With the increasing rainfall on a warming planet, a new computer model reveals that it may take a downpour to cause widespread disruption of road networks. With the combination of data on road networks with the hills and valleys of topography, the model shows "tipping point" at which even small localized increase in the rain causes widespread road outages.
To get these findings, the investigators used data from the impact of Hurricane Harvey on the Houston area, and those results were published in Nature Communications.
The lead author of the research and an assistant professor of computer science at Rensselaer Polytechnic Institute, Jianxi Gao, said that to prepare for climate change, they need to know where flooding leads to the hugest disruptions in transportation routes. Network science typically points to the highest interactions or the most heavily traveled roads. And that is what the scientists see here. A little bit of flood-induced damage can cause unexpected widespread failures.
As a network scientist, Gao worked with environmental scientists at Beijing Normal University and a physicist at Boston University to reconcile traditional network science models that predict specific disruptions impact a road network with environmental science models that predict how topography influences flooding. Traditional network science predicts continuous levels of damage in which case knocking out minor roads or intersections would cause only minor damage to the network. But because of how water flows over land, adding topographical information yields a more accurate prediction.
There is an increase in Florida from 30mm to 35 mm of rainfall knocked out 50 percent of the road network. Also, Gao discovered in New York that runoff greater than 45mm isolated the northeastern part of the state from the interior of the United States.
Also in the Hunan province of China, an increase from 25mm to 30mm of rainfall knocked out 42 percent of the provincial road network. In the Sichuan province, an increase from 95mm to 100mm in the rain knocked out 48.7 percent of the rural road network. Overall, an increase from 160mm to 165mm of rainfall knocked out 17.3 percent of the road network in China and abruptly isolated the western part of mainland China.
Based on the comparison of predicted results with observed road outages in Houston and South East Texas caused by Hurricane Harvey, the researchers were able to validate their model which predicted 90.6 percent of reported road closure and 94.1 percent of reported flooded streets.
In conclusion, Gao said that they cracked the data. Hurricane Harvey caused some of the most extensive road outages in U.S. history, and their model predicted that damage. With the addition of 3D information, it creates more unusual failure patterns than they expected, but now they have developed the mathematical equations to predict those patterns.
