Participation in off-road vehicle recreation has increased dramatically, particularly on National Forest lands in the western United States.  The propagation of engine noise negatively impacts wildlife populations and the quality of visitor experiences, and largely determines the extent of the ecological ‘effect zone’ around motorized recreation routes.  However, modeling noise propagation is complex, and to date, methods have not been customized for application to recreation planning or forest landscapes.  We reviewed eight existing software tools and spatial models available for developing predictive models of noise propagation, and evaluated them on the basis of their cost, ease of use, and capacity to incorporate various factors that are likely to affect sound propagation in wildland settings.  Based on the results of this review, we decided to adapt the System for the Prediction of Acoustic Detectability (SPreAD) – a model developed nearly 30 years ago by the U.S. Forest Service and Environmental Protection Agency – to an ArcGIS toolset.  SPreAD was designed as a system of worksheets and tables to predict the acoustic impacts of off-road vehicle activity, based on weather, topography, vegetation and other environmental characteristics.
Results/Conclusions

In this presentation, we will illustrate the development of SPreAD-GIS and our subsequent modifications to the model.  To validate the model, we will compare predicted noise propagation patterns with field measurements of motor vehicle noise collected during summer 2008.  We will also demonstrate the application of SPreAD-GIS to recreation planning and wildlife monitoring in Sierra National Forest, using the model to explore alternative scenarios for motorized route designation.  The results of this project will help to estimate the ecological effect zone around motorized recreation routes and provide land managers with much-needed tools for monitoring recreational disturbances and managing wildlife impacts.