Construction of model-based extreme wind fields for the assessment of the Dutch primary water defenses

The joint KNMI-Deltares WTI2017 wind modelling project aimed to address the knowledge gap regarding “Determination of open water winds” and to support the inclusion of the dimensions “time” and “space” in the determination of the Hydraulic Boundary Conditions (HBC). The project is successfully approaching its end. A high-resolution atmospheric model, the HARMONIE model, has been setup, calibrated, validated and used to produce open water winds covering the Dutch water systems in the period from 1979 to 2013 with a time resolution of 1 hour on a grid with a spacing of 2.5 km. Subsequently, directional extreme wind distributions over open water covering all waters, influencing the determination of the Hydraulic Boundary Conditions (HBC) of the Dutch primary water defences have been determined. These extreme value distributions and corresponding wind velocity time series have been made available in a digital deliverable (Van den Brink and Caires, 2015). These can now be used directly in the safety assessment of flood defences (WTI) computations and also to determine time- and space-evolving extreme winds allowing the inclusion of the dimensions “time” and “space” in the determination of the HBC. This final step of the joint KNMI-Deltares WTI2017 wind modelling project is the goal of this study. The digital deliverable of Van den Brink and Caires (2015) is extended with MATLAB scripts. The scripts allow the determination of time- and space-evolving extreme wind fields by the Combined max-stable (CMS) lifting method using the data and extreme values distributions provided in the deliverable of Van den Brink and Caires (2015).