Runoff rates should be limited the greenfield runoff rate in order to not increase flooding offsite from its natural drainage scenarios. For greenfield sites this is imperative. For brownfield sites this should always be the first option however we understand how this may not always be achievable and therefore there are other options.

With restricting runoff rates, there will inevitably be the need for storage. This storage does not need to only provide the benefit of flood mitigation. This is because well designed drainage schemes can incorporate above ground storage features that also promote amenity and biodiversity. The provision of SuDS and green infrastructure provides numerous socio-economic benefits and is consistent with national and local policies in seeking to conserve and where appropriate enhance biodiversity. In order to minimise the land take associated with SuDS features in developments wherever possible, above ground storage should be integrated with public open space. The integration of above ground storage and open space does not always have to be in the form of an empty detention/infiltration basin. Where possible, basins and amenity features such as informal play areas can be merged to create multifunctional spaces. By doing so, the amenity of the basin is greatly enhanced whilst still providing its primary purpose.