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Curb cuts are a form of BMP [[Inlets|inlet]].  

Curb cuts are a form of LID/BMP [[Inlets|inlet]].  

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.'''

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{| class="wikitable"

{| class="wikitable"

|-

|-

!Flow direction

!Flow direction

{{#widget:WolframAlpha|id=664012476f5d9635d57cd58920e763e6}}</div>

{{#widget:WolframAlpha|id=664012476f5d9635d57cd58920e763e6}}</div>

   

   

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>

*''W'' is the available curb cut width (m)}}

*''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.  

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|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.  

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 m³/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 m³/s (i.e. 0.038 m³/s) would enter the bioretenteion cell through the inlet as designed.

48% of the 0.08 m³/s (i.e. 0.038 m³/s) would enter the bioretention cell through the inlet as designed.

==Curb cuts gallery==

==Curb cuts gallery==

{{:Curb cuts: Gallery}}

{{:Curb cuts: Gallery}}

 

[[category: modeling]]

[[category: Calculations]]