Improving Forest Road Management: An Analysis of Factors Influencing Road-to-Stream Connectivity In the Wall Creek Watershed, Umatilla National Forest, Oregon

By Sara McCune

Whitman College, Walla Walla WA

 

Road networks are an integral part of the hydrologic system of many forested watersheds.  The U.S. Forest Service (USFS) alone has over 616, 379 kilometers of roads on its land—more than the total mileage of all interstate highways.  Numerous studies have shown that roads contribute vast amounts of sediment to streams, negatively impacting the stream ecosystems.  Because the USFS has limited resources, it is important that it target for improvement roads that have strong negative effects on their watersheds.  To do this, forest managers must understand the factors that create “high-risk” roads.  In this study, we used the Geomorphic Road Analysis and Inventory Package data collection method to inventory road features that may relate to sediment and water delivery in the Wall Creek Watershed, located in Oregon’s Umatilla National Forest.  Inventories included data on flow path length, drain point type, flow obstructions, elevation and vegetation.  We used these data in a model to determine which road features most strongly predicted stream connectivity probabilities.  Results suggest that stream connectivity is best predicted by a model that includes distance from stream, drain point type, and elevation.  These findings can be used to adjust road management plans to diminish sediment input into streams, and to improve the overall health of the watershed.