How many miles inland tsunami can go depends on wave height, topography and coastline, but generally tsunami can go 1 to 10 miles inland, with extreme cases 20+ miles in flat low-lying areas, though most damage within 1 to 2 miles. For example, 2011 Japan tsunami with 10 to 40 metre waves went 6 miles inland in Sendai plain, 2004 Indian Ocean tsunami with 10 to 30 metre waves went 2 to 3 miles inland in Banda Aceh, and 1960 Chile tsunami went 2 miles. Tsunami inundation distance calculated by elevation, with wave height 10 metres can flood flat land up to 1 mile inland if elevation less than 10 metres, with each metre of elevation reducing distance. In Australia, tsunami risk low, but modelling shows 5 metre tsunami could go 0.5 to 1 mile inland in low-lying coastal areas like Sydney and Brisbane. For comparison, hurricane storm surge goes similar 1 to 3 miles. Factors affecting distance include coastal slope, river valleys which channel water further inland up to 10 miles, and tide. So tsunami can go 1 to 10 miles inland, with most damage within 1 to 2 miles, extreme 20 miles in flat deltas like Bangladesh, but for average 3 to 6 metre tsunami, 0.5 to 2 miles inland is typical, requiring evacuation to high ground 2 miles inland or 100 feet elevation.
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