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Long water waves in fjords: dynamics of the moving shoreline

Awarded: NOK 51,999

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2011 - 2011

Entry of sea waves into narrow bays, such as fjords, and river mouths usually leads to an intensification of wave regimes, which is well-known by various photos of tidal and tsunami bores. For certain bathymetry configurations the wave can propagate witho ut internal reflection even in the cases, when the depth varies strongly along the wave path. With an application to a tsunami problem it means that destructive tsunami wave can propagate over large distances without reflection and transfers all its energ y to the coast that leads to an abnormal wave amplification and runup. The central aim of this project is to develop the analytical theory of long wave runup in fjords focusing on situations of abnormal wave amplification and runup (the worst case scenar io). For this purpose I will (i) find rigorous and approximated solutions of wave runup in U-shaped bays with analytically determined longitudinal profiles and study the dependence of runup height on bathymetry variations; (ii) develop analytical dissipa tive model of wave runup by considering a variable dissipation, which may approximate dissipation caused by wave breaking and bottom friction; (iii) apply the developed model to experimental data of ship wave runup in Tallinn Bay, Baltic Sea. In order to find rigorous analytical solutions of nonlinear shallow water theory in 1D and 2D cases as well, a number of methods of nonlinear wave physics and mathematical physics will be used. The outcome of this research will be the new analytical formulas for wa ve runup, which can be applied to hazard assessment of water waves in fjords. For example, it may explain the 2009 tsunami event in American Samoa, where the maximum runup height reached 17.6 m in the village of Poloa and the inundation reached an impress ive 500 m along the bed of the Leafu River. The results of the project can also be applied to forecast and mitigation of marine natural hazards in Norway.

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