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Managing Degraded Off-Highway Vehicle Trails in Wet, Unstable, and Sensitive Environments

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Trail Management--Responding to Trail Degradation

Management Components

The task of trail management ranges from planning, designing, and constructing trails to maintaining them. In an ideal world, every trail would have a formal, well thought-out management plan and a staff dedicated to its implementation. Unfortunately, that is not the case. In Alaska, the term 'orphan trail' has been coined to describe active trails that receive no management oversight at all. Trail management should include elements from these five basic building blocks:

Trail Location Documentation

Trail location documentation is plotting the location of the trail in a geographic database. A simple sketch of a trail location on a U.S. Geological Survey topographic map is better than no location data, but documenting the alignment with a mapping-grade global positioning system (GPS) unit is best. The GPS unit can record geographic coordinates of a trail alignment that can overlay digital topographic maps or be downloaded into a geographic information system (GIS). The GIS allows trail locations to be plotted over other geographic databases such as land ownership, soils, and terrain. Accurate trail location information is also critical for obtaining a legal right-of-way easement for a trail alignment.

Trail Condition Assessment

Condition assessment is an inventory of the physical character of a trail alignment. It documents conditions and problems and provides a baseline for monitoring changes over time. This assessment can be used to set priorities for trail prescription mapping (next section) and provide general information for future trail improvement work.

The assessment should evaluate the entire trail length, not just problem sites. This ensures that the assessment will provide a basis for evaluating condition trend during future monitoring efforts. Condition assessments can be conducted with manual data collection using a measuring wheel, tape measure, or odometer in the traditional "trail log" approach. The author has developed a simple alphanumeric system to classify individual trail segment conditions (table 3).

Table 3--Trail impact classes.

Impact class Subclass Description
A 1 Minor loss of original surface vegetation (over 80 percent remaining)
2 Moderate loss of original surface vegetation (40 to 80 percent remaining)
 
B 3 Most original surface vegetation stripped away (less than 40 percent remaining)
4 Exposed roots on trail surface
 
C 5 Almost total loss of root mass
6 Only exposed mineral or organic soil at surface
7 Erosive loss of less than 2 inches of soil, or compaction and subsidence less than 2 inches deep
 
D 8 Erosive loss of 2 to 8 inches of soil, or compaction and subsidence 2 to 8 inches deep
 
F 9 Erosive loss of 9 to 16 inches of soil, or compaction and subsidence 9 to 16 inches deep
10 Erosive loss of more than 16 inches of soil, or compaction and subsidence more than 16 inches deep
11 Trail segment intermittently passable during dry conditions
12 Trail segment impassable at all times
 

For quick assessments, trail segments can be classified using classes A to F. For more detailed assessments, the numeric subclass designators can be used.

Trail segments with class A impacts have yet to experience significant degradation. Class B segments are generally new trails or lightly traveled routes. Segments with class C impacts display the beginnings of detrimental impacts, but have not yet been seriously degraded. Monitoring these sites should be a high priority. Segments with class D impacts display degradation due to poor site conditions or excessive use. Mitigation may be needed to stabilize impacts. Segments with class F impacts are seriously degraded trails, probably with significant environmental impacts. These sites should receive a high level of management attention. Methods to respond to the degradation of classes D and F trail segments are detailed later.

While table 3 presents a classification system for manual assessment, a much more powerful and descriptive assessment can be made by using a mapping-grade GPS receiver that attaches line, point, and area descriptors with collected trail alignment coordinates. The author has developed a trail condition mapping legend (table 4) that can be used with standard mapping-grade GPS software and equipment. The legend contains a fairly complete list of trail condition attributes, and it can be used as the starting point to develop a customized legend appropriate for any specific trail system. When the data elements in table 4 are loaded into a menu-driven GPS mapping system, they can be collected easily during trail condition mapping.

Table 4--Trail condition mapping legend (bold text identifies the more important data fields).

Feature element Menu selection options
LINE FEATURE
TRAIL SEGMENT
  Trail segment type (feet) Single track, double track, or multibraid 6 to 20, 21 to 40, 41 to 80, 81 to 160, 161 to 320, 321 to 480, wider than 480
  Trail track type Main, secondary, abandoned, access, cutoff, spur
  Trail surface grade (percent) Zero to 6, 7 to 20, 21 to 40, steeper than 40
  Side slope (percent) Less than 20, 21 to 60, 61 to 100, steeper than 100
  Trail surface Vegetated, native organic, wetland vegetated, floating organic, native fine mineral, mixed fines and gravel, sand, gravel, cobble, imported gravel, gravel over geotextile, wood chips, timbers/planking, corduroy, paved, porous pavement panel, rock, water crossing, other
  Trail impact rating None
Loss of surface vegetation
Exposed roots
Less than 2 inches erosive loss or surface subsidence
2 to 8 inches erosive loss or surface subsidence
9 to 16 inches erosive loss or surface subsidence
17 to 32 inches erosive loss or surface subsidence
33 to 60 inches erosive loss or surface subsidence
More than 60 inches erosive loss or surface subsidence
  Mud-muck index None, muddy, extremely muddy, muck hole, multiple muck holes, seasonally impassable, impassable at all times
  Trail drainage Well drained, moderately well drained, poorly drained, saturated, ponded, water running across surface
  Stone hindrance (percent) None, less than 10, 11 to 25, 26 to 75, 76 to 100
  Track width (feet) One to 3, 4 to 6, 7 to 12, 13 to 20, 21 to 30, 31 to 40, 41 to 60, over 60
  Vegetation stripping Single track, wheel track only, full width of trail
  Type of use Multiuse, foot only, motorized only
  Season of use Multiseason, winter only, thaw season only
ROAD SEGMENT
  Road type Access, primary, secondary, subdivision, unimproved, other
  Road surface Paved, gravel, dirt
  Road width (feet) 8 to 12, 13 to 16, 17 to 20, 21 to 30
LINE GENERIC
  Line type Text entry
POINT FEATURE
WATER MANAGEMENT
  Type Water bar, grade dip, rolling dip, round culvert, box clvert, open drain, sheet drain, check dam, ditch
  Condition Serviceable, poor
  Culvert size (inches) Numeric entry
STREAM CROSSING
  Type Unimproved ford, improved ford, bridge, culvert
  Stream name Text entry
  Stream width (feet) Numeric entry
  Approximate flow
(cubic feet per second)
Numeric entry
PHOTO POINT
  Frame/reference No. Numeric entry
  Bearing (degrees) Numeric entry
ANCHOR POINT
  Type Beginning, middle, intersection, angle, end
REFERENCE POINT
  Type Milepost, trailhead, trail marker, survey marker, property marker, road crossing, junction, gate or barrier, other
  Mileage Numeric entry
POINTS OF INEREST
  Type Scenic vista, pullout, shelter, campsite, cabin, structure, powerline, fence, staging area
HAZARD
  Type Text entry
SIGNS
  Type Informational, directional, regulatory, warning
  Text Text entry
POINT GENERIC
  Type Text entry
AREA FEATURE
PARKING AREA
BRAIDED IMPACT AREA
GENERIC AREA

Figure 6 displays a GPS plot of a complex trail system with a large number of braided trail segments. Note the highlighted trail segment at the top of the image. The 'Feature Properties' data frame to the right of the screen lists the characteristics of that trail segment as it was mapped in the field. Similar data detail can be extracted for every line segment, point, or area feature displayed on the screen. The 'Feature Properties' box shows the location, date of data acquisition, and precision of the data collected.

Image of a computer mapping program showing a trail map and dialog boxes for position properties and feature properties.

Figure 6--This computer screen display shows the mapping
legend for a complex trail system with a large number of
braided trails. The feature properties (data box on the right)
relate to the bolded trail segment at the top of the display.

Data collected with this level of sophistication should be downloaded into a GIS system. While a GIS requires a relatively high level of technical support, it can have tremendous payoffs for trail management. Once downloaded, the data can be subjected to a wide variety of map and tabular analysis, including overlay with other geographic information such as soils and terrain. Attribute values can be used to generate trail segment impact ratings and to identify critical problem areas. The length and area of trail segments can be calculated to help estimate mitigation and maintenance costs. When the condition inventory is incorporated into a GIS, it provides a baseline of trail conditions that can be used to plan and track monitoring efforts, evaluate trail performance across varying soils and landscape units, and plan future work.

Based on the author's experience and some limited contract work conducted by the Bureau of Land Management in Alaska, about 8 miles of trail can be mapped per day by a two-person crew mounted on OHVs using the GPS-based system. Production rates vary depending on trail conditions, weather, access, staff experience, and equipment performance. Office support work is required in addition to the field work. Allow about twice as much time in the office as in the field to set up equipment, load data dictionaries, download data, edit data, and integrate the data into a GIS.

Trail Improvement Prescriptions

Trail prescriptions focus on identifying locations for specific treatment applications, such as surface improvements, ditches, brush control, water management, and water-crossing structures.

The crew preparing trail prescriptions needs to be knowledgeable of the treatments available for specific trail ailments. Unlike condition mapping, which requires just a basic knowledge of field inventory technique, prescription mapping requires expertise in trail planning, construction and maintenance, and knowledge of the trail construction and maintenance resources that are available.

Prescription mapping can be greatly assisted by GPS/GIS technology. Table 5 is a prescription mapping legend developed by the author. It identifies a wide range of treatments and can be adapted readily for use on any trail systems.

Table 5--Trail prescription mapping legend (bold text identifies the more important data fields).

Feature element Menu selection options
LINE FEATURE
TRAIL SEGMENT
  Trail type Active, inactive, new segment, access, water crossing, other
  Surface Treatment No treatment, light water management, heavy water management, grading/leveling, gravel cap, gravel/geotextile, porous pavement, corduroy, turnpike, puncheon-boardwalk, abandon--no treatment, abandon with light rehabilitation, abandon with heavy rehabilitation
  Gravel cap depth (inches) None, 2 to 4, 5 to 8, 9 to 12, 13 to 18, deeper than 18
  Trail width (feet) Numeric entry
  Surface treatment priority High, medium, low
  Ditching None, left (outbound), right (outbound), both
  Ditching priority High, medium, low
  Brush control None, left, right, both
  Brushing priority High, medium, low
  Root removal None required, required
  Cut-and-fill section (percent side slope) None, less than 15, 16 to 45, 46 to 100, more than 100
LINE GENERIC
  Type Text entry
POINT FEATURES
ANCHOR POINT
  Type Beginning, middle, intersection, angle, end
REFERENCE POINT
  Type Milepost, trailhead, trail marker, survey marker, property marker, road crossing, junction, gate or barrier, other
  Mileage Numeric entry
REQUIRED WATER MANAGEMENT
  Type Water bar, grade dip, rolling dip, culvert (diameter in inches, less than 8, 9 to 16, 17 to 36, larger than 36), check dam, open drain, other
WATER CROSSING
  Type (feet) Unimroved ford, improved ford, bridge (shorter than 12, 13 to 24, longer than 24)
PHOTO POINT
  Reference number Numeric entry
  Bearing Numeric entry
POINT-OF-INEREST DEVELOPMENT
  Type Scenic vista, pullout, shelter, campsite, cabin
FIX HAZARD
  Type Tree removal, stump removal, rock removal, guardrail, fill hole, other
SIGN NEEDED
  Type Informational, directional, regulatory, warning
  Text Text entry
SIDE SLOPE FEATURE
  Type Switchback center point, climbing turn center point
GRAVEL SOURCE
TIMBER SOURCE
STAGING AREA
POINT GENERIC
AREA FEATURE
GENERIC AREA

A prescription inventory collected with a GPS system provides an excellent basis for cost and labor estimates, but it does not have the familiar '1+00' trail log references typically associated with trail inventory work. Therefore, ground location reference points should be established before or during the inventory. Markers every one-quarter mile--or every 1,000 feet--are not too close for detailed surveys. Measuring wheels and OHV odometers are common measuring devices for establishing approximate milepost locations. Labeled flagging, lath, or metal tags should be placed at these standardized reference points. The more permanent the markers, the better.

Trail Improvement Implementation

Improvement implementation is planned trail maintenance, stabilization, or mitigation based on a trail improvement prescription. Improvement actions should be based on standard design specifications or commonly accepted management practices. Commonly accepted practices are best described in the following Federal and private publications:

Building Better Trails. 2001. International Mountain Bicycling Association, P.O. Box 7578, Boulder, CO 80306. Phone: 303-545-9011; e-mail: info@imba.com; Web site: http://www.imba.com. May be purchased both in HTML and PDF formats from the Web site or the IMBA office. 64 p. in printed book format.

Installation Guide for Porous Pavement Panels as Trail Hardening Materials for Off-Highway Vehicle Trails. 2001. Kevin G. Meyer. USDI National Park Service--Rivers, Trails, and Conservation Assistance Program Technical Note, 2525 Gambell St., Anchorage, AK 99503 (attached as Appendix B).

Lightly on the Land--The SCA Trail Building and Maintenance Manual. 1996. Robert C. Birkby. The Mountaineers, 1001 SW. Klickitat Way, Seattle, WA 98134.

Off Highway Motorcycle & ATV Trails Guidelines for Design, Construction, Maintenance and User Satisfaction. 2d Ed. 1994. Joe Wernex. American Motorcyclist Association, 13515 Yarmouth Dr., Pickerington, OH 43147. Phone: 614-856-1900; fax: 614-856-1920, e-mail: ama@ama-cycle.org; Web site: http://www.ama-cycle.org.

Trail Building and Maintenance. 2d Ed. 1981. Robert D. Proudman and Reuben Rajala. Appalachian Mountain Club, 5 Joy St., Boston, MA 02108.

Trail Construction and Maintenance Notebook. 2000. Woody Hesselbarth and Brian Vachowski. Tech. Rep. 0023-2839-MTDC. United States Department of Agriculture, Forest Service, Missoula Technology and Development Center, 5785 Hwy. 10 West, Missoula, MT 59808-9361.

Wetland Trail Design and Construction. 2001. Robert T. Steinholtz and Brian Vachowski. Tech. Rep. 0123-2833-MTDC. United States Department of Agriculture, Forest Service, Missoula Technology and Development Center, 5785 Hwy. 10 West, Missoula, MT 59808-9361.

In addition to these references, supplementary information is available from the Missoula Technology and Development Center. Call 406-329-3978 to request the latest list of recreation publications and videos. Many of these are available through the Federal Highway Administration's Recreational Trails Program. To obtain a list of publications and an order form, go to Web site: www.fhwa.dot.gov/environment/recreational_trails/publications/trailpub.cfm.

Each of these documents provides valuable information on trail design, construction methods, maintenance, or general trail management. While some may be regional in nature or focus on specific types of trails, their basic concepts can be adapted to OHV trails.

Trail Maintenance and Monitoring

Each trail alignment should receive regular maintenance at least once a year, preferably early in the season of use. Primary activities should include maintaining water-control structures, ditches, and culverts, and clearing fallen timber.

Periodic inspections also should be made of bridges, especially after spring breakup or floods. Maintenance crews also should report on problem areas and maintenance concerns. In many cases, periodic, systematic maintenance can head off major trail degradation.

Monitoring to detect changes in trail conditions, including a complete condition assessment, should be conducted about every 5 years, depending on levels of use and a trail's soil and terrain characteristics. This frequency could be increased if significant environmental values are at risk, but enough time should pass between assessments to filter out changes due to seasonal effects, weather effects, or the subjectivity of inventory crew personnel. The same inventory classification system should be employed during each monitoring with key components such as trail surface character, trail impact rating, trail drainage, mud-muck index, and track width recorded from identical menu selection options.

Management Response to Severely Degraded Trails

Managing severely degraded trails presents a formidable challenge to resource managers. Severely degraded trails tax traditional trail management techniques and sometimes force managers to investigate and test innovative management methods, refining them for local conditions. No single set of responses can meet every situation, but a framework can help guide the process.

The trail degradation issue must be addressed on several fronts. The National Off-Highway Vehicle Conservation Council (NOHVCC), a nonprofit OHV advocacy group, uses an approach they call the Four Es. They are:

  • Education
  • Evaluation
  • Engineering
  • Enforcement

Education is needed to teach users about responsible riding and appropriate environmental ethics. In addition, resource managers and technicians need to be educated about effective trail management practices. Evaluation is necessary to develop methods to document use, assess impact, and evaluate mitigation methods. Engineering is necessary to develop trail improvement techniques and equipment modifications to reduce impacts. Enforcement is necessary to manage use within acceptable impact limits. In many locales, enforcement isn't a viable option. In those areas, enforcement may be implemented as "encouragement," encouraging users to conduct their activities in a sustainable manner. This might best be achieved by providing trail location maps that direct users to sustainable trails and trail signs that encourage appropriate use.

I would also add a fifth E: 'Enculturation' (the process of modifying human behavior over time). Enculturation can best be accomplished by the steady application of education, appropriate evaluation techniques, progressive engineering, appropriate enforcement, and encouragement.

The five Es show how broadly the issue of degraded trails must be addressed. Unfortunately, this report addresses a only a few of the five Es. It is intended as a tool to help educate trail managers and users about OHV trail degradation. In addition, the section on trail condition inventory presents an important evaluation component, and the following section identifies engineering solutions within a range of management options. These options include:

By evaluating these options and developing a forum with users, advocacy groups, and the environmental community, trail managers can resolve many of the conflicts between degraded trails and environmental resources.

Trail Rerouting

Few OHV trails are planned trails where a full range of environmental considerations was carefully weighed before construction. In fact, few trails are specifically constructed for OHV use. Most OHV trails developed as individual riders followed game or foot trails or passed through natural corridors to remote fishing, hunting, or cabin sites. In Alaska, many OHV trails develop along routes that originally served as dogsled or snowmobile trails.

Because of the unplanned nature of OHV trails, many of them cross soils and sites poorly suited for the level of use occurring on them today. For example, a trail that originally developed from a game trail may not be suitable as a primary access route into a heavily used recreation area. A winter route across snow-covered wetlands doesn't necessarily provide a good alignment for a summer OHV route.

When numerous segments of a trail have been significantly degraded by the level of use, trail managers need to ask the following questions:

right arrowDo opportunities exist to reroute the trail onto better soils and terrain?

right arrowIf yes, what is the cost of stabilizing the existing route compared to constructing a new trail alignment and rehabilitating the old one?

In some cases, moving a trail or segment may be an effective method of responding to trail degradation. For example, moving a trail from a foot slope to a side slope may significantly reduce trail wetness. Moving a trail from an open wetland to an adjacent woodland may stop trail braiding. Figure 7 shows an example where rerouting should be considered.

Photo of a heavily used OHV trail.

Figure 7--A heavily used OHV trail
in Alaska crosses two distinct soil
types. In the foreground, the trail passes
through a mixed forest ecosystem where
the soils support use along a single track.
In the background, the trail crosses degraded
wetland soils where users have created a
braided trail. Managers should consider rerouting
the trail to stay within the forest system.

A rerouting assessment should follow this process:

  • Obtain and evaluate aerial photography of the trail alignment.

  • Obtain soils data for the area surrounding the trail. Soil survey reports are available from the USDA Natural Resources Conservation Service.

  • Conduct a site visit. Take available aerial photography and soils data with you. Visit the site during the primary season of use. Evaluate the trail conditions on the ground to identify relationships between vegetation communities, terrain, soil conditions, and trail performance. Table 1 may be of some assistance. Use aerial photographs to identify adjacent areas that might support trail use. Identify alternative trail routes on aerial photographs and flag those routes on the ground.

  • Identify the long-term benefits of the new route compared to continued use of the existing route.

  • Develop a trail design for the alternative route. Develop a detailed construction plan. Identify any stabilization or reclamation work that is needed on the abandoned trail alignment. Identify methods to redirect use onto the new alignment using barriers, markers, or signs.

Decisionmakers and environmental groups may object to constructing new alignments where existing trails have failed, so it is important to have photos documenting the difference between trail segments on degraded sites and trail segments on more suitable sites. Illustrate the sustainability of the pro-posed new location to build consensus for the reroute option.


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