Fine sediment storage in an eroding forest trail system

Abstract

ABSTRACT We measured fine sediment accumulations (FSA) adjacent to eroding off-highway vehicle trails in Ouachita National Forest, Arkansas. Measured trailside FSA was 643 m3. Extrapolated to the entire trail network, this amounts to 216 t ha−1 of trail surface, with a residence time of <1 yr. Natural topographic features are the main storage sites, accounting for 83% of the total, and constructed features for 16%. More than two thirds occur in channels indicates high sediment connectivity. For all types of FSAs, the single largest deposit accounted for about 30% or more of the total. These hotspots are found where topographically suitable storage sites occur downslope of an area of above-average rates of, or recent, trail erosion. Because in many cases trail erosion occurs without evident gullies or rills, these accumulation foci are effective ways to identify erosion hotspots. Relatively small amounts of fine sediment are stored in low-order stream channels. However, the low storage amounts (4,060 m3 estimated for all low-order streams) and lack of silt and clay indicate that fine sediments are highly mobile once reaching streams. Overall, results indicate predominantly short-term storage of fine sediments and high connectivity with and rapid movement through the fluvial system.