TLS-Based Quantification of Mangrove Drag for Numerical Wave Modeling

Accurate characterization of the structure of mangrove forests is crucial to understanding their role in coastal protection and ecosystem dynamics. This study evaluates the use of Terrestrial Laser Scanning (TLS) for high-resolution, nondestructive measurement of mangrove morphological parameters in the dense forest environment of the TAHURA Ngurah Rai (Benoa), Bali. A Trimble X9 scanner was used to generate 3D point clouds in a 200 × 200 m² area, capturing detailed structural features of Rhizophora mucronata, including stems, canopies, and prop roots. Comparative analysis between 60 measurements of the diameter of the TLS derived from manual stems showed strong agreement, with a coefficient of determination of <img src=image/14843577_01.gif>=0.8523, a root mean square error (RMSE) of 0.00145, and a nonsignificant paired t-test result (<img src=image/14843577_02.gif>=0.815), confirming the precision and statistical equivalence of the measurements based on TLS. The structural parameters of 30 trees in a representative 10 × 10 m² subdomain were extracted to calculate the volume of vegetation and the frontal area. These inputs were used to estimate drag coefficients (<img src=image/14843577_03.gif>), which yielded a mean value of 0.759, which closely aligns with previously reported reference values (<img src=image/14843577_03.gif>=0.725). The results highlight the reliability of TLS for quantifying vegetation-induced hydraulic resistance and support its integration into hydrodynamic models for the assessment of wave attenuation. TLS-based structural mapping offers significant advantages for scalable and reproducible ecological modeling in mangrove-protected coastal zones.