Design for Tsunamis – Coastal Engineering Considerations

While a major tsunami is an uncontrollable event, a number of structural measures can be taken to minimise damage and loss of life. To implement and innovate such measures it is essential to have a good understanding of the underlying coastal engineering aspects which include the tsunami generation, wave propagation and wave actions (inundation, forces and scour). Simple guidelines are given for estimating the forces in terms of the incident wave height. Japanese experience has provided procedures for calculating the horizontal forces and their use of wave pressure based on three times the incident wave height is recommended, while noting that in some cases this will be conservative. Vertical forces may also be significant and are discussed. A framework for considering design concepts groups concepts as wave reduction, action reduction, damage reduction and/or survival, and some design concepts are outlined. The role of the structure in the disaster limit state and its impact on adjacent structures and the locality need to be considered – is the damaged structure to be a barrier? an open waterway? or a safe refuge?