InTrans / May 03, 2019

Transportation research investigates flooding impacts

January and February 2019 brought unprecedented amounts of snowfall in the Midwestern states including Nebraska, Iowa, South Dakota, Wisconsin, and Minnesota. Before the snow could melt and the ground could thaw, heavy rainfall fell primarily in northwest Iowa and northeastern Nebraska causing major runoff from both the rainfall and snowmelt. The saturated and frozen soil could not absorb any of the moisture, resulting in widespread flooding.

The Spencer Dam, a dozen levees, and at least five bridges were destroyed in Nebraska alone. Many communities have been cut off or evacuated because of these floodwaters. Travel has been made impossible in some areas due to roads being underwater or bridges being washed out. As snow continues to melt and rain continues to fall, some rivers could continue to rise. As all of this water flows south, Missouri and Kansas have started to flood in areas.

Nebraska governor Pete Ricketts stated in an interview with NPR’s Mary Louise Kelly, “We also have a lot of roads that are out, as I’ve mentioned. And these are roads that allow people to commute. Some of, for example, our kids can’t get to school because bridges are out. So those will be the types of things that our Department of Transportation (DOT) is prioritizing.” Ricketts added that Nebraska has about 200 miles of roads that cannot be used and about 16 bridges in need of repair because of the flood.

Iowa, too, has suffered extensively from these events. Iowa Farm Bureau Federation’s (IFBF) economists say the state may see upward of $2 billion in damages from recent flooding, noting that there have been multiple breaches in levees with roads and bridges rendered unsafe or impassable.

To study such events and help Iowa and other states deal with floods, a team of researchers at Iowa State University’s Department of Civil, Construction, and Environmental Engineering and Institute for Transportation (InTrans) is working with the Iowa DOT.

Alice Alipour, assistant professor of civil, construction, and environmental engineering, is leading a team of researchers to understand the adverse effects of floods on built infrastructure, propose mitigation strategies, and plan for possible failures such that the disruption to the transportation system is minimized.  “We understand that natural hazards, in this case floods, are going to happen,” Alipour said. “Our goal is to prevent major dysfunctionality in the network and to plan for possible failures such that the closures in the road network do not adversely impact the everyday lives of the communities or the long-term economy of the state.”

Alipour and her colleagues at Iowa State, including Omar Smadi, take a multi-scale approach to studying the Iowa road network. “As the project co-PI, my role is to determine the impacts of these natural hazards, flooding for example, on the performance of the physicals assets such as pavements, so that further analysis can be carried out to assess the overall impact on the transportation network,” said Smadi.

At a smaller scale, they look into individual transportation assets such as bridges, culverts, and segments of the road pavement and assess the vulnerability of each asset to flood events of different intensity. At a larger scale, they consider the whole transportation network of the state and assess the damage to the community functions due to closure or failure of any of those assets.

“This is an end-to-end approach that we take,” Alipour said. “With a proper understanding of the vulnerable segments of the road network and the impact it could have on the communities, agriculture, and economy of the state, we loop back the consequences to design, mitigation, and post-event recovery efforts. This will provide a resilient network, in which evacuation and disaster relief efforts can be prioritized and efficiently accomplished for the communities affected by these events,” Alipour continued.

Smadi said: “When managing our transportation infrastructure, it is critical to consider risk as required by the two most recent highway authorizations, MAP-21 and FAST acts. Understanding the vulnerability of the transportation network aids in evaluating the risk and addressing that risk as part of the decision making process”.

Building on previous findings of the research team at Iowa State, the project with Iowa DOT is in its first phase. The goal is to provide a fully functional resilience assessment and enhancement tool that can be used for decision making purposes.