SWMManywhere: a workflow for generation and sensitivity analysis of synthetic urban drainage models, anywhere

Improvements in public geospatial datasets provide opportunities for deriving urban drainage networks and
simulation models of these networks (UDMs). We present SWMManywhere, which leverages such datasets for
generating synthetic UDMs and creating a Storm Water Management Model for any urban area globally.
SWMManywhere’s modular and parameterised approach enables customisation to explore hydraulicly feasible
network configurations. Key novelties of our workflow are in network topology derivation that accounts for
combined effects of impervious area and pipe slope. We assess SWMManywhere by comparing pluvial flooding,
drainage network outflows, and design with known networks. The results demonstrate high quality simulations
are achievable with a synthetic approach even for large networks. Our sensitivity analysis shows that manholes
locations, outfalls, and underlying street network are the most sensitive parameters. We find widespread
sensitivity across all parameters without clearly defined values that they should take, thus, recommending an
uncertainty driven approach to synthetic drainage network modelling.