NC State University conducted hydrologic and hydraulic modeling and engineering analyses, coordinated technical meetings, and organized community outreach efforts focused on flood mitigation for the Neuse River Basin. The objectives of the study were to better understand the sources and nature of riverine flooding, test potential flood mitigation measures, improve early warning systems for transportation-related infrastructure, evaluate future storm severity and identify potential improvements to local floodplain ordinances. Hydrologic and hydraulic models acquired from North Carolina Emergency Management served as the foundation for much of the modeling efforts, which focused primarily on Smithfield, Goldsboro and Kinston. In addition, two-dimensional hydraulic models were developed to evaluate the effects of bridges at several locations. Modeling indicated limited flood reduction benefits for increasing the capacity of bridges along the river with the exception of the combined expansion of three bridges in Smithfield. Tributary crossings subject to flash flooding were evaluated and prioritized for replacement in the three communities and the least impacted, most critical north-south and east-west routes were identified. Upgrades could further be prioritized by focusing on developing these routes into resilient corridors that would provide access during and shortly after flooding events. NCSU also developed recommendations for improving early warning of transportation impacts during extreme flooding. Relationships between the incipient point of flooding for nine critical road locations and river stage at nearby USGS stream gages were established. Locations where new river gages should be installed to improve road closure prediction and validation of modeling efforts were recommended. Working with UNC-Chapel Hill, NCSU also identified more stringent floodplain protection protocols that would help flood-prone communities improve their resilience to flooding. Modifications to existing floodplain ordinances for Smithfield, Goldsboro and Kinston were prepared. Finally, modeling of future storms considering a warming climate and continued development south and east of Raleigh revealed that expanded urban growth will result in a relatively small increase in peak discharge (6.2%) compared to a potential very large increase (158%) that is estimated for a Matthew-scale event by end of the century (2070-2100), if we continue with business as usual (i.e., no efforts to reduce emissions). This peak flow increase would raise flood levels by more than 2 feet in the communities along the River.
