Modeling forest road runoff and erosion at multiple temporal scales in Florida panhandle region, USA

Forest roads are critical infrastructure for accessing forested areas, yet their surfaces can generate substantial runoff and sediment that threaten both road integrity and water quality. This study examines the temporal dynamics of runoff and erosion along a typical unimproved forest road at the Chipola Experimental Forest in the Florida Panhandle Region from 2000 to 2023, using the Water Erosion Prediction Project (WEPP) model. We quantified runoff and erosion at multiple temporal scales - daily, monthly, and annual - and evaluated the effects of two mitigation methods: a gravel surface and a compacted “graded aggregate base” design. Sensitivity analyses were performed on key soil erodibility parameters, and the influence of different rainfall recurrence intervals on runoff and erosion outcomes was assessed. The results indicate a strong correlation between precipitation patterns and both runoff and erosion, with increased precipitation observed during the 2013–2023 period corresponding to elevated annual runoff and soil loss. Mitigation methods substantially reduced erosion: gravel surfaces decreased erosion by more than 90%, while compacted surfaces reduced it by 50%. However, the compacted surface also increased runoff by approximately 20%, indicating a trade-off between erosion reduction and runoff mitigation. Sensitivity analysis revealed that critical shear (τ c ), effective hydraulic conductivity of surface soil (K e ), and rill erodibility (K r ) are the most influential parameters for erosion prediction. Runoff and erosion were also found to be sensitive to rainfall recurrence intervals, with storms of lower recurrence intervals dominating annual runoff and sediment yield. These findings offer critical insights for designing and managing forest roads under changing climate conditions and informing infrastructure improvements that enhance road durability while minimizing erosion and its environmental impacts.