The Effects of Off-Highway Vehicle Trails and Use on Stream Water Quality in the North Fork of the Broad River
Managing forests for recreational benefits, such as off-highway vehicle (OHV) use, as well as other ecosystem services such as clean and abundant water, can often present challenges for land managers when one ecosystem service conflicts with another. We conducted research in the Chattahoochee-Oconee National Forest to assess whether the presence of OHV trails, and trail use, were associated with greater total suspended solids (TSS) concentration and turbidity in streams during storm events in 2015â€“2016. We used a paired watershed approach, with a treatment watershed containing the Locust Stake OHV trail system on the North Fork of the Broad River, paired with a reference watershed similar in all respects except for the trail system presence and use, Kimbell Creek. During the study period, mean streamflow rates across all sampling times flows were 19% greater at Locust Stake compared to Kimbell Creek, but mean stormflow rates were 29% less. During storm sampling, average storm TSS concentration at Locust Stake was greater than at Kimbell Creek, 101.1 mg L-1 compared to 65.3 mg L-1. The results indicate that the greater the storm flow, the greater the TSS concentration for each storm event sampled across both watersheds. TSS concentration was linearly and positively related to storm flow, with R2 values ranging from 0.11 to 0.92 for all events in both watersheds. Across all sampling dates, the concentration of TSS per unit storm flow was greater in Locust Stake than in Kimbell Creek, and was 7-fold greater in Locust Stake after OHV trails were open compared to when they were closed for maintenance and assessment. When trails were closed, TSS concentration per unit storm flow was still significantly greater at Locust Stake compared to Kimbell Creek, by 4-fold. Our results suggest that the Locust Stake OHV trail system presence and use are associated with poorer water quality, with greater water quality when trails were closed. Forest managers face a well-defined set of tradeoffs between providing OHV recreation and water quality benefits that warrants careful planning and monitoring.