By examining infrastructure failures, Purdue-led research aims to enhance urban community resilience

Suresh Rao studies failure. Specifically, he examines failures of the infrastructure networks that provide critical services to cities. By examining breakdowns and recoveries in urban infrastructure, he and his team are learning how to design and operate cities better — and help urban communities become more resilient.

Rao, Professor of Civil Engineering and the Lee A. Rieth Distinguished Professor of Environmental Engineering, views cities as complex systems, a conglomeration of engineered networks (utilities, power grids, roads), the institutions that manage them, and the communities that expect their demands to be met reliably and affordably. These three elements — engineered networks, socio-economic institutions that manage them, and communities that receive the services — must work together to maintain the essential balance between security, resilience, and sustainability.

Vital graduate student research

Over the past five years, Rao and his team of graduate students have developed strong international collaborations with colleagues in Asia, Europe and Australia as part of a National Science Foundation project. The PhD students work with a larger group to gather data from multiple global cities. They then analyze these data with three goals in mind: They create models for understanding the interdependence of urban networks, simulate their failure-recovery, and develop science-based guidance for better engineering design and operations.

Cities experience disruptions from inevitable and commonplace shocks, such as pipe bursts, road collapses and water supply contamination. They also suffer large-scale disasters, such as earthquakes, fires, tornadoes and floods. Modern cities in advanced countries recover quickly. This is not the case in developing countries, where the cumulative impacts of such common and infrequent shocks have serious repercussions, such as low service and no service to large portions of urban communities.

Adaptive infrastructure

"The key word is adaptiveness," Rao says. Resilience of complex systems is a recursive process, and the adaptive cycle comprises four essential steps —sensing, with the aid of big data; learning, based on analysis of that data; anticipating, based on data modeling; and then adapting, which entails managing or transforming the urban system structures. Communities that work toward these steps can move from merely reacting to large events to anticipating them and recovering from natural hazards with minimal disruptions.

Rao says, "We need to have a paradigm shift in engineering design and engineering practice."

Surprising similarities

"We are working with international colleagues, studying 50-70 cities around the world, with populations from a few thousand to a few million," Rao says. The team has gathered data on water and road networks and on how the structure and functions of these engineered networks compare with natural networks like river networks, ecological networks and social networks. This data set incorporates 125 urban infrastructure networks in over 50 cities.

Rao and his team are focusing on road, water and drainage networks. They have seen, for example, that the larger the network, the more it resembles a natural network.

"My graduate students' work shows that in cities, everywhere in the world, the urban infrastructure functionally is the same — in spite of our engineering. The way it carries traffic, for example," Rao says. "It is an extraordinary thing to think about. Because they've all been designed by engineers over these hundreds of years. And why? Because we humans are part of nature."

Rao's team is analyzing these data in conjunction with international colleagues to learn and adopt global resilience principles. "We use complex network science to find the major differences and commonalities between these networks," he says.

"On the surface, cities look different, but the topology, their network structure, is the same. They evolve in surprisingly similar ways and function the same way." For example, all over the world, pipes and cables are laid near roads. Failure in one network can propagate to the co-located networks. Pipe bursts erode soil beneath roads and lead to potholes and even road collapse. Similarly, when roads are washed out during floods, pipes and cables are affected.

How urban communities cope with failures

Rao says it's also important to collaborate with social scientists when analyzing network failures and service losses. "How do people cope with network breakdowns?" he asks. "And how are people in New Orleans different from people in Houston — or Berlin or Amman or Cape Town? We want to know how different urban communities cope with inadequate services, especially in poorer or marginalized neighborhoods. And what coping and adapting strategies do urban communities deploy when there is a lack of services, both on a daily basis, and during failures from shocks?

"Cities are not only about roads and pipes and buildings; they're about people," he says. "Our work focuses on the resilience of urban communities, and in the long run developing sustainable uses of natural resources."

Rao says that improving urban resilience requires us to re-examine engineering design and operations and to develop better resource and infrastructure management strategies. "Isn't this our professional role in society: to use science and engineering to serve the public?"

At collaborative workshops, Professor Suresh Rao and his student team meet with researchers from around the world to forge solutions for resilient cities. Last spring, the team attended the Synthesis Workshop held at the University of Florida. (front row from left): Elisabeth Krueger (Purdue); Prof. Olaf Buettner (Germany), Soohyun Yang (Purdue); Prof. James Jawitz (Florida); Prof. Suresh Rao; Prof. DK Kim (South Korea); Katie McCurley (Florida); Amanda Desormeaux (Florida). (back row, from left): Prof. Dietrich Borchardt (Germany); Prof. Mike Annable (Florida); Prof. Gavan McGrath (Australia/Ireland); Sam Arden (Florida); Prof. Haki Klammler (Florida/Brazil); Nathan Reaver (Florida); Brady Evans (Florida); Anamika Shreevastava (Purdue); Chris Klinkhamer (Purdue).