Methodology for a stormwater sensitive urban watershed design

In urban stormwater management, decentralized systems are nowadays worldwide experimented, including stormwater best management practices. However, a watershed-scale approach, relevant for urban hydrology, is almost always neglected when designing a stormwater management plan with best management practices. As a consequence, urban designers fail to convince public authorities of the actual hydrologic effectiveness of such an approach to urban watershed stormwater management. In this paper, we develop a design oriented methodology for studying the morphology of an urban watershed in terms of sustainable stormwater management. The methodology is a five-step method, firstly based on the cartographic analysis of many stormwater relevant indicators regarding the landscape, the urban fabric and the governance. The second step focuses on the identification of many territorial stakes and their corresponding strategies of a decentralized stormwater management. Based on the indicators, the stakes and the strategies, the third step defines many spatial typologies regarding the roadway system and the urban fabric system. The fourth step determines many stormwater management scenarios to be applied to both spatial typologies systems. The fifth step is the design of decentralized stormwater management projects integrating BMPs into each spatial typology. The methodology aims to advise urban designers and engineering offices in the right location and selection of BMPs without given them a hypothetical unique solution. Since every location and every watershed is different due to local guidelines and stakeholders, this paper provide a methodology for a stormwater sensitive urban watershed design that could be reproduced everywhere. As an example, the methodology is applied as a case study to an urban watershed in Belgium, confirming that the method is applicable to any urban watershed. This paper should be helpful for engineering and design offices in urban hydrology to define a sustainable and decentralized stormwater management plan and redaction of performance standards at the watershed scale. The method applied in this paper toggles the decentralized stormwater approach from a common experimental point of view to an oriented problem-solution point of view.