Energy Dissipation in Steep Concrete Flume

[DASkurky]

Is there a calculation to design energy dissipation blocks in a steep concrete flume running perpendicular to a roadway?

The drainage area is roughly 2.5 acres with a 100yr flow rate of +/-12cfs. The concrete flume is 2' wide for 250LF on a 3:1 hill and the velocity will be approaching 20fps. At the bottom will be a large rip rap plunge pool but I would like to add concrete blocks (maybe 4"x4" or 6"x6") staggered every so often along the length of the flume to beat up the water and dissipate the energy. Anyone done this before?

Thanks in advance!! Dave

 

[gbam]

FHWA's HEC14 should have the design for your situation.

 

[cvg]

build steps instead of blocks. the steps will dissipate energy, be easier to construct and overall the structure will be safer and not so enticing to skate boarders

 

[Drew08]

It sounds like you want a USBR Type IX Baffled Apron. See USBR EM25: Hydraulic Design of Stilling Basins and Energy Dissipators, Section 9.

http://www.usbr.gov/pmts/hydraulics_lab/reportsdb/action_list_all.cfm

 

[dicksewerrat]

We used Large box culverts cut in half. so we had 2 U shapes. Installed them in a step pattern down a hillside into a river. We installed them so the next one up the hill rested on the lower one and shotcreted them to seal the opening on the hill side. It worked well about a 95 foot drop. Other than that, I always wanted to put channel in with an Ogee curve at the bottom to get the water to fly up and out into the river. The powers that be told me that the Army Corps of Engineers would reject it because we might sink a boat or two.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[cvg]

I believe you are talking about a OGEE spillway with a flip bucket, very enticing for knucklehead skateboarders trying to catch some air...

 

[SMIAH]

A ski jump (trajectory basin) is effective when the approach energy head is at least 50 m and the discharge (in m3/s) is smaller than 250(H-Ho) with Ho = 8 m (Mason, 1982, 1993)...

 

[SMIAH]

100yr flow rate of +/-12cfs