Extraction of beach cusp morphological characteristics and short-term evolution based on UAV aerial survey in Western Guangdong beaches

Beach cusps are typical rhythmic landforms, their formation and evolution mechanisms are important in coastal dynamic geomorphology． In this work the central beach of Donghai Island in Western Guangdong was studied． UAV aerial survey technology was used to obtain short-term comparative image data, high-precision digital surface models were generated using visible-light imagery． Morphological parameters (beach cusp spacing, depth and height) were extracted using the contour method, Pearson correlation analysis was used to analyze short-term evolution characteristics． Beach cusp morphology was found to show a significant trend toward homogenization in the monitoring period． The number of cusps increased (from 25 to 48), their spatial distribution became more regular, spacing remained stable, while the mean depth and height decreased, with an overall reduction in the dispersion of parameters． Under the influence of stable moderate swells (wave height 0.6–0.9 m, E and ENE directions), the correlations among morphological parameters decreased significantly, and the spacing-height relationship became completely decoupled． This indicates that the beach cusp system was in a phase of morphological construction and adjustment dominated by positive feedback within the self-organization process． Significant deviations were observed between measured values and predicted values of edge wave theory, suggesting that explanatory power of edge wave theory is limited under hydrodynamic conditions and timescale of this monitoring period． This study demonstrates applicability and reliability of UAV aerial survey technology for extracting and monitoring morphological characteristics of beach cusps; this provides a high-resolution empirical case for understanding short-term evolution processes of coastal landforms．