Hydraulic Efficiency of Continuous Transverse Grates for Paved Areas

The hydraulic behavior of several continuous transverse gully grates is studied. Their use is common in some urban or impervious areas (squares, airport pavements, parks, pedestrian areas, etc.) where isolated inlets turn out to be ineffective in collecting the whole runoff into the sewer system during a storm event. Normally, manufacturers of such structures provide information about the bearing capacity, but little concerning their hydraulic behavior. Some grates with various widths were tested at the Technical University of Catalonia hydraulic laboratory for different approach flows and a large set of longitudinal slopes. Experimental equations were obtained to relate hydraulic efficiency of these structures to some relevant flow parameters such as the Froude number and the hydraulic depth. The first equation achieved may be used as a first approach to design a surface drainage system considering a constant circulating flow, whereas the second expression does not depend on flow values and could be used in storm-water and wastewater software packages to design surface drainage systems and for dual drainage modeling.