Methodology for Safety Assessment 2021: XBeach BOI – sensitivity analysis and model validation
De Roo, S.; Trouw, K.; De Maerschalck, B. (2026). Methodology for Safety Assessment 2021: XBeach BOI – sensitivity analysis and model validation. Version 4.0. FHR reports, 18_037_6. Flanders Hydraulics: Antwerp. VIII, 62 + 5 bijl. pp.
Part of: FHR reports. Flanders Hydraulics Research: Antwerp, more
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Document type: Project report
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| Abstract |
Since the 2015 Coastal Safety Assessment, XBeach is applied for the morphodynamic modelling of the normative storm conditions. Being under continuous development, a further validation of the newest XBeach version was necessary upon use in the 2021 Coastal Safety Assessment (SA21).
A thorough sensitivity analysis learned about the differences between the released XBeach versions. Some physics got integrated or improved and the model’s architecture was adjusted at some points. Based on a (limited) model validation with field measurements, it was found that the BOI (Beoordelings- en OntwerpInstrumentarium) settings, calibrated in the framework of the methodology update of the Dutch Coastal Safety Assessment, are also suitable for use along the Belgian coast. Only the wetslp parameter, determining the critical avalanching slope under water, was slightly lowered to 0.10 (instead of 0.15). No structural bias was found in the model’s performance and the scatter index was acceptably low, being 0.14 and 0.30 for the modelled retreat distance and erosion volume respectively.
The XBeach model set-up and settings for the 2021 Coastal Safety Assessment are now based on the validated 2DH application of XBeach as described in this report. For this assessment, the entire Belgian coast will be divided into 28 coastal areas. For each of these coastal areas, the morphodynamic response to a 45-hour normative storm will be assessed and the safety level will be evaluated. |
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