does it go over a minor road, does it go over a busy road, the amount of people, time of day, is it rush hour or not?” she said.
The normal standards for what counts as flooding doesn’t quite capture the reality for residents in some coastal cities, including Miami.
Last year, NOAA released a study that said in 2018, Miami only experienced one day of high tide flooding. That was in a year where roads in Miami and Miami Beach were impassable multiple times.
The lead author said that’s because NOAA’s standard for flooding doesn’t reflect how much of Miami is low-lying and flood-prone. It’s probably also why Moore’s study found something similar, said Brian McNoldy, a University of Miami senior research scientistuninvolved with the study.
“If you’re in the lowest-lying place, that threshold is probably not tuned for you. So you may experience flooding more often,” he said.
This uncertainty is one of the reasons Miami is investing in a network of smaller flood gauges throughout the city to identify when and how often vulnerable areas flood.
Another possible finding from this data: Miamians are getting used to flooding.
“As you get more frequent floods, there’s suggestive evidence that you start to see a decline in the remarkability of a given flood,” Moore said.
In other words, when you experience flooding regularly, it stops being new or different. Like a traffic jam, it just becomes another part of life in South Florida.
“To people who don’t live around here, the fact that our streets flood once or twice a day is crazy, but we’re used to it,” McNoldy said. “It’s a big deal that our roads flood every day. It affects your life.”
Moore’s study doesn’t show this effect as clearly as her last study, where she analyzed tweets about the heat. In that analysis, it was more clear that as temperatures are getting hotter, people are less likely to tweet about how hot it is because they’re used to it.
In this flooding study, Moore said, it’s hard to tell whether people tweet less about flooding because they’re used to it or because of the hundreds of millions of dollars some South Florida cities are spending to keep communities dry.
What is clear is that the sea is rising. South Florida has seen about eight inches of sea rise since the 1990s. McNoldy found that in the last five years, the annual King Tides have started to surpass even some of the most dramatic floods in Miami’s past.
“The high water marks that we used to only experience with passing hurricanes we’re now seeing comparable water levels just during the highest of high tides,” he said. “That’s pretty crazy.”
The study did have limitations. The researchers only looked at tweets in English, not Spanish or Haitian Creole, so it doesn’t account for all of Miami’s population. And few people use Twitter regularly. A Pew study found only 22 percent of Americans have a Twitter account, and of those users, 10 percent write 80 percent of tweets.
This story was produced by the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the Sun-Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.