A simple hydrological approach to design inlet systems in urban areas according to risk criteria

Abstract

Storm drain inlets are used to collect urban runoff and discharge it to an underground sewer system. Inadequate attention to inlet capacity can cause undue hazard to the security of many urban activities. Inlets can be considered as hydrological limits of a series of sub-catchments that jointly represent the whole urban basin. Generally rational method is successfully used in a lot of urban drainage procedures of calculation. Its frequent use is due to the reduced size of the basins in urban areas. Normally spacing between two adjacent drainage grates is of the order of tens and subcatchment areas are lower of a hectare, consequently it’s convenient to use rational formula. In the design phase it’s possible to determine the optimal spacing among inlets to fulfil the risk criteria admitted by Public Administrations. In this case an adequate know-how of inlet hydraulic efficiency is required and generally the lack of this information represents the most important difficulty in the design phase. In this paper an inlets design methodology based on FLUMEN-UPC research about hydraulic efficiency of surface drainage elements is presented. It can be applied theoretically for each type of grate and each type of street geometry without previous experimental tests.