Stormwater Disconnection: Transient Scenario Analysis of Intervention Flexibility

Urban drainage networks protect people, society, and the environment from the hazards presented by domestic and industrial effluent, and urban stormwater run-off. However, urban drainage networks are financially and carbon intensive, and their failure results in damage to people and the environment. The likelihood and magnitude of failure is anticipated to increase in the future as a result of pressures including climate change and urbanisation. The rate and extent of these pressures manifesting is uncertain. Sustainable drainage systems (SuDS) are structural measures that can be retrofitted to replace or augment an urban drainage network, reducing the likelihood of failure now and in the future. Adaptation of infrastructure to encroaching future pressures requires infrastructure constructed in the present to be flexible. An existing method for assessing flexibility is combined with transient scenario analysis to enable the flexibility of conventional solutions, and source-control and regional-control retrofit SuDS interventions to be compared in two real-world case-study catchments. A new multi-criteria assessment framework is proposed for the comparison of these interventions. A method for distributing retrofit SuDS within an urban drainage catchment is developed from first principles. It is a hydraulic modelling method based on identifying potentially disparate locations within an urban drainage catchment that possess similar times of concentration to a point of interest within the network. The concept of the efficiency of stormwater disconnection is introduced. The developed method is shown to be more effective at identifying efficient disconnection locations than existing methods in two real-world case study catchments.