Extreme weather and high-water situations require emergency measures that can be applied quickly, safely, and under pressure. Therefore, within the Interreg North-West Europe project BONSAI, exercises involving various temporary water safety measures were conducted in the Marnewaard on April 14 and 15, 2026. The societal relevance is significant; Water authorities, Rijkswaterstaat, Defence, safety regions, and international partners must be able to rely in crisis situations on measures that not only make sense on paper but are also feasible in the field. 

During the two-day practical exercise, mobile flood barriers, bracing, formwork methods, and sandbag techniques were constructed, partially loaded with water, evaluated, and subsequently dismantled. The exercise revealed clear differences in ease of use, assembly speed, transportability, stability, susceptibility to leakage, and ease of clearing. The Europallet system and Haawal, in particular, proved to be robust and practically deployable. For TubeBarrier and Buitink Flexibele Waterdam, points of attention emerged regarding handling, couplings, seepage, emptying, and cleaning. For bracing, it became apparent that standardization, clear work instructions, and good visual support are crucial. 

The main conclusion is that practicing under conditions as realistic as possible is indispensable. Only in practice does it become apparent whether systems align well, how participants understand instructions, and what safety and execution questions arise. The report therefore recommends further improving work instructions, testing more variants and higher dikes, paying attention to the connection between systems, and actively sharing the acquired knowledge via, among other channels, the Wiki Noodmaatregelen website. A follow-up question is how these lessons can be translated into widely applicable tools, training, and standard working methods for crisis organizations. 

The research and the exercise were made possible in part by co-financing from Interreg North-West Europe and are part of the BONSAI project (NWE0400542). The exercise was conducted with the involvement of, among others, the Crisis Team Waterkeringen, Defence, STOWA, Deltares, Dutch and Flemish water managers, and knowledge partners.

This report is the English translation of the Dutch report 'Evaluatie crisisoefening Marnewaard. Een oefening met mobiele keringen, bekrammingen en zandzakken (wel opkisten)' (STOWA 2026-25A)