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Thread: Grade reversals

  1. #1
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    Grade reversals

    ok fellow trail builders...give me the benefit of your vast experience concerning grade reversals and moving water off of the tread....is it better to 'surf' the contour with short ups and downs or is it better to excavate vertical undulations into a trail?? Is there a real advantage to either? Do both methods get the water off ??? I try to incorporate one or the other as much as possible..but what is your experience??? ( assuming there is always a built-in outslope of about 5% on most of the tread--going to 15% for nicks, etc) Which is more fun to ride??

  2. #2
    Builder of Trails
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    I find it easier to design the trail using the contour lines and build the line than to try to excavate vertical undulations into the trail.

    To make it even easier to incorporate drainage features, you can use the soil you're grading or excavating while creating the bench cut to build fun rollers that also act as grade reversals. I've been using this technique more frequently with great results. It cuts down on construction time b/c there is less soil to broadcast with less impact to the downhill side of the tread.

    Just be sure to actually plan where the rollers go so that they fit the flow of the trail. Get creative, too, by building double rollers that can be pumped or even jumped.

    D

  3. #3
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    Its really nice to see the rolling grade reversal being used in place of the log or rock water bar. Especially near a switchback. But those RGR's are labor intensive and it takes some skill to get it to work right. I see many RGR's failing after a year or so due to a tread cutting too far into the soil. So, those vertical undulations are better for the majority of trail construction, and use the RGR at your critical points. And as duratti says, the double roller can be a great addition to your trail. So my perfect flowing trail goes something like this. If your trail is heading down, the rider goes; um, um, flat trail, um, rgr, switchback, flat trail, um, um, flat trail, um, um, rgr, etc. If the rider is going up that same trail, they have little pockets of flat trail or even tiny downhill sections where they can recover and then continue going up.
    Best of luck.

  4. #4
    featherweight clydesdale
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    Outslope can be defeated through compaction and displacement, so the grade reversals are important whether they are designed (exist by way of planned ups and downs along the contour) or manufactured (dirt piled up dirt rolling grade dip style).

    My preference is for designed grade reversals. It shows more thought on the part of the designer. Manufactured dips often need more frequent cleaning out, though that's often cause the trail is exceeding the half rule.

  5. #5
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    Thanks for the wonderful input and sharing your expertise.

  6. #6
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    99% designed in grade reversals

    Our organization has tried many different types of constructed dips like wooden water bars, stone water bars and rolling grade dips. They all have two related problems. 1) The dip and the rise are not large enough. The small rise often fails, allowing water to run down the trail, either do to damage to the water bar or do to trail compaction. The small size of the dip means it often fills with sediment and allows water to flow over the rise. The dip of a rolling grade dip is 10 or so feet long and 12 inches deep while the rise is usually much shorter. A designed in dip can easily have a length of 50 feet and a depth of 24-36 inches with the rise equally large in the positive direction. 2) The second problem with constructed dips is they are maintenance intensive. If the maintenance doesn't occur the water diversion fails and the water damages the trail. Rather than count on maintenance that may never happen, design the trail so it is sustainable even without maintenance by using designed in grade reversals.

    With already built trails, constucted dips may be your only option to save the trail. However, when you build these dips it is really necessary to commit to preforming the necessary maintenance of the dip to keep it working. The first option when working with problematic existing trails is to consider doing a reroute. Only use constucted dips as a last resort.

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