Difference between revisions of "Curb cuts"

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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 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 is often undersized for LID applications'''
he OPSD collection of standard drawings includes:
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{| class="wikitable"
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|+The OPSD collection of standard drawings for curb cuts include  
|+The OPSD collection of standard drawings for curb cuts include  

Revision as of 21:07, 8 November 2017

Curb cuts are a form of BMP 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?
As this inlet width is directly proportional to longitudinal slope; the required curb cut increases rapidly on steeper roads.
Standard width (450 mm), as included in OPSD drawings is often undersized for LID applications

The OPSD collection of standard drawings for curb cuts include
Flow direction From asphalt catchment From concrete catchment
30 - 45 deg 605.020 [1] 605.010 [1]
90 deg 604.020 [1] 604.010 [1]

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 depressed apron.

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]