Can we take this road back? The effectiveness of legacy road restoration practices in headwater basins of western United States National Forests

Abstract:

Development and expansion of road networks in headwater basins managed by the National Forests in the western United States led to substantial concerns about non-point source sediment contributions and their effects on water quality and aquatic habitat in the late 20^th century. As timber production decreased in the 1990s and funding for road maintenance declined, concerns increased about the potential of abandoned or poorly maintained roads, a legacy of historical forest management, to continue degrading water quality. In response, substantial effort in decommissioning and upgrading forest roads to reduce watershed impacts was initiated, with substantial funding provided by Congress via the Legacy Roads and Trails Program starting in 2008. Important questions have been asked about how well the treatments restore watershed conditions and processes, how well particular treatment types work, which treatments are most effective for the cost, and how practices can be improved. We present the results of a monitoring program, perhaps the largest of its kind, evaluating these questions using a longitudinal study of 50 sites in the western United States. At each site, control and treated road segments (on the order of 10 km ea.) were selected and thoroughly inventoried before treatment, immediately after treatment, and after the first major storm (or after 7 years had elapsed since treatment). Measurements and analysis examined effects on hydrologic connectivity, sediment production and delivery, infrastructure component condition, mass wasting (gullies and landslides), and stream channel adjustments. Broadly, treated roads showed substantial improvement in many aspects of watershed impact, though some impacts were addressed only minimally. Conditions on some untreated roads actually worsened, as had been hypothesized. No treatment completely eliminated risk and site productivity was rarely treated, so some effects of roading remain even with decommissioning. Although the great majority of actions led to improvement, changes in practices for road drainage improvement and stream crossing excavation could further reduce post treatment risks.