Trail sustainability

[walsh]

As cabin fever heats up and makes us go for each others' jugulars over what conditions permit riding, etc., I was wondering if the trail experts could direct some of that energy towards a question of mine. It might be a "teachable moment" for folks like myself, who rode for a while before realizing that trails need to be maintained, just like our bikes.

In the environmental field, arguments about what is "good" and "bad" make great political fodder, but no progress is made until we try to quantify things. (And frequently, the answers are surprising.) In my very limited brush with the theory behind sustainable trail building, in New Mexico in a dry alpine climate, bench cut trails were designed so that they would last for 200 years of strictly regulated hiking use. Furthermore, as we removed ponderosa pines and other trees from the path of the trails, we knew that though it seemed destructive, the system of trails and campsites concentrated all human impact to less than 2% of the overall wilderness area.

I found myself wondering what the designed life expectancy of the more vulnerable local trails is, compared to the hardier trails north and west of the Beltway. How much does this realistically vary by user group (hiking vs. equestrian vs. MTB)? Can poor weather use by a few users reduce that sustainability all the way to zero? And can the same thing happen due to a high water event?

I doubt the answers will be clear enough to expain to a bad-weather rider that he's contributing to an 80% decrease in trail longevity, but perhaps the trail gurus can at least help me help me understand my own impact a little better. Anyone? Or do I need to sign up the next time the Trail crew comes to town and get my answers there?

[BikerMiker]

A well-designed trail should have a lifespan of at least 50 years. That's what I try to design and build as a (former) liaison.

For the last 8 years at Patapsco, I tried to focus on lots of small projects that added up to a more rideable trail system regardless of weather. I wanted something that would recover faster from weather events and degrade SIGNIFICANTLY less year-to-year that what was already there. I could give you specific examples, but A LOT of large sections of trail are now almost impervious to weather (almost) and recover within 24 hours of major events.

Poor design is the main problem with trails. Well designed trails last almost forever and show very little use year to year. Even trails in the watershed and Gambrill degrade and erode because they are not designed perfectly (no system is).

Rock is the only material that is considered impervious to degradation and then only certain types of rock.

Users exacerbate problems but design and construction allow the problems to happen and have a multiplier effect on degradation as it applies to user-passes. This is the main reason that IMBA Trail Solutions came into being. This is why I'm trying to focus on new stuff so that it can be designed as 'correct' as possible and have little or no maintenance.

I don't do maintenance if I can avoid it. I try to 'fix' trails so that they don't need maintenance. A trail that requires regular maintenance is a failure in my book.

Ask away. I'll answer what I can.

mike

[spin]

The absolute worst thing a mountain biker can do to a trail (at least in Virginia), is ride it when it's extremely muddy. I've heard the rule of thumb is that for every mountain bike on the trail, the bike removes 1 pound of dirt from the trail after a ride. So if 50 people ride on a muddy trail, 50 pounds of dirt have been removed from the trail.

In Richmond, we've been going back through the James River Park System and reinforcing the down side of the slopes with rock. We've even removed wooden crib walls that were poorly constructed and put in rock, in the hopes that the trail would need very little maintenance in the future.

We've also run into a snag along the way. One of our trails that connects to the JRPS, is Forest Hill Park. The "Friends of Forest Hill Park" have a small contingency that are opposed to trails and mountain bikers in Forest Hill Park. They've complained to Richmond's Parks and Rec department two years in a row (despite us having an MOU) and had our trail maintenance halted both times.

Personally, I believe that they're hoping they can cause the trails to be shut down by the city by not allowing us to do regular maintenance. Fortunately, about 75% of the trails were well constructed and aren't feeling the effects of erosion. They are already fairly sustainable. So it will be a LONG time before they get so bad that the city closes the trails to all users. Meanwhile, we have a fight on our hands... :(

[dan_hudson]

Water on trails EQUALS Bad...

On fall line trails ("mostly up/down" rather than "mostly across"):
-users loosen dirt
-water flows down tread
-water takes dirt away
-loss of dirt creates rut and/or exposes rocks
-users move to the side because they don't like ruts/rocks
<repeat>


Trails on flattish land:
-users compress trail
-water collects on compression because there is nowhere lower
-collected water soaks ground making it soft
-users push softened dirt away, making compression deeper (aka a hole!)
-users don't like hole and/or wet area and move to the side
<repeat>


Fall line trails can be really really fun! But you can't "fix" them. Water bars and/or check dams are a band-aid, but if the trail is already going pretty much up/down the hill there is no way to get the water off, so no way to arrest erosion.

Trails on butt-flat land can be fixed, but only by making the trail higher than the surrounding area so you can move the water off. Or by armoring the whole trail so there is nothing for collecting water to soak. But both are back-breaking and/or expensive.

Trails that are more sustainable are those which don't allow water to collect or run down them. They're also trails that are fun and people want to use! After all, if no one ever used a trail, good chance it wouldn't compress and/or grasses & trees would start to grow on it and erosion would not likely take place no matter how flat or fall line.

Why do we care? I think most people can agree that a tricky fall line trail is a hoot (and not just on a bike). And, for better or worse, some folks like mudding it up. We care (or should care) because we have a longer view than just one day on the trail - the fish in the creek, the sediment in The Bay, etc. More selfishly, if all trails become a muddy or eroded mess, good chance we won't get permission from the land owners to build more. That's another thing most of us can probably agree on - more trails EQUAL good.

Back to sustainable. The short story is that it is easiest to build a sustainable (aka fun and stable) trail where you have nice side slope. And the steeper the side slope, the steeper the sustainable trail can be. The books available from IMBA go into the gory detail - the basic rules and when/where you can break them!

The key is putting a trail in the right place. And if it's in the right place and maintained occasionally (which is easier than we're used to 'cause it's in the right place!), why not 100+ years? The good CCC trails on federal land are getting near that old (the bad ones blew up long ago!). FWIW, many of the trails we ride are not in the right place, which is why we "maintain" them continuely to keep'em passable. But we patchup them up also with the hope of someday getting permission to really fix (aka replace) them.

To muddy the waters a bit... The trails under the powerline at Wakefield were designed/built to be as sustainable as possible. But the lack of canopy-cover, the dirt itself, freeze/thaw, etc, conspire to make it a mudfest in the winter months despite the best efforts. The long-term answer, sadly, is armoring much of it (so buy Larry some more buckets!). Anyway, it can be complicated.

In conclusion, if trails are sustainable:
-more people will have fun
-owners will let us create more trails
-folks will see the value of open space and preserve more land
<repeat>


Adenddum... Muscle power users seem to have similar impacts on sustainable trails. Bikes can cover more ground maybe. And horses (hopefully!) weigh more. But if the trails are "good", it seems to be a wash. "Bad" trails - wet or fall line? Then we start pointing at one another. Linear tire paths vs heal strikes. Equestrians not relating because they're above it all. The common foe is bad trails & water! If water is on your trail, flowing down or sitting, you're likely hosed in the long-run regardless of the finger pointing.

Sorry to be long-winded. My penance for starting the poo-storm which I'm guessing inspired this thread.

[BikerMiker]

Trails on butt-flat land...

I don't know what YOU are into, but I don't even LOOK at flat butts... That's purely inflammatory! It's on!

mike :p

[punga]

To muddy the waters a bit...

Haha... I get it :p

Thanks for good write up.

punga!