The Virginia Airport is located at the bottom of a large urban catchment in Durban North, Durban. Sections of the catchment are characterised by steep slopes and high runoff coefficients due to the large percentage of impervious pavements.

Subsequently, the resulting stormwater runoff during flooding events produces volumes that exceed the current stormwater infrastructure capacity, which is designed for a one in ten year storm return interval.

This results in excess stormwater runoff becoming overland flow as it cannot enter the stormwater network. The overland flow accumulates at a critical point, where three sub catchments combine, at Virginia Airport. The overland flow floods the adjoining road infrastructure and enters the Virginia Airport premises, and flows into the airport buildings.

The stormwater network infrastructure capacity is further hampered by the constriction of the culvert outlet, which provides the exit point for the stormwater runoff into the ocean. The culvert exit point is constricted by the ingress of marine sediment during tidal cycles. T

he marine sediment accumulates in the culvert, preventing the culvert from operating optimally. Although periodic flushing occurs during smaller rainfall events, the initial choking effect compounds large flooding events.

This project involved detailed 1D and Quasi-2D modelling of the catchment that assisted the design process to alter the storm discharge characteristics in order to mitigate flood inundation at the Virginia Airport. The project required a multi-lateral approach of solutions in order to mitigate future flooding events.

 

Download the technical paper OR read our article in the May edition of IMIESA