Natural SurfaceTrail Design Principles<br />Bruce Weidenhamer<br />Volunteers for Outdoor Arizona<br />www.VOAz.org<br />
PURPOSE 1 <br />Make is easier and safer for people to get from Point A to Point B<br />PURPOSE 2<br />Reduce the environm...
Muscle-powered<br />Motorized<br />Winter<br />Handicapped<br />Wide Range of Skill Within User Groups<br />Wide Range of ...
<ul><li>Trail steepness is probably the single most important factor in trail design *
Erosion increases exponentially with steepness due to increases in the speed of runoff
A.K.A Rise over Run
Grade should be measured, not guessed *</li></ul>4<br />Grade<br />
<ul><li>Trails are heavily impacted by accumulated runoff from the hillside above the trail
The area of a tread watershed extends from the ridge top down to the trail and along the trail from trail crest to grade r...
How much water will the slope absorb (bedrock vs. grassy meadow vs. 6” deep pine needles)
How quickly will the water accumulate on the slope (snow melt vs. gentle rains vs. massive thunderstorms)</li></ul>5<br />...
<ul><li>Distinct terrain features incorporated into the trail to add visual interest and to integrate the trail more close...
Most anchors are vertical features like rocks and trees</li></ul>Gateways<br />Vertical anchors in pairs.  Gateways do not...
Trail systems are more like ski resorts than highway systems.<br /><ul><li>Many different trails with different challenges...
Beware of transitions between different types of trail
Pinch trail with rocks or logs to slow down traffic</li></ul>7<br />Trail Usability<br />
<ul><li>Trails that hold up well overtime with minimum trail maintenance
Reduced soil loss
Minimal impact on natural area
Sustainable trails are a Land Manager priority
Often referred to as IMBA Standard Trails</li></ul>8<br />Trail Sustainability<br />
9<br />Why are there so many bad trails?<br />The “trail” builders priorities and constraints were often very different<br...
Least possible construction effort
Infrequent usage – spring/fall, once every couple of months
Closely follow water
Take steepest route to increase challenge
Take easiest route to minimize challenge</li></li></ul><li>10<br />Why are there so many bad trails? (cont.)<br />Many tra...
Straight uphill to summit is not best route for trail
Shortest route to lake is not best route for trail
Large human-built structures like walls and bridges
Throw it in and waterbar it later</li></li></ul><li>Contouring Trail<br />Half Rule<br />10% Rule<br />15% Rule<br />Frequ...
12<br />Always Build Contouring Trail<br /><ul><li>Trails should always contour along a hillside *
No fall line trails or trails on flat ground
Contouring trails require significantly greater construction effort
Profile of opposite sides of trail must be distinctly different *
Even on nearly flat ground you can often contour along the edge of small rises</li></li></ul><li>Contouring Trail<br />
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Trail designprinciples[1]

  1. 1. Natural SurfaceTrail Design Principles<br />Bruce Weidenhamer<br />Volunteers for Outdoor Arizona<br />www.VOAz.org<br />
  2. 2. PURPOSE 1 <br />Make is easier and safer for people to get from Point A to Point B<br />PURPOSE 2<br />Reduce the environmental impact of people getting from Point A to Point B<br />PURPOSE 3<br />Give people a pleasant, interesting outdoor experience while getting from Point A to Point B<br />2<br />Three Core Purposes of Trails<br />
  3. 3. Muscle-powered<br />Motorized<br />Winter<br />Handicapped<br />Wide Range of Skill Within User Groups<br />Wide Range of Desired Challenge Within Groups<br />3<br />Four General Types of Trail Users<br />
  4. 4. <ul><li>Trail steepness is probably the single most important factor in trail design *
  5. 5. Erosion increases exponentially with steepness due to increases in the speed of runoff
  6. 6. A.K.A Rise over Run
  7. 7. Grade should be measured, not guessed *</li></ul>4<br />Grade<br />
  8. 8. <ul><li>Trails are heavily impacted by accumulated runoff from the hillside above the trail
  9. 9. The area of a tread watershed extends from the ridge top down to the trail and along the trail from trail crest to grade reversal
  10. 10. How much water will the slope absorb (bedrock vs. grassy meadow vs. 6” deep pine needles)
  11. 11. How quickly will the water accumulate on the slope (snow melt vs. gentle rains vs. massive thunderstorms)</li></ul>5<br />Tread Watershed<br />
  12. 12. <ul><li>Distinct terrain features incorporated into the trail to add visual interest and to integrate the trail more closely into nature
  13. 13. Most anchors are vertical features like rocks and trees</li></ul>Gateways<br />Vertical anchors in pairs. Gateways do not need to actually exist *<br />Edges<br />Linear features that mark the transition line between two environments<br />6<br />Anchors<br />
  14. 14. Trail systems are more like ski resorts than highway systems.<br /><ul><li>Many different trails with different challenges and levels of difficulty</li></ul>Design Trail to Reduce User Conflicts<br /><ul><li>Open straight trail results in higher trail speeds and require longer sightlines to prevent conflict.
  15. 15. Beware of transitions between different types of trail
  16. 16. Pinch trail with rocks or logs to slow down traffic</li></ul>7<br />Trail Usability<br />
  17. 17. <ul><li>Trails that hold up well overtime with minimum trail maintenance
  18. 18. Reduced soil loss
  19. 19. Minimal impact on natural area
  20. 20. Sustainable trails are a Land Manager priority
  21. 21. Often referred to as IMBA Standard Trails</li></ul>8<br />Trail Sustainability<br />
  22. 22. 9<br />Why are there so many bad trails?<br />The “trail” builders priorities and constraints were often very different<br /><ul><li>Get there quickly – shortest possible distance
  23. 23. Least possible construction effort
  24. 24. Infrequent usage – spring/fall, once every couple of months
  25. 25. Closely follow water
  26. 26. Take steepest route to increase challenge
  27. 27. Take easiest route to minimize challenge</li></li></ul><li>10<br />Why are there so many bad trails? (cont.)<br />Many trails that were built as recreational trails were often not built using modern trail design principles<br />Major changes in trail building attitudes and techniques in last 100 years<br /><ul><li>Philosophy used to be to force nature to submit
  28. 28. Straight uphill to summit is not best route for trail
  29. 29. Shortest route to lake is not best route for trail
  30. 30. Large human-built structures like walls and bridges
  31. 31. Throw it in and waterbar it later</li></li></ul><li>Contouring Trail<br />Half Rule<br />10% Rule<br />15% Rule<br />Frequent Grade Reversals<br />11<br />Five Critical Trail Design Rules<br />
  32. 32. 12<br />Always Build Contouring Trail<br /><ul><li>Trails should always contour along a hillside *
  33. 33. No fall line trails or trails on flat ground
  34. 34. Contouring trails require significantly greater construction effort
  35. 35. Profile of opposite sides of trail must be distinctly different *
  36. 36. Even on nearly flat ground you can often contour along the edge of small rises</li></li></ul><li>Contouring Trail<br />
  37. 37. 14<br />Half Rule<br /><ul><li>No trail steeper than 50% of the cross-slope grade
  38. 38. If the natural slope of the hillside is 16%, then the trail should be no steeper than 8%.
  39. 39. The dividing line between a contouring trail and a fall line trail
  40. 40. Rule applies even if cross slope grade is very slight*</li></ul>© “Trail Solutions” IMBA, 2004<br />
  41. 41. 15<br /> 10% Rule<br /><ul><li>No trail grade steeper than 10%, on average
  42. 42. 10% as measured over the entire run of the trail
  43. 43. Above 10% grade trails begin to have water runoff problems
  44. 44. The steeper the trail (>5%), the harder it is to build in grade reversals</li></li></ul><li>16<br />No Trail Grade Steeper Than 15%<br /><ul><li>No individual sections of trail steeper than 15% (absolute)
  45. 45. Short sections of 15% grade trail are OK if carefully designed
  46. 46. Trail sections steeper than 15% OK in rare circumstances (bedrock, armored, stairs, etc.)</li></li></ul><li>Frequent Grade Reversals<br /><ul><li>A grade reversal is a short section of trail that descends and then climbs a short way
  47. 47. Grade reversals force water off the trail
  48. 48. No long continuous grades
  49. 49. Grade reversals create smaller tread watersheds
  50. 50. Grade reversals built into the natural flow of the trail
  51. 51. Constructed dips and water bars are an attempt to add grade reversals later</li></li></ul><li>18<br />Guiding PrincipleTrail Is Anchored Into Nature<br /><ul><li>Trail blends with nature rather than fighting nature
  52. 52. Trail route highlights the attributes of each natural environment
  53. 53. Takes advantage of natural features like overlooks or rock formations
  54. 54. Switchbacks incorporate natural features in a way to draw you to them
  55. 55. Grade reversals incorporate natural features to make them seem natural</li></li></ul><li>Determine Land Manager Concerns – What the LM wants and doesn‘t want<br />Identify Control Points - Identify control points both on paper and in the field<br />Locate Trail Route – Determine best route including acceptable grades<br />Layout Trail Corridor – Define the trail corridor within the route<br />Flag Tread – Finalize the exact alignment of the trail and mark the tread<br />19<br />Five Stages Of Trail Layout<br />
  56. 56. Determine Land Manager Needs/Concerns<br /><ul><li>Serve the needs of the Land Manager
  57. 57. Site visit with Land Manager
  58. 58. Be a neutral party
  59. 59. Do not build a trail to favor the users you most identity with
  60. 60. Do not build a trail to favor your personally preferred level of challenge
  61. 61. Layout trail to improve all user experiences while reducing conflicts between user groups.</li></ul>20<br />
  62. 62. 21<br />Land Manager Approvals<br /><ul><li>Environmental Concerns
  63. 63. NEPA Review
  64. 64. Archeological Concerns
  65. 65. How old does trash have to be before it becomes artifacts (50 years)
  66. 66. Work closely with LM when getting approvals
  67. 67. High-value species</li></li></ul><li>22<br />Control Points<br /><ul><li>Positive control points – points the trail should traverse
  68. 68. Negative control points – points the trail should avoid
  69. 69. Seasonal Control Points – springs and low areas
  70. 70. Construction Control Points – crossings and saddles
  71. 71. Two general control point categories; must and should
  72. 72. User behavior may dictate some control points</li></li></ul><li>23<br />Determine Trail Route<br /><ul><li>Visually flag control points, one color for positive and one color for negative
  73. 73. If flag at exact control point would be hard to spot, flag a highly visible spot near it
  74. 74. Add flags at intermediate points
  75. 75. Perform route layout in both directions
  76. 76. Visualize the required trail construction</li></li></ul><li>24<br />Reduce Grade by Adding Length<br /><ul><li>Climbing a grade is the most demanding trail layout task
  77. 77. Adjust grade by adjusting length of trail *
  78. 78. Doubling the trail length between two points will reduce the grade by half
  79. 79. Turn locations on flat spots are a type of positive control point.
  80. 80. Building lots of extra contouring trail may actually be the least work option * </li></li></ul><li>Climbing Turns<br /><ul><li>If you cannot find a flat spot you will have to locate the turns on a slope
  81. 81. Climbing turns should not be used on slopes greater than 7-10% grade
  82. 82. Climbing turns should have a minimum diameter of 20-30 feet
  83. 83. An average mountain biker should be able to easily ride around a climbing turn</li></li></ul><li>26<br />Switchbacks<br /><ul><li>Switchbacks should be a last resort option
  84. 84. Switchbacks are very difficult and time consuming to build correctly
  85. 85. For correctly built switchbacks plan on 10-15 people for two days
  86. 86. There is a tendency to fudge the steepness of climbing turns to avoid building a switchback
  87. 87. Very long runs of trail between switchbacks will reduce the total number of switchbacks*</li></li></ul><li>Switchbacks<br />
  88. 88. 28<br />Making Good Trail Route Choices<br /><ul><li>Determining the trail route is the phase with lots of wandering around in the woods.
  89. 89. Go back at different times of day or with different people*
  90. 90. What if all of the route choices are poor?
  91. 91. Problems may have to be overcome with trail construction techniques.</li></li></ul><li>29<br />Other Trail Route Considerations<br /><ul><li>Avoid environmentally sensitive areas
  92. 92. Avoid archeological areas
  93. 93. Pick a route to minimize trail construction effort
  94. 94. Avoid areas with problem soil conditions
  95. 95. Pick a route to minimize trail maintenance later.
  96. 96. Utilize sections of old roads or trails, if they meet the design criteria</li></li></ul><li>30<br />Determine Trail Corridor<br /><ul><li>Next define the best corridor within new route
  97. 97. Corridor is much narrower than route
  98. 98. If there is no workable corridor within the route , the route may have to be moved
  99. 99. Flag the corridor, gradually increasing the number of flags as corridor is finalized</li></li></ul><li>31<br />Grade Reversals<br /><ul><li>Build in lots and lots of grade reversals
  100. 100. The taller the tread watersheds the closer the reversals must be
  101. 101. With highly erosive soils and large tread watersheds, reversals must be very close together (< 10’ crest to dip)
  102. 102. Constantly slide the contouring trail up and down the cross slope *</li></li></ul><li>32<br />Flag Tread<br /><ul><li>Begin marking the tread with widely spaced pin flags or whiskers
  103. 103. Walk the flag/whisker line many times in both directions.
  104. 104. Anchor high points of rises (climb above trees and rocks)
  105. 105. Anchor low points of dips (dip below embedded rocks, thorny plants). </li></li></ul><li>33<br />Flagging Methods<br /><ul><li>Tread flagging is the best way to share exact trail alignment
  106. 106. The Crew Leader must be able to visualize where the trail will go
  107. 107. Tread flags must sometimes explain three dimensional construction
  108. 108. Humans while walking tend to straighten curved lines, even Crew Leaders
  109. 109. Anchor high points and low points of grade reversals with pairs of flags</li></li></ul><li><ul><li>Gullying of trail tread (too steep, fall line)
  110. 110. Trails that remain on the flats
  111. 111. Rocks in tread
  112. 112. Water bars
  113. 113. Climbing turns that should be switchbacks
  114. 114. Multiple constructed switchbacks in sequence
  115. 115. Elevation gain immediately followed by elevation loss or level followed by steep grade</li></ul>34<br />Indications of Poorly Designed Trail<br />
  116. 116. 35<br />I would often notice while hiking…<br />...a section of trail was significantly better than the previous sections. I could maintain a steady hiking pace on generally good footing. The tread wasn’t plagued by rocks and seemed well-maintained.<br />And I would think, what a coincidence…<br />...the trail is contouring with no significant fall line areas. The grade of the trail isn’t too steep and there are lots of grade reversals.<br />
  117. 117. 36<br />Now when I notice…<br />...a section of trail is significantly better than the previous sections. <br />I understand it is because…<br />...the trail is contouring with no significant fall line areas. The grade of the trail isn’t too steep and there are lots of grade reversals.<br />

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