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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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Longitudinal profiles of the reference study site and three reaches crossed by trails surveyed in early September 2009 at approximately 10–15 points per reach including measurements of depth-to-refusal that were differentiated as frozen ground or rock (sand to cobble/coarse till) (A location of the above trail, B location of the below trail monitoring stations, Hc location identified channel initiation points, and Tr location of trail crossings of the stream channel)
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Fig8: Longitudinal profiles of the reference study site and three reaches crossed by trails surveyed in early September 2009 at approximately 10–15 points per reach including measurements of depth-to-refusal that were differentiated as frozen ground or rock (sand to cobble/coarse till) (A location of the above trail, B location of the below trail monitoring stations, Hc location identified channel initiation points, and Tr location of trail crossings of the stream channel)

Mentions: To understand how streams and their channels have been impacted by trail crossing points, we analyzed the form and behavior of three channels intersected by the Tanada Lake Trail and compared these to a nearby reference site stream. The reference stream initiates from the toe of a fen set in a small basin, transitioning from a peat body with a steepening channel, 2.3%, that cuts down to armored till up to large-cobble size (Table 3). A distinct headcut is indicated in Fig. 8a where the channel steepens to >6% over a short distance. The largest trail-crossed stream, TC-1, initiates from a pond above the trail system and has a shallow gradient, 1.1%, and a channel composed of cobble transitioning into gravel below the active trail crossing. TC-3 initiates from a tussock fen transitioning into black spruce muskeg with an average slope of 2.0% and a steep headcut dropping >15% over a 2 m channel distance (Figs. 8c, 2d). As a result of the intense trail use it is difficult to tell if this was a natural transition or whether it was due to erosion and thaw subsidence. The entire channel of TC-3 is composed of organic soils and peat, stabilized to some degree by spruce and willow roots. The TC-4 channel initiates at a transition between organic and mineral soils, is mainly composed of silt and sand underlain by coarse till and an obvious, but moderate, headcut with a 4% slope over 3 m (Figs. 8d; 2c).Table 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)

Longitudinal profiles of the reference study site and three reaches crossed by trails surveyed in early September 2009 at approximately 10–15 points per reach including measurements of depth-to-refusal that were differentiated as frozen ground or rock (sand to cobble/coarse till) (A location of the above trail, B location of the below trail monitoring stations, Hc location identified channel initiation points, and Tr location of trail crossings of the stream channel)
© Copyright Policy
Related In: Results  -  Collection

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

Fig8: Longitudinal profiles of the reference study site and three reaches crossed by trails surveyed in early September 2009 at approximately 10–15 points per reach including measurements of depth-to-refusal that were differentiated as frozen ground or rock (sand to cobble/coarse till) (A location of the above trail, B location of the below trail monitoring stations, Hc location identified channel initiation points, and Tr location of trail crossings of the stream channel)
Mentions: To understand how streams and their channels have been impacted by trail crossing points, we analyzed the form and behavior of three channels intersected by the Tanada Lake Trail and compared these to a nearby reference site stream. The reference stream initiates from the toe of a fen set in a small basin, transitioning from a peat body with a steepening channel, 2.3%, that cuts down to armored till up to large-cobble size (Table 3). A distinct headcut is indicated in Fig. 8a where the channel steepens to >6% over a short distance. The largest trail-crossed stream, TC-1, initiates from a pond above the trail system and has a shallow gradient, 1.1%, and a channel composed of cobble transitioning into gravel below the active trail crossing. TC-3 initiates from a tussock fen transitioning into black spruce muskeg with an average slope of 2.0% and a steep headcut dropping >15% over a 2 m channel distance (Figs. 8c, 2d). As a result of the intense trail use it is difficult to tell if this was a natural transition or whether it was due to erosion and thaw subsidence. The entire channel of TC-3 is composed of organic soils and peat, stabilized to some degree by spruce and willow roots. The TC-4 channel initiates at a transition between organic and mineral soils, is mainly composed of silt and sand underlain by coarse till and an obvious, but moderate, headcut with a 4% slope over 3 m (Figs. 8d; 2c).Table 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