LiDAR-Based Sub-Canopy Surface Water Detection in a Post-Mining Environment

Remote sensing surface water detection is most often performed with the use of spectral water indices on satellite or airborne imagery. However, such an approach is not accurate for inundated densely forested areas, as vegetation canopy obscures the surfaces beneath them. Adjustment of thresholding, improving spatial resolution, or performing spectral unmixing will not overcome an issue of physically obscured terrain. In this paper, we propose a different approach—using Aerial Laser Scanning (ALS) Light Detection and Ranging (LiDAR)-based sub-canopy water detection. The methodology utilizes LiDAR’s ability to penetrate through vegetation canopy and exploits the strong absorption of Near-Infrared (NIR) irradiation by water, resulting in the absence of laser returns. The results of testing the methods in a densely vegetated post-mining area enabled detection of surface water; delineation of water body boundaries; and, additionally, an estimation of water surface elevation in three anthropogenic lakes that formed in the result of water table rebound following cessation of mine dewatering. The proposed methodology can be used in different environments, especially where field access is limited, such as post-mining sites with a risk of ground instability.