Appropriate duration for 10 Year Rainfall

[jkhor]

If the Council requirement is to design the structure for a 10 Year design frequency.

Can someone please explain which stormwater duration is appropriate to use for the design of say drains within a commenrcial area? I was thinking of using rainfall duration of 10 minutues to size the drains.

 

[cvg]

Your question is unclear. By stormwater duration, do you mean rainfall duration? If you really mean "rainfall duration" than 10 minutes is probably inappropriate. In fact, most 10-year storms will last much longer than 10 minutes, perhaps as long as 24-hours. If you mean "time of concentration" instead, than you need to calculate the time of concentration for your site.

 

[jkhor]

Thanks cvg,

Yes, for this site, the time of concentration is 10 minutes. So will use "rainfall duration" of 10 minutes intensity with frequency of 1 in 10 year for design of drainage structures.

For example in Florida.
1 in 10Y Rainfall intensity(10 minutues duration)=7.5in/H
1 in 10Y Rainfall intensity(60 minutes duration)=3.2in/H