However , during the North Sea flood of 1953 it turned out that they were not adequate .
Between 1906 and 1935 around 120 km of muralt walls were put into place , about a third of all Zeelandish coastal dykes at the time .
During the North Sea flood of 1953 it turned out that they were not adequate .
Between 1906 and 1935 around 120 km of muralt walls were put into place , about a third of all Zeelandish coastal dykes at the time .