Comparative study among different methodologies to determine storm sewer inlet efficiency from test data.

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. Several agencies and manufacturers of grates have investigated inlet grate interception capacity by hydraulic tests. Actually the reference in this field is the Hydraulic Engineering Circular No.12 published by U.S. Department of Transportatio n; it describes a semi-theoretical method for estimating inlet efficiency but was elaborated for some different types of grates and its use is limite d to these ones. Recently Neenah Foundry Company, in its recent catalog, presented a research project about inlet grate capacity but this methodology suffers from the same restriction. The Hydraulic Department of the Technical University of Catalonia started a new research line in the field of inlet hydraulics and one of the goals was the finding of a formula usable for each type of grate and street geometry, even that could be applied to inlets not previously tested but similar to those used in the experimental campaign. A comparative study among these methodologies was carried out and it was demonstrated the similarity of the results in terms of efficiency.