Difference between revisions of "Curb cuts"
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{{Plainlist|1=Where: | {{Plainlist|1=Where: | ||
*''W<sub>T</sub>'' is the width of the inlet in m, | *''W<sub>T</sub>'' is the width of the inlet in m, | ||
*''Q'' is the flow perpendicular to the inlet in m<sup>3</sup | *''Q'' is the flow perpendicular to the inlet in m<sup>3</sup>/s | ||
*''S<sub>0</sub>'' is the longitudinal slope | *''S<sub>0</sub>'' is the longitudinal slope | ||
*''n'' is Manning's 'n' (between 0.012 and 0.016 for concrete, depending on surface treatment), | *''n'' is Manning's 'n' (between 0.012 and 0.016 for concrete, depending on surface treatment), |
Revision as of 20:21, 29 September 2017
Sizing[edit]
To completely capture linear flow travelling along a gutter perpendicular to a curb inlet, the inlet must be of width:: Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle W_T=0.817Q^{0.42}S_{0}^{0.3}\left (\frac{1}{nS_{x}}\right)^{0.6}}
Where:
- WT is the width of the inlet in m,
- Q is the flow perpendicular to the inlet in m3/s
- S0 is the longitudinal slope
- n is Manning's 'n' (between 0.012 and 0.016 for concrete, depending on surface treatment),
- Sx is the cross slope
Where the intention is to capture only a proportion of the flow, the ratio of flow entering the curb inlet may be calculated:: Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle R_c=1-\left ( 1-\frac{W}{W_T} \right )^{1.8}}
Example[edit]
A curb cut of 3 m is proposed as an inlet for an offline bioretention cell receiving runoff from an adjacent roadway. The gutter and the curb are made from smooth concrete with Manning's 'n' = 0.013. The x-slope is 3% and the longitudinal slope of the road is 2%. The design storm produces flow of 0.08 m3/s.
The width of inlet to capture 100% of this flow is:: Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle W_T=0.817\times(0.08)^{0.42}\times(0.02)^{0.3}\left (\frac{1}{0.013\times0.03}\right)^{0.6}=9.71\ m}
The proportion of water entering the bioretention cell under these flow conditions would be:: Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle R_c=1-\left ( 1-\frac{3}{9.71} \right )^{1.8}= 0.48}
48% of the 0.08 m3/s flow would enter the bioretenteion cell through the inlet as designed.
Curb cuts Gallery[edit]
Curb cut into a bioretention facility in Hinsdale, IL.
Decorative aggregate in the center of the facility reduces erosion and dissipates power inflow around the inlet area. A monitoring/maintenance well can be seen in the foreground.
Photo credit: CNTCurb cut into a bioretention facility in Brown Deer, WI.
Aggregate is used to reduce erosion around the inlet area.
Photo credit: Aaron Volkening