Convertiing concentrated flow to sheet flow

[kkoloj]

Has anyone used anything other than dispersion walls or rip-rap to convert concentrated flow to sheet flow? I am trying to drain a sloping (5-10%) residential property to an existing, natural ravine at the back of the lot. We could also use a sump pump to get the water up the slope to the street at the front of the house.

Thank you for any feedback.

 

[francesca]

By dispersion wall do you mean level spreader? If it's just a residential property (i.e. one of them) then you could divert the roof drains into parallel PVC pipes that are buried in the lawn on level. See here for more details. Or I guess you could have the downspouts fill a rain tank that could be used to irrigate the yard.

 

[kkoloj]

francesca:

Yes. Except the dispersion wall is actually a wall (e.g., 6" block) in a concrete "detention basin" about 15" deep. There are three levels of protection: (1) you have area drains in the concrete basin that drain under the wall down slope and feed into a perforated pipe (level spreader), (2) for larger events you core holes in the wall so that when the perforated pipe becomes saturated the basin will fill up and water will empty through the cored holes, and (3) in catastrophic flooding water can simply spill over the top of the 15" high block wall.

Sorry for the lengthy reply. Have you had any problems with sump pumps?

 

[blueoak]

The problem with sump pumps for a single residence is that it won't be maintained and you end up with concentrated flow again or you get water at the foundation. I am a big fan of passive drainage systems.

I prefer dropping water into a channel as concentrated flow. If the channel isn't stable (e.g. bedrock) I like to armor it for the little flows from the pipe or lined ditch and during large events there is normally enough flow in the channel that eliminates any scouring potential. I do not see sheet flow on projects because you have to worry about seepage into the bank and possible sloughing. The areas I have worked the drier you keep the bank the better. This seems to be especially true if irrigation water may be running through the drainage system.