The Oakdale drainage area is located in the South Norfolk Historic District in the City of Chesapeake. This stormwater basin is primarily comprised of residential properties that were developed in the first half of the 20th century. In recent years, this area has begun to experience a higher frequency of flooding events, likely due to increased rainfall intensity and duration, changes in drainage patterns, and local system constraints dye to re-development efforts in and around the area. To address this increasing challenge, the City requested an independent consultant to investigate several proposed solutions from a previous study and evaluate their efficiency for reducing flooding, with the understanding that the preferred alternative should provide the most cost-effective solution for improving storage and conveyance of stormwater.

For this project, capacity and conveyance analyses were performed using a City provided Storm Water Management (hydrologic and hydraulic) Model (SWMM) of the Oakdale drainage area using the PCSWMM software. Simulations for the 1-, 10-, and 100-year SCS 24-hour Type II design storm conditions were developed. Each simulation was run on the existing conditions model using several combinations of a wet pond, upsized pipe, flow diversion, and a flow control structure. The model results and engineering analysis indicate that a combination of a wet pond with a control structure, pipe upsizing, and flow diversion was the most efficient and cost-effective solution.

The City of Chesapeake Public Works Department has selected the most cost-effective and efficient solution to improve the existing system flooding conditions. Additionally, the City Staff has incorporated additional design considerations to provide more operational flexibility and easy maintenance of the stormwater flood mitigation facilities.

This presentation will discuss several critical aspects of the project including the analysis methodology, key assumptions, final engineering results, particular design considerations, O&M aspects incorporated in the design and future recommendations.