Shallow Ford Stream Crossing
Shallow Ford Stream Crossing
(OP)
Hi,
Could anyone recommend a reference (or any ideas) for a shallow ford (low flow)stream crossing for a walking trail - concrete or otherwise?
I have seen a couple of NRCS details which utilize small stone held in place by large boulders down stream, but I don't feel that these will be permanent enough for our application.
Thank You
Could anyone recommend a reference (or any ideas) for a shallow ford (low flow)stream crossing for a walking trail - concrete or otherwise?
I have seen a couple of NRCS details which utilize small stone held in place by large boulders down stream, but I don't feel that these will be permanent enough for our application.
Thank You





RE: Shallow Ford Stream Crossing
So we recommended that concrete be used through the stream portion. Due to the velocities the concrete path required a vertical stem wall on the upstream side to help resist the stream force to overturn the path. That was 20 years ago and the path is still functioning today. The concrete made for an expensive bike path, but it was offset by the reduced annual maintenance issues.
Here's some additional info on stream crossings. There is a small detail shown as well:
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Good luck.
RE: Shallow Ford Stream Crossing
RE: Shallow Ford Stream Crossing
RE: Shallow Ford Stream Crossing
How seasonal is this flow? Is it after every rain or does it take a good sized event to experience flows? Do you live in snow country?
If it is really seasonal, and not much flow, you might even use a small rectangular channel across the sidewalk, with a prefab grate on top. Small flows can go through it, larger flows can overtop it.
RE: Shallow Ford Stream Crossing
RE: Shallow Ford Stream Crossing
The stream we are crossing is in a FEMA regulated floodplain and drains a fairly large area. When I said low flow, that probably was not the correct term. Any time it rains the crossing will be impassable.
There is rock roughly 4-5' below the streambed. Based on what I am reading here and elsewhere, I am thinking of proposing a concrete crossing and keying a cutoff wall on both the upstream and downsteam end into the rock. The area between the cutoff walls and under the concrete crossing would be filled by washed stone.
Are there other issues I should be looking at? - And is this overkill for a walking trail?
RE: Shallow Ford Stream Crossing
I would look into the requirements for a 404 permit as indicated by CVG above. The link below give you an idea of when a 404 is or isn't required. It's an interesting read, which this post has inspired me to look into as well.
Probably worth while to at least contact the Army Corps and document it. They might tell you a 404 isn't needed as its 'only a walking trail'.
If it drains a fairly large area, you will need to quantify the amount of storm flow. I think 300 acres and less you can use the rational formula. Are you planning on designing to the 100 year storm for the peak flow through?
How about a prefabed walking bridge or something like that. Hard for me to say, I just don't have a good feel of what the area looks like and what you need to do.
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RE: Shallow Ford Stream Crossing
How about a "landing mat" or other metal grating, staked down?
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RE: Shallow Ford Stream Crossing
The ACE in my region has actually encouraged these types of stream xings for trails for a few reasons. One, the timbers do not create a concern with water quality, but pouring concrete next to a sensitive stream crossing does concern them, particularly during construction. Second, the actual "impact" to the stream bed is limited to only the area under the railroad ties, which again would be less than a concrete structure.
Sorry, can't offer any specs, but volunteer trail builders have been installing these successfully over the last ten years, so I'm guessing there's not much to specs for this type of construction.
RE: Shallow Ford Stream Crossing
After taking a closer look at it, and doing some more reading, I think you are right. We are going back to the original thought utilizing stone. We have done some velocity calculations just assuming bank full and it is somewhere in the range of 3 fps. I think the stone is a reasonable solution.
Thanks for all the great ideas.