The realization and function of the northern basin of the Delta project

Abstract

The Dutch defence line appeared to be inadequate to withstand stormsurges of exceptional strength. In 1916 a heavy storm caused severe floodings and damage in the northwestern part of Holland, a disaster which led to the closing of the dangerous Zuyderzee. And in 1953 a stormsurge of even greater strength, with a floodlevel which surpassed all the floods of the past, hit the south-western delta, formed by the rivers Scheldt, Meuse and Rhine. After this new disaster a plan was immediately adopted, a plan somewhat similar to the Zuyderzee project, providing in the closing of three dangerous inlets, the Haringvliet, the Brouwershavensche Gat and the Eastern Scheldt. The location of the dams was planned as close as possible ta the sea, thus achieving maximum shortening of the coast-line and the largest protected area behind the dams. Needless to say that both the entrance ta the ports of Antwerp (Western Scheldt) and Rotterdam (Nieuwe Waterweg) should remain open for the ever increasing shipping, which entailed however that the dykes along these waterways should be modified and/or improved in accordance with the new stormsurge criteria. The dykes mentioned above and of course the new dams are ta be made to withstand a 'superstorm' having a frequency of occurrence of once in 10,000 years, (1% in 100 years). Once built, the plan ensures the safety against an attack an the south-western part of the Netherlands (see figure on pages 6 and 7). Naturally the main purpose and the leading policy of the plan is safety but other advantages are: the shortening of the coast-line, meaning less maintenance and fewer risks, whereas the existing dikes along the enclosed basins form a secondary defense, strang enough to withstand floods; the improvement of the watermanagement by restricting the salt intrusion from the sea; with the sluices in the Zuyderzeedike and three weirs in the lower Rhine (Lek) the Haringvlietsluices form a system by which the freshwater from the Rhine and the Meuse can be distributed according to the needs.