The Effect of Bathymetry Changes on The Palu Bay Coastline Post Tsunami 2018

As a result of the disaster on September 28 2018, significant changes occurred in the coastal area of Palu Bay. These changes have caused other problems in the coastal area of Palu Bay, including changes in the coastline and subsidence of parts of the land along the coast of Palu Bay and causing the potential for tidal flooding. Taman Ria Beach is one of the beaches located on the coast of Palu City, Central Sulawesi, where along the beach there are residential areas, hotels, shopping centers and community recreation areas with very high community activity. Based on the impact caused by the Tsunami disaster, it has indicated that there has been a change in the coastline in the coastal area of Taman Ria Beach, Palu City, Central Sulawesi. So the Taman Ria Coastline experienced quite significant changes due to coastline shifts and abrasion, based on the results ofGoogle Earth In 2018, the maximum abrasion that occurred was 58.19 meters and the minimum abrasion was 1.02 meters. Therefore, to solve the problem of coastline changes, it is necessary to conduct research and develop models to predict coastline change patterns using the GENESIS software numerical model (Generalized Model for Simulating Shoreline Change). The aim of this research is to determine changes in the Taman Ria Beach line in the next 5-10 years using GENESIS software. The method in this research is GENESIS, a numerical simulation model software designed to predict coastline changes and modeling coastline changes using two scenarios, namely scenario 1 without any coastal protection buildings and scenario 2 with coastal protection buildings.seawall. Simulations of coastline changes that occur at Taman Ria Beach show that coastline changes occur in the form of accretion and abrasion along the coastline. 5 year simulation results of coastline changes in scenario 1 maximum accretion of 7.95 m and maximum abrasion of -6.8 m in scenario 2 maximum accretion of 3.65 m and maximum abrasion of -2.45 m. And the 10 year simulation results of coastline changes in scenario 1 maximum accretion of 13.75 m and maximum abrasion of -12.5 m in scenario 2 maximum accretion of 5.5 m and maximum abrasion of -2.5 m.