Analysis of Changes in Hydrodynamics Patterns and Sedimentation due to Coastal Reclamation Plans in Surabaya

Surabaya is the designated location for a National Strategic Project involving island reclamation of approximately ±1,100 hectares in its eastern coastal waters. Understanding the environmental ramifications of such a large-scale project is crucial. This research addresses this need by investigating the project's impact on current dynamics and sedimentation, aligning with Sustainable Development Goals (SDGs) 11 (Sustainable Cities and Communities) and 14 (Life Below Water) by evaluating the ecological consequences of major coastal infrastructure. The method applied is numerical modeling using Delft3D software. The model's accuracy was successfully validated against field observations for both west and east monsoon seasons, showing strong agreement with Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) values below 0.29 m and 8%, respectively. The simulation results indicate significant changes in current patterns following reclamation. Velocities generally increased, particularly on the seaward side of the islands during the west monsoon (from 0.01-0.20 m/s to 0.03-0.25 m/s) and on the inner side during the east monsoon (from 0.03-0.22 m/s to 0.09-0.35 m/s). Before reclamation, sedimentation was evenly distributed along the coast (0.5 to >1.5 m/year). After reclamation, while most of the area still experienced similar sedimentation rates, the project induced significant localized erosion. Notably, erosion was predicted in the canal between the reclaimed islands and on their inner side, with values ranging from-0.5 to-1.5 meters per year, altering the previously uniform depositional environment.