Determining the Location of Coastal Protection Structures in Sealing with Sedimentation Problems using Hydrodynamic Modeling

Abstract Lamong Bay is a water area located between the coasts of Gresik and Surabaya. The geographical condition, which is the estuary of several rivers, makes this bay area face sedimentation problems. The process of sedimentation is caused by the movement of sediment, which is divided into 3 types: Bed Load, Suspended Load, and Wash Load. The relatively gentle slope of the topography also affects the accumulation of sediment. One very effective solution in dealing with sedimentation is the existence of coastal protection structures. The existence of coastal structures aims to resist the movement of sediments influenced by ocean currents. Thus, this study aims to determine the type and location of coastal protection structures in reducing the rate of sediment transport in the study area. The method used is numerical modeling using Delft3D software. Modeling validation is done by finding the deviation value of the modeled tides with tides from the BIG tide station. The validation calculation method uses statistical calculations with the Root Mean Square Error (RMSE) method, Mean Absolute Percentage Error (MAPE), and R correlation to find the relationship between modeling and measurement. Sediment types in the Lamong Bay area consist of silt, clay, and sand, with the largest composition in the silt type at 84%. Alternative 1, where the structure is placed in the south of the bay area, shows a cumulative sedimentation value of 0.130 m, while alternative 2 in the north shows 0.180 m. Hence, alternative 1 is more effective. This study contributes to SDG 9 by promoting resilient infrastructure to manage sedimentation issues effectively.