Flooding due to sea level rise has added an average of at least 23 minutes to the time people in the coastal US spend commuting over the course of a year. By 2060, even a modest amount of additional sea level rise could increase that delay ten-fold, amounting to billions of hours of wasted time for commuters.
“It’s here. It’s now. It’s a delay that is already occurring,” says at Florida State University.
Hauer and his colleagues looked at census data representing 74 million actual commuting routes in more than 200 counties on or near the US coasts. They used a traffic model to calculate normal commute times on these routes. They then calculated how tidal flooding changed these commute times, using tidal gauge readings taken between 2002 and 2017 to model levels of inundation and an algorithm to account for commuters rerouting to drive around flooded areas.
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After screening out extreme events related to storm surge, they found that flooding-related delays increased from an average of around 12 minutes per person per year in 2002 to an average of 23 minutes per person per year in 2017. In some areas, the increase in delay length was even more marked. Residents of coastal counties in Florida, for instance, saw a 360 per cent increase in the length of delays since 2002; coastal residents in South Carolina saw a 225 per cent increase.
“Living in Florida, and before this living in Georgia, I was intimately aware of [high-tide] flooding that was beginning to crop up in coastal areas,” says Hauer. “It turns out it’s pretty widespread. We just haven’t had a good way of quantifying it or how common it is.”
Future sea level rise driven by climate change will lead to more delays, according to the new model. The researchers found that if the world is on course for a rise of 0.3 metres by 2100, considered to be a low-end scenario, there would be 183 minutes of delay per year to the average commute time in these counties in 2060. A high sea level rise scenario of 2.5 metres by 2100 would lead to 643 minutes of delay in 2060.
While most commuters wouldn’t notice what might amount to a few seconds when spread across daily commutes, the time adds up, says at the University of New Hampshire, who wasn’t involved with the study.
Jacobs and her colleagues found in lost time. The cost is expected to rise into the hundreds of billions this century if steps aren’t taken to prevent flooding by, for example, raising roads or building sea walls.
“It’s these nickel-and-dime-ing effects of the high tides that are happening frequently,” she says, adding that the averages mask more acute delays in particular places. “Those are the floods that are going to cause people in these communities to really have to deal with these changes.”
Environmental Research
