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Evaluating Curb Inlet Efficiency for Urban Drainage and Road Bioretention Facilities

Department of Civil Engineering, Auburn University, Auburn, AL 36849-5337, USA
College of Hydrology and Water Resources, Hohai University, No. 1 Xikang Road, Nanjing 210098, China
Key Laboratory of Urban Stormwater System and Water Environment, Ministry of Education, Beijing University of Civil Engineering and Architecture, Beijing 100044, China
Author to whom correspondence should be addressed.
Water 2019, 11(4), 851;
Received: 4 April 2019 / Revised: 15 April 2019 / Accepted: 17 April 2019 / Published: 23 April 2019
(This article belongs to the Special Issue Design of Urban Water Drainage Systems)
PDF [4001 KB, uploaded 26 April 2019]


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 (S0, 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 S0 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 (S0, 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 S0, 10 Sx, 10 Qin, and 10 Lci combinations) and comprehensively compared with three equations in previous studies. The 100% intercepted gutter flow (Qg100) equations were derived, and over-prediction of Qg100 from previous methods was strongly correlated to smaller S0. 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 S0 is small. View Full-Text
Keywords: curb inlet; overland flow; two-dimensional simulation; bioretention; intercepted flow; inlet efficiency curb inlet; overland flow; two-dimensional simulation; bioretention; intercepted flow; inlet efficiency

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Li, X.; Fang, X.; Chen, G.; Gong, Y.; Wang, J.; Li, J. Evaluating Curb Inlet Efficiency for Urban Drainage and Road Bioretention Facilities. Water 2019, 11, 851.

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