rip rap scour protection design
rip rap scour protection design
(OP)
I am looking for a design guide for rip-rap placement downstream of a vertical drop water control structure. I am looking for a design including stone sizing and length and width of the apron to prevent erosion of the river bed. The site is a 70' wide river which will flow over this submerged weir (stoplogs)There is a 2-5' difference between headwater and tailwater depending on conditions. Everything I have found relates to pipe or culvert discharges where the flow is not re-entering a downstream channel. This is a temporary control structure, so I would like to avoid creating a stilling basin/concrete apron if possible. Flows over this 70' wide structure range from 1100 to 5500 cfs running at about 3' deep over the top of the stoplogs. Any guidance would be appreciated.
Thanks in Adavance
Thanks in Adavance





RE: rip rap scour protection design
If this is a stream, it'll be a water of the state, so whatever you propose to do to it will need to be approved, and the USACE may need to be involved. It's probably worth a call to your local corps office who will be able to advise you, and they may have a publication on temporary channel stabilization. Better yet, follow this link.
RE: rip rap scour protection design
RE: rip rap scour protection design
RE: rip rap scour protection design
I'll check my ref's, but with these velocities you might consider a concrete blanket and add cobbles and boulders to the surface. This may provide some habitat or natural value that you could leave it in.
RE: rip rap scour protection design
RE: rip rap scour protection design
Intrusion Prepakt
www.marineconcrete.com
RE: rip rap scour protection design
RE: rip rap scour protection design
Make sure you check buoyancy, logs with +3 ft of water may have large uplift force to restrain against, in addition to the issue of potential undermining from scour hole.
This drop + apron sounds well-suited for gabions & reno mattress, consider checking those out. (no flotation, excellent scour resistance)
RE: rip rap scour protection design
I like bltseattle's mention of a reno mat with a thick geotextile. This will allow for much smaller stone than 12". This way if you have some scour the mat will drop into it. Also you can tie in thicker gabions at the end to produce a limited roll. This can shorten the length. However, with straight stone you may not need to go back to remove it. Sorry I think I boxed my stream references.
RE: rip rap scour protection design