R&D highlights edition 2019

PROJECTS Flood risk 10 SFINCS - RAPID FLOOD SOLVER FOR COASTAL SYSTEMS We have developed a new model for rapid assessments of coastal flooding: SFINCS (Super-Fast INundation solver for Coastal Systems). Modelled maximumwater elevations for Jacksonville with observation points in circles Modelled maximumwater depths for the community of Pantufo for a 100-year return period compound event season of 2017 (that included Irma, Maria and Harvey). Coastal flooding during storms can be caused by tides, storm surges, individual waves, precipitation, or combinations of these types of forcing. The term used for combinations of these different forces is ‘compound flooding’. Advanced process-based models (such as Delft3D or XBeach) can be used to simulate compound flooding accurately. However, these calculations are made sporadically since advanced model systems are quite computationally demanding. SFINCS (Super-Fast INundation solver for Coastal Systems) is an alternative approach that has been established to optimise computational demand and the required physics. SFINCS solves a set of simplified depth-averaged shallow- water equations in which horizontal viscosity and advection terms are neglected. The SFINCS model was used to hindcast the compound flooding at Jacksonville, Florida, caused by Hurricane Irma in 2017. The model results indicate that combined coastal, pluvial and fluvial components resulted during Irma in the flooding of Jacksonville, with hundreds of people needing to be rescued. Accuracy and efficiency were tested by comparing the SFINCS results with an advanced modelling train using Delft3D-FLOW and Delft3D-WAVE models. SFINCS produced very similar flooding results to the Delft3D simulations but it was in the order of 100 times faster. Another unique model functionality of SFINCS is that it can include individual waves. This functionality is needed to compute wave run-up and overtopping, and it was used, for example, in a climate variability study for several communities in São Tomé and Príncipe. The high computational efficiency of SFINCS made it possible to simulate hundreds of different scenarios and therefore consider compound flooding due to waves and rainfall while also including sea level rise. Applications of SFINCS range from the probabilistic forecasting of compound flooding to climate variability studies with considerable perturbation. Extreme events like tropical cyclones can inflict tremendous amounts of damage on coastal communities due to flooding and high wind velocities, as shown by the recent hurricane Contact: Tim Leijnse, Tim.Leijnse@deltares.nl , t +31 (0)88 335 8051 Ap van Dongeren, Ap.vanDongeren@deltares.nl , t +31 (0)88 335 8351 Further reading : https://repository.tudelft.nl/islandora/ object/uuid%3A53037d4d-d7a9- 4f71-9b22-8c329f2b384c?- collection=education

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