DelDOT SR 9 Resiliency Study

State Route 9 (SR 9) in Delaware is highly susceptible to coastal flooding due to its low elevation and proximity to the Delaware River and Bay. This vulnerability is expected to worsen with sea level rise (SLR). In response, the Delaware Department of Transportation (DelDOT) initiated a resiliency study for SR 9 beginning just north of Army Creek in New Castle, DE, and ending at Little Creek in Kent County. The study evaluated DelDOT’s infrastructure, including 45 miles of roadway and 23 bridges, to assess current and future flood vulnerabilities and prioritize mitigation efforts.

Utilizing GIS data from FEMA, NOAA, and USGS, the study established existing average daily water elevations and extreme storm events. Flood elevations were then projected to the years 2050 and 2100 by applying SLR estimates. Roadways, bridges and culverts vulnerable to flooding were identified and ranked based on factors such as ADT, flooding severity and proximity to essential facilities. Short and long-term mitigation strategies were developed to alleviate flooding including relocation/realignment, elevating roadways/bridges, multi-span bridges, viaducts, and levees. Each approach was analyzed for cost using an SR 9 cost-estimator tool developed as part of this study, constructability, and flood mitigation.

The project was delivered in an interactive ArcGIS StoryMap format and through a web application, offering DelDOT a suite of tools for planning, decision-making and public engagement. The SR 9 Resiliency Study provides DelDOT with the resources to take a proactive approach to managing flood risks to ensure long-term safety and connectivity of the SR 9 corridor.

This project provides a model for assessing future flood vulnerability of transportation infrastructure and developing comprehensive mitigation strategies. Engineers and transportation agencies can benefit from this study’s use of interactive planning and decision-making tools to ensure long-term resilience for essential infrastructure.

Learn more about the study here: https://resiliency-deldot.hub.arcgis.com/pages/sr9-study-goal