Stormwater Conveyance Down a Steep Slope
Stormwater Conveyance Down a Steep Slope
(OP)
Hello,
I am trying to convey stormwater from a pond outlet down a steep slope (approx. 32% slope or 17.7 degrees) and need some help with my design.
We are proposing the use of buried pipes and manholes and I am wondering if this is the best approach. Can someone suggest alternatives for both above ground and below ground conveyance. And if our proposed approach is used, what sort of manholes can be used to limit the amount of fill required and still dissipate the energy of the flow?
I am trying to convey stormwater from a pond outlet down a steep slope (approx. 32% slope or 17.7 degrees) and need some help with my design.
We are proposing the use of buried pipes and manholes and I am wondering if this is the best approach. Can someone suggest alternatives for both above ground and below ground conveyance. And if our proposed approach is used, what sort of manholes can be used to limit the amount of fill required and still dissipate the energy of the flow?





RE: Stormwater Conveyance Down a Steep Slope
RE: Stormwater Conveyance Down a Steep Slope
RE: Stormwater Conveyance Down a Steep Slope
RE: Stormwater Conveyance Down a Steep Slope
RE: Stormwater Conveyance Down a Steep Slope
RE: Stormwater Conveyance Down a Steep Slope
RE: Stormwater Conveyance Down a Steep Slope
I live in a rather hilly region and have completed several of these types of designs. As cvg has said your best best would be to size your pipe smaller to ensure full flowing conditions with some kind of energy dissipation located at the downstream end if required. It may be beneficial to consider pipe materials as well in this case due to 1) higher velocities and 2) Given the slope, there may be a possibility for our pipe joints to separate. Considering a single section of HDPE or Cobra Lock PVC may be an option to consider. Placing perforated pipe at the bottom of the slope may be something you would want to look at in more depth and also consult a geotechnical engineer as this added moisture may be a cause of toe failure down the road.
Outside the scope of the storm sewer, constructability may be an issue. Given the overall vertical drop and slope of the hill, I would assume that you would assume that you would want to disturb as little as possible on the slope to maintain slope stability. This being said, regardless of soil type, you'd want to maintain as much tree'd vegetation as possible and use a long armed shovel and small compaction equipment.
Hope this helps.
RE: Stormwater Conveyance Down a Steep Slope
RE: Stormwater Conveyance Down a Steep Slope
I know of a project of similar slope that as a State park, and the Parks department did not want any trees cut (scars). And other projects dumping over the slope had caused washouts. Solution was a pipe on the surface, snaking around trees to the toe of the slope, then into a stilling basin constructed of large rocks. I believe it was 8" corrugated HDPE, and secured with a strap & duckbill anchors at intervals.
RE: Stormwater Conveyance Down a Steep Slope
RE: Stormwater Conveyance Down a Steep Slope