Urban street setup and building density may be intensifying flood severity: Study

The setup and density of urban neighborhoods may be exacerbating the intensity of flood risks in areas already suffering from climate-induced weather extremes, University of California (UC) researchers determined in a new study.

Cities worldwide have become increasingly prone to flooding due to the compounding impacts of stronger storms and population growth, the authors noted. But "urban form" — construction density and street networking — may be intensifying that flooding, according to the study, published Monday in Nature Communications.

While strategies aimed at making cities more resilient to floods have already begun to emerge, relatively little information is available as to how urban form contributes to concentrating these deluges, the researchers explained.

They therefore decided to harness statistical mechanics to generate a new formula that could help urban planners more easily assess the flood risks associated with land development shifts.

Lead author Sarah Balaian, a UC Irvine doctoral candidate in civil and environmental engineering, stressed the importance of deploying such tools in a future marked by more severe weather events.

Densely concentrated masses of people — many of whom lack adequate protection or escape routes — could be especially vulnerable to these conditions, she said in a statement.

"Detailed modeling worldwide is presently impossible for many cities because of inadequate data, so our team was motivated to develop a new way of looking at flood risk based on the form of the built urban environment,” Balaian added.

To generate their formula, the researchers said they found inspiration in how physicists develop universal theories that apply to complex systems, such as disordered and porous materials.

In the same manner, they created a formula that could help account for city-to-city variations in flood hazards at a neighborhood-scale worldwide, according to co-author Mohammad Javad Abdolhosseini Qomi, a UC Irvine associate professor of civil and environmental engineering.

“We can probe differences between cities experiencing flood hazards," Qomi said, noting that they were able "to show links between flood losses, urban form and observed rainfall extremes.”

Co-author Brett Sanders, a UC Irvine professor in both civil and environmental engineering and in urban planning and public policy, touted the new formula for its basis in thousands of flood simulations across many different urban forms.

“The equation can also be taught in our classes so that the next generation of civil engineers is able to anticipate the potential impacts of land development on flood hazards," Sanders added.