Wave record and flow regimes of the 2004 Indian Ocean tsunami in Sri Lanka

Tsunami waves that impacted upon the coastline of Sri Lanka on the 26(th) December 2004 were investigated with respect to their hydrodynamic interactions and resulting complex flow regimes. Field surveys showed that a large island with a narrow and steep continental shelf was subjected to destructive waves, which swept around a 900 km swathe of coastline from the eastern seaboard (facing the seismic source in Sumatra) to the western or shadow side with comparable magnitude and intensity. Waves impacted the coastline directly (orthogonally) and were also reflected and refracted according to the geomorphology of the coastline. Three waves of different magnitude and competence inundated the coastal plain as far as 2 km inland in about four hours. The maximum wave heights and run-up elevations exceeded 12 m. Inundation was dependent on the direction of wave approach, coast to inland topography and the coastal bathymetry. The results generated by GPS-based mapping surveys define the flow regime of this megatsunami in Sri Lanka. They have an application in ongoing programmes of coastal community awareness and disaster management and can be utilized in planned evacuation procedures in a similar future scenario, thus minimizing loss of life.