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TRAIL DESIGN AS AN INDIRECT TOOL FOR WILDERNESS USERS MANAGEMENT:POTENTIAL OF GIS MODELLING

MARTIN LEDANTDEPARTMENT OF GEOGRAPHYUNIVERSITÉ DE LIÈGE, BELGIUM

I N T R O D U C T I O N

The definition of wilderness, although it mayvary widely according to sociological and culturalfactors, is often balanced between two ideas.They are expressed in the American WildernessAct of 1964. Wilderness is firstly an area “whichgenerally appears to have been affectedprimarily by the force of nature, with the imprintof man’s work substantially unnoticeable”.Secondly, it must have “outstandingopportunities for solitude or a primitive andunconfined type of recreation”. This definitionthus states that wilderness is an area dedicatedto Nature’s own will but also recognize that itsexperiential opportunities should be madeavailable to human recreation.

This ambiguity between dedicatingwilderness to both Nature and humans is at thebasis of one of wilderness paradoxes. Indeed,wilderness areas can easily cope with thepassage of a few visitors, but the increasedabundance of visitors in those areas isdestroying the very thing that is tried to beprotected (Knight and Cole, 1991). Excessiverecreational use affects both the ecological andexperiential sides of the wilderness and may bethe main threat to wilderness today (Hendee etal., 1990).

Ecological impacts of recreation includeanthropogenic erosion, disturbance of biota viatrampling, water pollution and wildlifedisturbances. Experiential impacts include areduction of opportunities for solitude, areduction of feeling of naturalness (i.e.devegetated campsites, improper shortcut), andannoyance by other visitors behaviours (Hendeeet al., 1990).

Some of these impacts can be eliminated orreduced by management of wilderness users.However, management can enter in conflict as

well with the wilderness experience by interferingwith users’ freedom. Thus, it is fundamental thatonly the minimum management is applied toachieve the objectives required. In thisperspective, management which act on thefactors which influence people’s choices ratherthan directly on people’s choice appear to be themost appropriate as they do not interfere withusers freedom and their wilderness experience.For instance, educating people can prevent themajority of the “unskilled actions” or carelessbehaviour such as littering or plant harvesting.On the other hand, recreation always has aminimal impact which is unavoidable, forinstance every user generates a “presence”which might diminish other’s feeling of solitude.Another example is trampling of soil andvegetation which difficultly avoidable. However,some management measures exist to reducethose unavoidable impacts.

A big and growing part of recreationalactivities in the wilderness are associated withtrails (Cordell et al., 1995 in Linn and Brown2003). As discussed further, trails have a stronginfluence on people behaviour, and reverselymuch of the recreational impacts are dictated bythe presence of trails. In the light of the abovediscussion the understanding of the processes oftrail formation, their potential or desired locationsmay prove itself to be a useful tool for indirectmanagement. Actively designing the layout oftrails can enhance the wilderness experienceand reduce the biological impact of users withminimal visible management interference. It isthis idea that this present essay is dealing with.In support to the discussion an insight into thepotentiality of GIS based model in mappingusers’ behaviour and “desire lines” for effectivemanagement. This model is applied to the

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particular location of the Ennerdale Valley in thewestern Lake District (Great Britain). Particularconsiderations to this particular location arebeing stressed.

C O N S I D E R A T I O N S R E G A R D I N G T R A I L S

Trails result of the repetitive humantrampling of the soil cover. Trampling has at leastthree effects on the natural environment: loss ofvegetation cover, soil compaction and soilerosion (Cole, 2004). The vegetation around atrail can be seriously affected by trampling.Liddle (1997) reports a reduction in number,vigour and heights of plants subjected totrampling. Soil compaction can increase waterinfiltration and increase runoff and erosionpotential. Trails can become deeply eroded whenthe disposition of the trails allows water to bechannelled down the tread (Hendee et al. 1990).Finally, when intensity of usage is high, theerosion induced can be very severe. Lance et al.(1989) describes how the increase in use afteran access road and chairlift were built in the1960s in the Cairngorms had a dramatic impacton the width of the majority of the trails. Inaddition, trails can affect the wildernessexperience if they proliferate in anarchic patternswhich scar the landscape. Multiple, parallel orbraided trails or shortcuts form when people areunhappy with the trails they are following.

Trails can therefore be seen as a negativeimpact resulting from recreational use. However,trails are also a great opportunity to managewilderness users’ impact.

First, a major quality of trails is that peopletend to follow them. Helbing et al. (1997)demonstrated that pedestrian movements areaccessible to mathematical description becausethey rely of self-organisation. Human psychologywants that someone would rather choose to walkon a trail rather than across the land. This isbecause they are easy to find, easy to travel,and easy to use (Hesselbarth et al, 2007). Thepractical implication of this statement is that ifusers are provided with an efficient trail networkuse patterns can be influenced.

Secondly, it appears that the spatialdistribution of hiking impact at a large scale ismostly “concentrated along trail corridors, withlittle impact off trails” (Cole, 2004). Furthermore,

it has been shown that the relationship betweenfrequency of use and intensity of impact iscurvilinear (Fig. 1). This means that in placeswith low amount of visitors small increases infrequency create more damage than if the trailwas already frequently used. This implies thatencouraging the use of a restricted number oftrails and discouraging users to venture outsidethe trails has the potential to limit the overallimpact. This can be done mainly by informationand education (Cole, 2004) or by providing traillayout meeting users’ satisfaction requirements.

To summarize: people are attracted to trailsand their impact can potentially be concentratedaround those trails. This has good implicationsfor the ecological side of wilderness. However,this has also negative implications on thewilderness experience. Indeed, people might notwant to be constrained on a set of paths, andeven less when those concentrate other usersand human impacts. This problem can be solvedby having recourse to an intelligent andsustainable design of the trails layout.

Trail design has the potential to (1) solveproblems attached to the trail itself related earlierand (2) consider the wilderness experience ofthe trail user.

First, it is recognized that trail conditions areinfluenced by their environmental characteristics(Leung and Marion, 1996). Among them, terrainand topography play a major role. A largeamount of literature exists in the United Statesrelating of the effect of trail slope and othergeometrical parameters on trail deteriorationwhich should be considered while building a trail.

Secondly, studies suggest that resistanceand resilience of vegetation covers may vary. Forexample Cole (1995b) shows that groundcoverplants of forested site, usually composed of moreerectile and broad-leaved types, are morequickly lost due to trampling than ones in open

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woodlands or meadows. Similarly, soilssensitivity to trampling may vary. Studies haveshown that erosion is most severe is soils ofhomogeneous textures (sand, silt or clay ratherthan a combination) and that lack rocks (Bryan,1977; Root and Knapik, 1972 in Hendee et al.1990). Considering this, locating trails in lesssensitive areas may reduce drastically the trailconditions and prevent the formation of new trails.In areas where this option is not feasible, trailconditions can be preserved by engineering-surfacing, bridging or ditching but those oftenresult in undesirable effect on wildernessexperience and should be kept to a minimum.

Secondly, although designing the physicalsetting might go against experiential values, itseems that on the contrary this technique hasthe potential of encompassing wildernessexperience criterion. Hendee et al. (1990) seetrail design as “a unique opportunity for managerto subtly program visitor’s experiences almost asthough they could write a script that visitor had toact out”. Indeed, both the sequence of visualexperience and the level of challenge can bemanipulated in order to enhance the wildernessexperience. By intelligently designing the trails,anthropogenic features or trail trafficobservations can be reduced and scenic orecologic beauty can be improved. On the otherhand, the trail can be made deliberatelychallenging with a relatively high degree of riskor on the contrary easier in consideration ofpeople with different abilities. However, thedesign must also consider that the trail takes thepath of least resistance; otherwise, users willcreate their own trail (Hesselbarth et al, 2007).

Trail design may sound attractive on paper; itis often not an option. The first reason is thatmost wilderness trails today are trails that werehistorically built in other purposes than recreation(i.e. fire control, or people transportation) andconsequently doesn’t meet the train designconcepts. The second reason is that trailconstruction, relocation and maintenance isexpensive and the available funds are oftenscarce.

However, if proactive trail designing isn’talways an option, understanding the actualnetwork in a particular wild area, the reasonsresulting in the apparition of a trail, the character

of a trail and the experience it provides may helpthe manager taking decision concerning possiblererouting or areas which require attention.

T R A I L M O D E L L I N G

Following this approach, a GIS model wascreated. The model is based on algorithms morecommonly used in modelling of hydrologicalprocesses. Digital terrain models are used todetermine the direction in which water flows,subsequently the amount of water passing byevery location of the study area, and finally mappotential streams. The approach of the presentmodel is very similar except it doesn’t deal withaccumulation of water but with accumulation ofwilderness users.

To determine the “users accumulation”, weneed to determine in what direction a user wouldgo at every location of the area assuming thatthis direction follows the least cost path betweenthat point and an access point of the area (i.e.Car parks or trails access in the valley). The costof movement is determined mainly by the slopeand secondly by the roughness of the land cover(see table 1). The directional information has theform of the BACKLINK output computed via thefunction PATHDISTANCE in ArcGIS (see anexample in map 1).

The “backlink” information can then be usedto compute the “users accumulation” usingFLOWACCUMULATION function in ArcGIS.Each pixel of the area accounts for one unit(user) which makes it way to the entry point

Table 1. Cost of Movement Parameters

Land cover friction

Land cover Time cost (s.m-1)

Broadleaved and mixed woodland 0.72

Coniferous wodland 0.72

Dense scrub Barrier

Heathland 0.72

Improved Grassland 0.9

Open Water Barrier

Unimproved grassland 0.9

Valley wetland Barrier

Human featuresReclassififed as

nearestaffectation

Rocks and Crags +0.18

Vertical Factor Correction

Follows Naismith's Rule

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following the least cost path. The algorithmcomputes for every pixel the amount of unit or“users” which have flowed through. When thisvalue is normalized by the total area considered,the percentage of the area accessible from eachpixel is obtained. It appears that certain linesdrain the majority of the area and therefore canbe expected to concentrate the users. Thisconcentration increases as the trail gets nearerto the source (see map 2).

However, trails are most of the time notrelated to one and unique source. When thereare multiple entry points, each entry maygenerate its own set of trails. To take this factorinto account, the above procedure was repeatedfor 9 entry points in total (2 car parks, 7 trailentrances in the valley). A weighted average wascalculated from the 9 layers (Arbitrarily: weight ofa parking = 4 weight of a valley entrance). Thevalue of a pixel doesn’t longer represent the totalarea drained through the pixel. Instead it is anindicator of the extent of the area accessiblefrom that point considering that the user may becoming from different entry points (Map 3). Fromthis information, the likeliness of an actual pathto occur can be estimated.

D I S C U S S I O N

The modelled trails and the existing trails(rights of way) show some co-occurrence. Forinstance, for the trails around the lake, along thecrests or at the bottom of the valley there is ageneral co-occurrence. Another interesting pointis that the model recognized a path of leastresistance downhill of the Pillar (see map 3 point1) where an actual trail exists through the rocksand crags. This shows that the assumption thatusers follow path of least resistance is confirmedto some extend. For instance, around the lakethe trail is flanked between the slope and thelake, and in the valley following the river is theeasiest option.

However, at the smaller scale, the modeldoesn’t always indicate the same path as inreality. This is the case for the trail coming downof the Pillar, but it’s also true in some instancessuch as around the rock at “the corner of thelake” (point 1, 2). The trail recognized by themodel may be the least costly overall; thebehaviour of hikers on the terrain might not be

dictated by long distance evaluation of difficultybut by decision taken on the basis of shorterdistance evaluation. That’s why users may preferto choose to follow the lake, even though it willbe longer overall. The increase in length ordifficulty may also be deliberate for the sake ofscenic beauty or work out.

Users may prefer existing paths to shorterand easier path for psychological reason citedearlier. It’s the case of the two first trails climbingup the south side of the valley (4). Landownership might also play a certain role indetermining trails patterns and once those areremoved managers may want to pay attention toformation of new trails. This is particularly true inplaces where terrain doesn’t impose muchconstrains and where the model consequentlyindicates a high density of trail crossing indifferent directions (5).

On the other hand, some paths indicated bythe model don’t exist at in reality. This may beexplained by the fact that the model consider ahomogenous usage of the valley (one pixel =one unit) as where in reality some part of thevalley might be more used than others. Thereare two instances at least supporting this idea.First the trail which runs behind the hill at the endof the lake (6) and secondly the trails on theSouth-East side of the valley (7). None of thosetwo exist in reality, probably for the fact thatusage is concentrated on the south-west side ofthe valley, with all its smaller valley and peaks.However, the apparition of a trail in those areasmight become likely if pressure on wildernessexperience increase and people start to look forcalmer places.

C O N C L U S I O N

Some aspect of the model may of course besubject to discussion; in particular the relevanceor sensitivity of certain parameters such as thelocation of sources and their weight in the finalresult. However for the time being, it is safe toadmit that such modelling of wilderness user’sbehaviour and trail formation can be a potentialtool for assessing the location of impacts ofrecreational use of wilderness in a given area.Furthermore, the model could be improve byintroducing experiential notions such as scenicand ecological beauty on one hand, andecological sensitivity on another in order to

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design a trail layout which maximize wildernessexperience and minimize its impact. However,such measures, as said earlier, are difficult toimplement in practice. This is especially true inregions of the world where wilderness isn’t onlyunder the pressure of recreational use but alsounder the one of other kinds of use such as

forestry, or farming. This fact adds on the lack offund the necessity to deal with trails which

dates from other time in history when wildernesspreservation and experience were not issues.

Word Count: 2681

References:

Cole D.N. (2004) Impacts of Hiking and Camping on Soils and Vegetation: A Review, in Buckley R(2004) Environmental Impacts of Ecotourism

Cole D.N. (1995a) Experimental Trampling of Vegetation. I. Relationship Between Trampling Intensityand Vegetation Response. The Journal of Applied Ecology, Vol. 32, No. 1, (Feb., 1995), pp. 203-214

Cole D.N. and Landres P.B. (1996) Threats to Wilderness Ecosystems: Impacts and Research Needs.Ecological Applications, Vol. 6, No. 1, (Feb., 1996), pp. 168-184

Cole, D.N. (1995b) Experimental trampling of vegetation. II. Predictors of resistance and resilience.Journal of Applied Ecology 32: 215-224.

Fritz S. and Carver S. (1998) Modelling Naismith’s Rule: Implications for the wilderness indicatornaturalness. Available from: http://www.geog.leeds.ac.uk/papers/98-7/ Accessed 9th May 2008

Helbing D. et al. (2001), Self-organizing pedestrian movement. Environment and Planning B: Planningand Design 2001, 28:361-383

Hendee J.C., Stankey G.H. and Lucas R.C (1990), Wilderness Management. Fulcrum Publishing,Golden, Colorado (1990).

Hesselbarth W., Vachowski B., Davies M.A., (2007) Trail Construction and Maintenance Notebook 2007Edition. Available online from: http://www.fhwa.dot.gov/environment/fspubs/07232806/index.htmAssessed on 9th May 2008

Lance, A.N., Baugh, I.D., and Love, J.A. (1989) Continued footpath widening in the CairngormMountains, Scotland. Biological Conservation 49, 201-214.

Leung, Y., and Marion, J.L. (1996) Trail degradation as influenced by environmental factors: a state-of-knowledge review. Journal of Soil and Water Conservation 51, 130-136.

Liddle, M.J. (1975). A selective review of ecological effect of human trampling on natural ecosystems.Biological Conservation. 7: 17-36.

Lynn N.A. and Brown R.D. (2003), Effects of recreational use impacts on hiking experiences in naturalareas, Landscape and Urban Planning 64 (2003) 77–87

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