Marcus N. Gomes Jr., Cesar A. F. do Lago, Eduardo M. Mendiondo

Infiltration low-impact development (LID) techniques allow the slow infiltration of surface water, reducing peak volumes and flows. Their design consists of specifying the surface area and a maximum ponding depth to guarantee the minimum volume required to combat the effect of excessive urbanization. Arbitrary specifications of the design height (i.e., the maximum ponding depth) of these LIDs can lead to under-sizing of the minimum area required. In this paper, an optimized design model for retention catchments (MoDOBR) is developed, implemented, and tested under four examples. We hypothesize that is necessary to match the maximum ponding depth with the depth required to store excess runoff in case the media and the underdrains are clogged. The model solves mass balances on the surface of the LID and at the interface of the saturated soil layer. The results of four numerical examples are presented, and the influence of different soil types is discussed through sensitivity analyses. Overall results indicate that if the LID is designed in sandy soil, it requires a surface area of 2.9\% of the catchment, while if it is designed in clayey soil, the required area would be 50\% of the catchment area for a 5-year rainfall design storm.