Simulation of flooding and drying as an essential element of meteotsunami modelling

Abstract

Meteotsunamis, sea level oscillations of meteorological origin with periods similar to those of tsunamis, can, in extreme cases, reach significant wave heights and cause large damage to property and even a loss of life. In this study we have taken a historic meteotsunami in the Adriatic Sea with a wave height of 6 m and attempted to improve upon previous numerical simulations in order to model it as accurately as possible. The great Adriatic meteotsunami of 21 June 1978 was most pronounced in Vela Luka Bay on Korčula Island where sea level oscillations alternately flooded the town and dried out the harbour. Previous data analysis and numerical modelling have shown that the cause of the flood was a travelling air pressure disturbance that caused Proudman resonance in the open sea, with the waves being further amplified by the basin's funnel shape, reflection at the bay head and constructive superposition with the waves coming in from the open sea. To model the sea level oscillations we used a finite element model with a flooding and drying option included, with the entire Adriatic Sea as the modelling domain. A synthetic air pressure disturbance propagating from the Italian coast and over the island at varying speeds and directions was used as the only forcing field in the model. This new setup resulted in a successful reproduction of harbour flooding and drying and an increase in modelled wave heights.