Modeling the Effects of Forest Road Density on Streamflow in the Blue Ridge Mountains

Abstract

Forested watersheds have often been managed for flood mitigation. Studies have shown that forests have the potential to minimize peak flows during storm events, yet the relationship between forests and flooding is inexact. Forest roads, usually found in managed systems, can potentially magnify the effects of forest harvesting on water yields. A distributed hydrologic model (DHSVM) was calibrated for a 760 ha watershed in the Blue Ridge Mountains of North Carolina. The impacts of forest road density were evaluated by running the model using uniform input parameters but changing road densities. Road densities tested were 0.5, 1.0, 3.0, 4.3, 6.0 and 12.0 km km-2. Results indicate that increases in road density increased average streamflows at densities ≥ 4.3 km km-2. During small storm events, discharge was impacted at densities ≥ 6.0 km km-2 and streamflows were impacted during large rainfall events ≥ 3.0 km km-2 road densities. These findings indicate that forest roads can influence water yields and additional management efforts may be needed that can slow the water yield from forest roads.