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Notes on the Rhine Distributaries and Land Reclamation in the Netherlands

1944; Wiley; Volume: 104; Issue: 3/4 Linguagem: Inglês

10.2307/1790057

1475-4959

G. R. Crone,

Hydrology and Sediment Transport Processes

THE waters of the Rhine now reach the sea through three distributaries of varying importance, the Geldersche Ijssel, the Neder Rijn, and the Waal. Of the volume of the undivided Rhine above Lobith, approximately one-ninth flows down the Ijssel to the Ijsselmeer (formerly the Zuider Zee), two-ninths down the Neder Rijn, and two-thirds down the Waal. As evidence of the changing history of the hydrographic system, the two latter distributaries bear various names on certain stretches of their lower courses. Below Wijk bij Duurstede the Neder Rijn is known as the Lek, and this in turn as the Nieuwe Maas. The Waal below Gorinchem is known as the Merwede, and formerly some of its waters reached the Nieuwe Maas through the Oude Maas. Its main discharge is through the Nieuwe Merwede to the Hollandsch Diep, so that it is this estuary which now receives the bulk of the Rhine water. The present situation results from a combination of natural tendencies and control measures executed by the Dutch. Throughout there has been a marked tendency for the discharge through the south-westerly mouths to increase at the expense of the more northerly. In recent geological times there were two main Rhine exits, one to the east occupying approximately the present course of the Ijssel, and a western branch down a cut in the Veluwe glacial deposits, now known as the Geldersche Vallei. By the Roman period this section had been abandoned, and the main exit had developed farther westwards. Its course is marked by the Kromme Rijn, which leaves the Neder Rijn at Wijk and meanders to the neighbourhood of Utrecht, where it splits into the Vecht, continuing northwards, and the Oude Rijn, which enters the sea at Katwijk. To-day no Rhine water, except small quantities in times of floods on the main river, passes through these canalized rivers to the sea. The cause of this decline is largely related to developments in the Lek and Waal, which are explained by the physical history of the littoral as a whole. These two branches existed at an early period, but their importance was much less than it now is.