Numerical Simulation of the Morphological Change Impact of the 2004 Indian Ocean Tsunami in Peukan Bada, Aceh Besar

The tsunami's impact resulted in significant morphological changes around the coastal area of Peukan Bada, Aceh Besar District. Based on satellite images and field surveys conducted after the tsunami, most of the Peukan Bada sub-district was eroded, and a large amount of sediment was deposited. The research aimed to investigate the coastal sediment transport process during the tsunami's run-up and rundown phases. The study focused on the Ujong Pancu coast of Peukan Bada sub-district. To simulate the tsunami waves, the Cornell Multi-grid Coupled Tsunami Model (COMCOT) was used, which was developed by Cornell University. The sediment transport simulation was performed using the Delft3D-Flow module, developed by the Netherlands-based company, Delft3D. The 2004 tsunami was generated using a multi-fault scheme, validated by Romon in 2008. The sediment transport simulation was conducted at the inner layer of the simulation domain, where the Non-Linear Shallow Water Equation was employed. The Van Rijn sediment transport formula was used in the Delft3D-Flow morphological model. The results of the numerical model were validated in terms of tsunami run-up area at the inland part of the Ujong Pancu coast. The simulation showed that the 2004 tsunami deposited sediment at the eastern part of Pulo Tuan Island, located a few kilometers from the Ujong Pancu coast. The beach profile changes due to the tsunami waves were successfully simulated in this research. The interaction between the tsunami's hydrodynamic forces, bathymetric slope, topography, and land roughness led to complex sediment transport processes. The tsunami's waves caused erosion and sediment erosion and deposition in other areas. The research aimed to understand the sediment transport processes that occurred during the tsunami, resulting in morphological changes. The analysis of the morphological changes in the coastal area is beneficial for tsunami mitigation efforts, such as planning coastal protection structures, creating hazard maps, and planning evacuation routes. Additionally, the deposited sediment can be used by geologists to estimate the frequency of past tsunamis (paleotsunami deposits). This information can serve as a preliminary assessment for determining the likelihood of future large earthquakes triggering tsunamis. The research methodology involved preparing secondary data and setting up data on a computer. The data included parameters such as earthquake magnitude, bathymetry, topography, sediment parameters, and Manning's roughness coefficient maps. The COMCOT model was used to simulate the tsunami waves, which was validated using experimental data from the 2004 tsunami. The COMCOT model was used to generate and propagate tsunami waves from the earthquake's epicenter, using the Shallow Water Equations (SWE). The equations used in the COMCOT model are: ∂η/∂t + ∂hu/∂x + ∂hv/∂y = 0 (1) ∂u/∂t + u ∂u/∂x + v ∂u/∂y + gn2/4h3 * u^2 + v^2 = ∂η/∂x (2) Where η is the water surface elevation, h is the total water depth, u and v are the horizontal velocities, ρ is the water density, g is the gravitational acceleration, and n is Manning's roughness coefficient. The results of the COMCOT simulation were used to obtain the tsunami's height at the observation points (Obs 1 and Obs 2).