Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Diversion of Watercourse/culvert by introduction of new culvert

Diversion of Watercourse/culvert by introduction of new culvert

Diversion of Watercourse/culvert by introduction of new culvert

I am a graduate engineer and I have a task to provide the most sustainable solution that provides both a safe, cost effective and sustainable solution having minimal impact on the existing watercourse. My question is whether I can provide a steep gradient of 1:5

at the inlet of the culvert and then have a linear gradient throughout the rest. The new culvert has a proposed public road over it. How much cover does the culvert require (according to UK regulations it is 1.2m cover but does that include the thickness of the wall? Also is there any other things I have to take into consideration such as Scour protection at the outlet and how to calculate these. What about scour protection at the inlet? The road has also trees planted on an ireland style road where the road narrows? Any answers are much appreciated. Thank you! If you require more detailed information to assist in your answers please do let me know.

RE: Diversion of Watercourse/culvert by introduction of new culvert

I have not designed such a culvert section before so I could only talk about the general points. Before I retired I did have a lot to do with massive culverts systems in power plants.

I believe the 1.2m cover is to the top of the culvert surface if the backfill is soil. This is for the protection of the services from damaging by freezing. You may be able to reduce it within reason if you use structural backfill say lean concrete and beef up the culvert roof for the justification.

From the hydraulic point of view the 1:5 gradient of you culvert base slab is governed by the change of gradient upstream, gradient downstream as well as the cross sectional area.

For example you are mostly likely unable to provide original width of the water course by restricting the flow into a narrower man-made box. You can mitigate the scour effect by having an apron slab before and possibly after the culvert. In any case I would expect the culvert to marry in with the water course with two wing walls so as to fan the flow from a wide stream into the culvert and then widen it out back to the natural water course.

I can't see how anyone, including yourself, can answer your question without carrying a profile calculation. Depending on the downstream slope after the culvert you may have a hydraulic jump then so the apron will have to be designed to withstand it.

You are the designer so it is your god given right to arrange normal, subcritical, critical and supercritical flows in your system. You get this from profile computation which can be done by a spreadsheet. You will then understand how your system behaves and where the risks lie.

Without looking at any code I would say your culvert has to withstand 1 in 50 to 1 in 100 years flood.

RE: Diversion of Watercourse/culvert by introduction of new culvert

I don't work in the UK but there should be a design manual for roads and bridges which should outline the design process. Replacement culverts essentially look to see how the last one performed and make adjustments. New culverts require a hydrology assessment and then determine the size required. The construction specifications are all standard road specifications that you need to arrange.

RE: Diversion of Watercourse/culvert by introduction of new culvert

That steep a gradient would prevent aquatic organism passage, which probably would not satisfy your minimum watercourse impact criterion. That may not be an issue in the UK, but here in NY State, it would only be allowed if no other solution would work.

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. - http://xkcd.com/319/

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


eBook - Manufacturing the Cars of Tomorrow
In this ebook, we'll explore how additive manufacturing is going to transform the way cars are made. This includes commentary from thought leaders such as Ford's CTO, Ken Washington, Customer case studies of ways 3D printing is being used today, and a variety of part examples where 3D printing is already impacting how automobiles are made. Download Now
White Paper - Smart Manufacturing for Semiconductor
New technologies and approaches present great opportunities for semiconductor manufacturers to achieve high levels of innovation, yield and improvement. This white paper explores some of these cutting-edge technologies and how they can be applied effectively in the semiconductor industry. Read about how Smart Manufacturing is transforming the semiconductor industry. Download Now
White Paper - Analysis and Simulation in Aircraft Structure Certification
Organizations using simulation and analysis tools effectively see the benefits in their ability to achieve certification faster and with drastically less total cost than those who do not maximize these tools. Read this White Paper to learn about how digital tools such as analysis and simulation help in aircraft structure certification. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close