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Analyzing the impacts of off-road vehicle (ORV) trails on watershed processes in Wrangell-St. Elias National Park and Preserve, Alaska.

Arp CD, Simmons T - Environ Manage (2012)

Bottom Line: These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes.These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat.Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.

View Article: PubMed Central - PubMed

Affiliation: Alaska Science Center, U.S. Geological Survey, Anchorage, AK 99508, USA. cdarp@alaska.edu

ABSTRACT
Trails created by off-road vehicles (ORV) in boreal lowlands are known to cause local impacts, such as denuded vegetation, soil erosion, and permafrost thaw, but impacts on stream and watershed processes are less certain. In Wrangell-St. Elias National Park and Preserve (WRST), Alaska, ORV trails have caused local resource damage in intermountain lowlands with permafrost soils and abundant wetlands and there is a need to know whether these impacts are more extensive. Comparison of aerial photography from 1957, 1981, and 2004 coupled with ground surveys in 2009 reveal an increase in trail length and number and show an upslope expansion of a trail system around points of stream channel initiation. We hypothesized that these impacts could also cause premature initiation and headward expansion of channels because of lowered soil resistance and greater runoff accumulation as trails migrate upslope. Soil monitoring showed earlier and deeper thaw of the active layer in and adjacent to trails compared to reference sites. Several rainfall-runoff events during the summer of 2009 showed increased and sustained flow accumulation below trail crossings and channel shear forces sufficient to cause headward erosion of silt and peat soils. These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes. These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat. Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.

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Related in: MedlinePlus

Study segments characteristics along the Tanada Lake Trail sampled at 100 m increments
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Related In: Results  -  Collection


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Fig3: Study segments characteristics along the Tanada Lake Trail sampled at 100 m increments

Mentions: The study segment of the Tanada Lake Trail showed active and past erosion, thaw-subsidence, and braiding, with the extent of damage varying substantially depending on trail use, soil type, and associated vegetation. Over a 2 km straight-line distance, the trail crosses eight distinct soil-vegetation patches (Fig. 3); 35% of the length consisted of mineral soils supporting primarily white spruce forest, spike-rush meadows, or mixed grass-shrub meadows and the other 65% consisted of organic soils supporting black spruce muskeg, sedge fen, or tussocks-scrub bog. Sections of trail crossing mineral soils were typically single-thread tracks with largest amount of braiding in a dry meadow area where five semi-parallel tracks were observed. No notable ponding of water was observed in these sections during the survey conducted in early September 2009. Additionally, more than half of trails crossing mineral soil had some vegetative cover. Conversely, sections of trail crossing organic soils often had extensive braiding with an average of 8 semi-parallel tracks covering a width of 17–125 m, and up to 14 individual trails in one location (Fig. 3). About 25% of trail braids on organic soils were unvegetated, while the rest supported some vegetation on newly-formed or infrequently-used trails or had re-vegetated following inactivity. In addition, these areas were characterized by the presence of ponded water in trail depressions resulting from a combination of erosion and thaw-subsidence. Most notable was that more severely degraded trails were consistently found along the upslope edge (east side) of the trail corridor and also were more recent, based on an examination of the repeat aerial photography. Two perennial streams and at least two ephemeral channels were crossed by the trail and it was also at these locations that trail braiding, thaw-subsidence, and soil erosion appeared most severe.Fig. 3


Analyzing the impacts of off-road vehicle (ORV) trails on watershed processes in Wrangell-St. Elias National Park and Preserve, Alaska.

Arp CD, Simmons T - Environ Manage (2012)

Study segments characteristics along the Tanada Lake Trail sampled at 100 m increments
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3298735&req=5

Fig3: Study segments characteristics along the Tanada Lake Trail sampled at 100 m increments
Mentions: The study segment of the Tanada Lake Trail showed active and past erosion, thaw-subsidence, and braiding, with the extent of damage varying substantially depending on trail use, soil type, and associated vegetation. Over a 2 km straight-line distance, the trail crosses eight distinct soil-vegetation patches (Fig. 3); 35% of the length consisted of mineral soils supporting primarily white spruce forest, spike-rush meadows, or mixed grass-shrub meadows and the other 65% consisted of organic soils supporting black spruce muskeg, sedge fen, or tussocks-scrub bog. Sections of trail crossing mineral soils were typically single-thread tracks with largest amount of braiding in a dry meadow area where five semi-parallel tracks were observed. No notable ponding of water was observed in these sections during the survey conducted in early September 2009. Additionally, more than half of trails crossing mineral soil had some vegetative cover. Conversely, sections of trail crossing organic soils often had extensive braiding with an average of 8 semi-parallel tracks covering a width of 17–125 m, and up to 14 individual trails in one location (Fig. 3). About 25% of trail braids on organic soils were unvegetated, while the rest supported some vegetation on newly-formed or infrequently-used trails or had re-vegetated following inactivity. In addition, these areas were characterized by the presence of ponded water in trail depressions resulting from a combination of erosion and thaw-subsidence. Most notable was that more severely degraded trails were consistently found along the upslope edge (east side) of the trail corridor and also were more recent, based on an examination of the repeat aerial photography. Two perennial streams and at least two ephemeral channels were crossed by the trail and it was also at these locations that trail braiding, thaw-subsidence, and soil erosion appeared most severe.Fig. 3

Bottom Line: These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes.These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat.Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.

View Article: PubMed Central - PubMed

Affiliation: Alaska Science Center, U.S. Geological Survey, Anchorage, AK 99508, USA. cdarp@alaska.edu

ABSTRACT
Trails created by off-road vehicles (ORV) in boreal lowlands are known to cause local impacts, such as denuded vegetation, soil erosion, and permafrost thaw, but impacts on stream and watershed processes are less certain. In Wrangell-St. Elias National Park and Preserve (WRST), Alaska, ORV trails have caused local resource damage in intermountain lowlands with permafrost soils and abundant wetlands and there is a need to know whether these impacts are more extensive. Comparison of aerial photography from 1957, 1981, and 2004 coupled with ground surveys in 2009 reveal an increase in trail length and number and show an upslope expansion of a trail system around points of stream channel initiation. We hypothesized that these impacts could also cause premature initiation and headward expansion of channels because of lowered soil resistance and greater runoff accumulation as trails migrate upslope. Soil monitoring showed earlier and deeper thaw of the active layer in and adjacent to trails compared to reference sites. Several rainfall-runoff events during the summer of 2009 showed increased and sustained flow accumulation below trail crossings and channel shear forces sufficient to cause headward erosion of silt and peat soils. These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes. These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat. Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.

Show MeSH
Related in: MedlinePlus