See Report for more information and pictures. Tests without cuts in plastic sheet - During all test volumes the plastic sheets were kept in place due to the anchors and pins. - Some of the pins (only at the bottom/toe side of some layers) came loose due to vibration of the sheets (we presume the cause of vibration is flow of water between two sheets or turbulence of water). - The grass between the two damages was flattened by the current, a typical image for overflow tests. The grass remained in place, grass clumps with roots were not pulled loose by the current. - The trench of the lower damage was partly washed away by the water. This was to be expected as the grass layer could not be kept intact when the plastic sheet was dug in. The erosion of soil in the trench did not result in changing the stability of the top sheet. The function of the buried sheet therefore remained intact. Test with cuts in plastic sheet - The lower repair failed due to high impact of water exactly on the tear. Test was done for 30 min with 350 l/swater. The tear was made through both overlapping sheet layers. - The higher repair sustained all the test also with the tear. Both tears were around 1m in the middle of the test area. The tear was only made in the upper sheet of the overlapping sheets. The soil below the upper damage was not damaged further due to the overflow tests, as could be seen after removing the repair solution. - The grass between the two damages was flattened by the current, a typical image for overflow tests. The grass remained in place, grass clumps with roots were not pulled loose by the current. So, there was no change visible between the tests with and without the cuts in the plastic sheet.

After presenting the results and improvement points, a few points of discussion remain. First, an unexpected problem was the vibrating of the plasticsheets that resulted in the extraction of the pins. It's uncertain what the long-term effect of this phenomena is, but the process may likely give positive feedback and result in a large amount of deflection. If the sheet is not tight on the dike anymore, water will flow under it resulting in erosion. Further research into mitigating this effect will be necessary. This could simply include installing more pins or trying out different straight pins to reduce the free margin around the installationpoint. A second point of concern is the proposed use of a 3 meter wide plasticsheet. Although this will reduce installation costs and time significantly, applying this sheet size under storm conditions is likely problematic. This can be best tested out by waterboard personnel in a storm situation to see the actual effects. Third, the effects of installation errors at the head of a plastic sheetsection are not yet known enough. Some initial damage was seen at the head of the bottom section, but did not propagate. Although it is unlikely that water will flow under the sheet immediately because of its curved vertical installation, it remains a critical point. What happens during installationif the soil layer is very weak after digging? Installing another sheet over the head might be a solution, but this will need to be tested further to give a reliable advice. Fourth, a large part of the anchors remains in the dike, irrespective of the proposed solution in section 6c. Although we believe this problem to be inferior with respect to the reliability and installation time during a calamity at which human lives are at stake, it remains a drawback of the solution. A final consideration is the difference in material between our used Polytex®, a Tyvek®substitute. Although Polytex®has much lower costs, the UV resistance and quality of Tyvek®might be beneficial when storing and installing the solution for prolonged periods. More research on the material qualities can contribute to the actual reliability.

Concluding, the presented Tyvek design is an interesting solution that may well be a good contribution to the future flood protection arsenal of waterboards and other governments. The benefits related to low production costs, easy installation, and reliable storage and scaling make this innovative solution a possible advancement from classical flood protection measures, like sandbags. Further research is advised to analyse and mitigate the presented weaker spots and drawbacks.