Abstract
Making a deep cut on the curb inlet has been used in some sponge-city (SPC) projects for road-bioretention stripes to manage stormwater runoff since they were easily implemented in the field. The efficiencies of the deep-cut curb inlets in those projects were unknown for lacking equation to evaluate their efficiencies. Two kinds of retrofit scenarios are commonly used: (1) The curb-cut cases when the deep cut is made only over the width of the curb inlet; (2) the road-curb cut cases when both the curb inlet and a small part of the road surface have a deep cut. An updated two-dimensional flow simulation program, FullSWOF-ZG, was used to determine two important parameters in road curb inlet design: The 100% interception curb inlet lengths (LT) and the curb inlet efficiencies (Eci). Eight-hundred retrofit modeling cases were compared with the no-cut cases to quantify the efficiency improvement of the deep-cut curb inlets. The simulation results show both LT and Eci of the curb-cut cases do not improve much. This case study with limited combinations of longitudinal and cross slopes and inlet lengths demonstrated that Eci of the road-curb cut cases improves to a large extent so that they can be used in the SPC projects and other urban drainage projects to reduce the flooding potentials. A general equation used to design and evaluate the road-curb cut inlets can be developed based on more simulation cases with a wide range of input parameters in a future study.
Highlights
Curb inlets are important drainage components for urban stormwater management to traditionally intercept the surface runoff into underground stormwater pipelines or to capture runoff into road-bioretention stripes for infiltration and water quality improvement in many recent designs (Figure 1)
The FullSWOF-ZG was used in this study to simulate the two-dimensional overland flow on the road surface and developed from FullSWOF_2D
100% interception curb-inlet for curb-cut the 200 curb-cut cases with cut depths quite similar the LT for corresponding undepressed cases with cases the same slope different cutwere depths were quitetosimilar to the LT for corresponding undepressed withcross the same and upstream means if deep cutdeep is only theover curbthe inlet width, the cutthe depth cross slope and inflow
Summary
Curb inlets are important drainage components for urban stormwater management to traditionally intercept the surface runoff into underground stormwater pipelines or to capture runoff into road-bioretention stripes for infiltration and water quality improvement in many recent designs (Figure 1). The hydraulic performance of undepressed curb inlets (Figure 1b) for roadway drainage has been studied for more than 60 years, which was reviewed and summarized by Izzard [1], Li [2], and systematically documented in the Hydraulic Engineering Circular No 22 (HEC-22) by. Sx are is the curb length, Sx “curb-cut”curb curbinlet inlet(d). Lcithe the and cross slopesslopes of theof road d, w1 , and are the deep-cut depth and widths. W2 are the deep-cut depth and are longitudinal the longitudinal and cross thesurface, road surface, d, ww widths. The undepressed curb inlets have one cross slope for the road surface including the gutter and the curb (Figure 1b) In HEC-22, there are two steps to design curb inlet: (1) Calculate the 100% interception curb inlet length (LT , the curb-opening length when all upstream inflow is intercepted by the curb inlet) based on road longitudinal slope (S0 ), cross slope (Sx ), and roughness; (2) calculate the curb inlet efficiency (Eci , the curb inlet intercepted flow divide by the total inflow from the upstream boundary) based on curb inlet length (Lci ) and LT .
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