Abstract
The propagation of the tsunami into rivers in Hokkaido, generated by the 2011 Tohoku Pacific Coast Earthquake, is described using data from water level gauges in rivers. The tsunami first struck the Ohtsu (Tokachi River) and the Tottori (Shin-Kushiro River) gauge stations at the same time around 15:47 (UTC+09:00). The tsunami also intruded other six Class-1 rivers in Hokkaido. Detided water levels, recorded at the stations within these rivers, show the tsunami intruded several times, not once. Then a one-dimensional numerical method is applied to the simulation of the tsunami propagation up Tokachi River and Shin-Kushiro River in order to investigate the spatial waveforms and wave dispersion phenomena. The water levels estimated by the present method agreed well with those observed in both rivers, and significant differences were found in dispersive wave trains at the wave fronts in each river.
