44 Water-stonesat Willemstad indicating the height of former disastrous floods. The difference in height between the flood in 1775 and that in 1953 is about 4 feet. Both were extremes in their times. 150 microns, and the coast is unsheltered. The main mouth of the river Rhine, called Haringvliet, which is also the mouth of the river Maas, will call for a weir of great dimensions, because the ice, as well as the largest freshets, will have to be disposed of. On the other hand the great advantages of a short coastline are very attractive. The sea inlets would be turned into a fresh-water lake and the poisonous effect of the salt seawater, which spoils so much of our crops in the provinces of Zeeland and South Holland, would no longer be felt. Road communications between the islands and the thickly popu lated central area of the Netherlands would be improved, and last but not least our safety would be much more ensured. Still, some courage is needed for attempting to close the South West ern estuaries, since a work of that size has never been attempted before. First it has to be ascertained whether the work is humanly possible. Next come the considerations of safety and economy. Can the large inlets with their fast tidal currents and the loosest of sand bottoms be closed with our present technical equipment? The answer has not yet been given by the Delta Commission. The experience obtained in closing the 67 tidal gaps in 1953 seems to have given us the necessary courage. The work of the "second stage" is certainly more difficult than that of the "first stage" (the Zuider Zee project). The tidal range is about twice as great, which means that the tidal forces are about four times as strong. The depths are much greater, up to thirty metres, and there is no boulder clay available in the neighbourhood, as was the case with the Zuider Zee. The particle size of the sand is very small, about There is yet another factor which has not yet been mentioned, namely the subsidence of the Netherlands. Modern methods, based on atomic science, have proved that the age of the peat layer which must have been formed above the mean high-water level and now lies eighteen metres below that level, is about 7200 years. This means that the land is subsiding (or the sea level rising, or both) at a rate of a quarter of a metre per century. There is no doubt that the tides have been rising higher and higher in the course of the centuries, as is evident from the so-called water stones which the inhabitants have placed in the walls of their houses to mark exceptionally high floods. The threat of these ever-rising tides is serious of course. Ultimately the dikes may have to become very high indeed. Sooner or later a short coastline seems essential. The future threat of the sea must be faced, with a short but very strong coastline. consequences, must be studied for many years and the changes which the project would bring are to be predicted in such a way as to leave no doubt whatsoever. Surely, nothing should be left to chance when dealing with a formidable adversary such as the sea. It would certainly be desirable to have the shortest possible line of defense. Instead of having to heighten the many miles of dikes, which proved too weak during the last flood, we would prefer a dike between the dunes of the islands. Such a dike would only be from 12 to 15 miles long. This short dike could be made into a very strong line of defense, fit to receive the blows of the enemy for a thousand years to come. But the following questions remain to be answered. Is our present technique sufficiently advanced to construct those 12 to 15 miles of dike? Is the construction of such a dike justified? These questions will soon be answered, because a decision will have be taken one way or the other in the near future: either the existing dikes must be heightened or a new defense line will have to be erected. Medal struck to commemorate the floods of Februari 1953. On the left: the dove from Noah's Ark with the motto: Never Despair 70

Krantenbank Zeeland

Watersnood documentatie 1953 - brochures | 1954 | | pagina 72