sUAS-assisted mapping of large woody debris and beach volume changes in the Pockoy Island

Keywords: Large woody debris (LWD), roughness elements, beach erosion, Unmanned aerial system (UAS), Coastal management
Session Type: Virtual Poster Abstract
Day: Friday
Session Start / End Time: 2/25/2022 05:20 PM (Eastern Time (US & Canada)) - 2/25/2022 06:40 PM (Eastern Time (US & Canada))
Room: Virtual 40

Abstract

Large woody debris (LWD) on beaches is an essential roughness element affecting sediment transport by interfering with winds, waves, and tidal currents. Their geometrical characteristics and distribution density can affect erosion-deposition patterns on a beach. Pockoy Island, South Carolina, is a rapidly eroding shoreline. Its maritime forest has been destroyed in the retreating process, supplying LWD to the beach. This study aims to identify the characteristics and variations of LWD on Driftwood beach on Pockoy Island and analyze their impact on the beach changes. Image and 3D analysis were performed using high-resolution spatial data collected in May 2018 and July 2019, respectively, employing a small unmanned aerial system (sUAS). Canopy height model (CHM) and orthophoto images were used to identify the LWD characteristics. Kernel analysis was conducted to confirm more detailed distribution changes of LWD. The beach volume changes were analyzed by differencing the digital terrain models (DTM). The results show that deposition was dominant where larger and geometrically complex LWD were clustered, suggesting they promoted deposition. In contrast, where small and simple LWD were removed, erosion prevailed. This suggests that smaller LWD could not protect the beach from waves or tidal currents. This study proposes a new coastal protection strategy by showing that larger and complex forms of LWD could play a role as a natural beach protector through artificially clustering them.