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==Curb cuts Gallery==LSRCA curb.jpg| Curb cut used as a controlled overflow route from permeable paving to a bioretention facility with monitoring well, Lake Simcoe Region Conservation Authority, Newmarket, ONCurb cut CNT.jpg| Curb cut into a bioretention facility in Hinsdale, IL. <br>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. <br>[[Acknowledgements| Photo credit: CNT]]Curb cut AV.jpg | Curb cut into a bioretention facility in Brown Deer, WI. <br>Aggregate is used to reduce erosion around the inlet area. <br>[[Acknowledgements| Photo credit: Aaron Volkening]]</gallery>
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<poem>
Curb cuts are a form of LID/BMP [[Inlets|inlet]]. They include a variety of modified curbs and spillways.
They are well suited to retrofit scenarios and to collect runoff from catchments with relatively gentle longitudinal slope, and/or a greater cross slope. This might be the local topography of a parking lot or a piece of parkland?
As this inlet width is directly proportional to longitudinal slope; the required curb cut width increases rapidly on steeper roads.
'''Standard width (450 mm), as included in OPSD drawings should be compared to and modified for the flow requirements of the practice.'''
</poem>
{| class="wikitable"
|+The OPSD collection of standard drawings for curb cuts include
|-
!Flow direction
!From asphalt catchment
!From concrete catchment
!From either asphalt or concrete catchment
|-
|30 - 45 deg
|605.020 <ref name =OPSD>http://www.roadauthority.com/Standards/?id=b00e3771-6095-4257-b029-1d9879418039</ref>
|605.010 <ref name =OPSD/>
|605.040 Asphalt Spillways <ref name =OPSD/>
|-
|90 deg
|604.020 <ref name =OPSD/>
|604.010 <ref name =OPSD/>
|605.040 Asphalt Spillways <ref name =OPSD/>
|}
==Sizing==
==Sizing==
To completely capture linear flow travelling along a gutter perpendicular to a curb inlet, the inlet must be of width::
To completely capture linear flow travelling along a gutter perpendicular to a curb inlet, the inlet must be of width<ref>U.S. Department of Transportation, Federal Highways Administration. 2013. “URBAN DRAINAGE DESIGN MANUAL.” https://www.fhwa.dot.gov/engineering/hydraulics/pubs/10009/10009.pdf.[[File:USFHWA 2009.pdf|view here]]</ref>::
<math>W_T=0.817Q^{0.42}S_{0}^{0.3}\left (\frac{1}{nS_{x}}\right)^{0.6}</math>
<math>W_T=0.817Q^{0.42}S_{0}^{0.3}\left (\frac{1}{nS_{x}}\right)^{0.6}</math>
{{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 for complete capture (m),
*''Q'' is the flow perpendicular to the inlet in m<sup>3</sup>/s
*''Q'' is the design flow perpendicular to the inlet (m<sup>3</sup>/s)
*''S<sub>0</sub>'' is the longitudinal slope
*''S<sub>0</sub>'' is the longitudinal slope ratio
*''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), and
*''S<sub>x</sub>'' is the cross slope}}
*''S<sub>x</sub>'' is the cross slope ratio (typically between 0.015 and 0.04)}}
Where the intention is to capture only a proportion of the flow, the ratio of flow entering the curb inlet may be calculated::
Where the intention is to capture only a proportion of the flow, the ratio of flow entering the curb inlet may be calculated::
<math>R_c=1-\left ( 1-\frac{W}{W_T} \right )^{1.8}</math>
<math>R_c=1-\left ( 1-\frac{W}{W_T} \right )^{1.8}</math>
{{Plainlist|1=Where:
*''R<sub>c</sub>'' is the proportion of flow entering the curb cut, and
*''W'' is the available curb cut width (m)}}
Where the curb cut width is constrained and a greater flow into the BMP is desired, the effective cross slope may be increased by adding a depressed apron.
==Example==
==Example==
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 m<sup>3</sup>/s.
A curb cut of 3 m is proposed as an inlet for an offline [[Bioretention|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 1 in 25 year design storm produces a peak flow of 0.08 m<sup>3</sup>/s.
The width of inlet to capture 100% of this flow is::
The width of inlet to capture 100% of this flow is::
<math>R_c=1-\left ( 1-\frac{3}{9.71} \right )^{1.8}= 0.48</math>
<math>R_c=1-\left ( 1-\frac{3}{9.71} \right )^{1.8}= 0.48</math>
48% of the 0.08 m<sup>3</sup>/s flow would enter the bioretenteion cell through the inlet as designed.
48% of the 0.08 m<sup>3</sup>/s (i.e. 0.038 m<sup>3</sup>/s) would enter the bioretention cell through the inlet as designed.
<gallery mode="packed" widths=300px heights=300px>
[[category: modeling]]
==Curb cuts gallery==
{{:Curb cuts: Gallery}}
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[[category: Calculations]]