Making it Rain: A Stormwater Story
The City of Havelock is in the coastal plain of eastern North Carolina and is home to Marine Corps Air Station Cherry Point. The City is composed of assorted land uses, though residential lots are predominant. Both the east and west prongs of Slocum Creek flow through the middle of the city, draining approximately 50 square miles of the Croatan National Forest to the confluence with the Neuse River. The City has a history of flooding concerns associated with both hurricanes and thunderstorms. Flooding concerns are especially challenging in the eastern part of the city, due in part to the flat terrain, swampy conditions, and drainage from the national forest. As part of the City’s first stormwater master planning initiative, the City aims to identify locations and causes of flooding, develop proposed solutions, and form a strategic plan to implement drainage improvements in the future. A dynamic modeling approach was essential to understanding the behavior of storms through the various drainage systems, and to effectively evaluate proposed solutions. Infrastructure and flooding were evaluated using HEC-HMS and two HEC-RAS 2D models, one for the east and west prongs of Slocum Creek and the other, a rain-on-mesh model, for the channel and culvert systems throughout the city. Due to the flat topography and ambiguity of drainage basin boundaries, the 2D rain-on-mesh proved to be a powerful tool by having the model determine flow direction based on underlying terrain. Proposed improvements included channel and culvert upsizing, stream restoration, canal improvements, and opportunities to implement green stormwater infrastructure. Estimated construction costs, flood reduction potential, and co-benefits were assessed for each proposed solution. An online dashboard was created to serve as a platform for the City to visualize results, evaluate improvements, and serve as a center piece for developing a strategic plan. This presentation will demonstrate a practical example of how the latest developments in 2D modeling can be leveraged to evaluate urban watersheds with complex topography, hydrology, and hydraulics, as well as aiding in the development of comprehensive masterplans and tools for capital planning.
Author Bio
Connor Bottorff works within Hazen and Sawyer’s Stormwater team. For the past 7 years, he has led hydraulic and hydrologic modeling efforts on several projects to aid in watershed master planning and capital infrastructure improvements.
