Title
A Response to the Roadless Initiative Act: A Comparative Study of Sediment Generation from Existing and Recontoured Forest Service Roads
Abstract
The Chief of the Forest Service declared a moratorium on National Forest road construction until the impacts of existing roads is made acceptable. The Forest Service’s National Resource Agenda advocates the removal of several hundred miles of poorly constructed or maintained roads in the next 3-5 years (250+ miles on the Lolo National Forest alone). Yet, data on the effects of road removal is often viewed as inadequate. Current techniques for evaluating the effectiveness of road removal/recontouring are based on empirical studies and basic soil erosion properties extrapolated to forested environments.
The O’Brien Creek Watershed restoration project offers an opportunity to monitor the effects of road recontouring on sediment production and may be used to establish evaluation criteria for similar locations. This study compared sediment yield from existing Forest Service roads, newly recontoured roads, one-year revegetated-recontoured roads and natural/undisturbed sites. Two geologic formations with associated soil types were selected for sampling--Mount Shield’s formation, and Bonner formation. Two slope categories were sampled for each soil type: <45% slope and >45% slope. For all treatments, sediment runoff samples were collected using a rainfall simulator to generate rain, with five samplings over 2 days per site. Sample analysis determined percent infiltration, water and sediment yield, silt and clay content, and largest particle size removed. Hydrometer and sieve analyses determined particle size distribution. Soil bulk density and organic matter content were determined at each site. Statistical analyses are in progress. Some trends have been noted based on preliminary data.
Natural/undisturbed reference sites exhibited very little runoff or sediment yield; existing roads exhibited much more. When sampled soon after recontouring, recontoured roads generated more sediment and runoff than existing roads, but after one year, recontoured roads generated much less, and only a very little more than natural/undisturbed sites. Soil type seems to have more of an effect on sediment generation from recontoured roads, then did slope category; with the Bonner formation generating more sediment than the Mount Shield’s formation.
Start Date
14-4-2000 12:00 AM
End Date
14-4-2000 12:00 AM
Document Type
Poster
A Response to the Roadless Initiative Act: A Comparative Study of Sediment Generation from Existing and Recontoured Forest Service Roads
The Chief of the Forest Service declared a moratorium on National Forest road construction until the impacts of existing roads is made acceptable. The Forest Service’s National Resource Agenda advocates the removal of several hundred miles of poorly constructed or maintained roads in the next 3-5 years (250+ miles on the Lolo National Forest alone). Yet, data on the effects of road removal is often viewed as inadequate. Current techniques for evaluating the effectiveness of road removal/recontouring are based on empirical studies and basic soil erosion properties extrapolated to forested environments.
The O’Brien Creek Watershed restoration project offers an opportunity to monitor the effects of road recontouring on sediment production and may be used to establish evaluation criteria for similar locations. This study compared sediment yield from existing Forest Service roads, newly recontoured roads, one-year revegetated-recontoured roads and natural/undisturbed sites. Two geologic formations with associated soil types were selected for sampling--Mount Shield’s formation, and Bonner formation. Two slope categories were sampled for each soil type: <45% slope and >45% slope. For all treatments, sediment runoff samples were collected using a rainfall simulator to generate rain, with five samplings over 2 days per site. Sample analysis determined percent infiltration, water and sediment yield, silt and clay content, and largest particle size removed. Hydrometer and sieve analyses determined particle size distribution. Soil bulk density and organic matter content were determined at each site. Statistical analyses are in progress. Some trends have been noted based on preliminary data.
Natural/undisturbed reference sites exhibited very little runoff or sediment yield; existing roads exhibited much more. When sampled soon after recontouring, recontoured roads generated more sediment and runoff than existing roads, but after one year, recontoured roads generated much less, and only a very little more than natural/undisturbed sites. Soil type seems to have more of an effect on sediment generation from recontoured roads, then did slope category; with the Bonner formation generating more sediment than the Mount Shield’s formation.