Interception efficiency of grate inlets for sustainable urban drainage systems design under different road slopes and approaching discharges

To quantify the discharge capacity of grate inlets causing urban flooding due to insufficient drainage capacity, 285 experiments for six grate inlets under different approaching discharges, transverse and longitudinal slopes conditions were conducted using 1:1 scale experiment. These experiments indicated: (1) A smaller approaching discharge or a larger transverse slope leads to a higher interception efficiency. The longitudinal slopes weakly influence the interception efficiency of parallel grate inlets. The parallel grate inlet is preferred for its much higher interception efficiency than vertical grate inlet. (2) Six interception efficiency formulas with clear physical meanings using dimensional analysis have been proposed. (3) The average errors of the six current formulas are −1.26%–8.2%. This study can guide the planning and design of urban drainage systems.