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Can I just divide rainfall depth by time to get rainfall intensity.? 1

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Akel

Civil/Environmental
May 22, 2012
33
Hi,

I am being tasked with the design of an urban drainage system for an upcoming project in a yet undeveloped desert in the Middle East. I am usually provided with IDF curves for use in the rational method and I do design the drainage system using guidance from HEC-22.

For this particular project, I am not provided with IDF curves since none are available. The ONLY information provided is the precipitation depth vs. time. eg (not actual values):

Link

The authorities are really unhelpful and have told me to "design with whatever information you have".
The question is, can I divide the depth by time (equal to the time of concentration) and use that intensity as an input to the rational method? And if yes, is there any reference to back that up? Since I've searched and haven't found anything helpful.

Thank you.
 
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Yes - Your table appears to contain Depth-Duration-Frequency (DDF) data, which can be converted to Intensity-Duration-Frequency (IDF) data by dividing each depth by the corresponding duration. The two tables are completely equivalent.

Peter Smart
HydroCAD Software
 
Thank you psmart.
 
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