In this paper, waves against the new planned sea dike of Nabeta Polder were studied in the wind wave channel of our laboratory. In the repairing plan of the dike, its slopes are intersected by a 1 : 15 long berm, as shown in Figs. 1 and 2. The results indicate rapid decreasing of run-up height of wave, when the mean water level becomes low under the berm. If the wave conditions at the time of the Ise-bay typhoon were such that wave height, period, length and mean water depth were 2.6m, 7 sec, and 6.00m, (T. P. +4.70m) respectively, it would be predicted for such conditions from the model experiment that the mean value of run-up would be T. P. +7.50m, i. e., 2.8m above M. W. L. and the maximum value would be over T. P. +8.00m or 3.30m above M. W. L., that is, overtopping due to some waves might occur on the top of the dike (T. P. +8.00m) on type I, and that the maximum value of run-up would be T. P. +6.70m or 2.00m abve M. W. L., that is, overtopping due to any wave in the above conditions would not occur on type II.
On pressure under wave action, the maximum pressure would feel at a certain point on the slope below M. W. L., and the value could be inferred about 12 tons per square meter for both types, I and II.
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