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| <poem> | | <poem> |
| Curb cuts are a form of BMP [[Inlets|inlet]]. | | 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? | | 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 increases rapidly on steeper roads. | | 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 is often undersized for LID applications''' | | '''Standard width (450 mm), as included in OPSD drawings should be compared to and modified for the flow requirements of the practice.''' |
| he OPSD collection of standard drawings includes:
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| </poem> | | </poem> |
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| {| class="wikitable" | | {| class="wikitable" |
| |+The OPSD collection of standard drawings for curb cuts include | | |+The OPSD collection of standard drawings for curb cuts include |
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| !From asphalt catchment | | !From asphalt catchment |
| !From concrete catchment | | !From concrete catchment |
| | !From either asphalt or concrete catchment |
| |- | | |- |
| |30 - 45 deg | | |30 - 45 deg |
| |605.020 <ref name =OPSD>http://www.roadauthority.com/Standards/?id=b00e3771-6095-4257-b029-1d9879418039</ref> | | |605.020 <ref name =OPSD>http://www.roadauthority.com/Standards/?id=b00e3771-6095-4257-b029-1d9879418039</ref> |
| |605.010 <ref name =OPSD/> | | |605.010 <ref name =OPSD/> |
| | |605.040 Asphalt Spillways <ref name =OPSD/> |
| |- | | |- |
| |90 deg | | |90 deg |
| |604.020 <ref name =OPSD/> | | |604.020 <ref name =OPSD/> |
| |604.010 <ref name =OPSD/> | | |604.010 <ref name =OPSD/> |
| | |605.040 Asphalt Spillways <ref name =OPSD/> |
| |} | | |} |
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| ==Sizing== | | ==Sizing== |
| <div style="float: right">
| | 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>:: |
| {{#widget:WolframAlpha|id=664012476f5d9635d57cd58920e763e6}}</div>
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| To completely capture linear flow travelling along a gutter perpendicular to a curb inlet, the inlet must be of width:: | |
| <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> |
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| *''W'' is the available curb cut width (m)}} | | *''W'' is the available curb cut width (m)}} |
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| 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. | | 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. |
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| ==Example== | | ==Example== |
| 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 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. |
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| The width of inlet to capture 100% of this flow is:: | | The width of inlet to capture 100% of this flow is:: |
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| <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> |
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| 48% of the 0.08 m<sup>3</sup>/s (i.e. 0.038 m<sup>3</sup>/s) 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. |
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| ==Curb cuts gallery== | | ==Curb cuts gallery== |
| {{:Curb cuts: Gallery}} | | {{:Curb cuts: Gallery}} |
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| [[category: modeling]] | | [[category: Calculations]] |