Environment: Thresholds for flooding on the US east coast assessed

The remarkability of floods, as measured by the number of social media posts, can be used to estimate flood thresholds for counties along the east coast of the United States, reports a Nature Communications paper. The study suggests that 22 counties, which include several major cities such as Miami, New York, and Boston, could experience flooding at tide heights lower than existing flood thresholds.

The extent of flooding can be highly variable within a small geographic area, which makes determining the consequences of such events difficult. Despite the importance of localized information on the extent of flooding, gauge stations measuring tide heights in the US are sparse and the severity of flooding is not standardized across these stations.

Frances Moore and Nick Obradovich developed a measure of the remarkability of flood events, based on the number of flood-related posts on social media. Using data from 473,000 tweets from 237 counties between March 2014 and November 2016 combined with daily tide height data from tidal gauge stations, they estimated county-specific flood thresholds for shoreline counties along the Atlantic and Gulf coasts of the United States. They identified 22 counties where noticeable flooding is more common than given by the tide gauge threshold; almost a quarter of which were along the Texas Gulf Coast.

The authors note that their remarkability thresholds were estimated using social media users, which represent a subset of the population. They also suggest that as floods become a more regular occurrence, this may decrease the remarkability of flooding events and evoke a smaller social media response. However, they conclude that current standard measures may underestimate populations exposed to flooding.

doi: 10.1038/s41467-019-13935-3

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