Effect of Land Cover on Tsunami Overland Flow Propagation: A Case Study of Painan, West Sumatra, Indonesia

Abstract

Tsunami overland flow may cause severe destruction to the affected coastal area. Several tsunamis had hit Indonesia. Studies have shown that there is a high probability of a massive earthquake in the Mentawai fault, Sumatra, Indonesia. A massive earthquake with a magnitude of over 8 Mw might occur in the next 50 years. The nearshore tsunami propagation and inundation in Painan City, West Sumatra, Indonesia, is assessed using HEC-RAS. Various land cover types are simulated to investigate their effects on the tsunami overland flow. The model showed satisfactory results. The model can show the known behaviors of tsunami propagation in urban areas and in rivers. It was found that there is a significant effect of land cover types on the inundation at the coast. Inundation depth increases with roughness along the coast. On the other hand, high roughness decreases the inundated area. Furthermore, the land cover has a significant effect on the velocity. The velocity is much lower in higher Manning’s value. Simulation with a high surface roughness shows a significant reduction in both inundation area and velocity. The high roughness causes a blockage effect for tsunami propagation. Thus, the Tsunami cannot penetrate further inland. The information can be used for land use control suggestions. These provide significant information for future mitigation plans, e.g., placement of evacuation buildings and evacuation routes.