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Curb cuts are a form of LID/BMP [[Inlets|inlet]]. They include a variety of modified curbs and spillways.

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 width 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 should be compared to and modified for the flow requirements of the practice.'''

'''Standard width (450 mm), as included in Ontario Provincial Standard Drawings (OPSDs) should be compared to and modified for the flow requirements of the practice.'''

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{| class="wikitable"

{| class="wikitable"

|+The OPSD collection of standard drawings for curb cuts include

|+The Ontario Provincial Standard Drawing (OPSD) collection for curb cuts  

|-

|-

!Flow direction

!Flow direction

!From asphalt catchment

!From asphalt curb and gutter

!From concrete catchment

!From concrete curb and gutter

!From either asphalt or concrete catchment

!From either asphalt or concrete outlet

|-

|-

|30 - 45 deg

|30 to 45 degree

|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/>

|605.040 Asphalt Spillways <ref name =OPSD/>

|-

|-

|90 deg

|90 degree

|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/>

|605.040 Asphalt Spillways <ref name =OPSD/>

|}

|}

==Sizing==

==Sizing==

==Example==

==Example==

Three (3) curb cut inlets of 1 m width each, representing a total curb cut width of 3 m, are proposed 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 cross-slope ratio 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.  

Three (3) curb cut inlets of 1 m width each, representing a total curb cut width of 3 m, are proposed 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 cross slope ratio 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 from the road drainage area.  

The total width of curb cut inlets required to capture 100% of this flow is:

The total width of curb cut inlets required 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>

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

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

==Curb cuts gallery==

==Curb cuts gallery==

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[[category: Calculations]]

[[category: Calculations]]