Optimal design of urban drainage networks

In this paper, a general procedure is proposed for the optimal design of urban drainage networks. The approach employed is based on the utilization of a standard Genetic Algorithm (GA), which represents, at the same time, a modification, a generalization and an extension of a procedure already adopted in the past for the optimal design of water distribution networks. The approach is firstly tested by comparing the results obtained by writers and by other researches for a specific urban drainage network taken from the literature. Then, a second case of study is considered, taken from the literature too, in order to evaluate, by sligtly different versions of the procedure proposed: i) potential advantages which could be obtained considering the possibility to allow to the network ending node elevation to be not fixed “a priori” but variabile, in a predetermined range of values, up to the value recognized as maximim by the “a priori” reasoning; ii) the need to respect the technical constraint for which the sizes of channels/conduits downstream a node should be not lower than the corrisponding sizes of all the channel/conduits upstream the node itself; and iii) the opportunity, in several case of practical interest, to relax one or more constraints of the problem, such that connected to reaching of the self-cleaning velocity during the peak wastewater flow period