Effect of the area on the performance of low impact development practices placed at catchment-scale under long-term simulation

Abstract Previous studies highlighted the effectiveness of Low Impact Development (LID) practices in reducing urban surface runoff, but their long-term performance at different implementation areas remains unclear. This study addresses this gap by simulating surface runoff reduction and its implications on the stormwater drainage system of the Universidade Federal de Lavras, Brazil, evaluating five LID practices—bioretention cell, rain garden, infiltration trench, permeable pavement, and vegetative swale—implemented across 10%, 15%, 20% and 25% of the impervious area. Results showed that, under frequent rainfall events, i.e., low-intensity events, increasing the percentage of area treated with LID practices did not produce significant reductions in the flow rate, peak flow rate, or flooding volume of the evaluated urban drainage system. For the conditions considered in the present study and when the objective is primarily hydrological, such as increasing infiltration depth, a minimum treated area corresponding to 10% of the total impervious area is sufficient. Thus, this finding is context-specific and may not be appliable to all drained areas, although it provides an initial direction for further investigation. The simulations also showed that LID performance is governed more by storage capacity and the consequent increase in exfiltration opportunity time than by the specific practice type itself. Therefore, among LID practices that include soil and storage layers, technical feasibility and economic criteria should guide the selection process.