City planners defending against future coastal storms will have to contend with increasing rainfall driven by both climate change and urban buildup. But which is the more important factor?

New findings from researchers at Princeton and the South China University of Technology show that climate change and urbanization both play a role in storm-driven rain with the potential to lead to flooding and landslides. But the importance of each factor depends on how close the rain is to the city center.

“In the urban core, they are overall comparable,” said co-lead researcher Gabriele Villarini, a Princeton professor of civil and environmental engineering and the High Meadows Environmental Institute. “But as you go further out, the role of climate change becomes more predominant.”

In a Jan. 28 article in the journal Communications Earth & Environment, the researchers concluded that climate change has generally enhanced rainfall from tropical cyclones in coastal regions. Urbanization has exacerbated heavy rain in central city areas, potentially increasing the threat from surface runoff and flooding.