Bridge Engineering Center

About the research

Conventional culverts are mainly designed to transport water underneath roadways with minimal headwater buildup, resulting in low to moderate peak flow attenuation. On-road structures (ORS) offer an alternative by using the roadway embankment as a dam, restricting flow into the culvert to provide flood storage during large precipitation events.

In this project, statewide geographic information system (GIS) analyses were conducted that identified approximately 250,000 potential ORS locations with a combined storage capacity of 2 million acre-feet and a pool area covering 900,000 acres, representing about 2.7% of Iowa. A methodology was developed to automate the hydrologic design of individual ORS, enhancing the identification of those that offer significant peak flow reduction benefits. In addition, the peak flow reduction benefits were quantified at the HUC12 watershed scale for ORS systems. For a 50-year storm event, peak flows at watershed outlets were reduced by approximately 18%.

The research outcomes are accessible through a web portal named the Iowa Department of Transportation (DOT) On-Road Structures (IDOT-ORS) information platform. This platform facilitates the dissemination of results, allowing various stakeholders to view information on ORS locations, expected pool and drainage areas, structure designs, and inflow and outflow hydrographs for several return periods. The platform can be accessed at https://hydroinformatics.uiowa.edu/lab/idot-ors/.