Tsunami inundation is the horizontal distance inland that the waves travel from the shoreline.  Tsunami waves can continuously flood or inundate low lying coastal areas for hours.  Flooding can extend inland by 300 meters (~1000 feet) or more, covering large expanses of land with water and debris.  

Inundation distances can vary greatly along the shorelines, depending on the speed, height and intensity of the tsunami waves, the undersea features, and the topography (particularly the height) of the land.  The higher and faster the wave, the tsunami would reach a greater distance inland, however areas are generally at greater risk if they are less than 7 meters above sea level and within less than 2 km of the shoreline.  One coastal community may see no damaging wave activity, while another nearby community can experience large and violent waves.  When the tsunami reaches the coast and moves inland, the water level can rise many metres.

Source:ITIC