Infiltration, Erosion, and Vegetation Recovery Following Road Obliteration

Abstract

Forest roads are obliterated to lower the risks of surface erosion and mass failures. One purpose of the road obliteration is to return the compacted forest roads to productive pre-road conditions, i.e., a forest floor with high infiltration capacity, low interrill erodibility, and high vegetation ground cover. It is important to know how these characteristics recover following road obliteration. Infiltration capacity, interrill erodibility, and vegetation ground cover are essential parameters for modeling erosion from obliterated roads for erosion prediction models such as the Water Erosion Prediction Project (WEPP). We chose three sites located on the Payette National Forest, Idaho. Rainfall simulations were conducted on 1 1 m plots with three replications in two consecutive years. Three 30 min storm events with an intensity of 89 mm h-1 were applied to each plot. Photos were taken to determine vegetation ground cover. Infiltration capacity and interrill erodibility in this study were determined as 9.0 mm h-1 for saturated hydraulic conductivity and 3.2 106 kgs m-4 for interrill erodibility. This study postulated a history of saturated hydraulic conductivity on a forest road from prior to road building to years after obliteration. The low elevation (1400 m) site had vegetation ground cover of 27% after three years following road obliteration, while the other high elevation (1800 m and 2200 m) sites had 8% after four years. We conclude that four years was not sufficient time for obliterated roads to return to the pre-road (forest floor) conditions, especially for infiltration capacity.