Identification of Abandoned Logging Roads in Point Reyes National Seashore

Abstract

Temporary roads are often placed in mountainous regions for logging purposes, but then never decommissioned and removed. These abandoned forest roads often have unwanted environmental consequences. They can lead to altered hydrological regimes, excess erosion and mass wasting events. These events can affect sediment budgets in streams, with negative consequences for anadromous fish populations. Maps of these roads are frequently non-existent; therefore, methods need to be created to identify and locate these roads for decommissioning. Abandoned logging roads in the Point Reyes National Seashore in California, an area partially under heavy forest canopy, were mapped using object-based image processing in concert with machine learning. High resolution Q1 LiDAR point clouds from 2019 were used to create a bare earth model of the region from which a slope model was derived. This slope model was then subjected to segmentation algorithms to identify and isolate regions of differing slope. Areas of differing slope were then used in a Convolutional Neural Network (CNN), and a maximum likelihood classifier to delineate the historic road network. The accuracy assessment was conducted using historic aerial photos of the state of the region post-logging, along with ground surveys to verify the presence of logging roads in areas of question. This method was successfully able to identify road networks with a precision of 0.991, and an accuracy of 0.992. It was also found that the CNN was able to identify areas of highest disturbance to the slope gradient. This methodology is a valuable tool to decision makers who need to identify areas of high disturbance in order to mitigate adverse effects.