Phasing LID Implementation for Flood Mitigation in Urban Drainage Systems Considering Climate Change Scenarios and Using Genetic Algorithms

This paper presents a novel methodology for phasing the implementation of a low impact development (LID) system in urban drainage systems (UDSs). The methodology consists of the combination of various elements including physically based event simulation of UDSs, event hyetograph generation at various return periods considering climate change, and metaheuristic for the identification of suitable locations and expansions of LID systems in the various UDS subcatchments and in the various phases of construction. The metaheuristic used is the bi-objective genetic algorithm (i.e., the genetic algorithm with two objective functions, namely the total cost of the interventions and the flood volume to be simultaneously minimized) to yield a Pareto front of optimal trade-off solutions. The applications to the calibrated UDS serving the industrial area of the city of Brescia (Northern Italy) prove the capability of the methodology to offer cost-effective solutions to significantly attenuate flooding by reducing the rainwater volumes entering the underground network, with no need for structural interventions underground. The methodology also proves flexible to accommodate variations in intense rain events because of climate change.