The City of Virginia Beach has completed the Upper West Neck Creek Drainage Basin Stormwater Master Plan (UWNC DB SWMP) which encompasses approximately 20 square miles and includes over 100 simulated flood areas (SFAs). This is the first large drainage basin completed since the Linkhorn Bay Drainage Basin Stormwater Master Plan case study (approximately 3 square miles and 17 SFAs), and the second of 15 SWMPs that will ultimately be completed. Applying the case study methodologies and typical solutions to the larger and more complex UWNC DB has uncovered several unique challenges. The most significant challenge in this area of the City is tailwater influence. This presentation will provide a brief overview to the City-wide SWMP objectives, the threat that high tailwater poses to achieving the desired level of service (LOS), the many options considered to minimize or eliminate this threat, and ultimately the benefits provided by the City’s innovative approach to combine the objectives from two City-wide planning efforts to provide more resilient solutions for the UWNC DB SWMP.
However, understanding and mitigating the tailwater influence is only half the battle! The remainder of the presentation will provide a brief overview of typical solutions that were required to achieve the desired LOS, as well as others that were considered but found to not meet the project objectives. The presentation will culminate with a detailed discussion of a representative SFA and the associated flood mitigation project that was ultimately proposed to illustrate all facets of the discussion in a practical application. Considerations for the proposed project included stormwater pump stations and gate structures, closed and open system conveyance improvements, diverting water to outfall locations with more favorable tailwater conditions, residential and commercial property acquisitions, use of City property for increased runoff storage, project phasing, reduced LOS, and more. Be sure to attend to see what elements were ultimately employed for the final solution!