Effectiveness of forestry BMPs for roads

 

Forestry professionals generally recognize Best Management Practices (BMPs) as effective core elements of forestry nonpoint source control programs. Nevertheless, some stakeholders are challenging the effectiveness of forestry BMPs in context of legal proceedings such as NEDC v. Brown – a case in which the U.S. Court of Appeals for the Ninth Circuit has ruled that some forest roads are subject to “point source” permit requirements of the Clean Water Act. The U.S. Supreme Court is considering two petitions seeking review of the Ninth Circuit’s decision.

In 2011, NCASI initiated a review of available technical information about the effectiveness of forestry BMPs for roads. The review was conducted by Drs. George Ice and Erik Schilling. Their report was published recently as NCASI Special Report No. 12-01,Assessing the Effectiveness of Contemporary Forestry Best Management Practices (BMPs): Focus on Roads. This Special Report is available for download at www.ncasi.org.

Ice and Schilling demonstrate that forestry practices have changed dramatically over the past several decades and that BMPs can be highly effective in minimizing water quality impacts. In some cases, legacy road conditions such as poor locations along streams challenge the ability of land managers to improve road performance. Nevertheless, inventories of road conditions show that the forestry community is addressing identified problems. Direct deliveryroad segments are being disconnected from streams; poor road/stream crossings are being identified
and corrected; and landslides from forest roads are being reduced.

In the few cases where there have been opportunities to compare water quality impacts from past and contemporary practices, reductions in sediment loads of 80% or more have been attributed to today’s BMPs. There is evidence in some of these cases that increases in sediment following contemporary harvesting are not from the road network but from in-channel scouring, perhaps due to increased stream flow as a result of reduced evapotranspiration. What is clear is that these changes in water quality are often small compared to the variability seen in response to natural disturbance and annual weather cycles.

The effectiveness of road BMP packages is enhanced by redundant measures to prevent sediment delivery to streams. For example, some BMPs reduce erosion of sediment from road surfaces while others control sediment movement in runoff as it moves away from the road.

Sediment delivery from roads to streams varies greatly depending on factors such as slope, soil type, surface roughness and precipitation (form and frequency). Most road segments are not significant sources of sediment because they are located and designed in ways that prevent delivery.

The forestry community is implementing BMPs in all regions of the United States to control erosion and sediment movement from the subset of road segments that has greatest potential to deliver sediment to streams. In the few states that have identified forest roads as important sources of sediment (e.g., California), BMP
implementation is mandatory and occurring in context of regulatory forest practice programs.

Despite this progress, some stakeholders remain skeptical about the effectiveness of silvicultural nonpoint source control programs that employ BMPs under either regulatory or non-regulatory programs. It will continue to be important to provide information about the effectiveness of individual BMPs, the effectiveness of BMP packages applied at a watershed scale, and the level of implementation to address lingering concerns. The forestry community has conducted literally hundreds of research and monitoring efforts to refine BMPs and to test their effectiveness. The resulting database provides a crucial toolbox for land managers and agencies to practically address water quality concerns related to forest roads.

 

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