Over the last five years, the City of Virginia Beach has completed the development of the hydrologic and hydraulic models for all 15 drainage basins throughout the City’s nearly 500 square miles. Each of the 15 drainage basins model has been calibrated and validated against data observed during historical storm events that caused flooding in the City between 2012 and 2016. The need to combine all drainage basins models into one master model was based on the following:
1. The drainage basins are interconnected through overflow links during high intensity and less frequent storm events (25-, 50-, 100-yr);
2. To provide submodels to help with the stormwater drainage analysis for private developments and CIP projects; and,
3. To update the City’s HAZUS study to determine Benefit-Cost Ratios (BCR) for proposed flooding mitigation projects as part of the Stormwater Master Plans.

The process to develop the master model for the entire City started with converting the 2D areas into 1D, adding overflow links between drainage basins to represent the hydraulic connection between the adjacent basins, develop a process for establishing initial depths for multiple receiving waters and at/upstream of the City’s stormwater pump station wet wells. The City’s master model has over 15,000 subcatchments, over 20,000 junction nodes, over 14,000 storage nodes, over 2,700 miles of conduits, and 31 pump stations.
This presentation will describe the process of developing the master model, how to overcome technical issues encountered during the process, and the next steps to refine the master model.