A hybrid stormwater management system for a residential development : an experience

Managing stormwater runoff involves controlling the quantity and quality of runoff to mitigate adverse effects on receiving environment. Stormwater runoff can be managed by implementing stormwater management systems that can be integrated with various stormwater management devices. A project was undertaken to solve stormwater runoff problem for a residential subdivision development. The extent of impervious layers will be greatly increased (after development) and therefore the total runoff volume generated in post development will be greater than the pre-development conditions. As a result, the capacity of existing stormwater drainage system will become inadequate. Therefore, the aim of this project was to design a feasible and effective stormwater management system for the residential development, taking environmental, social, cultural and economic factors into consideration. Three options were evaluated in this project during the design stages; a centralised system, low impact design, and a hybrid system. Based on the option evaluation process, a stormwater management system was designed to meet regulatory objectives and design criteria to have sufficient treatment, retention and detention capacity for rainfall events in post-development condition. To cope with the increase in runoff volume, a hybrid stormwater management system (i.e. a combination of conventional and low impact design devices) was designed, as accepted by the client. The chosen hybrid stormwater management system would be sustainable and cost-effective, and could be the most feasible system in terms of managing hydrologic impacts of stormwater runoff from post development for the site.