Exploring trade-offs between cost and peak flow reduction toward identifying optimal LID designs combining green roof and permeable pavement

Abstract

ABSTRACT This study aims to apply a cost-effectiveness approach to identify optimal Low Impact Development (LID) designs for peak flow management when two specific practices are simultaneously employed: Permeable Pavement (PP) and Green Roofs (GR). Four design parameters were considered, associated with coverage ratios and underlying layer thicknesses of the LIDs. The results showed that optimal costs and parameters were more affected by the level of peak flow reduction than by storms’ intensity and duration. The best settings occurred with permeable pavement treating 100% of the adjacent impervious area. In this case, the optimal designs were dominated by smaller coverage ratios (20 to 60%) and deeper (190 to 330 mm) storage layer of PP, combined with a very small or non-existent area of GR. The findings of the present study demonstrate how the optimization of design parameters may lead to more economic LID designs and provide additional guidance for LID practice implementation and to assist in the decision-making process for the most cost-effective and sustainable solutions.