A Resilience Based Assessment Method for Primary Stormwater Management Systems Urban Flood Control

Urbanization results in considerable land use changes in urban areas, increasing potential flood impacts. However, the majority of the main urban stormwater management systems are still pipe based systems, collecting excess water from urban sub-catchments and transferring it to outlets. This system is highly reliant on the structure of the piped drainage network and its capacity. In addition, stormwater drainage network structures are predominately acyclic systems that transfer load from sources to outlets by gravity. This type of network structure provides a minimum level of connectivity without alternative pathways between source nodes and destinations.

Water sensitive design (WSD) in stormwater is a new sustainable development approach that attempts to overcome the constraint of drained city systems and move toward a resilient system not only for flood control but also by protecting natural freshwater resources and ecosystems. To conduct WSD in stormwater, many approaches have been introduced to improve reducing peak flow and flood volume in the system. However, there is not a robust framework to quantify the change in the resilience of stormwater management systems using these approaches.

This paper introduces an index based methodology to quantify the resilience of primary stormwater management systems in terms of the network structure and hydraulic capacity dimensions. In the hydraulic capacity dimension, the degree of resilience for a primary stormwater system is quantified by accounting for the temporal nature of system robustness and functionality during the conveyance of different extreme rainfall events. To demonstrate this approach, a resilience-based approach is introduced to determine the best practicable option for a stormwater management plan within an urban catchment using WSD approaches by considering the two main objectives of WSD for flood quantity controls. These two aims are controlling flood volume and peak flow rate generated in an area in order to control the flow quantity downstream. These two objectives impact directly on hydraulic performance capacity (HPC) of the affected primary stormwater management system within the urban catchment by improving the robustness value and altering recovery and loss rates of the system.