A modular Pan-European Flood Catastrophe model

Abstract

<p>The flood event “Berndt” in North-Western Europe in July 2021 demonstrated to stakeholders the critical importance of understanding present-day events, their spatial-temporal coherence and magnitude, and the probability of their occurrence. The shear size of multi-country events such as “Berndt” necessitate a large scale and highly automated approach to the modelling of their characteristics.</p> <p>To this end, we (AXA, Fathom and Deltares) developed a modelling framework that can efficiently compute very large event sets and worked on improving its underlying skill by making the framework highly modular. The framework consists of the following modules: a synthetic weather generator, which may sample many thousands of years of continuous weather data at daily and sub-daily time scales; a gridded hydrological model forced by the synthetic weather that produces long-term hydrological timeseries and derived statistics, and a subcatchment-scale fluvial and pluvial flood model archive, produced from large amounts of simulations with the Fathom hydraulic flood model engine. Its modular character allows for exchanging components, improving existing components or modifying parameters to assess sensitivities or uncertainties.</p> <p>In last year’s contribution, we presented our first synthetic simulations of weather and hydrology. In this year’s contribution we have improved stochastic weather generation and have established a full 10,000-year event set and flood catalogue, both under the present climate and a future climate projection that encompasses several assumptions. We will show the statistics and spatial configuration of past events according to our catalogue, including “Berndt 2021”, and how the statistics of extreme events will change according to the defined climate scenario simulation.</p>