1. Natural SurfaceTrail Design Principles Bruce Weidenhamer Volunteers for Outdoor Arizona www.VOAz.org

2. PURPOSE 1 Make is easier and safer for people to get from Point A to Point B PURPOSE 2 Reduce the environmental impact of people getting from Point A to Point B PURPOSE 3 Give people a pleasant, interesting outdoor experience while getting from Point A to Point B 2 Three Core Purposes of Trails

3. Muscle-powered Motorized Winter Handicapped Wide Range of Skill Within User Groups Wide Range of Desired Challenge Within Groups 3 Four General Types of Trail Users

5. Erosion increases exponentially with steepness due to increases in the speed of runoff

6. A.K.A Rise over Run

7. Grade should be measured, not guessed *4 Grade

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. How much water will the slope absorb (bedrock vs. grassy meadow vs. 6” deep pine needles)

11. How quickly will the water accumulate on the slope (snow melt vs. gentle rains vs. massive thunderstorms)5 Tread Watershed

13. Most anchors are vertical features like rocks and treesGateways Vertical anchors in pairs. Gateways do not need to actually exist * Edges Linear features that mark the transition line between two environments 6 Anchors

15. Beware of transitions between different types of trail

16. Pinch trail with rocks or logs to slow down traffic7 Trail Usability

18. Reduced soil loss

19. Minimal impact on natural area

20. Sustainable trails are a Land Manager priority

21. Often referred to as IMBA Standard Trails8 Trail Sustainability

23. Least possible construction effort

24. Infrequent usage – spring/fall, once every couple of months

25. Closely follow water

26. Take steepest route to increase challenge

28. Straight uphill to summit is not best route for trail

29. Shortest route to lake is not best route for trail

30. Large human-built structures like walls and bridges

33. No fall line trails or trails on flat ground

34. Contouring trails require significantly greater construction effort

35. Profile of opposite sides of trail must be distinctly different *

38. If the natural slope of the hillside is 16%, then the trail should be no steeper than 8%.

39. The dividing line between a contouring trail and a fall line trail

40. Rule applies even if cross slope grade is very slight*© “Trail Solutions” IMBA, 2004

42. 10% as measured over the entire run of the trail

43. Above 10% grade trails begin to have water runoff problems

45. Short sections of 15% grade trail are OK if carefully designed

47. Grade reversals force water off the trail

48. No long continuous grades

49. Grade reversals create smaller tread watersheds

50. Grade reversals built into the natural flow of the trail

52. Trail route highlights the attributes of each natural environment

53. Takes advantage of natural features like overlooks or rock formations

54. Switchbacks incorporate natural features in a way to draw you to them

57. Site visit with Land Manager

58. Be a neutral party

59. Do not build a trail to favor the users you most identity with

60. Do not build a trail to favor your personally preferred level of challenge

61. Layout trail to improve all user experiences while reducing conflicts between user groups.20

63. NEPA Review

64. Archeological Concerns

65. How old does trash have to be before it becomes artifacts (50 years)

66. Work closely with LM when getting approvals

68. Negative control points – points the trail should avoid

69. Seasonal Control Points – springs and low areas

70. Construction Control Points – crossings and saddles

71. Two general control point categories; must and should

73. If flag at exact control point would be hard to spot, flag a highly visible spot near it

74. Add flags at intermediate points

75. Perform route layout in both directions

77. Adjust grade by adjusting length of trail *

78. Doubling the trail length between two points will reduce the grade by half

79. Turn locations on flat spots are a type of positive control point.

81. Climbing turns should not be used on slopes greater than 7-10% grade

82. Climbing turns should have a minimum diameter of 20-30 feet

84. Switchbacks are very difficult and time consuming to build correctly

85. For correctly built switchbacks plan on 10-15 people for two days

86. There is a tendency to fudge the steepness of climbing turns to avoid building a switchback

89. Go back at different times of day or with different people*

90. What if all of the route choices are poor?

92. Avoid archeological areas

93. Pick a route to minimize trail construction effort

94. Avoid areas with problem soil conditions

95. Pick a route to minimize trail maintenance later.

97. Corridor is much narrower than route

98. If there is no workable corridor within the route , the route may have to be moved

100. The taller the tread watersheds the closer the reversals must be

101. With highly erosive soils and large tread watersheds, reversals must be very close together (< 10’ crest to dip)

103. Walk the flag/whisker line many times in both directions.

104. Anchor high points of rises (climb above trees and rocks)

106. The Crew Leader must be able to visualize where the trail will go

107. Tread flags must sometimes explain three dimensional construction

108. Humans while walking tend to straighten curved lines, even Crew Leaders

110. Trails that remain on the flats

111. Rocks in tread

112. Water bars

113. Climbing turns that should be switchbacks

114. Multiple constructed switchbacks in sequence

115. Elevation gain immediately followed by elevation loss or level followed by steep grade34 Indications of Poorly Designed Trail

116. 35 I would often notice while hiking… ...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. And I would think, what a coincidence… ...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.

117. 36 Now when I notice… ...a section of trail is significantly better than the previous sections. I understand it is because… ...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.