Merits and Demerits of using Rational Formula
Merits and Demerits of using Rational Formula
(OP)
Dear All,
I have designed a sewerage network of a small catchment(less than 200 hectare) using maximum value of the run off based on Rational Formula. The pipes were sized using Manning Equation.
Now I am trying to understand the merits and demerits of using Rational Formula and Manning Equation, any other formula which could have been used for run off estimation.
Please can anyone suggests some points in this regard.
Regards
I have designed a sewerage network of a small catchment(less than 200 hectare) using maximum value of the run off based on Rational Formula. The pipes were sized using Manning Equation.
Now I am trying to understand the merits and demerits of using Rational Formula and Manning Equation, any other formula which could have been used for run off estimation.
Please can anyone suggests some points in this regard.
Regards





RE: Merits and Demerits of using Rational Formula
http://www.stormh2o.com/SW/Articles/Voodoo_Hydrolo...
RE: Merits and Demerits of using Rational Formula
There have been extensive discussions on this site as to the pros and cos for the rational method including its limitations. The term "small catchment" is a relative term depending on the actual size of your catchment. For the rational method, I have seen in literature the cut off to be anywhere between 160 to 200 acres. That's only 65 - 80 hectares more or less.
Look up the following threads for initial search: thread194-174764: New to urban drainage design, struggling with general design procedure and/or thread162-198581: Volume of Runoff Rational Method Formula
It would appear to me that based on your "size" description, that you may need to look at a different method.
RE: Merits and Demerits of using Rational Formula
RE: Merits and Demerits of using Rational Formula
Very true, it all depends on the local agencies and I have seen the area cut off with different area cut offs. As an example the 160 Acre came from a state agency. I do have to mention again and I agree with you that a different method may be in line for this one.
RE: Merits and Demerits of using Rational Formula
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RE: Merits and Demerits of using Rational Formula