Een aanpasbaar afvoercomplex in de Nieuwe Waterweg

Abstract

The Dutch Delta Approach has been set up with the aim of ensuring water safety in the Netherlands and improve it where necessary. The open connection of the Nieuwe Waterweg has become the subject of debate. So far, the Dutch Delta Approach do not take closure of the Nieuwe Waterweg into account. A group of six engineers do anticipate on the closure of the Nieuwe Waterweg and have prepared a scheme for that purpose, called: Plan Sluizen (or Plan Spaargaren). The closure scheme includes provision of navigation locks and a discharge complex. Focus of this report will be on the development of and checking the technical feasibility of the design for a flexible discharge facility in the closure.
At present a part of the river Rhine water is discharged through the Nieuwe Waterweg to the North Sea. Since the water cannot be rerouted, a discharge facility must be included in the closure complex.
First, the Nieuwe Waterweg, as a part of the Rhine-Meuse delta has been analysed and the effects of climate change in this area have been mapped out. Subsequently the report zooms in into the closure, lock and discharge complex that has to be constructed in the future. The two most important requirements are: the closure must be able to withstand the normative water level at sea, including expected sea level rise; the discharge complex must be able to discharge a 20% of the normative Rhine discharge at every random moment.
Looking into the location of the closure and discharge complex went hand in hand with deciding whether to construct one large complex accommodating all components at one location, or to divide the components over two locations. A location for all the components together would be positioned in the Nieuwe Waterweg. When dividing the components of the closure complex, the two locations to be considered are somewhere in respectively the Oude Maas and the Nieuwe Maas, close to the Beneluxtunnel.
A discharge method using Venturi was chosen. Venturi tubes can be used in natural flow conditions, driven by a water head, and improve the efficiency of pumps constructed into the Venturi tube. In future there will be a time when the natural water head has become too small, due to sea level rise, to discharge the required amount of water. The discharge sluice will be changed into a pumping station.
It turns out that 72 pumps are needed with a capacity of 50 m3/s for normative river discharge conditions in 2100. For the normative discharge in 2018 no pumps are needed. For average river discharge, coinciding with storm surges, discharge using the natural water head is possible up to 2100.
The dimensions of the discharge structure were determined. The structure will be adaptable by using different modules in the centre piece of the Venturi tubes.
After determination of the overall dimensions the stability of the structure has been checked. Concrete calculations have been made to check the concrete dimensions of the main parts of the discharge structure.