IMPROVING TRANSITIONS AT GRASS COVERED DIKE SLOPES USING THE WAVE OVERTOPPING SIMULATOR

Most tests with the Wave Overtopping Simulator on grass covered dike slopes have been performed on operational dikes. They showed that transitions and obstacles reduce the strength of the grass cover. The tests in 2023 were performed on sections where innovative solutions were constructed in the dike before testing. The aim was to make transitions stronger than the grass cover itself. The governing transitions were a geometrical transition (from slope to berm) and a transition from smooth asphalt to grass on a horizontal plane. The tests showed that all innovations were successful under test conditions. Moreover, where the front velocity over a slope will increase due to gravity, a horizontal berm reduces the front velocity significantly, giving smaller loads to transitions on the berm. The present tests showed that the underlayer of boulder clay was in this case much more erosion resistant than normal clay. Finally, a cliff erosion test has been performed in order to determine whether an asphalt road on the berm may reduce or terminate cliff erosion. The road terminated cliff erosion.