Predesign of an Urban Rainfall Drainage Network with Genetic Algorithms

The pre-design of an urban storm drainage network is proposed with an optimization method consisting of two parts: in one part, the connection of the manholes is proposed so that there is little water flow in the pipes; in the other part, it is based on a genetic algorithm to find the lowest cost of acquisition of the pipes and of the excavation necessary for their installation, complying with several hydraulic and constructive restrictions recommended in construction manuals of networks of this type. The described procedure is made from the linking of the pipes that make up the network (network layout) trying to obtain the smallest sum of the lengths. It is considered that the conduits are of circular section, where their diameters only take commercial values. The slope of each pipe in the network is calculated so that the hydraulic depth of the water flow is 80% of the pipe diameter, in order to approximate the flow conduction capacity of the liquid within it. Finally, its application to a real case is demonstrated, and the hydraulic performance of the pre-designed network is evaluated by simulating the non-permanent free surface flow in the network using the EPA-SWMM 5.1.015 model, in order to ensure that the hydraulic restrictions and assumptions made for permanent flow are met.