Quantification and modeling of foot trail surface erosion in a dry sub‐tropical setting

Abstract

ABSTRACTAnthropogenic disturbance often increases surface erosion and this may have potential detrimental effects on downstream aquatic resources. Foot trails are often overlooked as they represent only a small fragment of the landscape, yet they can be important sources of sediment, particularly in pristine areas. The trail network above East End Bay on the island of St Croix in the US Virgin Islands is the sole anthropogenic source of terrestrial sediment in the area. Concern over the potential for trail erosion to stress nearshore coral reefs of the East End Marine Park led to trail reconstruction and restoration efforts. The objectives of this study were to: (1) quantify trail erosion rates; (2) identify key factors controlling erosion rates; (3) develop an empirical trail erosion model. Sediment production was measured from 12 trail segments with sediment traps from November 2009 to October 2011.Annual trail erosion rates ranged from 0.6 to 81 Mg ha−1 yr−1. The lower values were from abandoned trails with a dense vegetation cover, while the highest rates were associated with devegetated trails immediately following construction or restoration. Trail erosion was a function of rainfall, slope, and vegetation cover density raised to the negative 1.7th power. Annual trail erosion rates were one‐ to three‐orders of magnitude higher than measured surface erosion rates on undisturbed hillslopes. The absence of rills or gullies suggests that traditional parametric or repeated transect monitoring commonly used to assess trail erosion may greatly underestimate actual sediment production rates. The new empirical trail erosion model serves as a tool to assess the effects of trail construction and restoration activities in the generation of sediment from small catchments in East End Bay and in other similar settings. Copyright © 2014 John Wiley & Sons, Ltd.