Global-to-local scale storm surge modelling on tropical cyclone affected coasts

The physics of extreme high-water during coastal storms covers a wide range of scales, from tides and storms propagating over long distances to the shape of local bays, reefs and islands all contributing to what is potentially extreme high-water. Traditionally, modelling of storm-surges is mostly performed at a regional scale, sometimes extended with nested more detailed models to account for local effects. With the development of more and more accurate global tide and surge models this division may shift. In this study we show the recent advances of the Global Tide Surge Model, since our previous report [9] of version 1, including Self-Attraction and Loading (SAL) representation, dissipation of internal waves, grid refinements near the coast and bathymetry at the South Pole. An open question is now, how to incorporate local effects with a global model. One option is to mimic the traditional approach and use the global model as a template for a regional model. Another option is to bypass the regional model and directly nest a detailed model in the global one. We will show an example of the first in this paper. An example of the second is planned as a collaborative initiative between Deltares and Risk Frontiers. An important question is what level is needed at the various scales needed to obtain accurate results. We will present both cases at the conference.