A Faster Approach to Quantify Large Wood Using UAVs

Abstract

Large wood (LW, log at least 1 m-long and 0.1 m in diameter) in river channels has great relevance in fluvial environments. Historically, the most used approach to estimate the volume of LW has been through field surveys, measuring all the pieces of wood, both as single elements and those forming accumulation. Lately, the use of aerial photographs and data obtained from remote sensors has increased in the study of the amount, distribution, and dynamics of LW. The growing development of unmanned aerial vehicle (UAV) technology allows for acquisition of high-resolution data. By applying the structure from motion approach, it is possible to reconstruct the 3D geometry through the acquisition of point clouds and then generate high-resolution digital elevation models of the same area. In this short communication, the aim was to improve a recently developed procedure using aerial photo and geographic information software to analyze LW wood stored in wood jams (WJ), shortening the entire process. Digital measurement was simplified using only AgiSoft Metashape® software, greatly speeding up the entire process. The proposed improvement is more than five times faster in terms of measuring LW stored in jams.