Difference between revisions of "Curb cuts"

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*''S<sub>0</sub>'' is the longitudinal slope ratio
*''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), and
*''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 ratio}}
*''S<sub>x</sub>'' is the cross slope ratio (typically between 0.015 and 0.04)}}


Where the inlet width is constrained or 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>


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*''R<sub>c</sub>'' is the proportion of flow entering the curb cut, and  
*''R<sub>c</sub>'' is the proportion of flow entering the curb cut, and  
*''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 small depressed section.
<math> 


==Example==
==Example==

Revision as of 18:18, 31 October 2017

Sizing[edit]

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To completely capture linear flow travelling along a gutter perpendicular to a curb inlet, the inlet must be of width::

Where:

  • WT is the width of the inlet for complete capture (m),
  • Q is the design flow perpendicular to the inlet (m3/s)
  • S0 is the longitudinal slope ratio
  • n is Manning's 'n' (between 0.012 and 0.016 for concrete, depending on surface treatment), and
  • Sx 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:

  • Rc 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 small depressed section.

The proportion of water entering the bioretention cell under these flow conditions would be::

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

Curb cuts gallery[edit]