The real price of leaf blowing
Anyone who rides all winter in the mid-latitudes must be aware of the downsides to leaf blowing. Leaves are critical to controlling soil erosion in woods, especially in winter. Please view my video:
In the mid-atlantic region, the real price we pay for a few weeks of fast, leafless mountain bike riding in the fall is about 4 months of poor walking or riding conditions and significant trail degradation throughout the winter and early spring.
Watched your video with interest, and wish to add..
Occur regardless of ground cover, and in colder climates wreak havoc on roads, and buildings.
While ice needles form by soil's capillary action. Different soils are more prevalent.
Yes, leaves provide an insulative layer that lessens ice needle formation.
I'm not for, or against leaf-blowing, and ride a SS due to snapping derailleurs, yet in the video a bias comes through loud & clear. Without trail maintenance this regions trails would disappear in only a few years, as evidenced by the # of blowdowns that become log piles. And I feel that soil erosion is more a matter of grade % than it is leaf cover.
The best is the one you want to ride most often..
I haven't watched the video yet, but if you are relying on leaf cover to prevent soil erosion, then you are dealing with poorly designed trails.
Grit, spit, and a whole lot of duct tape!
Leaves *may* help insulate bare soil, but freeze/thaw will still occur, especially in flat or poorly drained areas (as your video seemingly portrays). If leaves are left on, and riders/hikers use the trails regardless of conditions, when wet/thawing, the leaves will be pushed into the soil which introduces slower drying/less stable organic materials into the mineral soil, which will take longer to dry, perpetuating the freeze/thaw problem.
Leaves also create a moisture barrier, which works two ways. Yes the do help disperse rain, but also takes forever for the bottom layer of compacted leaves, and the trail underneath, to dry out.
Trails designed to allow water to sheet flow across, rather than down the trail, carry minimal sediment, and dry much faster without leaves.
Not true where the trails are snow covered in winter. Can't speak for your area though.
Originally Posted by ameletus1
I prefer spot treating the leaves.
First, it's a helluva lot of work to get all the leaves off all the trails. Labor that could be better spent making existing trails more fun, or repairing problematic spots, or even building new trails in the first place.
Second, I don't believe it is necessary to remove them all.
If riders are using the trail, the leaves will get crushed and broken down, and the wind will blow away the smaller pieces. In places where leaves collect and hold moisture, it is important to clear them out, but there is probably a problem with the trail in that place, anyway. Maybe it just needs to be debermed. But something needs to be addressed to prevent the leaves and moisture from collecting there in the first place.
I'm seeing that many new riders get too used to the heavily maintained and heavily used "park" type trails that they get really whiny about trails that are allowed to be a bit more rugged. They get whiny about leaves that are left in place, not because they create a maintenance issue, but because they crash. Sometimes it's because they're riding balls-out into a leafy corner and there is less traction so they go down. Sometimes it's because the leaves covered up a rock or a root. The result is the same. These people think that leaves should be cleared from ALL trails and that trail conditions are always supposed to be the same.
Unfortunately there is no real cure for freeze thaw. You may get a few rides in early in the fall if the leaves are left on, but once you are in full on freeze thaw, riding on leaf covered trails will only mix the leaves into the soil and create a solid that dries very slowly.
Each trail is different and each winter is different. There is no correct answer on leaf blowing, and it really is up to those who maintain the trails to make the decision. If you think you can do better, then get involved with the group maintaining your trails. If you don't have time under your belt maintaining trails, then posting videos on MTBR pushing you agenda (which I suspect is wanting to ride in freeze thaw conditions), is just a waste of time.
I have no bias but every spring it seems the leaf blown trails are the 1st to be ready to ride and in the better shape then the non-blown ones.
2014 S-Works Epic WC
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That makes sense, and it would fall under my spot treatment philosophy. Early in the spring, the wind probably plays more of a role in drying things out than during other times of the year, so getting wet leaves off the trail that are still covering parts of it would help.
Originally Posted by irishpitbull
Riding the trail when it's frozen helps crush out some of that frost heaved soil and seems to help pack it back down somewhat.
I would counter that in your video, you are drawing spurious conclusions based on what you think you are seeing. You are comparing sites with different positions on the hillside, and other differences that govern the behavior of soil moisture far more than frost heave. You have drawn these conclusions with no testing or statistical analysis to support them.
While it is generally correct that leaf litter dissipates the energy of rainfall and reduces soil displacement, you are not controlling for soil compaction. The soil on trail tread is heavily compacted, while the soil throughout the rest of the forest is generally not. We WANT compacted soil on trail tread. It makes for an enjoyable riding experience, and keeps the trail durable. Root exposure on trails has more to do with that compacted soil than with erosion. Those roots were sitting at the surface already, and became more exposed as the soil compacted.
The problems you are seeing are exacerbated by the fact that the trails in your video are "built" (I say that loosely) on very low-relief trail. Soil compaction creates the cupping of the trail that indytrekracer mentioned. That is what allowed for the soil displacement you illustrated in your video. The coverage of that soil on the bridge suggests that most of that soil displacement occurred in one or more high energy events. Heavy rainfall, where the soil's infiltration capacity was exceeded by the precipitation rate. That causes surface runoff. With proper trail design, we want surface runoff to flow off the SIDE of the trail, not down its length. This allows that surface runoff to flow into areas with leaf litter and downfall to reduce the energy of the flow, it allows that water to go to places where there is higher infiltration capacity (uncompacted soils underneath leaf litter).
On to your discussion about the leaf litter preventing freeze/thaw cycles. You are correct about one thing, that the leaf litter serves as insulation, reducing how frequently the soil is frozen. However, you have drawn the incorrect conclusion based on this observation. That soil under the leaves never froze. The reason it's not muddy is because it is higher on the hill than the muddy portion of the trail you illustrated. You shouldn't be out riding or hiking the trail when it just squeaks above freezing and begins to thaw out. When the soil sticks to your boots or to your tires, you're damaging the trail. Time your visits to the trail such that you're using them when the trail is still frozen. That means early in the morning and late at night. No mud.
Deep snow serves the same insulating function as leaves. Ever been on a snowy trail and your tire or boot tracks turn brown, even though it is well below freezing and the sun is not shining on the trail? It's actually better for riding conditions if the snow is shallow and the trail is frozen solid. During the cold season, appropriate riding conditions occur in a pretty narrow range. Visit the trails when the conditions are appropriate. Stay off when they are not.
The criteria begin to change in the springtime when two things occur: First, when the worms start coming out. They start becoming active when the freeze/thaw cycles have really dissipated and you start having warmer days (that help dry the trails out). Whether the trails are ready to ride depends heavily on local conditions. Recent precipitation, soil type, and topography make big differences. The next thing to affect trail conditions may seem odd, but leaf out makes quite a difference. When the trees begin leafing out, that means they're pulling up soil moisture. This helps wet soil to dry out faster.
None of these factors have anything to do with dead leaves on the trails. However, as irishpitbull mentions, in the springtime, trail tread exposed to the air may dry out faster. In part, this has to do with allowing air to circulate around the soil. As the wind blows over, it will help moisture evaporate more quickly from the surface of the trail. It also affects the sun exposure to the trail tread. Warm sun on that soil also helps accelerate evaporation. The insulation of the leaf litter on the trail will prevent those two factors from affecting the evaporation of the moisture on the trail tread.
In some places, that won't be a big deal. The trails see such low traffic that the small amount of moisture won't affect much and they'll have plenty of time to dry. Spots high on the hillside, on south facing slopes, soils with high infiltration rates (sandy or rocky soils), or areas exposed to a lot more wind or sun have factors that help dry the trail tread, so some leaf litter won't be a big deal. However, some spots need it. Deep valleys oriented perpendicular to the prevailing winds will tend to be sheltered and need all the help they can get. Trails on northern slopes won't get much sun exposure, if any at all, and will need all the help they can get. Areas with difficult drainage issues should have the leaves removed, as those leaves not only provide insulation and prevent evaporation, but they act as sponges as they decompose and keep keep the trail wetter longer. This is great for forest plants, but not for forest trails.
Builder of Trails
While I'm in the leaf-blow-the-trails camp, here's a different reason: *Safety.
Clearing trail of leaves does several things to make the trails safer for users.
- Better traction on most soil types
- Exposes roots, rocks, stumps, and other obstacles in the tread
- Exposes stumps and rocks on the edge of the tread
While some will argue for the experience of leaving the leaves on to counter my second reason, personally, it's not the experience I'm going for. I'm blind in one eye and don't need extraneous stuff like that to have a great ride.
I acknowledge that blowing leaves doesn't expose all the risks on the edge of the tread, it helps.
*I design, build, and maintain trails where this matters for risk of closure if something untoward happens.
Real afficianados use rakes, as it makes the trails taste better. More 'terroir' , if you will.
A chacque person sa gout!
"We LOVE cows! They make trails for us.....
And then we eat them."
Your trails aren't mine. All leaf blowing is not bad here in New England. I find better thawing and drainage on cleared trails. Drainage easier to keep clear as well. I think the issue comes down to local topography and soil conditions, all will vary for each area.
I actually did a test on the trail I designed and built here in NC. Having the luxury of seeing the trail mature/evolve from the very beginning is nice and makes it easier to really quantify the effects of trail maintenance. I tried a full year of not blowing leaves off the trail and there were two things I noticed: Lot's of clogged/bermed up drains that stayed muddy well into the Spring and trail creep where there is a lack of physical barriers. Especially around muddy areas. That was the longest, hardest Spring cleanup of the 5 miles of trail I've ever had to do! Now I remove the leaves in 2-3 stages in the Fall after the majority of the leaves are down. Then leave what ever falls after that until the Spring. Some leaf litter usually gets moved by riding without having a thick mat of leaves on the trail. Plus a back pack leaf blower blows more than just leaves out of the drains and actually makes drain clearing easier and more efficient!
I deal with many trail coordinators in our area (Charlotte) and I leave it up to there best judgement on whether to remove the leaves or not. Most usually do remove and the one that doesn't actually benefits from it due to a high volume of sand content. Plus, they're the ones that have to clean/maintain the trail. Riding time usually trumps trail work time in the Spring so the less time doing trail work leaves more time for riding! Which is why we all do this anyway, right?
follow-up from ameletus1
My post and video generated more response than I expected, but I am glad to see it. Some responses seem to imply that I have some sort of "agenda"--I do, but I think it is the same as everyone else's, namely I love mountain biking on woodland singletrack, and I want to preserve the best riding experience. I have been riding the trails at Fair Hill (where I shot the video) for 20 years, logging over 18,000 miles in that park alone! I am also a biologist. I frequently walk the same trails and pay close attention the plant and animal communities, right down to the soil-inhabiting fauna. Beginning in 1996 I constructed and continue to maintain a small trail system in the woods behind my workplace in adjacent southeastern PA which I ride daily at lunchtime. I have monitored the changes wrought by leaf blowing at Fair HIll (a practice that only really took off about 5 years ago) and compared to my trails where leaves are always left on the trail (by the way, this does not mean mine are not maintained--there is plenty of other work to do!).
I do not advocate a "one size fits all" philosophy of trail management. I made it clear in my post that I was talking about the mid-latitudes, where for most of the winter there is no snow cover but there are daily freeze-thaw cycles. My video is specific to trails in northeastern MD where this is the case. I agree that farther north, where there is snow cover all winter, we have a different situation (although there will still be transitional periods in late fall and early spring where I believe you will see trail degradation due to leaf blowing). In more southerly climes, frost heave is less likely to be an issue.
NateHawk, who posted the most elaborate reply, says, "Early in the spring, the wind probably plays more of a role in drying things out than during other times of the year, so getting wet leaves off the trail that are still covering parts of it would help." Where I live, early in spring you are still experiencing freeze thaw cycles which, on bare soil, brings up moisture from the deeper soils. So bare trails stay wetter. And in my local climate, it is not as if spring is a time of zero precipitation, when you are just waiting for things to dry out from winter.
NateHawk also says: "While it is generally correct that leaf litter dissipates the energy of rainfall and reduces soil displacement, you are not controlling for soil compaction. The soil on trail tread is heavily compacted, while the soil throughout the rest of the forest is generally not. We WANT compacted soil on trail tread. It makes for an enjoyable riding experience, and keeps the trail durable." I agree that soil compaction on trails is a good thing, but this occurs with or without leaf cover. Just brush aside leaves in the middle of the trail (as I do in my video) and compare with adjacent off-trail areas. The problem in my area is, the nightly frost heave that occurs on bare sections of trail loosens up the (previously compacted) soil, which then makes it highly susceptible to erosion from rain events. The rain that caused the soil to wash over the bridge in my video was a minor event; the freshly thawed frost heave just made it ripe for erosion. With leaf cover you maintain soil compaction (i.e., no frost heave) AND the benefits of raindrop energy dissipation.
No soil conservation expert would recommend bare soil as good conservation practice. For many years the Soil Conservation Service advocated that sod is the best way to stabilize soil in open areas. Heavy bike or even foot traffic through a grassy area tends to pack down the soil to a nice fast surface, but eventually kills the grass, which results in trail gullying even where gradient is modest. Thus, at Fair Hill, in open fields we often see a succession of tracks. Once a track becomes gullied a few inches, riders then avoid those and start a new, parallel track. A succession of 3 or 4 tracks is often evident. Sod must be living to afford soil protection. Leaves on woodland trails perform the same function, but since they are already dead, heavy traffic does not compromise their conservation abilities (unless it is horse traffic, of course--then all bets are off!).
NateHawk also suggests that one should stay off the trails in winter when they are muddy (which at Fair Hill where I ride means most of the time, except for night and very early in the day, when they are frozen). Problem is, trails at Fair Hill are only open during daylight hours, which leaves only an hour or two at dawn on most winter days when the ground on blown trails is still frozen--not long enough for the 25 mile ride I usually do. The good news is, leaf covered trails are never muddy! Why should we stay off the trails all winter just so the bare ground lovers can have their leaf-free trails for a few weeks in the fall?
Regarding safety concerns many trail-blowing advocates invoke, I can't believe people riding around on 29 inch fat tires complain so vehemently about leaves concealing roots and rocks. Perhaps those folks should either stick to roads or work on their riding skills.
Your bias is unfounded, and while you may ride lots & care greatly - it's misguided. Besides exerting bias, getting into the age old wheel size debate further weakens the stance.
The best is the one you want to ride most often..
Very interesting thread. Our local group is very much in the "Non-Leaf Blowing" crowd.
We have very rocky trails here and can ride pretty much year round. The thing keeping me from riding now is the snow/ice. I'll even shred in the powder but not after we got a 1/4 inch of sleet..
My view of the situation is leaving the leaves while in my area is a total push whether it hurts or helps the trail is one based upon the group not wanting to work on the trails.
They justify there lack of trail work by using the leaves decision to support them.
I have one trail that I consider my home trail and we come in and clear the leaves and cut out trees when they fall and it is my goal to be removing leaves as my little group of trail builders grow.
In a high traffic, soft soil area I could see the leaves as being a "means to an end" to help the trail survive.. as well as keeping some ppl from riding cuz the trails are difficult to follow at speed..
I guess I am just more surprised some one is actually out their blowing leaves off a trail. Jesus people it's nature not a f'ing shopping mall. If you have problems riding on wet nasty leaves either use tires better suited it, slow down, work on your skills or all of the above.
Not sure where you live but trails in my area have way to many remote miles, and leaves to even consider this a part of trail maintenance. Especially when there is so much real maintenance that needs to be done.
Now I will agree it can be used a tool to clear areas that need to have drains cleared, create, or work on an out slope.
Sent via my heady vibes from the heart of Pisgahstan
Stay on the trail. No braiding. Go.
I have a device that can access the total knowledge of man. I use it to look at pictures of cats and argue with strangers.
EXACTLY, man! Ten or 15 years ago, the very idea of blowing leaves in the woods would have seemed preposterous. Leaf blowers are a solution looking for a problem! And NOT leaf-blowing is a not sign of laziness (as suggested by the previous post). In fact, I would say walking around with a backpack leaf-blower is about the least physically-challenging form of trail maintenance. If we were to limit trail crews to only non-powered tools, how many leafless trails do you think we would see?
Ride it for a week or two and the leaves will mat down. If you are still having trouble following it, maybe you should stick to roads.
Re: The real price of leaf blowing
Perfect, and fitting. ^ This is actually me doing VA's Southern Traverse (SMT) on 11/13/10.
Originally Posted by Trail Ninja
It's a remote ridgeline singletrack that sees little traffic, or maintenance.
Never had I seen so many leaves, it was like skiing deep powder, impossible to see rocks, stumps, or the trails edge. On sidehill exposures it was very sketchy.
This is not the situation near Metro DC, where tails are easily accessed, maintained, and used heavily.
The best is the one you want to ride most often..
This is a great conversation... I really appreciate the time and consideration the author put into sharing his observations. It is the discussion for me that will advance greater awareness regardless of conditions or region you live.
In N Calif in the Western Sierras, we can get massive build up of organics on the trail. Both Oak leaves and Pine Needles. In addition, each winter brings lots of sticks and pine cones onto the trail. This becomes a major problem when it gets more than a inch thick. With many miles of trail to maintain... regional solutions and tactics are key.
I have found that blowing the trails removes too much of the darker mulched organics in addition to the top cover, leaving more of the base clay soils exposed. This definitely is more muddy when wet and degrades the surface more both through traffic wear, greater compaction/displacement and splash erosion. The real problem though for us is, if blown clean, halfway through the year (no rain in summer), the trail is covered with mercury like dust. (further erosion through displacement and not healthy)
My new solution is to pull a light chain link drag behind my ROKON. This scatters surface rocks, sticks, pine cones and most leaves and pine needles off the tread without disturbing the base layer that is Knit together, partially broken down litter. This removes the majority of the fresh spongy type material while leaving enough other organics to reduce wear.
I got to say, my biggest surprise is reading that people still believe that out-sloping trails is effective. Narrow surface trails with moderate use compact and displace soils fast enough to cup a tread every year defeating out-sloping. That is a lot of maintenance! California is plagued all up and down our coast with (once) beautiful trails that have suffered massive failures due to the lack of annual outter edge maintenance(side slope built). When out-sloping fails, water can travel 100s of feet accumulating enough energy to erode. I have found that trails with frequent grade reversals do not have this problem. (different discussion )
We mostly build our trails with a much wider base, but keep the active thread narrow. When you factor speed, flow and intended usage, building in a 4-5ft wide corridor can actually be pretty narrow with the newer bike that are intended to ride like way faster. A 4ft fully-benched & properly outsloped trail w/ 2ft thread is actually pretty darn easy to maintain. After many years of building with this technique, I still have to return to fix a single cup on a trail.
Originally Posted by zachi
I agree that a grade reversal is, by itself, a better drainage solution than outsloping. Efficiency come from a mix of various techniques well blended together.
A trailbuilder from the north
I admit, I still generally out-slope where it does not contradict needed cambering. I feel I need to kick out-sloping in the nuts often though because I see so much defensive resistance from our own state parks and others to do anything else. This is especially frustrating where multipurpose trails have out-sloped turns that fly in the face of needed cambering causing excessive lateral wear on the trail and dangerous riding environments.
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