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== Page Under Construction (Section: Spacing of Road Gullies) ==
== Spacing of Road Gullies (UK standards: BS EN 124 and BS7903) ==
The following section describes the [https://newwww.sthelensstandardsforhighways.govco.uk/mediatses/330117attachments/5126_haa869ed8e-102_00.pdf4470-4286-aef4-7d11af24a597 Spacing of Road Gullies] guidance (UK standards: '''BS EN 124''' and '''BS 7903''') which provides a method for determining road gulley capture rates.
The method depends on the following '''Hydraulic parameters:'''
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* Cross-fall, ''S<sub>c</sub>'' (also expressed as a fraction).
 
* Manning’s roughness coefficient, ''n''. Usually ''n'' = 0.017 for a conventional road surface. Other values are given in the following '''Table 1'''. (For more details, please see Section: 4.35, Table 15.3N of the [https://newwww.sthelensstandardsforhighways.govco.uk/mediatses/330117attachments/5126_haa869ed8e-102_00.pdf4470-4286-aef4-7d11af24a597 guidance]).
 
'''Table 1:''' Values of Manning's ''n''
<br>[[File:Table1Table1N.jpg|450px750px|]]<br>
 
* The grating type (P, Q, R, S or T), or the size and angle of kerb inlet.
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'''Calculation of Gully Flow Capture Rates based on Equations'''
<br>The equations given in SectionAppendix 5C (p.g: 25) of the [https://newwww.sthelensstandardsforhighways.govco.uk/mediatses/330117attachments/5126_haa869ed8e-102_00.pdf4470-4286-aef4-7d11af24a597 guidance] can be used to determine flow capture rates at different depths, to determine the depth-discharge curve for use within TUFLOW. The method requires the calculations of the flow capacity of the kerb channel and flow collection efficiency of the gully grate.
*As a first step, a gully grate type: P, Q, R, S or T should be selected. The selection of the grating type will determine the design value ''G<sub>d</sub>'' (grating parameter) from '''Table 2'''. (For more details, please see AnnexTable BA.2, Appendix A of the [https://newwww.sthelensstandardsforhighways.govco.uk/mediatses/330117attachments/5126_haa869ed8e-102_00.pdf4470-4286-aef4-7d11af24a597 guidance]).
 
'''Table 2:''' Determination of grating type ''G<sub>d</sub>''
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*Further, a Water Depth against the kerb ''H'' (m) range should be provided. (Please note: The depth range can be changed, but the following equations that are used to calculate the flow capacity are only valid up to the kerb height).
 
*With the above parameters, the calculations of the i) Flow width (''B'' in m), ii) Cross-sectional area (''A<sub>f</sub>'' in m2), iii) Hydraulic radius (''R'' in m), iv) Flow rate (''Q'' in m3/s) and v) Flow collection efficiency (''ŋ'' (%)) based on the Equations 6C.1-10C.5 which are presented in SectionAppendix 5C of the [https://newwww.sthelensstandardsforhighways.govco.uk/mediatses/330117attachments/5126_haa869ed8e-102_00.pdf4470-4286-aef4-7d11af24a597 guidance] can be completed.
 
*Finally, the resulting depth-discharge data can be used in the TUFLOW pit inlet curves.<br>
 
The SpacingGully ofFlow RoadCapture GulliesRates template here:(Excel file aboveFile) includes a calculation tab which can be used for the completion of the above calculation processprocesses. Based on calculations and Equations (11)C.6 and (12)C.7 of the [https://newwww.sthelensstandardsforhighways.govco.uk/mediatses/330117attachments/5126_haa869ed8e-102_00.pdf4470-4286-aef4-7d11af24a597 guidance] the gullymaximum flowallowable capturespacings rateupstream of the gully can be further calculated (For more details, please see Appendix C, p.g: 25).
 
'''Key assumption'''<br>'''Note:''' This method assumes that the route the flow takes around the trap limits the discharge from the gully pot to 10 l/s. This limit is effective in both directions, so any negative head on the gully would create -10 l/s flow back up through the gully and flood onto the road. <br>
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