August 15th, 2020 was a memorable day for residents of the Colony Pines and Windsor Great Park Neighborhoods as stormwater overtook streets, yards, and residential structures, compounded by overtopping of storage basins and their accompanying floodwalls. These communities are located in the Stoney Run watershed, characterized as an urban residential region after being developed largely in the 1950-80’s, with drainage composed of various piped systems, open channels, and major storage basins. While damage caused by the ~75-yr storm was unfortunate, the City of Newport News was able to collect valuable data from this event which would aid GKY’s assessment of the current drainage system as well as identification of flood reduction options.
Initially, it seemed clear that undersized storage basins and recent development were to blame for this flooding, but using advanced 1D-2D Stormwater Management Modeling, the City of Newport News and GKY worked together to create a calibrated existing condition model which was then used to sort through a myriad of potential causes for flooding within the watershed—including new development, permitting constraints, and inadequate piped drainage systems, among other factors. Ultimately, modeling results led to identification of the key factors which define flooding within the study area as well as several potential improvement projects to provide an increased level of flood protection.
Careful decisions and creative modeling efforts were required to analyze this complex watershed as well as deliver a product which could provide insight to citizens and local government officials alike. This study not only serves as a great example of modern 1D-2D SWMM modeling capabilities, but also demystifies the process required to understand and address increasingly common and complex urban flooding.