stormwater flow through a gravel berm

[DenverJ]

High all.

I am trying to figure out how to model the following:

I have a 400 foot square gravel pad with a level surface. There is a gravel berm running along the fill slope sides creating a "pond". The berm is approximately 18" high and 4 to 6 feet wide at the base. What I am trying to do is model the rate of runoff through this gravel berm using HydroCAD. Any suggestions how I might to this?

 

[beej67]

Anything you come up with will be speculative.

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

http://www.campbellcivil.com

 

[chicopee]

Is the pooling of water due to sediment filling the interstitial spaces between stones?

 

[DenverJ]

For modelling purposes, the assumption in this case, due to Pennsylvania DEP's infinite wisdom, is that the surface of the gravel pad is impervious. The only outlet would be through the gravel berms along the perimeter, which would be constructed with a clean, well sorted gravel.

 

[cvg]

you can calculate a flow rate by estimating the hydraulic conductivity and the hydraulic gradient. Sediment and debris clogging will greatly reduce it. As Beej already stated, your result will be at best a SWAG.

your value will vary greatly depending on your assumptions

Hydraulic Conductivity
(m/sec)
Gravel 3×10-4 to 3×10-2
Coarse sand 9×10-7 to 6×10-3

http://www.aqtesolv.com/aquifer-tests/aquifer_properties.htm