Satellite derived bathymetry for rapid investigation for possible navigational channel design for coastal wind farm installation: a case study at Silavathurai, Sri Lanka

Abstract

A rapid bathymetric survey was required for the transportation of wind turbines and blades to the Silavathurai coastline, Sri Lanka via sea. This area is a shallow uncharted area which makes this task a challenge. To overcome this limitation, remote sensing techniques were used to derive the bathymetry of the area using Sentinel-2 satellite images because of its high-resolution capabilities. The empirical bathymetric method was used by incorporating band ratio techniques that involves comparing different bands of the satellite imagery in estimating water depths. Three band combinations (Green–Blue, Red–Blue and Red–Green) were used and evaluated for their effectiveness in estimating water depths. The findings showed varying degrees of correlations between the in-situ measurements and bathymetry values. Green–Blue band combination gave the strongest correlation (R2 = 0.91) among the band combinations, indicating that it is most suitable for bathymetry estimation in such situations. Further, various depth zones were also tested for correlation analysis, which reveals higher correlation values for shallower depths. Then, accuracy analysis was done based on the computed Root Mean Square Error (RMSE) values and Green–Blue combination gave the least overall RMSE value (1.06 m) with the measured depths. Finally, the derived bathymetry data from the satellite images played a vital role in designing the navigation channel, ensuring safe transport of wind turbines for the Silavathurai wind farm project. The study emphasises the effectiveness of the remote sensing approach in determining bathymetry for shallow areas, offering insightful information for coastal renewable energy projects.