The girders of a great number of bridges were washed away and/or their approach fills were significantly eroded by the great tsunami of the 2011 Great East Japan Earthquake. Many of the bridges close to coastal lines are required to have high resistance against not only seismic load but also tsunami load. The geosynthetic-reinforced soil integral bridge (GRS-IB), has been developed and it has been verified that this new type bridge has high seismic stability. Results from small scale hydraulic model tests showed that the stability against tsunami load of GRS-IB is substantially higher than the conventional type bridge, having a girder supported by bearings. This high performance can be attributed to the fact that the girder, the abutments (i.e., facings) and the approach fills of GRS-IB are structurally integrated to each other and accordingly the resistance of the backfill against erosion is very high.