ABSTRACT
Since 1970, stormwater detention has been the recommended approach for reducing peak flood flows and mitigating flood damage in urbanized areas. For a given case, the detention volume at the stormwater system outfall is determined by the upstream tributary area, watershed’s imperviousness, and allowable flow release. The major elements in detention basin design are composed of the basin geometry, inflow energy dissipator, trickle channel, permanent infiltration pool, outlet box, and outfall culverts. A detention facility in a drainage network should be placed at a strategic location in order to effectively attenuate peak flood flows. During the preliminary study, it is necessary to evaluate all feasible combinations among the key factors. Decision-making relies on impact assessments using numerical stormwater simulations for the entire watershed with and without the proposed detention basin. In this chapter, the hydrograph method is introduced to approximate the required detention volume. At the preliminary stage, the basin under design is firstly shaped with a rectangular or triangular geometry. At the final stage, the basin under design can be future refined using the detailed design information.
