# Measuring trail outslope



## Walt Dizzy (Aug 18, 2003)

I need to do a better job with this. Riding some older trail I've built, it's obvious the trail has too much outslope because my bike wants to run off the trail and down the hill.

The way I've measured this is to plant a McLeod in the middle of the trail, then walk 5-10 yards up or down the trail and guess whether the tip of the handle sits over the outer edge of the McLeod.

When I can get people to actually do this, the outslope generally seems to come out OK. But it seems like people other than myself have difficulty making this procedure work (they get tired and don't want to keep walking up and down the trail? Get confused about what to look for?), so I'm looking for a way to use a level instead.

What I plan to do is to is attach a small level to a 30" long board (my target tread width) with pads attached to each end so we don't end up with the board rocking over small irregularities. The level will be shimmed to read level with a 5% outslope.

My questions to the readers of this thread are:

-Is this a reasonable way to measure outslope? More to the point, have you tried doing it this way and had your volunteers reject it?

-Measuring outslope technique: I've never worried about it, but it seems to me upon thinking more that ideally it should be measured on the fall line instead of at a right angle to the trail. In practice, I doubt if I can get volunteers to do it this way. Maybe it's not even important at the trail grade we will be working at. I'm trying to keep all new trail grades under 7%.

In my ideal world I would get time to train volunteers to build the way I want, than make adjustments to how I present the issues to get a result that is acceptable based on what they actually do. The reality is I get have one day a year to get somewhere between 5 and 50 people to do something useful. Some of them have done trail work before, some barely know which end of a shovel to hold.

Walt


----------



## Woodman (Mar 12, 2006)

A good Smart Level is the easy way to do this. You are right, too much outsole will force all users to the outside edge. If you have enough trail undulation to shed water, too little outsole is a non issue. In many soil types and with high traffic counts, outsole will disappear pretty quick and thus why trail roll is so important (especially where it rains a lot, we had 5" over 12 hrs last week). Outsole is over rated in my opinion, and I stopped measuring it a long time ago. As mountain bike trail builders, we are of course building lots more insloped sections to improve flow. 

Question: If your trail is outsloped and 5% and the tread is 10% where is the water going? Answer- towards the 10% AKA down the trail. But hopefully not very far because you have trail undulation designed in.


----------



## pinkrobe (Jan 30, 2004)

We use a magic stick.









It's a 2' long 2x4 cut at an angle with a $0.99 level screwed to it. Put it on the ground, if the level reads level, you've got 5% outslope. We have several of these gizmos that we always bring to trail days. The volunteers really like them because they can check their work really easily.


----------



## Walt Dizzy (Aug 18, 2003)

Woodman said:


> A good Smart Level is the easy way to do this. You are right, too much outsole will force all users to the outside edge. If you have enough trail undulation to shed water, too little outsole is a non issue. In many soil types and with high traffic counts, outsole will disappear pretty quick and thus why trail roll is so important (especially where it rains a lot, we had 5" over 12 hrs last week). Outsole is over rated in my opinion, and I stopped measuring it a long time ago. As mountain bike trail builders, we are of course building lots more insloped sections to improve flow.
> 
> Question: If your trail is outsloped and 5% and the tread is 10% where is the water going? Answer- towards the 10% AKA down the trail. But hopefully not very far because you have trail undulation designed in.


Thanks, excellent point! I need to do more with undulation of the trail.

Walt


----------



## Walt Dizzy (Aug 18, 2003)

pinkrobe said:


> We use a magic stick.
> 
> 
> 
> ...


A magic stick? Love it, thanks.

Walt


----------



## Woodman (Mar 12, 2006)

Should have noted that you can get a Clino App for your smart phone if you have such (I am old school and refuse to carry my dumb phone in the woods, trail work and riding are sacred time away from technology).


----------



## aero901 (Apr 11, 2012)

I usually just eyeball the outslope where it is used. When working with volunteers, I usually tell them to make the tread nearly flat and have someone with more experience come after and shape the outslope (also by eye). With that said, we have had more problems with trail sections having too much outslope (pushing riders off the trail) than not enough and holding water.

I have also shifted my thinking towards relying more on grade reversals and other humps/pumps/dips to deal with water. Think of them as a "plan B" in case the outslope isn't doing its job. 

Save some spoils from cutting in the tread/backslope and use them to create small elongated rollers (less than 1' high) once in a while on steeper grades. Placing these rollers by large trees that are close to the trail can also help protect their roots from damage as the soil compacts and wears away over time. It's a little more work but also makes the ride more interesting.


----------



## SeaHag (Jul 14, 2011)

Woodman said:


> Should have noted that you can get a Clino App for your smart phone if you have such (I am old school and refuse to carry my dumb phone in the woods, trail work and riding are sacred time away from technology).


Our club has not yet invested in a clinometer...and I nearly always have my phone along for before/after pictures. Do you know the name of that app? Or whether it's available for Android phones?

Thanks!


----------



## BonkedAgain (Aug 23, 2005)

Walt Dizzy said:


> The way I've measured this is to plant a McLeod in the middle of the trail, then walk 5-10 yards up or down the trail and guess whether the tip of the handle sits over the outer edge of the McLeod.


What we tell people around here is


Look up the trail
Plant the McCleod so that the sharp edge of the blade is facing down the trail
Look at the spot on the blade that is half-way between the handle and the downhill edge of the blade
Put your feet on the downhill side of the blade, toe-to-toe, so that the centerline between your boots is halfway between the handle and the downhill edge of the blade
Stand up straight and see where the top of the handle hits the centerline of your body.
If the top of the handle hits your centerline then you are good. If the top of the handle is on the uphill side of your body then there isn't enough outslope. If the top of the handle is on the downhill side then there is too much outslope.

This all works because your body will be naturally plumb when you stand up straight, so instead of trying to eyeball a vertical line from the top of the handle to the blade of the McCleod you are using a cheap plumb-line, your body.

As long as people actually do this and don't try to eye-ball the outslope I have seen good results. It has been my experience that very few people can accurately eye-ball outslope.


----------



## Ridnparadise (Dec 14, 2007)

I think this is a really good thread. Outslope is such a difficult trail building issue. Putting aside IMBA standards; assessing the trail you are working on and the specific location of each of your outslope questions will make a significant difference to the way a trail rides and lasts. One grade does not suit all.

The purpose of outslope is to avoid trail erosion from fast-moving surface and sub-surface water. Crossing steep grades it is tempting to think that requires a steep outslope, whereas it probably needs the back-slope reduced and more frequent grade reversals. However, on flatter terrain you really want outslope to exceed the trail grade as much as possible. Speeds are lower, ruts and cupping happen faster and being thrown off the trail by the outslope on a gentle trail is "challenge" rather than "risk".

A general aim is that water running along the trail should be progressively sheeted off. Just as that means water bars are not required, it also does not imply a consistent outslope. If you progressively outslope the trail leading into and out of grade reversals (drains) and remove the outslope at the high points, riders can hook up on the high points. Further, if you encourage the high points to direct riders away from the most outsloped bits of trail, then insecurity is reduced. The actual gradient becomes less important, because it varies.


----------



## Walt Dizzy (Aug 18, 2003)

Woodman said:


> If you have enough trail undulation to shed water, too little outsole is a non issue.


Do you have any links handy explaining how to design trail undulations properly? Here's my problem: Due to limitations in space to work in, and hill slope, it seems like I'm constantly fighting to get my trail grade correct. Correct as in having the trail grade always less than 1/2 of the fall line of the hillside I happen to be working on.

Do trail undulations (grade reversals) make it acceptable to have short sections of trail that exceed the 1/2 rule? Or not?

Walt


----------



## Walt Dizzy (Aug 18, 2003)

aero901 said:


> I have also shifted my thinking towards relying more on grade reversals and other humps/pumps/dips to deal with water. Think of them as a "plan B" in case the outslope isn't doing its job.
> 
> Save some spoils from cutting in the tread/backslope and use them to create small elongated rollers (less than 1' high) once in a while on steeper grades. Placing these rollers by large trees that are close to the trail can also help protect their roots from damage as the soil compacts and wears away over time. It's a little more work but also makes the ride more interesting.


I have completely changed my thinking on benchcut spoils. Instead of looking at them as refuse to be scattered discreetly, they have become a valuable resource. As you state, burying tree roots is a great way to protect trees we build around. Making rollers on the trail is one way I can think of to deal with trail sections that are difficult to design undulations in.

(Also, I'm putting in much more effort into building switchbacks as compared to making climbing turns and hoping they hold up.)

Walt


----------



## Ridnparadise (Dec 14, 2007)

Walt Dizzy said:


> Do trail undulations (grade reversals) make it acceptable to have short sections of trail that exceed the 1/2 rule? Or not?
> 
> Walt


Yes. Think of it this way. If you don't have short sections more than the half rule, you have to excessively outslope the trail on steep terrain to make water flow off it. Pics make trail grades look flattened compared to outslope, but the aim is to split natural falline water flow at high points and divert it into grade reversals steeper than the half rule. The following section of trail is about 13% average grade on a slope of 20-35%















On flat terrain the alternative is to dig drains deeper than the exits can handle without massive excavation. If you pick the natural drainage sites first, then clear the surface into those drains, you can judge the outslope needed into the drains and feather it off up to the high points. What that means is that on steep terrain the water may "fall" off the trail anywhere near or in a drain and on flat terrain it will gently sheet across the trail as it falls towards and into a gentle, but open drain (grade reversal) that may be equal to the slope and more than 5%


----------



## Ridnparadise (Dec 14, 2007)

Walt Dizzy said:


> I have completely changed my thinking on benchcut spoils. Instead of looking at them as refuse to be scattered discreetly, they have become a valuable resource. As you state, burying tree roots is a great way to protect trees we build around. Making rollers on the trail is one way I can think of to deal with trail sections that are difficult to design undulations in.Walt


We would counsel against using spoil for building up undulations and features, including over roots. It just does not last predictably. Adding rock ballast under it generally does not help and in the end rock becomes exposed and unfavourable. That's not to say we don't do it at times, but digging down and using natural features when going "up" gets a more sound and lasting result. I posted a few pics in reply to one of your other posts. In the one on flat terrain, the spoil has been turned into small islands between the drains. We cover them with organic matter from day 1 to make it all look like it was there before we cleared the drains. On really steep terrain with lots of benching, discarding (broadcasting) may be unavoidable.


----------



## aero901 (Apr 11, 2012)

Walt Dizzy said:


> Do you have any links handy explaining how to design trail undulations properly? Here's my problem: Due to limitations in space to work in, and hill slope, it seems like I'm constantly fighting to get my trail grade correct. Correct as in having the trail grade always less than 1/2 of the fall line of the hillside I happen to be working on.
> 
> Walt


If you don't have natural grade reversals to work with it isn't too difficult to create them during trail layout even on steep side slopes. The key is to flag gradual turns into the trail and this will naturally create grade reversals on the steeper stuff. The steeper the side slope the more gradual the turns need to be or else you start breaking the half rule.

This is the process I use in this situation:

1) Find a route, using the clinometer, with the desired grade and mark it using flagging ribbon on trees at eye level. It is good to be able to see 3 or more flags at a time (20ft/6m spacing usually works well).

2) Imagine the previously flagged route as the centerline of a gradual sine wave. Use pin flags to trace the path of this sine wave while dodging trees and other obstacles. The wavelength should be adjusted depending on the trail grade/ rider speed but not change dramatically between iterations.

Another technique is to use larger trees as trail anchors while routing the peaks of the sine wave above them. The trail is then routed below the elevation of the tree bases between trees (forming the wave troughs) while still minding the half rule. The spacing of the anchor trees selected will depend on the speed of riders on the trail (larger spacing for faster/steeper sections again).

On really steep side slopes (+40%), 1-2ft variations to each side of the centerline should be plenty to set up grade reversals.



Ridnparadise said:


> We would counsel against using spoil for building up undulations and features, including over roots. It just does not last predictably.


I agree not to use the fill method on steeper side slopes where there is opportunity to create proper grade reversals using the terrain. Much less work doing it this way as well. Fill is best used in flatter areas where options are limited for creating elevation changes.

The durability of fill depends a lot on the type of soils used and how well they are compacted. We have silt/clay soils largely absent of rocks and they hold up very well in this application when properly compacted. We use a tamper and compact every 4-6" lift. Removing organic material from this dirt before compacting is very important to get everything to stick together.

If the soil doesn't have enough moisture it is impossible to get it to compact. On the other hand, if it is too wet, compaction will drive out the water forming a gelatinous blob of dirt that will set up like concrete in a few days _if left undisturbed_.


----------



## trailville (Jul 24, 2006)

SeaHag said:


> Our club has not yet invested in a clinometer...and I nearly always have my phone along for before/after pictures. Do you know the name of that app? Or whether it's available for Android phones?
> 
> Thanks!


I use an android app called "Swiss Army Knife" that has an assortment of tools in it included a tool called "Bubble Level" that works great. It shows degrees was surprisingly accurate when I ran some tests (you may need to calibrate it). 
It's not like you can just lay your phone on the trail though. It's best to have something flat you can lay across then put the phone on that, but you can also try to hold the phone and eyeball it level to the trail surface (not as accurate, but helps when that's all you have).


----------



## trailville (Jul 24, 2006)

*Trail Spoils*:thumbsup:
I'm also another one that uses trail spoils. Good dirt is a wonderful thing, I hate to see it thrown away. We have some good clay soil, and when I see what the BMX Dirtjumpers are able to do with the stuff (building amazingly firm very steep kickers), I would certainly hope I can use it a little here and there to shape a trail .


----------



## BonkedAgain (Aug 23, 2005)

trailville said:


> I'm also another one that uses trail spoils.


You are lucky that you have good dirt to work with. Around here, where decomposed granite is the most common soil type, the spoils don't hold together unless heavily compacted when wet. This is an arid region and we don't like to drag out mechanical compactors, so the spoils are generally not that useful. More often than not it just gets scattered when used as tread base. We try to discourage using spoils for building up tread. If we do use spoils then we accept and expect that much of it will erode away. We compensate for that by piling on more spoils, hoping that with enough rain and compaction from users it will erode down and stabilize at the intended tread level.


----------



## trailville (Jul 24, 2006)

BonkedAgain said:


> You are lucky that you have good dirt to work with. Around here, where decomposed granite is the most common soil type, the spoils don't hold together unless heavily compacted when wet.


I remember years ago being in Denver briefly for work and they must have had a big wind storm the day before. Everything in the city was coated with this nasty coarse ground up rock stuff. I'd never seen anything like that before.


----------



## robbiexor (Aug 22, 2011)

A digital level that will read in % is the best way. Since you can't have one for every builder, we tell our crews to build the trail visually flat. This usually results in a 3-7% outslope, even though they think they built 0%.

If you tell them to shoot for 5%, they'll give you 10+.

Tell them to build it flat, check the work with a digital level, no magic involved.


----------



## blum585 (Mar 28, 2012)

No Majik? What fun is that Robbiexor?


----------



## Dave_schuldt (May 10, 2004)

There's nothing wrong with doing a belly flop on the trail. You can really see the slope and flat spots with you eyes at trail level.


----------



## Woodman (Mar 12, 2006)

Not a smart phone guy so I don't know the specific name opt the APP.



SeaHag said:


> Our club has not yet invested in a clinometer...and I nearly always have my phone along for before/after pictures. Do you know the name of that app? Or whether it's available for Android phones?
> 
> Thanks!


----------



## Woodman (Mar 12, 2006)

I will add to this. We cheat the half rule all the time, in fact we have to. Everyone should remember, there are no IMBA Standards. Read the very front of the book, it clearly states the ideas expressed are not intended to be standards. They are instead guidelines. But the half rule is the one we break more often than any other. Yes, the key is more frequent undulation in the form of larger grade reversals and smaller drain dips. If you have good soils with binders (clay based) then put it to good use. If you soil is **** then don't attempt rollers or undulation using that but go deeper with the tread dip portion. Here in western NC, we go every 25-50 feet max for spacing of positive drainage feature and don't rely at all on outsole.


----------



## Woodman (Mar 12, 2006)

This depends greatly on the soil type. With clay based soils, I hate to see any of it cast away and wasted, we use it in the tread to create undulation.


----------



## Ridnparadise (Dec 14, 2007)

I'm not a fan of built-up trail. It's not durable enough as a general rule regardless of soil type. It attracts a hammering from riders, rather than being more subject to weather effect. In particular, stone in fill and berms always gets exposed and then increases local impact erosion, so it gets worse. Progressively available clay applied at the right moistness is the exception - and holy grail. However, casting heavy soil and clay away is physically difficult and doesn't look good or return to natural well. It can be used to create visual features near the trail that either assist with drainage, or visually guide riders in a way that will assist drainage.

Anyway, back to the topic at hand. Outslope is important, but not at any set gradient and not universally (eg berm). If you need outslope in some particular spot, then you only need to manage 2 issues - will it drain appropriately and will it drain appropriately after riders scrub debris and effectively cup your outslope. In short, will you be there to clear debris from all your drains regularly, or better still, will the scrubbage hold silt, continue to spill into the drain and maintain the rage, or will it all turn to a bog over time!

You will need local knowledge and a bit of gut to work out the repercussions of outslope to rider speed to erosion effect over time. If you just want to know if you have effective outslope, it's not rocket science - pour water on and observe.


----------

