Methodology to estimate hydraulic efficiency of drain inlets

Effective drainage of roadway pavements is essential to the maintenance of street service level and traffic safety. Storm drainage inlets are used to collect urban runoff and discharge it to an underground sewer system. Inlet efficiency governs both the rate of water removal from the gutter and the amount of water that can enter into the storm sewer system and it depends upon inlet and road geometry as well as the hydraulics of the approaching flow. In the present study a methodology to assess inlet efficiency from experimental tests is presented. An empirical relationship is proposed to obtain the hydraulic efficiency as a function of inlet and street flow characteristics. According to this procedure inlet efficiency could be estimated on the basis of grate geometry and the hydraulics of the approaching flow. The procedure was compared with other methodologies proposed in recent years in the field of urban hydrology.