Swale Design with use of Level Spreader

[emilyno]

Hi, I am working to design a swale for a parking area with a total drainage area of 1.22 acres. The asphalt will cover 37,500 sf. How do I go about designing this grassed swale?

The swale will drain to a level spreader.

Thanks, I am new to all of this!

 

[froude]

If your reviewing agency accepts it, I would use the Rational Method to determine your runoff. Then you could likely use Manning's Equation to determine the physical parameters of your swale.

 

[beej67]

What state are you in? Is the 'grassed swale' intended merely to convey flow or provide a water quality element?

It's highly likely there are criteria for grassed swales (for water quality) and level spreaders dictated to you by your state agency. North Carolina and Georgia, for instance, are significantly different in their design criteria for each. Start with that.

If all you're doing is a simple grassed swale for conveyance, and you have no other criteria to go on, then you should use Rational Method to determine your design flow, Manning's equation to establish your swale dimensions, and the weir equation to set your level spreader length.



Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[msquared48]

There are two different analysis that have to be performed on all bioswales.

One is the hydraulic analysis, and one the water quality portion. You want to make sure that the swale can handle the max required flow without erosion, but still have adequate flow time within the swale to satisfy the water quality issue.

Check the requirements of the local jurisdiction which should be based on the latest EPA regs.

And don't forget the BMP's for construction too.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com