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The Brussels Environment Agency designed a decision-support tool (QUADEAU) for the sustainable management of stormwater in urban and developed areas. The tool aims to evaluate and compare alternative scenarios for reducing water runoff in public spaces inside any neighbourhood. QUADEAU is an easy to use tool for urban designers and watershed practitioners allowing the evaluation of the hydrological efficiency of any public space in a renovation or a new urban project designed with best management practices (BMP). It is a tool thought out to provide processes of optimization and selection of BMP to meet the hydrological objectives and the program needs of the public space project. This paper describes how QUADEAU is setup and how BMP are evaluated inside the tool. Any public space project is modelled in the tool by giving specific characteristics of all areas of the project. Connections between surfaces of the project are introduced within the tool by creating flow networks. BMPs are selected according to site constraints and program requirements of the urban project before being designed by giving values to specific parameters for each BMP selected. The hydrological efficiency of the project, i.e. the amount of water that does not reach the outlet because it has been managed earlier in BMP, is evaluated during and after the design rain event. The tool gives the user the opportunity to optimize his project if the hydrological efficiency does not match the hydrological thresholds determined in function of the imperviousness of the neighbourhood, the type of project and the local hydrology.

As in most cities, the natural water cycle is disrupted in the Brussels-Capital Region (BCR) because of the large and still increasing soil waterproofing in private parcels and public spaces. Consequently, severe and recurrent floods occur in the whole region. Major public works, such as stormwater reservoirs and combined sewers have proven their limits to mitigate this increasing risk. The Brussels Environment agency asked to develop a tool, at the neighbourhood scale, to promote Best Management Practices (BMPs) in the public space: the QUADEAU tool. This sustainable stormwater management tool evaluates the hydrological efficiency of a public space in a renovation or new urban project. The public space projected is modelled in the tool by characterizing all areas of the project, by creating the flow networks between these surfaces and by designing the BMPs used in network in the project. Then the tool calculates the total volumes of stormwater that percolate through the soil, evaporate, accumulate in the BMPs and finally flow into the outlet. The flow into the outlet has to match the hydrological thresholds determined in function of the total imperviousness of the neighbourhood, the type of project and the local hydrogeology. QUADEAU aims to be used for the predimensioning and for the optimization of all specific characteristics of the BMPs. QUADEAU is designed to easily adapt to all type and size of project. The tool, encoded within an Excel spreadsheet, is intuitive and easy to use for most individuals without specific engineering knowledge.

Major conventional and traditional public sanitation networks are out of date and have proven their limits to sustainably manage stormwater. Decentralized approach to stormwater management, whereby best management practices (BMP) are dispersed throughout the site project, has gained popularity in recent years. Stormwater BMPs provide an actual, alternative and more sustainable approach than the conventional practice of routing runoff through pipe systems. The selection of the appropriate stormwater BMP to a site project requires experiences and a fine appreciation of many selection criteria. BMPs may be selected according to a wide range of criteria regarding the land use characteristics, the site characteristics, the catchment characteristics, the quantity and quality performance requirements and the amenity, environmental, community and participation requirements. This paper gives a BMP selection aid tool based on a literature review of many public space projects designed with stormwater BMPs. BMPs are classified according to the land use and their position in the stormwater management train. The classification of BMPs proposed in the tool, and based on actually built project, is then compared to the BMPs selection guidelines found in the literature. It appears that, related to land use criteria for the selection of the appropriate BMP, the implementation of BMPs in developed projects is poorly correlated to the guidelines of the literature.