Estimation of Hydraulic Efficiency Loss in Storm Drain Inlets Due to Surface Clogging of Tjeir Grates

This work presents the hydraulic characterization of the existing surface drainage system of the town of La Almunia de Doña Godina (Spain). This is a preliminary activity before the modeling tasks simulate the functioning of urban drainage system during extreme rainfall events. It is well known that, during these types of meteorological events, urban drainage systems partially lose their efficiency and that this performance reduction is also influenced by the clogging phenomenon of surface grated inlets. Therefore, it is clear the need to simulate urban pluvial flooding scenarios considering the inlets hydraulic efficiency and the related effects of clogging phenomena to achieve reliable results in terms of hazard assessment. In this work, data collection was carried out on all the existing grated inlets of the municipal urban drainage system. This activity included the identification of the type of grates, their exact geographic location, their geometry and dimensions, as well as their state of maintenance with special regard on the percentage of the clogged area and the related shape pattern. Thus, five clogging patterns were defined, which allowed the estimation of hydraulic efficiency and clogging coefficient according to an experimental methodology recently developed by the Universitat Politècnica de Catalunya. These results will allow, in a subsequent phase of the research, to model the hydraulic behavior of the drainage system under different grated inlets clogging conditions, as such as different rainfall intensity events, with particular emphasis on extreme ones.