Evaluating Curb Inlet Efficiency for Urban Drainage and Road Bioretention Facilities

An updated two-dimensional flow simulation program, FullSWOF-ZG, which fully (Full) solves shallow water (SW) equations for overland flow (OF) and includes submodules modeling infiltration by zones (Z) and flow interception by grate-inlet (G), was tested with 20 locally depressed curb inlets to validate the inlet efficiency ( Eci), and with 80 undepressed curb inlets to validate the inlet lengths ( LT) for 100% interception. Previous curb inlet equations were based on certain theoretical approximations and limited experimental data. In this study, 1000 road-curb inlet modeling cases from the combinations of 10 longitudinal slopes ( S 0, 0.1–1%), 10 cross slopes ( Sx, 1.5–6%), and 10 upstream inflows ( Qin, 6–24 L/s) were established and modeled to determine LT. The second 1000 modeling cases with the same 10 S 0 and 10 Sx and 10 curb inlet lengths ( Lci, 0.15–1.5 m) were established to determine Eci. The LT and Eci regression equations were developed as a function of input parameters ( S 0, Sx, and Qin) and Lci/ LT with the multiple linear regression method, respectively. Newly developed regression equations were applied to 10,000 inlet design cases (10 S 0, 10 Sx, 10 Qin, and 10 Lci combinations) and comprehensively compared with three equations in previous studies. The 100% intercepted gutter flow ( Qg 100) equations were derived, and over-prediction of Qg 100 from previous methods was strongly correlated to smaller S 0. Newly developed equations gave more accurate estimations of LT and Eci over a wide range of input parameters. These equations can be applied to designing urban drainage and road bioretention facilities, since they were developed using a large number of simulation runs with diverse input parameters, but previous methods often overpredict the gutter flow of total interception when the longitudinal slope S 0 is small. View Full-Tex