HomeMy WebLinkAbout18 Building Better Trailsl·M·B·A
Designin~ Constructing and
Maintaining Outstanding Trails
The International Mountain Bicycling Association
' '
I
,/
I ' / '
/ ' / I r..,""' ,,,,,...--___
/ >
I
\
Published by the International Mountain Bicycling Association
PO Box 7578, Boulder, CO 80306 USA
(303 ) 545-9011
email : info @imba .com , website : www.imba .com
Text copyright 2001 by International Mountain Bicycling Association
Facing Page Photo : Roman Roth
Building Better Trails
By the International Mountain Bicycling Association with con t ributions
from Mike Riter, Jan Riter, Joey Klein , Rich Edwards and Jen Edwa rds.
This publication is available at www.imba .com in both HTML and PDF
formats . Additional copies can be purchased from the website or by contact-
ing the IMBA office. Visit www.imba .com for many other trailbuilding and
trail management resources.
M, £ S ,, A
I
I
I
Table of Contents
About IMBA
Introduction
Chapter 1 -Trailbuilding Philosophy
Chapter 2 -Trail Design Process
Chapter 3 -Trail Construction
Chapter 4 -Trail Maintenance
Chapter 5 -Trailbuilding Resources
Appendix A -Building Challenging Trails
Glossary
} \,
•. /\ ! ___ ,--.,\ 1'' ~ . \! I
I' !,.-"-l_ ) I
/ :''\J /
/
/
\ > /~{ 4875fT
-.?
" /
Table of Contents V
/ \\/
/ I /r<':111 /
page VI
page VII
page 1
page 4
page 23
page 38
page 44
page 46
page 56
, I
I
I if
.•//
/ I
(
' '
\
i
i
"
'\ -\
~ \ :-
(
\
VI Building Better Trails
About IMBA
IMBA was founded in 1988 as a coalition of California mountain bike
clubs concerned about the closure of trails to cyclists . IMBA's founders
believed that mountain biker education programs and innovative trail
management solutions should be developed and promoted .
While this first wave of threatened trail access was concentrated in
California, IMBA's founders saw that crowded trails and trail -user conflict
were fast becoming wo r ldwide recreation issues . This is why they se lected
International Mountain Bicycling Association as the organization 's name.
IMBA's mission has always been to encourage responsible mountain
biking, support volunt eer trailwork, assist land managers with trail
management issues, and improve relations among trail user groups.
IMBA has members in all 50 U.S. states and 30 other countries. This
includes 32,000 individuals, 400 bicycle clubs, 200 bicycle retailers and
120 corporate supporters. IMBA's Rules of the Trail are recognized
worldwide as the standard code of conduct for mountain bikers . IMBA
members annually contribute more than 500,000 hours to trailwork projects
on public land and help build more than a thousand miles of new trails each
year for cycling, hiking and horseback riding .
IMBA continues to bring out the best in mountain biking through
education, trail construction, volunteer support, management advice,
cash and grants for trail improvement, and worldwide leadership. IMBA
gives mountain bikers national and international clout - a voice that is
heard and respected by Federal land managers, environmental groups,
the mainstream media, and other trail users . IMBA works closely with the
U.S. Forest Service, Bureau of Land Management, many Nationa l Park
Service units and state, local and international agencies .
IMBA's key projects include the Subaru/IMBA Trail Care Crew, the
National Mountain Bike Patrol , IMBA Trailbuilding Schools, IMBA Epic
Rides , IMBA State Representatives Network, mountain b i king programs
for children and several international initiatives.
For more information, visit www.imba .com or call or write our head -
quarters : IMBA, P.O. Box 7578, Boulder, CO 80306 USA ; phone (303)
545-9011 .
f
I
I
I ( ,-
" I\ { . { \.
f \ I ~"\..._\ '" I I r§ ( ,\"
\ /\ '-\"-( r'
{.
Introduction VII
Introduction
IMBA supports the development of trails that encourage public access
to natural settings without harming the ecosystem . IMBA promotes concepts
that reduce trail erosion , increase sustainability and lessen user conflict.
Building a constituency for the outdoors is vital to ensure the future of
open space. If people visit and enjoy the outdoors, they'll support preserva -
tion of natural and undeveloped land .
Two world-renowned Subaru/IMBA Trail Care Crews spend 10
months each year traveling coast-to-coast in Subaru Outbacks.
E S A
I
/
I
I
>
/ ,.
('
I --------~
Trailbuilding Philosophy 1
Chapter 1 8
l·M·B·A Trailbuilding Philosophy
What is a sustainable trail?
• It supports current and future use with minimal impact to the area 's
natural systems .
• It produces negligible soil loss or movement while allowing vegetation to
inhabit the area .
• It recognizes that pruning or removal of certain plants may be necessary
for proper maintenance.
• It does not adversely affect the area 's animal life .
• It accommodates existing use while allowing only appropriate future use .
• It requires little rerouting and minimal long -term maintenance.
-From the National Park Service, Rocky Mountain Region, January 1991
2 Building Better Trails
IMBA works to create sustainable trails . Two key considerations are
proper siting and construction to reduce erosion . Minimal maintenance is
important because trai ls are just one of many facilities tha t land managers
must care for. The less time, labor and money needed for trail mainte-
nance, the more likely trails will remain open for mountain biking and
other public use .
Achieving balance between soil protection and recreation is what good
trail design and construction are all about. A good trail is both sustainable
and fun . Trails also must be appealing enough to keep users from wandering
off and increasing the risk of erosion .
The Problem: Erosion
Erosion is the natural process of wearing down and moving rock and
soil by wind and water. Trail erosion can be accelerated by a combination of
trail users, water and gravity.
All trail users loosen soil , especially on steeper grades where they
resist gravity. Water compounds the process if it's allowed to channel or
"focus" down the trail. Water takes loose soil with it, cutting deeper into
the tread (clear path for travel) each time it flows .
The goal is to encourage sheet flow - a dispersed flow of water down
a hillside. When water is allowed to focus, it can do more damage than any
trail user. Erosion is min i mized when trails are designed to make water sheet
rather than focus .
The Solution: Contour Trails
A contour trail gently traverses a hill or sideslope. It's characterized
by a gentle grade and a tread that outslopes slightly toward the low side.
These features minimize tread erosion by encouraging sheet flow of
water across the trail.
Subtle undulations in a trail create grade reversals and grade dips
that also defend against water damage . These features diminish erosion
by redirecting water off the trail.
Contour trails are sustainable , environmentally friendly and appealing to
users . They thwart water damage in ways that are nearly invisible.
Trailbuilding Philosophy 3
While not many land parcels have contour lines as visible as those
in this photo, contour lines play a key role in trail design. Trails
that follow the contour are much more sustainable than trails
that go straight up and down the slope.
Blending with Nature
Straight lines are rare in nature, and they're rare in good trails. Trails
should blend with the land . When building or mainta ining a trail , the goal is
to complement natural processes . Determine what that means for the area ,
then imitate it. A contour trail that snakes and dances across a hillside can
be invisible from below. Trails that are pleasing to the eye are usually friendly
to the land .
4 Building Better Trails
Chapter 2
Trail Design Process
fJ
l·M·B·A
Ten key steps for planning and designing an appealing, sustainable trail:
1. Get permission from the landowner or management agency and form
a partnership .
2. Identify ownership boundaries .
3. Determine who the trail users will be and the experien c es they desire.
4. Familiarize yourself with the area and identify control points.
5. Conceptualize a trail system that incorporate loops.
6. Plan a contouring route with sustainable trail grades, an outsloped trail
tread and grade reversals .
7. Determine the type of trail flow.
8. Walk and flag the proposed trail corridor.
9. Develop a construction plan with the trail users, work crew and land
manager.
10. Flag the exact tread location before beginning construction .
I
I ~
I ,.-r-~
( c
' v _......._\ , ,\ . J\ I ,
'
Trail Design Process 5
1. Get Permission
Establish a professional relationship with the la ndowner or land
manager. Get permission before you do anything . Clear and frequ e nt
communication is the backbone of all good partnerships .
A professional relationship ac complishes more and creates an
"everyone wins" situation . Meeting with different user groups gives
everyone a sense of ownership and ensures the trail's future.
Let land managers know you 're part of an organized group. Present a
written proposal that describes how and where you want to improve the
trail system . For their part, land managers should seek input from users on
trail projects .
Groundbreaking on Federal land may require a National Environmental
Protection Act (NEPA> study. Some trail projects fall under a Category
Exclusion that can save land managers time and money. It may take a while to
obtain a permit, but it must be done. Protection of the land always comes first.
Be patient and willing to compromise. Great trails often result from a
blend of ideas .
2. Identify Ownership Boundaries
Locate the boundaries , then find the people who own or manage the
land within them . This is crucial so the trail is not built on land that's off
limits . In some cases , trails should divert people away from boundaries . For
example, you wouldn't want users to go near a rifle range .
A well -presented trail system can gain access to areas not in the original
plan . Landowners adjacent to open space may be willing to allow use of
their property, too .
\ -; /"
'/
:\\' ( ' (! \ (, \,_'\._,I ) I '--: ',\ . / ,-' /
/
/
/ /
I
/
3. Determine Trail Users
Think about the potential trail users . Does the trail system accom -
modate their needs and desires? Think about the futu r e as well . Will
different trails be necessary to serve a growing population and
evolving mix of users?
A trail 's design shapes the experiences of those who use it. The best
trail system offers somet hing for everyone by recognizing that each trail user
is unique.
It would be wrong to assume that all mountain bikers want challenging
terrain or that all hikers want solitude. Even so, it's possible to make a few
generalizations about trail users .
Foot Travelers
Walkers: They usually want a relatively brief jaunt. They do fine on short
trails that give them a direct path from one natural feature to another.
Hikers: They 're usually familiar with the outdoors and like a more
strenuous walk. They can handle difficult terrain and steep grades . They
will generally stay on trails that are direct yet interesting .
Rock Climbers: They use trails to reach climbing areas . Contour trai ls may
meander too much for their needs. They prefer fall-line trails that provide direct
access. To be sustainable, fall-line trails must be armored with rock or have a
sturdy staircase with excellent drainage.
Backpackers: This group yearns for a backcountry experience, and will
travel many miles to reach it. Even though they have an intended destina-
tion they are less apt to shortcut because they carry heavy loads that hinder
maneuverability. Gentle trail grades linking natural features help keep long
distance foot travel interesting . Water sources should be regularly spaced
and near suitable camping sites .
Trail Runners: They enjoy connecting trail loops to add variety in their
workouts . Most runners want several miles of rolling contours with occa-
sional challenging sections .
Trail Design Process 7
Equestrians: People on horses are the heaviest, widest and tallest non -
motorized users . Their trails require a wide corridor and a high ceiling .
Contour trails with a durable tread are the most sustainable . When designing
a trail for horses , dogs and other pets, include water crossings or drink stops .
Endurance Athletes: Some trail runners, mountain bikers and equestrians
like to push their limits. These people seek trail networks that are as much
as a hundred miles long. A large network is more appealing than multiple
laps of a short loop.
Disabled Trail Users: The Americans with Disabilities Act is a 1990 federal
law that helps disabled people have equal access to public facilities . With
improved skill , endurance and equipment such as off-road wheelchairs, more
trail opportunities are being sought. Suitable trails have a wide, smooth tread
with a gentle grade (an average of five percent) and no staircases .
Motorized Users
ATVs: All -terrain vehicles require a 4 -to 5-foot-wide tread that's open and
flowing . Their wide tires and horsepower allow travel on sandy or rocky tra ils .
Fitted with racks, ATVs are popular with hunters, fishermen and others who
take loads into the backcountry. Land managers and trail crews find ATVs
useful in many work situations .
Motorcycles: Also known as dirt bikes, they require more operator skill than
ATVs and can be used on narrower trails . Riders prefer trails that are open
and flowing , and they can cover more than a hundred miles a day. Sensitive
tra ils can be armored to withstand the weight.
8 Building Better Trails
j
• J
I
'(
Mountain Bikers
Beginner Cross-Country Riders: Casual cyclists like gentle, relatively short
trails . As they become more skilled, they often seek longer, more d ifficult
trails . Rough, arduous or twisty sections satisfy the need for tec h nical
challenge and help cont rol speed . Mountain bikers tend to stay on t rails if
they're fun to ride .
Avid Cross-Country Riders: These experienced cyclists are comfortable in
the backcountry. They're typically self-sufficient, carrying tools, water, food,
clothing and sometimes a first-aid kit. Avid riders seek trails that let them cover
from 10 to 100 miles in search of solitude, nature and challenge. Desirable
trails feature several miles of connecting loops with natural obstacles .
Downhillers: These are advanced riders with sophisticated equipment that's
specifically designed fo r descending steep and technical t rails. They like
steep, difficult trails . The most sustainable are rocky contours with many
grade reversals . It's helpful to have a vehicle shuttle for reaching the top . Ski
areas that provide summer lift service are popular with downhillers.
Technical/Trials Riders: They like challenges such as drop-offs , ledges, logs,
elevated bridges, dirt jumps and seesaws . Some riders want these technical
features within cross -country rides , while others prefer them as a stand -alone
experience. One solution is special -use areas, similar to snowboard parks at
ski resorts . On backcountry trails, these technical features should blend with
nature, flow with the trail and be built well.
Trail-User Summary
People enjoy trails for solitude, escape, exercise, training, fresh air,
social interaction and many other personal reasons . But all trail users have
one thing in common : They want to be outside, in a natu ra l setting . The
number and variety of trail users has increased dramatically in just a few
years. The best trail systems offer variety, challenge, long distances and
sustainability. They keep users on -trail by providing the experiences
people want.
i I
( I \
'
t"'
I \
( ''-.; .. ,
/I
Trail Design Process 9
4. Familiarize Yourself With the Area
Save time in the field by studying maps, aerial photographs, master plan s
and so on . In some areas, a Geographic Information System (GIS ) study ma y
have already been done. A detailed GIS might have many layers of informa-
tion on one map , including ownership, topography, hydrography, soil s,
vegetation , habitat and slope grades . Use these resources to become fam ili ar
with the area and begin establishing control points .
When it's time to go into the field , take your compass , map an d
altimeter. A global positioning system (GPS ) is also a valuable tool. It can
help you pinpoint boundaries , control points and trail mileage.
In forested areas, the ideal time to survey is during autumn or winter
when visibility is at its best. Return in spring or summer to check water levels .
Control Points are places that influence where a trail goes. The
beginning and end are basic control points . Others include parking area s,
trailheads, structures, slopes for turns or switchbacks, road or wa t er
crossings and other trails .
In addition, desirable control points can be places you want trail users
to visit. These include scenic overlooks, waterfalls, rock outcroppings, histor-
ical sites, archeological sites, lakes, rivers and other natural features or
points of interest. Consider the mix of users and the control points or terra in
that will appeal to them . Design the trail to connect these places, keep ing
the route interesting along the way.
Inappropriate control points are places you want users to avoid . Exampl es
are low-lying wet areas, flat ground that may hold water or sand , extremely
steep sideslopes, fall lines, environmentally sensitive wildlife habitat or pla nt
communities, certain water crossings, riparian areas, unresearched archeolog -
ical sites and private property. If there's an inappropriate control point, keep tra il
users well out of range. People are notorious for spotting something interesti ng
and creating their own unsustainable social trail to it.
Water crossings present special challenges as control points . Can a
stream be forded or should a bridge be built? Geography and regulatio ns
usually provide the answer. Consult land managers and check other t rai ls
in the area to see what's customary. In general , design trails to avoi d
frequent water crossings .
/
,/
/I
I
I
\ . I ' I I
I /I
/I
' I
' \ \ (~ ' / /
/
10 Building Better Trails
/
' •/ , Ji
)
j , .. /<
\
s I-..
I
A rock outcropping is a great example of a desirable control point.
\ 1
i. /)
i /l
' ( ~
r'
;
.,.J
·,~_)
I "--. /\-i . , / \-\
)r "' '""-' •. '\ I "' ,, /' ,. ~ \'-.( ·' 1-,-~ ' . J -~ \'v\J J I ' .\ r
\ ----..; . .../,... I N "-·--
\
I
I f "--i t\f. r--.,, \ -/
\ J\_· ..j ./ .J l
/; / _ __,,-' __ _;_'~~ -~-w!_'b ________ -\-I
~/.L -(-- -\ -------~
Trail Design Process 11
5. Conceptualize Loops
Trail systems with loops are appealing because they offer the most
variety. People love the adventure of starting down one path and returning
to the same point from another direction. Loops let people enjoy trails of
varying distances, difficulty or ecosystems.
Several different types of loops can work for a trail system , depending
on geography. A park that parallels a river may use linked loop trails that
follow the water. Each loop is like a link in a chain . Users can choose a
small loop, a combination of loops or take the whole outer loop. In moun -
tainous terrain, a trail may climb one drainage to a summit, then descend
another drainage . Stacked loop-trail systems make optimum use of
available land .
In metro areas, the core trail leading from the trailhead or parking lot
should be wide and smooth to appeal to a variety of users . People like to
travel side by side and socialize at the start. Because a core trail is the
entrance to the rest of the system , it gets the most use . Other loops branch
from it and become narrower and more challenging as they get farther from
the trailhead . Users seeking difficult or remote experiences are willing to
travel greater distances.
ME S A
I
I
/
n
/
\Ii
~-., ,, l / \ '\
(_
\. .. I \
i
(,
STACKED LOOP TRAIL SYSTEM
Loops provide options . The majority of the system can be shared use, with a few
areas designed for single use. Keep core loops near trailheads open and flowing
to accommodate the widest variety of users. Outer loops can become progres-
sively more technical and strenuous for people who want challenge .
,, I
\
,'
Trail Design Process 13
6. Plan a Contour Route
Now you can begin to connect the control points . Mark each o n e
on a topographic <topo> map . Use green for desirable points, red for
i nappropriate ones.
Draw a contouring route connecting green points while avoiding red
points . Also avoid fall lines -the most direct route from the top of a hill
to the bottom . That's the path water takes .
Look for natural contouring corridors, but don 't let ease of constru c-
t ion override proper design . The best trails require few man -made
structures such as staircases, water bars, bridges and turnpikes. Place
the trail on the uphill side of large trees so it's less likely to impact root
systems . In the northern hemisphere, south -facing slopes may be
desirable because they dry faster. In hot or desert environments, cooler
north-facing slopes may be better.
The ideal ground drains well yet has cohesive soil <sticks together). Some
soils are much more resistant to impact and loosening than others . Sand
drains well but is not cohesive . Clay is highly cohesive but doesn 't drain well .
Silt, another main soil type, falls somewhere in between .
Trail Grade
"Water always wins ; the trick is not letting it play the game."
-Mike Riter, Subaru/IMBA TCC1
Sustainable trail grades minimize the effects of water and people. Good
grades are usually shallow and address factors such as topography, soil type,
rainfall and the number of trail users .
MES A
I
I
I
I l
(~
,
' J\
I
!
' \ / \ I -,
/ \
'-'
14 Building Better Trails
j
Joey Klein of the TCC
works with a clinometer.
Clinometer.
Determining the Steepness
or Grade of Trails.
A clinometer measures a grade
in degrees or percent. For highways ,
roads and trails , percent is used
because it's more p recise. Percent
of grade is the relationship between
vertical gain and horizontal
distance, known as "rise over run ."
It's found by dividing rise by run . For
example, a 100-foot section of trail
that gains 1 O feet of elevation has a
10 percent rise (1 O divided by 100
equals 0 .1 m. Therefore, the trail has
a 10 percent grade.
Digital Level.
_l ____
Trail Design Process 15
The Half Rule
A trail tread grade shouldn't exceed half the grade of the hillside or
sideslope that the trail is traversing . If the grade does exceed half the
sideslope, it's considered a fall-line trail. Water will flow down the trail rather
than sheet across it. Measure the sideslope, then keep the trail tread grade
under half of that figure to ensure good drainage.
For example, if you're building across a hillside with a sideslope of 20
percent, the trail tread grade should not exceed 10 percent.
There is a limit to this half rule : A trail cannot be indefinitely steep .
There can be short, steep sections, but try to limit the maximum tread grade
to 15 percent. Of course, this depends on a number of factors, including soil
integrity, rainfall, trail flow and number of users . Consider the surroundings
to decide what works best.
Trail grades can be steeper on solid rock. But earthen sections
between rock may need to be fortified or armored to prevent soil
loosening and erosion .
The 10 Percent Rule
Generally, an overall trail grade of 1 O percent or less is sustainable.
However, there may be steep places where this grade can 't be achieved .
Trail tread grades can be as high as 15 percent as long as the trail's overall
grade doesn 't exceed 1 O percent.
Begin flagging the route with conservative grades under 8 percent.
This allows flexibility in case there's an inappropriate control point. By
staying under the maximum grade, you can adjust the route without
starting at the beginning .
Outslope in Contour Trail Design
As the trail contours across a hillside, the tread should tilt slightly away
from the high side . This tilt, called outslope, ensures that water will sheet
across the trail. Outslope is a major reason why contour trails work. For
more information, see Chapter 4 .
S A
,
./
/;
(1
I
I
I
I
The Half Rule
Fall line = 20 percent grade
Trai l tread = 1 O percent grade ~l ~
This t rail is p roperly desig ned to be
we ll be low 50 percent of si des lope .
Wate r co min g down the hillsid e w ill
cross th e tra il and flow off of it ,
min im iz in g erosio n.
Trai l tread = 15 perce nt grade
This trail is poo rl y designed beca use its grade
exceeds 50 percent of sides lope. Wate r wi ll
ru n down t he t rail , bu ilding vo lum e and ve loci-
ty and ca rry away tread material loosened by
users . This t rail should have bee n des igned
with a max imum grade of 1 O perce nt.
Grade Reversals
A well -built trail has gentle trail grades, an outsloped trail tread and
g r ade reversals. As the trail snakes across a hillside, a subtle left or r ight
turn c reates rolls or undulations -grade reversals that help divert water off
t he tra il. A contour trail on a steep slope may need grade reversals every
2 0 t o 50 feet, depend i ng on soil type and rainfall. The steeper the grade,
th e more grade reversals you should have .
To reduce the need to build water-diversion structures later, the origina l
desi gn should encourage smooth water runoff through subtle grade
c hang es . Without proper maintenance, any trail will eventually lose
outsl ope. Grade reversals act as a backup to prevent water from focusin g.
Fo r more details, see Appendix A.
I
\" ./ ~ \.;
\
\ --,
s~
I
I
I
' i
I
) -s·~
(
'-. /\ /'{ ' J \, r--/ -. ,, " '\I ..J '-.\ , . \.I ,• ,--r..:; ,·' I j '-' 5 v>) ! ~-I
I ) I'----.J !\J , .... --...~ \ /
I i \ ''\_ ../ I /" --..._,
I / _ _____,....-.! /\! ~ :I-; I
I i· , , --- - _\_. r-J--(---------/~,,,,.------\_
/ --... ,., ..... r"Y ...... (-,-,/ -------..... ______ __,
Trail Design Process 17
GRADE REVERSAL
-----Trail alignments should follow the natural topography
using undulating grades -not linear grades.
----::::----::::--
Grade reversals direct water off trail surface and are self cleaning.
Grade reversals are effective before a water crossing, because they
divert water and sediment off the trail before they can reach the
stream.
Mf £ SA
/
I
/ c-_
' /
/ '...., / '')
\,}
(
\
18 Building Better Trails
7. Determine Type of Trail Flow
Trail users are defined by their means of travel (e .g ., foot, horse,
bicycle>, but this is just one distinguishing characteristic. Speed is important
too. For example, a mountain biker and a runner probably have a more
similar trail experience than a runner and a walker, because their speeds
are nearly the same .
Mountain bikers, runners and some equestrians travel faster than
walkers or hikers . A trail designed for them should have a certain tempo or
rhythm . We call this flow. Understanding flow can reduce erosion, user
conflict and accidents.
Contour trail designs can have three basic types of flow : open and
flowing , tight and techn ical, or a hybrid .
Open and flowing trails are relatively gentle. They have smooth
surfaces, a wide tread corridor, long sight lines, sweeping turns and few
technical challenges . They appeal to less -skilled cyclists and people who
enjoy traveling fast. Open and flowing trails are fine, but they invite higher
speeds and are also attractive to motorized users.
Open and flowing trail in the Utah desert.
Trail Design Process 19
Tight and technical trails have sharper turns and twists, rougher
surfaces, a narrower tread and natural obstacles. They provide challenges
and thrills for mountain bikers while keeping speed down , which in turn may
reduce user conflict. Smooth trails can be made more technical by adding
rocks or logs , a process known as texturing .
Tight and technical trail near Bellingham, Washington.
Hybrid trails successfully blend features of the above two types . Hybrid
trails are often a good choice for urban areas . These trails may be wider, yet
twisty with a rocky, technical tread . Trees , brush and obstacles should be
below eye level , allowing for long sight lines that help reduce user conflict.
Slightly wider trails allow users to pass each other, while technical chal -
lenges reduce speed and add variety.
Proper transitions are essential when open and flowing sections are
combined with tight and technical sections . Transitions should occur
gradually or be atop hills . Abrupt transitions are likely to make cyclists
brake hard and skid, resulting in braking bumps, and in some cases
forcing users off trail.
Flow is vital on trails for cyclists . Mountain bikers love the rhythm of a
trail where one turn blends into the next, and every descent leads into
another rise . A trail with good flow helps minimize erosion , user conflict, and
safety concerns .
TRAIL FLOW
Tight and Technical
J
/
/
/
Poor Design -Abrupt transitions from one type of design to another.
Trail Design Process 21
8. Walk and Flag Corridor
After the above preliminary work is done, use flagging tape to mark
the trail corridor you 're proposing. Once this general layout receives
environmental clearance and land manager approval , you can establish
the specific route .
Be sure you can see at least two consecutive flags from any point along
the proposed trail. There 's no such thing as over-flagging . Use plenty of
flagging to make your design clear to the construction crew, ensuring that
the trail is built the way you envision it.
When choosing your flag color, remember that yellow o r orange
don 't work well during autumn where hardwoods grow. Green won 't
stand out in summer. Fluorescent pink is good in most areas year-round .
Check with the local land manager to make sure other projects aren 't
being flagged with the color you intend to use . When tying flags around
tree trunks, put the knot on the si de you want the trail to pass . Also , put
flags at eye level so it's easier to establish grades with a clinometer.
9. Develop a Construction Plan
This step should involve trail users, land managers and the work
crew. Including the key players in decisions gives everyone a sense of
ownership and pride in the trail.
Reach agreement on trail dimensions, including corridor width , tread
width and ceiling . Cons ider how the trail will be built, how long it will take,
how much it will cost and who will provide the labor. Develop a timeline
for construction .
Many land management agencies require studies prior to new tra i l
construction . These may be biological, botanical, cultural, archaeological ,
or historical. Or, a simple walk-through by the area 's naturalist may be
sufficient. Studies can be expensive and time consuming , so be patient.
Make sure the plan you propose is exactly what you want, because
changing it after this step may require going through the entire process
again . Assessment studies usually cover a corridor 20 to 50 feet on
either side of the flag line.
(
i I
r )
22 Building Better Trails
)/. ,..
10. Flag the Final Alignment, Confirm Permission
Now you're ready to stake the exact location of the trail. This includes
the design details that give the trail its unique character and ensure its
sustainability. Flag the dimensions of the corridor, ceiling and tread . Identify
the obstacles that will be left in the tread or included in its design. Let
natural terrain features guide you .
Pin flags work best for marking tread location. Pin flags are reusable,
lightweight and can be placed almost anywhere. Short flags are fine for
desert or arid areas . Use long flags when there is vegetation .
For open and flowing trails, flags can be placed six or more feet
apart. A tight and twisty trail might require flags to be three to six feet
apart. It's important to keep spacing consistent. Each flag is like a dot -
connect the dots to mark the trail. This helps you visualize flow, grades,
grade reversals, turns and all the other key features .
Walk (or run if you can) the entire flag line in both directions, making
adjustments to improve flow. Avoid long, straight lines. Use natural
obstacles to accentuate curves and grade reversals . Be creative to produce
an exciting pathway.
A well -flagged tread resembles a serpentine line with rounded arcs .
Optimum flow comes from consistency in the radius of turns.
Outline the proposed tread by putting pin flags on the inside
(uphill) edge, the center, or the outside (downhill) edge . The downhill
edge is preferable because flags can remain during excavation to help
the construction crew envision flow and the depth of bench cut.
When building a crib wall to raise the trail's downhill edge, place
pin flags in the center of the trail to indicate the tread 's finished depth.
This is important for maintaining the grade.
Design Summary
By following these 10 steps you can create a contour trail design that
will withstand the test of time, people and water. There are exceptions to
every rule and some of these are covered in later chapters .
) !
( I
f \
I
I
I
i
I
Trail Construction 23
8
l·M·B·A
Chapter 3
Trail Construdion
Safety
Safety is paramount in any kind of trail work. Sharp tools, difficult ground,
weather, fatigue and natural hazards can cause injuries. Trail crews should
wear sturdy boots and gloves. Long pants and long-sleeve shirts are recom -
mended . Eye protection and hard hats are a good idea too .
Crew leaders should know the location of the closest medical facility
and who will go for help . When an accident happens far afield, time is
critical. Create an emergency plan before heading out. Make sure everyone
knows his or her responsibility during an emergency.
I
I
I
/
( ~
> /
Start each workday with reminders about tool safety and the emergency
plan . Cover these points:
1. Carry tools at the side, not on a shoulder.
2. Carry tools with the sharpest side facing down .
3. Carry only one tool in each hand .
4. When carrying just one tool, hold it in the downhill hand .
5. While working, maintain at least a tool-length distance to t he next person .
6. If a tool must be raised higher than waist level, advise nearby workers.
7. Before walking past others using tools, announce yourself and make eye
contact before passing .
8. Lay tools down on the uphill side with handles pointing towards the trail.
9. Stay alert for environmental hazards such as poison ivy, stinging insects,
poisonous creatures, sunstroke, altitude sickness, dehydration, hypothermia,
and so on .
10. Crew members with medical conditions must have their medication with
them. Know who is susceptible to heart prob lems, bee-sting allergies,
asthma and other common ailments.
11. Drink, eat and rest adequately. Avoid fatigue to reduce accidents.
Clearing the Trail Corridor
The trail corridor should be at least twice as wide as the tread width .
This can vary with the terrain and type of user the trail is designed for.
Leave grasses and trees when they're outside of the tread . Get approval
from the land manager if there is any question about tree removal. There
may be a size limit for cutting . When small trees and bushes are wi t hin the
tread, don 't cut them flush with the ground . They must be dug out, roots
and all , or they'll become "pungee sticks" when the trail compacts around
them . Cutting them at waist level leaves a handle for levering them out. Fill
the resulting hole to match the tread.
I
r \
\
Trail Construction 25
When trimming tree branches, always cut just outside the branch
junction . The resulting nub helps prevent disease from infecting the tree,
and the cut will heal quicker. When removing larger branches, start by
making a partial cut underneath . Then when the branch falls it won 't strip
protective bark.
(L) Rich Edwards of the Trail Care Crew clears a trail corridor. (R) Woody
plants should be dug out, roots and all.
Put cut trees and branches at least 1 0 feet from the corridor. Lay them
with the butt end pointing away.
Clear an area equal to the planned tread width . Also clear four feet
downhill from the tread's lower edge. Next, rake the duff and debris from the
tread area onto the uphill side. It can be used later to cover dirt removed
from the bench cut and give the trail a more finished look. If it's too steep
to rake uphill, rake downhill into large piles. Scatter dirt removed from the
bench cut over the downhill area . Cover it with the duff and leaf litter.
S A
\ :/
\\ I //
.r \ f I "\_~~" /'\///
~--/I
(
I
\
I
I
\ F , ______ __.
26 Building Better Trails
Full Bench Tread
When possible, excavate down and into the hillside to put the entire
tread width on mineral soil . This is called full bench tread construction . It
creates a consistent and stable tread . It takes more time to build, but it
lasts longer and needs less maintenance.
FULL BENCH CONSTRUCTION
INCOMPLETE FULL BENCH
Left with unfinished vertical
back cut, soil will slough off,
makin~ tread narrower.
Obtrusive back cut also forces
rider to outside of tread.
FULL BENCH CUT
Entire tread width is cut into
firm mineral soil. Tread
compacts uniformly and is
sustainable. 5 % outslope
ensures water sheets across
tread. Back cut is blended into
back slope. Proper back slope,
out slope and full bench cut
minimize maintenance .
HILLSIDE BEFORE TRAIL
Vegetation keeps water
sheeting slowly downhill.
Trail Construction 27
Partial Bench Tread
Not recommended : A portion of the tread width is excavated and placed
on the downhill side of the tread . This forms an incomplete or partial bench .
The tread rarely compacts consistently, and eventually it begins slipping
down the hill (tread creep). Partial bench construction usually results in an
unsustainable trail if it gets substantial use .
PARTIAL BENCH CONSTRUCTION
HALF BENCH
Relatively easy to construct,
but fill soil may collapse and
creep downslope, requiring
excessive maintenance.
PARTIAL BENCH WITH CRIB WALL
In some cases , tread must be
supported by a cribwall. Wall
holds fill soil in place and tread
is outsloped over top of wall.
28 Building Better Trails
Cribbed Bench
When essential roots or impenetrable rock make it impossible to
establish a full bench trail , a retaining wall can be built to support the
downslope side of the tread . Th is crib wall holds in soil , stopping the
tread from creeping downhill. It's important for the top of the wall to be
lower than the tread so water can sheet across . The co nstruction cost
of a crib-walled tread is usually at least twice that of a standard full
bench tread. On sides l opes of 100 percent or greater, a partial bench
supported by a crib wall will reduce the height of the backslope and the
trail's impact on the hillside.
Back-cut and Backslope
The uphill side of the tread where it blends i nto the slope above the trail
(the backslopel is called the back-cut. Often, the first rough cut of a full
bench tread produces a vertical back-cut. If left vertical, water can undercut
the backslope, which eventually sloughs off onto the tread . That's why it's
very important to blend the back-cut into the grade of the h ill. It lengthens
the t rail's life by preventing water from cascading onto the tread.
Outslope
Trail tread should have a subtle tilt (3 -5 percent) in the direction of the
fall line . This is known as outslope. It's the most important part of the tread
because water won 't sheet without it. Depending on soil type, newly
constructed tread can have up to an 8 -percent outslope to compensate for
settling . To estimate, stand a Mcleod on the tread to see if the handle leans
into or away from the hillside, and at how much of an angle . To measure
pre ci sely, use a digital level or clinometer.
The Edge
Throw excavated topsoil several feet downhill , away from the trail. If
topsoil is left near the edge, it can settle and become a berm that interrupts
sheet flow, causing water to puddle or flow down the trail. The ground
beyond the edge of the tread should slope away, if possible. This might
require digging and removing vegetation .
Trail Construction 29
TRAIL CROSS SECTION
Critical Point_/
(Rounded)
Side
Slo~
Back Slope}
(Gently blended)
...........
Trail Tread
<Outsloped 5010>
Trail
Ceiling
30 Building Better Trails
Tread Surface
This depends on who the primary trail users will be. Fo r more technical
trails, leave natural obstacles such as rocks and roots that aren 't a safety hazard
and won 't contribute to erosion .
On a bench-cut trail, remove rocks on the inside edge . If you don't, they'll
force users to the outside of the tread and cause the edge to break down . On
the other hand, obstacles on the outside edge will keep users in the center of
the trail. Remove logs that are parallel to the tread on the downhill side so they
won 't act as gutters.
Rocks
Large, stable, round rocks are good for the tread surface. So are reason -
ably square or rectangular rocks with ledges. But sharp , pointy rocks tend to
force users off trail. Remove them as well as loose rocks that are likely to work
free and create holes.
Roots
During construction, take out most roots with a diameter larger than a
pencil. This is especially necessary for roots running parallel t o the tread . They
will channel water and may force cyclists off-trail. Sometimes large roots that
are perpendicular to the tread offer an appealing challenge. But they might
force cyclists to the low side of the trail , causing widening (tread creepl . It
depends on the nature of the trail and whether leaving roots exposed will cause
significant damage to the tread or tree. Cutting large feeder roots near the
downhill side of a tree may kill it and cause it to fall across the trail. Sometimes
it's better to build a small crib wall and fill over large roots.
Turns
Two types of turns are used to reverse direction on hillsides in order to gain
elevation in a short distance. A climbing turn on the existing grade doesn 't
have a constructed turning platform or landing . A switchback turn reverses
direction with the help of a relatively level constructed landing . Both turns take
skill to locate and are difficult and expensive to build and maintain . Think of
them as a last resort. Whenever possible, it's better to gain elevation by maxi -
miz ing long contour trail sections .
CLIMBING TURN
_ Side Slope ~
(7 % Maximum)
Grade
Reversal
. •
Trail Construction 31
TOP VIEW
Maintain constant grade and radius through the turn section. Climbing turns
may not be sustainable on sideslopes exceeding 7 percent grade.
Outs lope
5%
-----
Turn Section
SIDE VIEW
---\ ~
Outslope
(5 %)
A climbing turn is any turn that ascends <or descends> on the fall line of a
sideslope. Improve sustainability by placing climbing turns on gentle
slopes and using grade reversals to drain water above them. Climbing
turns should have a large turning radius and barriers between legs to pre-
vent shortcutting.
32 Building Better Trails
1. Climbing Turns
Climbing turns are used on shallow slopes that don 't exceed a gr ade of
about 7 percent. To control cyclists ' speed and prevent skidding, climbing
turns should be free flowing and gentle . Keep the turn radius as wide as
possible, ideally 30 feet.
Minimize erosion by having a short uphill section or grade reversal
just above the turn . A grade reversal diverts water off the trail before it
reaches the fall -line section . Climbing turns are best used on elevated
ridges or slopes where water accumulation is minimal.
Because climbing t urns include a section of trail on the fall line, they
aren 't as durable as well -constructed switchbacks.
2. Switchbacks
Switchbacks are difficult to build but are more durable on steep slopes .
They will last longer than climbing turns if properly designed . We
recommend a version called the "rolling crown" switchback. It's carefully
eng ineered for good drainage.
Key Features of a Rolling Crown Switchback.
•It's located on a gentle slope (consider it a control poinO .
• Water drains off the back of the turn.
•Turns occur on a near-level platform that's slightly crowned (domed).
• The trail stays on the contour on both approaches .
• Bench cuts and crib walls are combined as needed .
• Material excavated from the top leg is used to build up the bottom leg
beh ind a crib wall.
• Crib walls are carefully built to ensure stability.
• The upper leg is insloped .
• The lower leg is outsloped .
• Approaches are designed to control user speed .
• Grade reversals in the approaches divert water.
•Switchbacks aren 't built directly above one another. They're staggered on
a hill side to prevent shortcutting and water accumulation .
)'
1\
! I fr .
1
1 \
\ ' . \
VJ'\ t., \_.,
~\ (.)
"'~ l. 'I
Trail Construction 33
ROLLING CROWN SWITCHBACK
TOP VIEW
Outslope
(5 %) Grade
J, Reversal
------Back Slope· -
I
Outs lope
(5 %)
Cut
Slope
Lower (climbing)
leg should nof
exceed 15 %
lnsloped Upper
Leg (5 %)
--
Crowned
Landing
(5 %)
Outslope /
Lower Leg (5%) /0
/
This shows the most sustainable type of turn on steep sideslopes. lnslope
the trailbed only on the upper leg as it transitions to the crowned landing.
The landing should have a 12-to 18-foot diameter, depending on trail width.
The landing is outsloped in all directions. Build a grade reversal just before
the upper leg to move water off the trail before it reaches the landing.
S A
I
>
I
I
I
~· -~.! ( ,:-'\ \ j
(
/ ) !. ··-~------~
34 Building Better Trails
Rolling Crown Switchback
Crib Walls
Build a crib wall (retaining wall) when you need to shore up the turning
platform . It's better to use rocks instead of logs, and better to use large
rocks (at least 50 pounds) than small ones . If you can lift the rock by
yourself, it's probably not big enough . Ideally, many of them will weigh at
least 150 pounds and be rectangular, not round . Excavate the footing, then
place large, well -anchored foundation rocks . The wall should tilt into the
slope -described as the wall's "batter." Batter should never be shallower
than 4 : 1, defined as an inward tilt of one foot for every four feet of height.
A 2 : 1 batter is better. Building large crib walls is difficult, so enlist the help
of someone who has experience.
Crib wall
Trail Construction 3 5
Water Crossings
A water crossing doesn 't always have water. It's also the site of a
potential conduit for water. Every crossing is important for two reasons :
1. It's where a trail has the most impact on water quality.
2. It's where water has the most potential to damage a trail.
When water from two sources join, it's called hydrologic connectivity. An
example is a trail that collects water and channels it into a stream. Runoff
from trails may carry soil that causes sedimentation, which can harm aquatic
plants and animals . A well -designed water crossing minimizes the trail 's
negative impact on water quality and the riparian corridor (the habitat along
the edge of a river or stream). Good design minimizes hydrologic connec-
tivity by building gentle grades near water crossings to direct flow off the
trail. Never design a trail with fall -line sections oriented toward water
crossings . This encourages land erosion and sedimentation .
When crossing a waterway, also consider how it may affect the trail. Will
water be diverted by the tread? What will happen when the waterway floods?
Even desert trails require careful consideration when intersecting with
possible drainages . What seems like a perennially dry gulch could channel a
roaring torrent following a cloudburst.
Bridges
These are the most common solution for water crossings . By putting the
trail above the water, you minimize the impact each has on the other. Make
the bridge high enough so the approach is on a gentle grade Of not leven .
Proper height also helps avoid flood damage. Make the bridge and adjoining
trail have good flow (no awkward transitions).
36 Building Better Trails
Tips for Successful Bridge Building:
1. Make bridges strong enough to support the heaviest potential user
(bicycle, horse, ATV, etc.l .
2. Build with materials that meet your needs and budget as well as what's
available . This could be wood, rock, metal or plastic.
3. For wooden bridges, screws hold much better than nails .
4. Extend approach ramps into the trail.
5. Avoid letting bridge stringers touch the ground, which can lead to rotting .
Sit stringers on sills of stone or replaceable wood .
6. When building with unfinished wood from the bridge site, use only
naturally rot-resistant species such as cedar, hemlock, locust, redwood or
cypress . In eastern North America, for example, locust is by far the most
rot-resistant wood .
7. Bark must be stripped or wood will rot and suffer insect damage.
8. Bridges and their approaches should not have sharp turns . A tight turn
onto a bridge deck is very dangerous when it's wet or icy.
9. If railings are required and the bridge is located just before or after a turn,
make the railing low on the inside edge to accommodate cyclists lean ing in .
10. Design the bridge so that users on either end can see each other and
slow or yield before meeting abruptly in the middle.
Before beginning work, consult an experienced bridge builder or at least
check with the U.S. Forest Service for its construction guides.
Trail Construction 37
Fords
Bridges can be expensive and may require a lengthy permitting process .
So consider an alternative -the armored ford . This lets users pass through
water but minimizes sedimentation . The approach to a ford is similar to one
for a bridge. Use care to prevent sediment runoff from the trail to the water.
Place stone to make a hard surface for the entrances and crossing . This
prevents trail users from degrading the banks or stirring up silt. Consult the
land manager before disturbing any creek or streambed .
Ford in Keystone, Colorado.
Culverts
A culvert is a large pipe that allows water to flow beneath the trail bed .
This is an appealing solution thanks to low cost and easy installation .
Tips for successful culvert installation:
1. Use a culvert large enough to handle the maximum expected flow.
Estimate this by checking the stream corridor. Culvert diameter should be at
least 24 inches, and sometimes two or more culverts may be needed .
2. Think about culvert maintenance before installation. The longer the
culvert, the more likely it is to clog -and the harder it is to clear.
3. Slope a culvert downstream on a grade of at least 1 O percent.
4. Armor the face of the tread surrounding a culvert. This helps it survive a
flood . Remember, the soil used to fill around a culvert will be less
compacted than the surrounding soil. It's susceptible to being washed away.
I
.I
38 Building Better Trails
fJ
l·M·B·A
Chapter 4
Maintenance
The same care, thought and hard work that go into new trail construc-
tion must be applied to trail maintenance. Thankfully, it shouldn 't take much
to keep a well -designed trail in good shape for many seasons.
Maintenance shouldn 't substantially change the chara cter of a trail or
diminish user experie nces . Just as a good trail appears to have always
been there, good maintenance should be almost invisible .
/
j
"It's simple : keep the users on the trail and the water off of it."
-Joey Klein, Subaru/IMBA Trail Care Crew
/
' I !
f .. I \
\
I
I
I
I
I
\ , "-,~ "'\' 1\f \ J . '.'" :·'), r\.~ I r I /-,,:'-~----
~,I
Maintenance 39
Corridor
Trim back vegetation each season -or more frequently, if necessary.
Maintain a high ceiling on trails used by equestrians . Keeping the
corridor open helps keep people on the trail. For example, cutting vege-
tation on a trail 's uphill side allows users to stay on the center of the
tread . Otherwise, they may be forced off the downhill side . Creative
pruning along alternate sides of a trail accentuates curves to keep a
twisty trail twisty. Don 't trim more than necessary. Over-trimming tends to
make a trail too straight, inviting speed . (Of course, many desert trails and
paths through open terrain don 't need trimming.)
Tread
Tips for maintaining the trail tread:
1. Look for places where water is being trapped on the tread . Try to do this
when it's actually raining . Remove obstacles or features that cause puddles
and force users off the trail to get around.
2. Restore the outslope and/or remove berms . This is often the primary main-
tenance job. If a trail has become insloped or developed a berm, it will collect
and channel water.
3. Fill and pack any holes or ruts after removing a problem .
4. Because certain soil types won't bond to each other, you may need to fix
a hole or a rut by skimming the surrounding tread down to its level. Don 't
forget to re-establish the outslope.
5. On trails with very steep grades, or in rainy areas , armoring may be
necessary to sustain the tread. Armoring means placing stones or other
highly durable material into the tread surface. When using stones, be
sure they're large enough not to be displaced by use . Proper armoring
helps a trail bed last indefinitely.
M1 ES A I -< .....
" /
I
/
\ !
/
i /
!
40 Building Bette r Trails
Natural Obstacles
Ro c ks may roll onto a trail and trees may fall across it. In most cases ,
these things should be removed . But sometimes natural obstacles are a
blessing, giving a trail an interesting, technical character. If the majority
of people can pass over or through an obstacle while staying on trail, and
it isn 't trapping water, consider leaving it. Obstacles help keep speed
down while giving experienced trail users the challenge they li k e. For
details, see Appendix A
Drainage
As just mentioned, outslope restoration and de-berming are essential to
maintaining sheet flow across a trail. However, many contour trail s (even
those with proper outslope> can benefit from improved drainage. If a trail
doesn 't have natural grade breaks or reversals to direct water, artificial ones
can be added . We recommend two types : rolling grade dips and knicks .
Rolling Grade Dips
A rolling grade dip <RGD> is an unobtrusive way to divert water off the
side of a trail by altering the grade. Water is pulled from the trail , not forced
off abruptly. RGDs are longer and subtler than traditional water bars . They
also are more effective than water bars because they're large and durable,
yet smooth enough to be negotiated by all users . They're a particularly good
drainage device for trails used by mountain bikers . Unlike water bars, they
don 't entice cyclists to ride off-trail to get around them . And cyclists won 't
impact the tread by braking hard as they approach .
Please visit the trailbuilding section at www.imba .com for more details
and photos explain ing RGD construction.
r
;i
(
,_ --""
;/I
Maintenance 41
ROLLING GRADE DIP
------SIDE VIEW
6-10 Fee t 10-20 Fe et
Rolling grade dips are a sustainable alternative to water bars. Dips are large
enough to be self-cleaning and subtle enough that cyclists won't steer around
them. A dip is longer than a bike and shaped like a knick. Use bondable soil
from a dip to make a long, gentle ramp just past it. The ramp should be near-
ly twi ce as long as the dip.
/
I /
\ I
\ \
'", "
I I ~
', ) -:--~-----~
42 Building Better Trails
Knicks
Like a RGD , a knick is smooth and subtle . This is a shaved -down section
of trail , about 1 O feet in diameter, canted with the hill's natural slope. Knicks
are typically built on flatter sections of trail where water tends to puddle.
They work well on non -cohesive soils .
KNICK
OVERALL VIEW
SIDE VIEW
5 -10 Fee t
Knicks are used on gentle terrain to direct sheet flow off the trail. In contrast to rolling
grade dips, soil from the knick is spread downslope off trail. The goal is sheet flow,
not concentrated runoff.
Knicks can be used on contour trails to accentuate natural grade breaks and direct
water off trails. Kn icks should be long and subtle to be self deaning, yet unobtrusive
to trail users.
Maintenance 43
Re-Routes
Too many trails have been ha stily design e d . Perhaps they were easy to
build , but now they're impossible to ma i nta i n. Has a certain trail become
a maintenance nightmare? Stand back and look at the big picture . We
often find that various problems along a se ction can be solved with one
contouring re -route .
Perhaps a trail is almost always muddy because it goes through the
lowest point in an area. It might have fall -line sections, steep grades, poor
flow or vulnerability to floods . Look for a new route that solves as many
problems as possible. Get permission and do the proper studies . Plant
removal or passage through a particular habitat may be issues when
proposing a re -route, but in the long run closing a bad piece of trail is better
for the environment.
Of course, a trail that's viewed by one person as a steep, eroded , main -
tenance nightmare might be someone else 's favorite challenge . When
re-routing around steep sections, look for special features that make the
new route challenging while keeping grades sustainable . See Appendix A
Think about trail flow. Does the new passage fit the flow of sections it
connects? Make the re-route more appealing than the old trail with a mix of
suitable grades, interesting features and sustainability. The new trail must
make users forget the old one. Make it more fun!
Trail Retirement
After constructing an appealing re -route, you need to close the old trail.
This means restoring its natural state.
Five Key Points for Retiring a Trail:
1. If the old trail was steep , check dams may be needed to hold sediment.
2. The old tread should be scarified, tilled or in some way loosened so tha t
seeds can grow.
3. Cover the old trail with duff, topsoil , plants, grasses and small trees from
the new construction .
4. Hide the visual corridor. Low-ly ing obstacles are not enough . Only when
the old trail is out of sight will users abandon it.
5. Education is important. Signs ex plaining the re -routing benefit help keep
people off the old trail.
44 Building Better Trails
fl
l·M·B·A
Chapter 5
Trailbuilding Resources
More Information
• IMBA Website : www.imba .com
• U.S. Forest Service : Trail Construction and Maintenance Notebook -Call
(406) 329-3900 to order.
• Student Conservation Association : Lightly on the Land. The SCA
Trailbuilding and Maintenance Manual -Call (800) 553-4453 to order.
• South Carolina Trails : www.sctrails .net
•Western Trailbuilders Association : www.trailbuilders.org
•American Trails : www.AmericanTrails .org
I
I !\ --\. I
c
'' \, \-I
\
,( ~ ,~
M
\ 11 i
~\:
Trailbuilding Resources 45
Professional Trail Design and Construction Services
• IMBA: www.i mba .com or (888) 442-4622
• Arrowhead Trails : www.arrowheadtrails.com or (720l 244-7804
•Trail Design Specialists : traildesign @mindspring .com or (678) 342-9549
Trailwork Tools
Trailwork tools aren 't discussed in this publication . We recommend the
U.S. Forest Service's comprehensive guide, Hand Tools for Trail Work. Call
(406) 329-3900 to order.
Zac Tools manufactures trailwork tools. Contact: zactools @aol.com ,
www.zactools .com, (805) 527-5207. IMBA members may receive a
price discount.
Recommended Zac Tool Products:
• 10-inch Mcleod, $41 (approximate retail price)
• Fiberglass Handle Pulaski , $65
We highly recommend Zac's 10-inch Mcleod fire rake . This is the classic
RockShox/IMBA Mcleod that's a combination heavy-duty rake and hoe for
clearing a fire line in matted leaves and loose debris . Supplement this tool
with a pulaski in rocky or bushy terrain .
Ben Meadows Company
This outfit provides excellent customer service and pricing on a number of
products -from Suunto clinometers to your everyday pin flags . Contact:
mail @benmeadows.com, www.benmeadows .com, (800l 241 -6401 ..
Recommended Ben Meadows products:
Suunto Self-Damping Clinometer. This instrument provides fast and accurate
height, slope and vertical angle measurements . Graduated 0 to ±90°, O to
±150 percent. Accuracy to 1° or 1 percent.
E s ' (
f' A I \. I
-v·
I j I
/
·:/ ,,,~ 'I
"' -\ \, 11 '~· . -./ / "''..r,....,>' !,/ ~ ,, / .,. -..
46 Building Better Trails
Appendix A fJ
l·M·B·A Designing Trails with Technical Challenge
In This Section:
1. Where to Locate Technical Challenges in a Trail System
2. How to Make Tough Trails Rock-Solid
3. How to Use Exposure to Add Challenge
4. How to Use Logs to Add Challenge
5. How to Build Short Ups and Downs (An Easy Way to
Toughen Trails)
6. How to Use a Clinometer
)
j/ J
;!
, 1-,....... f'.. -,.
Technical Trail Design 47
1. Where to Locate Technical Challenges in a Trail System
The Subaru/IMBA Trail Care Crews are sometimes accused of sanitiz-
ing trails . This is heard most often when an eroded gully is replaced with
a sustainable contour trail. But if the plan calls for a challenging trail , the
crew will build it burly and difficult to navigate. If the new path must be
ridable and walkable by everybody <including horses>, then that's the
specification followed .
IMBA crews have built several re -routes that are more sustainable and
more difficult to navigate than the problem sections. In each instance, the
locations were appropriate for technical features . Ideal spots for tough
sections are rural regions or remote parts of large, diverse trail systems .
Urban areas with a large trail -user population generally aren 't the best
place for aggressive trails. But there may be room for a challenging trail or
two when urban green space is large enough to support a more extensive
trail system.
In planning, think about all the people who will support and use the trail
system . Don't build a public system that will appeal to only a small percent-
age of potential users . Instead , build a diverse system that spans a variety of
desires and abilities.
A stacked loop system facilitates diverse trail styles . It typically includes :
A core or trunk trail. This begins at the trailhead , usually right off the
parking area . It can be a loop. It's heavily used because it connects to the
rest of the trail system . A core trail tends to be wider, smoother and have
longer sight lines than other trails . It may need to be designed to ADA
<Americans with Disabilities Act> specifications. It's often short <half mile or
less> and non-challenging, allowing leisurely strolling side by side or family
cycling . It doesn 't provide as much solitude or exertion as other sections.
Primary trails. These comprise much of the loop system , forming circuits
that don 't require use of challenging trails . Primary trails add some excite-
ment, though . Compared to a core trail , they typically have a narrower,
rougher tread with more elevation changes and tighter turns. A few chal -
lenging features may be appropriate.
S A I
I
I
~/ /
48 Building Better Trails
Challenging trails. The best location is at the back of a stacked loop
system , or in a trail system that's more than an hour's drive from a metro
area . The remoteness and rugged tread deters some users while providing
a high -quality experience for others . Challenging trails give runners, avid
cyclists and other enth usiasts a greater chance to find solitude as well as a
way t o test their skill and stamina .
One attraction of outdoor recreation is using physical talent to
overcome adversity while enjoying natural surroundings. People don 't walk
the Appalachian Trail because it's easy. Pushing limits and reaching goals
has been part of American outdoor recreation since the d ays of Roosevelt
and Leopold . We can grow our constituency by building dive rse trail systems
that satisfy newcomers as well as backcountry veterans .
2. How to Make Tough Trails Rock-Solid
As mountain bikers become more skilled and equipment improves, they
seek difficult trails to test their skill. For many riders, difficult means steep .
But as we 've seen , steep trails can create big erosion problems. We don 't
want people locking their brakes and taking the trail with them . To preserve
the land and ensure future trail access for cyclists, new trails must be routed
gradually across the slope and generally avoid the fall line . Some mountain
bikers may consider these contour trails too tame, so the design can add
elements that enhance technical challenge while not reduci ng sustainability.
Rock is effective because it "hardens" a trail as it increases d ifficulty.
Here are five ways to use rock in trail design :
Steeps. Locate solid rock slabs or faces where a trail can run straight down
the fall line without causing erosion . San Antonio riders are challenged by
The Wall - a 15-foot-high rock face that falls away at a 90-pe rcent grade. It's
a favorite challenge for local riders yet remains erosion free . When
designing a feature like this into a trail, open the outrun to prevent heavy
braking, or floor it with rock. Use a natural grade reversal or dip above the
steep to keep water off the trail.
Technical Trail Design 49
A steep rock section in WhistJer Bike Park, British Columbia.
Rock gardens. Route your trail
over and through rocky areas .
West Virginia 's Tea Creek
Mountain Trail has a rock garden
that everyone tries to clean but
r arely does. This rubbly section
batters bikes and appeals to
hikers and equestrians, too .
People expect rocks in nature
and won 't avoid them if they
seem natural. The key is that no
matter how difficult a rock
section might be, it still must be
the easiest route . This gives people
A nice East Coast rock garden.
no choice but to stay on the trail , preventing trail widening or shortc uts.
50 Building Better Trails
A narrow rock chute and drop.
Very old armored trail.
Rock chokes. A series of
boulders staggered o n either
side of the trail makes a
narrow choke or slot that
enhances the challenge . It
also reduces cycling speed .
Be sure this narrowing blends
naturally with the trail.
Otherwise, people will find it
annoying instead of interest-
ing , and may create a new
route around it.
Armoring. Use large rocks to "pave" a
trail and prevent erosion . Trailbuilders
in soggy Wales are forced to armor
entire pathways to escape year-round
mud . Large, ominous rocks are buried
in the tread, making the trail interest-
ing and dry. When armori ng , use
boulders that take two or three people
to move. This ensures that the rock
will stay in place. Bu ry at least a third
of each rock, taking c are to make the
section look natural. Experiment with
different placements to mimic natural
outcroppings.
Drop-offs. Incorporat e natural ledges or use rock to build short drop-offs.
This addition on a contour trail challenges cyclists ascending or descend-
ing . Six to 12 inches is the right height for most riders . Be sure dro p-offs fit
the overall flow of the trail. Put them in a bike-length series where riders
won 't be taken by surprise. This spacing makes it possible to climb as well
as descend . Transitions are important. A tight turn following a drop-off will
cause cyclists to skid or ride off the trail. Tall drops can offer two lines
one difficult and one easier using a ramp or chock stone.
Technical Trail Design 51
3. How to Use Exposure to Add Challenge
Build narrow trails with exposure and you're guaranteed to raise the
technical ante . Exposure is empty space beside the trail tread . It adds
challenge while retaining sustainability. Riding singletrack across a steep
hillside with nothing but air on one side always produces grins -and a shot
of adrenaline in even the most experienced rider. We 've ridden bench-cut
trails on slopes that exceed 45 percent. The exposure on such trails
provides a psychological challenge, too . A three-inch rock seems like a
boulder when a 50-foot drop looms on your side!
Adding exposure is even more effective in areas where it's uncommon
or unexpected . you don 't need mountains. Seek features such as rock
outcroppings, small embankments or any elevation change. A trail across a
slope will seem more challenging with a rock or thorny bush on the uphill
side, forcing cyclists to tightrope along the downhill edge.
Examples of great trails with significant exposure include Bootleg
Canyon, NV; Portal Trail, Moab, UT ; Shenandoah Mountain Trail, VA; Tea
Creek Mountain, WV; and many trails in Fruita , CO .
4. Using Logs to Add Challenge
Fallen trees. Leave them on the trail, but not all the way across . Some trail
users like logs for the test they present. Others will avoid them by going
around, even if it means leaving the trail. A well -designed trail accommo-
dates everyone, which means no major obstructions. Leave a log covering
only part of the trail , allowing an unblocked route to one side. This gives
users the option of scaling the log or skirting it. IThis won't work on tight
singletrack, however). Make sure there are good sight lines in both direc-
tions and that the direct line is over the log . Try to keep the trail narrow.
Don 't use logs as a way to make cyclists slow down . In fact, they may ride
faster in order to jump them.
Log ramps. A popular maintenance technique is using small logs to create
ramps before and after big logs . This is generally a bad idea. Most trai ls are
shared use, and these log piles are a big obstacle to horses and hikers . One
solution is to cut a gap and make the ramp optional. However, we 've seen
hundreds of ramps and only three or four were well constructed . Throwing
a bunch of rotting logs and branches at an obstructing log and calling it trail
maintenance is just being lazy. A well-built ramp uses logs at least 8-1 O
inches in diameter. If they need to be fastened, use rope or wire, not
dangerous spikes . Should you decide to make a ramp, build it well and take
pride in your work. Always create an easier option, too.
Log chokes. Conflicts between mountain bikers and other trail users often
result from the faster speed bikes travel. Just like traffic calming devices on
roads, the best way to slow cyclists is by narrowing the tread , creating tight
spots and adding curves . Make a log choke by staggering logs on either side
of the trail. Be sure this narrowing flows naturally with the trail. Othe r wise ,
cyclists and other users may avoid it by creating a route around it.
Balance beams. A log placed lengthwise next to the trail w ill be used as a
fun and challenging balance beam by people on foot and bikes . It's also a
handy place to rest. Place these logs upslope of the trail where they won't
impede drainage. Set them into the ground so they don't roll.
Log steps. Use large logs to make short steps or drop-offs . This is a good
way to challenge cyclists in an area without natural difficulties. A drop of 6-
12 inches is right for most users . Make sure steps fit with the trail's flow. Use
them in a bike-length series where riders won 't be taken by surprise.
Transitions are important - a tight turn following a step is awkward . Also, be
sure to account for water flow.
Technical Trail Design 53
5. How to Build Short Ups and Downs (An Easy Way to
Toughen Trails)
First, a reminder : Put trails on side slopes whenever possible. Avoid flat
areas because water or sand may accumulate . Flood plains, river bottom s,
plateaus, meadows, old roads -trails in these places can turn into mud bog s
or sand traps that require continual maintenance. On the other hand ,
contour trails along side slopes provide good drainage. They are far more
appealing and will pass the test of time . He re's how to add spice to contour
trails by using ups and downs .
Grade reversals. On sideslope traverses, make the route more interesting
by "surfing " the contour lines . Create a rolling trail that dips and rises
frequently. Reverse the g rade subtly every 20-40 feet. Visualize rhythmically
spaced "waves ." Remember that the trail grade must always remain less
than half the sideslope at 40 percent, no part of the trail should exceed 20
percent, and we recommend 10 percent as a maximum overall grade. Route
the trail on the uphill side of trees to use bench and avoid roots. Surf around
natural obstacles. Grade reversals make a trail fun and improve drainage .
Example of a grade reversal.
S A
I
I
I
54 Building Better Trails
Grade breaks. Lack of grade changes is a common trail design error. Long
runs of constant grade encourage excessive speed (if downhill) and they're
boring (if uphilB . Erosion will be a problem if water focuses down the path .
For these reasons , interrupt grades with breaks where possible. Short
descents mixed into long climbs help users regain momentum and catch
their breath . On downhills, short climbing interludes provide variety,
challenge and let cyclists get off their brakes . Grade breaks also ensure that
water doesn't gain speed and erode the trail.
Constant ups and downs. If your local terrain is generally flat, it's even more
impo rtant to use short ups and downs to challenge cyclists. Make use of
every available change in terrain . The 1996 Olympic mountain bike course
in Conyers , Georgia, is a good example. It's always undulating . Despite the
lack of big hills, the course is very challenging because racers never get a
chance to rest.
Grav ity drops. The goal is to create a large dip in the trail with an equal fall
and rise . Cyclists drop in and their momentum shoots them up the opposite
side . G drops are one p lace where the trail grade can be a bit steeper than
we recommend. The key is a smooth transition and clear sight line. If the
drop is designed correctly, the average rider won't need to brake . That's
important so dirt won 't be pulled down . G drops shouldn 't be used on trails
that have lots of hiker or horse traffic. These users tend to scrape a downhill
grade, increasing erosion . Good sight lines are key. Cyclists must be able to
see t he entire drop from either side. Remember to keep the trail grade
under half the sideslope grade, and limit steep sections to 15 -30 feet.
6. How to Use a Clinometer
A clinometer is also known as an inclinometer or "clino ." It's a hand -held
instrument that tells the slope of a hillside or grade of a trail , making it an
essential tool for building sustainable trails .
Step 1 : Zeroing the Clinometer
On level ground, stand about 20 feet from your partner and hold the clino
to one eye while closing the other.
Technical Trail Design 55
You 'll see a line and a rotating scale of numbers. Tilt the clino up or
down until the zeros align with the line . Now open your other eye and
extend the (imaginary) line onto your partner. The point where the line falls
on your partner is the "zero point."
Step 2: Measuring Grades
To measure or "shoot" the average grade of a hill, fall line, sideslope or
tread grade, have your partner stand directly uphill from you . Hold the clino
to your eye, keep the other eye open, and set the line onto your partner's
zero point. This time, instead of zeros, there will be a number behind the
line. This is the grade of the slope you're standing on . Most clinos have two
scales: degrees and percent. Always use percent.
It doesn't matter exactly how far away your partner is . What is important
is that both of you are standing on the same slope. If the slope changes in
between, you'll get an average of the two slopes . For example, if you stand
across a gully from each other, it would be possible to shoot a 0 percent
grade. You need to measure the two grades independently.
One Final Thought
The best trail systems strike a balance between protecting resources
and providing recreation . A well -designed contour trail system takes people
into nature while safeguarding the environment. Techniques for design,
construction and maintenance constantly evolve, but the goal is always the
same : Build trails that are sustainable and appealing.
M1£ s A I ~~
I
I
I
I
I ----\
\
56 Building Better Trails
8 Glossary of Terms
l·M·B·A
Rich Etchberpr
Back-cut -The vertical part of the bench cut that's blended into the
bac kslope.
Backslope -Slope on the uphill side of the trail. This should be a gradual
cha nge from the tread, slowing runoff by preventing a waterfall effect.
Bench cut -A semi-flat trail tread created by digging down to mineral soil
in the hillside. Care must be taken to preserve some outslope while making
a ridable and walkable path .
Berm -The ridge that develops along the downhill edge of a trail. It's caused
by tread compaction and soil displacement during trail use . A berm traps
water on the trail.
Bridges -Allows trail users to pass over ravines, bogs , creeks, rivers and
sim ilar obstacles .
Glossary of Term s 57
Climbing turn -A turn that transitions from one leg to the next as the trail
ascends (or descends) a hill.
Clinometer -Instrument used to measure the slope of ground . Also known
as an inclinometer or clino .
Contour trail -Pathway that gently traverses a hill or sideslope, following
natural contour lines as illustrated by a topo map . Allows water to sheet
across the trail , thus minimizing impact to the tread .
Control points -Places of interest that trail users will be attracted to
(desirable) or should avoid (inappropriate). Mark control points and use
them to determine the placement of a new trail.
Crib wall -A retaining wall that raises the trail significantly. Often used to
stabilize the trail tread and prevent it from collapsing down the fall line. Can
be built with rock or wood .
De-berming -Removing the berm , or ridge of dirt that forms along a trail's
downhill edge. Restores the tread 's outslope, allowing water to sheet off.
(See "outslope" and "berm .")
Directional use trail - A trail intended for travel in one direction only. May
be reversed periodically.
Drainage -Removal of water from the trail.
Erosion -The natural process of wearing down and moving rock and soil by
wind and water. Trail erosion can be accelerated by a combination of users,
water and gravity.
Fall line -Direction that water flows down a hill. The path of least resistance .
Fillslope -The portion of a trail that's constructed from excavated material.
Fillslope can be unstable so should not be used to build trail tread . Full
bench construction is preferred .
58 Building Better Trails
Flow -The rhythm or "feel" of a trail. Two basic types include "open and
flowing" and "tight and technical."
Full bench tread construction -Tread construction method of excavating
down and into the hillside. Puts the entire tread width on mineral soil, maxi-
mizing sustainability. (See "bench cut.")
Grade -Trail steepness . (See "percent of grade .")
Grade reversal -Brief change in trail grade direction, such as ro uting a
downhill section back up the hillside for a short distance . Used to divert
wate r off the trail.
Grade dip -Undulation in the tread that traps water and diverts it off the
trail. Makes trails more interesting and fun to use .
Half rule or 50 percent rule -If the trail grade exceeds 50 percent of the
hillside slope, gravity will pull water down the trail instead of across it. This
is known as "exceeding the fall of the hill ."
Hybrid - A trail design that blends "open and flowing " and "tight and
technical" features .
IMBA -International Mountain Bicycling Association , P.O. Box 7578,
Boulder, CO, USA 80306; (303) 545-9011 ; www.imba .com . Leading
resource for mountain bike-oriented trail design, construction, maintenance
and management information, and mountain biking in general.
Knick -Shaved -down section of trail, about 1 O feet in diameter, with an
exaggerated outslope. Like a rolling grade dip, a knick is used to she d water
off a trail.
Land manager -Any person responsible for decisions regarding the use of
publ ic or private lands .
Mineral soil -Dirt that's below the top layer of leaves, roots and other
organic material. When making a bench cut, always dig down to mineral soil
if possible.
Glossary of Terms 59
Multiple-use trails -Those used for more than one type of activity, such as
for cycling, hiking and horseback riding .
Open and flowing - A trail design marked by sweeping turns, higher speeds
and longer sight lines.
Outslope -Trail tread that's canted very slightly in the same direction as the
hill's slope. Allows water to sheet across rather than be trapped .
Percent of grade -Preferred method of measuring slope or a hill 's
steepness. For example, a grade of 10 percent means there is a rise or fall
of 10 vertical feet per 100 linear feet.
Re-route - A new section of trail that replaces an existing section . Re -
routing is often the best remedy for a poorly designed trail that requires
frequent maintenance.
Rolling grade dip -A non-obtrusive feature that diverts water off the trail
by altering the grade. It's essentially a man -made grade reversal.
Sheet flow -A dispersed flow of water. It minimizes erosion by preventing
water from achieving high velocity and carrying away topsoil.
Sill -Stone or timber supports that keep bridge stringers from contacting the
ground .
Singletrack - A trail so narrow that users must generally travel in single file .
Single-use trails -Designed for only one type of user. This can be a problem
if other users begin traveling the trail.
Slope -The natural (or man-made) pitch of the land , as shown on
contour maps . Generally refers to the hill , not the trail. The trail "slope"
is called "grade."
Social trails -Paths created by people who wander away from set trails .
Stringer - A structural component of a bridge. It spans from bank to bank
and supports the decking .
60 Building Better Trails
Subaru -Great cars! Sponsor of the Subaru/IMBA Trail Care Crews . Ask for
the heated seats .
Subaru/IMBA Trail Care Crews -IMBA's "Johnny Appleseed" program
for spreading expert information about trail design, construction, main -
tenance and management.
Sustainable trails -What every designer and construction crew should strive
for : low-maintenance trails that have minimal impact on natural systems .
Switchback -A sustainable turn on a hillside. The trail is routed onto a level
deck where it makes a transition to the opposite direction.
Texturing -Placing natural features (rocks , logs, etc.) back into the tread
to increase its technical nature. Helps limit speed, and thereby reduces
user conflict.
Tight and technical -A trail design that includes tight turns, natural
technical features and mandates slower speed.
Topographic map or "topo" map -Charts elevation changes and shows
features such as knolls, ravines, rivers and contours .
Trail corridor -The area around and above the tread . Remove fast-growing
impediments, but leave grasses and trees .
Tread -Ground on which trail users travel. It may include grass, bare dirt,
roots or rocks . Tread width varies depending on the type of trail and its users .
Tread creep -Describes a contour trail sagging or sliding down the hill .
Causes include bushes or trees protruding into the trail from above, exposure
of roots from an uphill tree, an improper bench cut or poor trail flow.
Turnpike -Trailbuilding technique that uses a combination of gravel, soil or
other filler material to make the tread higher than the surrounding water
table. Useful in low-lying areas with poor drainage.
62 Building Better Trails
[9 SOlJON