The Effect of Forest Road Density On Stream Discharge as Calculated by the Distributed Hydrology-Soil-Vegetation Model.

Throughout the country, foresters are studying the effects of logging and forest roads on watershed hydrology, peak flows, and stream health.  In the Pacific Northwest, a distributed hydrology-soil-vegetation model (DHSVM) has been used to predict the effects of logging on peak discharge in mountainous regions.  DHSVM uses elevation, meteorological, vegetation, and soil data to predict the hydrology of a catchment explicitly on a grid cell by grid cell scale.  The model is unique in its ability to consider the impacts of road networks on catchment hydrology due to the addition of a road and channel network algorithm.  This is of critical importance because it has long been recognized that forest roads can have very large impacts on water yields and water quality.  The primary objectives of this study were to determine whether or not DHSVM can be applied to the gentler slopes of the Appalachian Mountains and, if so, determine whether or not typical forest road densities affect stream discharge.  Calibration of the model was done using historical data collected from the Coweeta Long Term Ecological Research Station in the Blue Ridge Mountains of North Carolina.  Road density networks were created for densities of 0.5, 1.0, 3.0, 6.0, and 12.0 km/sq km.  The current road density of the study watershed is 4.0 km/sq km.  The information gathered from this study will be useful to both watershed managers and planners who are looking to understand the impact of road networks on forest streams.