Urban Stormwater Management by Green Infrastructure: Design and Comparison of Three Scenarios

Three scenarios for stormwater management in a 6.5 ha industrial area are investigated: (S1) separate stormwater pipe system with a downstream infiltration tank, (S2) succession of infiltration swales along roads and (S3) vegetated roofs and infiltration swales. Long-term simulations of the three scenarios are carried out with 6 min time step rainfall and evapotranspiration time series over 21 years (1992–2012). The model combines the Canoé® software for sewers and Matlab® codes for infiltration tank, infiltration swales and vegetated roofs. In scenario S1, the separate stormwater network includes 535 m of pipes and a 1600 m³ downstream infiltration tank. In scenario S3, all roofs are vegetated, with a storage capacity of 32 mm/m², allowing to divide by two the total length of swales compared to scenario S2 (408 m and 203 m respectively) with impervious roofs. Vegetated roofs allow a mean decrease of 42% of the annual runoff volume. Continuous simulations allow to study in detail the hydrological behavior of the infrastructures at all time scales (from the time step to multi-year scales) and analyze statistically the results.