5% outslope and horses- Mtbr.com
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  1. #1
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    5% outslope and horses

    Last night I gave a presentation to a local group of land stewards about sustainable trails. It was introductory in nature, we touched upon the 1/2 rule, 10% rule, and the need for 5% outslope on the tread itself.

    One of the equestrians in the group raised a question for which I had no immediate answer for. The fact that he was an equestrian is of no consequence it could just as easily been from a hiker or trail runner.

    Here goes.

    "Give that 10% is the recommended max average grade of a trail, and that is deemed fairly challenging (implying steep), how is it that you can have a 5% outslope without causing any problems while travelling on it?"

    I think the answer has to do with the tread width. Afterall if you are building a 30" wide tread (pretty wide) you are only looking at 1.5" from side to side. If we assume the width of the horse is 10" that is only 0.5" from hoof to hoof.

    I also pointed out that if we could build with less outslope and still have sheet flow we would, but it is not practical. So in the balance to keep users on the trail and water off we use 5% as the rule of thumb.

    I'm not sure if he like my answer.

    Anyone have any experience that would be useful here?
    Jason Murray
    Rep for Ontario, IMBA Canada
    Visit the IMBA Canada site to keep current on all things IMBA in Canada.

  2. #2
    JmZ
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    I think part of the answer has to do with direction of travel too.

    Developing a trail with a 7% outslope will feel like your ankles are rolling. It does become challenging and difficult to hike or ride.

    5% has a outslope that can be perceptible, but it doesn't hinder travel. If someone was walking perpendicular to that trail however it may be more noticeable.

    The best thing to do is to give 'em a quick demonstration. Put 'em on a trail, or if that's not possible just use a sheet of plywood and a brick or two. Slope the plywood to 5%, or 10% to show 'em what it will feel like when walking on it.

    The outslope is there to draw water off the trail, while limiting the grade of the trail is there to keep water from going too much in that direction. They are not trying to accomplish the exact same thing.

    I think the answer above is the same as you gave, but just worded a bit different.

    Good luck,

    JmZ
    JmZ

    From one flat land to another.

    Advocate as if your ride depends on it...

  3. #3
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    You're on the mark

    I would emphasize that you have worked with these guidelines, they have been proven in practice by many trail builders, and they do the job. IMO, there is always someone who is going to try to debate logic with you. Unfortunately in a public service role you don't have the option of dismissing people for being argumentitive.

    Another way to look at is that the recommended outslope stays the same regardless of the climb. Even a 0% grade should have a 5% outslope.

    The side slope and climbing slope of a trail aren't related. The mechanics of walking allow for an easy stride with a 5% side slope. You are on the right track with your analysis. Most people are about 1 foot across at the hips. That's only a 0.6" difference. Say double that for a horse. If your friend is worried about it, he should be aware that even on a so-called flat trail, local micro slopes may exceed that amount.

    Gravity makes walking up a 10% slope a chore. But you are not fighting gravity with a side slope! The issue with steep trail slopes from a construction/maintenance view is that steeper the slope, the more difficult it is to make the water shed off the side.


    Walt

  4. #4
    sunnyside up
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    Joint stress

    Quote Originally Posted by jmurray
    "Give that 10% is the recommended max average grade of a trail, and that is deemed fairly challenging (implying steep), how is it that you can have a 5% outslope without causing any problems while travelling on it?"

    I think the answer has to do with the tread width. Afterall if you are building a 30" wide tread (pretty wide) you are only looking at 1.5" from side to side. If we assume the width of the horse is 10" that is only 0.5" from hoof to hoof.

    Anyone have any experience that would be useful here?
    The equestrian's concerns probably have to do with the valgus/varus stress on the horse's ankles and knees. When the hoof, which is like a flat plate, hits the ground, one side of the hoof will hit first, then the other. This causes uneven stress on the joints. Also as the hoof leaves the ground, it can swing in and smack the other leg as the horse steps forward, even cutting the leg if the shoe has a sharp edge.

    The width of the trail and the width of the horse don't make any difference.

    I often see people running on the paved roadway in my town because the stone-dust side path has too much side slope. The camber of the road is milder and easier on their joints.

    Patty
    "...So forget all your duties, oh yeah! Fat bottomed girls, they'll be riding today..." Freddie Mercury

  5. #5
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    This begs the question how much outslope is too much? It is going to be individual for each horse.

    Roads are typically 2%. I mentioned that we would build the trail with only 2% outslope if we could still get the water to shed, but natural surface trails aren't nearly smooth enough for this to be enough to promte sheet flow across the tread. Or is it? So we have to strike a balance between enough outslope to shed water, but not too much to discourage trail users.
    Jason Murray
    Rep for Ontario, IMBA Canada
    Visit the IMBA Canada site to keep current on all things IMBA in Canada.

  6. #6
    sunnyside up
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    Jason,

    In my experience, trails that get a lot of horse use get troughed pretty fast due to compaction and scuff erosion, and eventually end up with the center of the tread lower than the outside edge, no matter how much outslope you build them with to start with. This evolution of the tread has almost nothing to do with water and everything to do with 1200 pounds of steel-shod post holing and clod kicking. Course once you have a trough, then you will get water erosion to go along with it, but it's not water that causes the trough to form, its lateral displacement of the earth from the horses either pressing/squishing it to the side, or kicking it out of the center where it lands on the edge.

    I find the best design is to lay out the trail with plenty of grade reversals, and to install overbuilt rolling grade dips in between. 2% outslope is fine to start with, but it's going to go away. Sheet flow on equestrain trails is a nice dream, and you can start out building a new trail that way, but you'd need to bring in a Sweko every 3 or 4 years to maintain it.

    In my neighborhood we have a trail that goes up a grassy knoll, and every 2 years the horses move over 4 feet because the trough gets too deep and narrow and it's uncomfortable to walk in it. If you look closely, you can see a decade's worth of old alignments in the 30 feet to the side of the trail. Eventually the gophers and grasses reclaim the old tread.

    Patty Ciesla
    (former horse trainer and equestrian center manager)
    "...So forget all your duties, oh yeah! Fat bottomed girls, they'll be riding today..." Freddie Mercury

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