New statistical mechanics formula suggests that urban street networks and building density influence flood severity

Cities around the world are increasingly affected by flooding due to the combined effects of more severe storms linked to global warming and urban growth. New research from the University of California, Irvine, suggests that urban form, particularly the density of buildings and the road network in a neighborhood, also affects flood intensity.

For an article published today in Nature CommunicationsResearchers in UC Irvine’s Department of Civil and Environmental Engineering have turned to statistical mechanics to generate a new formula that will make it easier for urban planners to assess the flood risks posed by land-use changes.

Co-author Mohammad Javad Abdolhosseini Qomi, associate professor of civil and environmental engineering at UC Irvine who holds a joint appointment in UC Irvine’s Department of Materials Science and Engineering, said he and his colleagues were inspired by how physicists study complex systems such as disordered porous solids, glasses and complex fluids to develop universal theories that can explain city-to-city variations in flood risk.

“The application of statistical mechanics has enabled us to develop an analytical model that can project flood risk at the neighborhood scale anywhere in the world,” Qomi said. “We can probe differences between cities exposed to flood risk. The platform has been shown to show links between flood losses, urban form and observed precipitation extremes.”

Lead author Sarah Balaian, a doctoral candidate in civil and environmental engineering at the University of California, Irvine, said we can expect the future to see more severe weather events and that concentrated masses of people, many with no means of protection or escape, will be heavily impacted by urban flooding.

“Furthermore, detailed global-scale modeling is currently not possible for many cities due to inadequate data, so our team was motivated to develop a new way of thinking about flood risk based on the form of the built urban environment,” she said.

Co-author Brett Sanders, a professor of civil and environmental engineering and professor of urban planning and public policy at UC Irvine, said the new formula was made possible by thousands of simulations of flooding in many different urban forms, simulations based on the physical laws of motion.

“We created a physical dataset of flood depth and velocity for different types of urban developments observed globally, and then used data analysis techniques to derive a relatively simple formula that can be used for planning and vulnerability assessments globally,” Sanders said. “The equation can also be taught in our courses so that the next generation of civil engineers can anticipate the potential impacts of land use on flood risk.”