A preliminary study on the impact of high-level pond tailwater discharge on beach topography: based on unmanned aerial vehicle LiDAR measurement data

Abstract

High-level pond aquaculture, as a typical aquaculture model along the South China coast, poses potential threats to coastal ecosystems due to beach topographic changes induced by its tailwater discharge. Supported by drone technology, this study employed a combined method of DJI Matrice 300 RTK UAV LiDAR surveying and ground GNSS RTK measurements to collect data from the beach area affected by high-level pond tailwater discharge in northern Longhaitian, eastern Leizhou Peninsula. The study aims to investigate the impact of high-level pond tailwater discharge on beach topography using DSM generated from UAV LiDAR data. The results show: (1) By verifying the accuracy of UAV LiDAR data (RMSE of 8.05 cm, 99% confidence interval [6.59,8.09] cm), confirmed the reliability and applicability of UAV LiDAR for monitoring beach topography affected by high-level pond tailwater discharge, with credible measurement data; (2) The beach exhibits significant spatial differentiation characteristics: the beach berm is eroded by aquaculture tailwater, with the central beach berm completely eroded away; (3) Compared to unaffected profiles, those influenced by high-level pond tailwater discharge show greater elevation change ranges, with maximum erosion depths exceeding 4 m and maximum sedimentation thickness approaching 2 m. The affected beach area demonstrates berm erosion, sedimentation in erosion gullies, and scarp erosion in the southern section, with maximum scarp erosion reaching approximately 5 m. The combined effects of tides and aquaculture tailwater discharge are the primary factors causing these phenomena. These research findings can provide technical support for the quantitative assessment of beach topography changes induced by high-level pond tailwater discharge.