Abstract
Characteristics of tsunami running up into rivers were discussed through analysis of observed tsunami profiles and numerical simulation. Tsunami form of the 2011 Great East Japan Earthquake Tsunami along Kitakami River, which was observed at Fukuchi Station (8.6 km from the river mouth) was compared with tsunami profiles observed along the coast and also on the ocean. River run-up of the 2011 tsunami along Kitakami River was simulated with Shallow-Water Equation model for more understanding on the characteristics of the observed tsunami form along the river.
On the ocean and also along the coast, the first wave was the highest, while the maximum water level at Fukuchi Station was recorded during the third wave. The wave height of the first wave rapidly got smaller with running up along the river due to the overflow of river embankments. On the other hand, the following waves ran up with the raised water level by the first wave to have less reduction of the wave height, resulting in the higher water level in upstream area than the first wave.
Due to the centrifugal force, the water level along the outer side of the curve of the river got higher to cause higher load and more overflow against the river embankment. Theoretical formula to calculate water surface slope based on the balance between pressure gradient and the centrifugal force shows good agreement with the simulated water surface slope around the breaching point of the river embankment of Kitakami River.
