New canalization of the Nederrijn and Lek: Design of a weir equipped with fibre reinforced polymer gates which is designed using a structured design methodology based on Systems Engineering

The Nederrijn and Lek are presently dammed by three weirs, build in 1960 till 1970, which are located near the village of Driel, Amerongen, and Hagestein after which they are named. Weir Driel regulates the distribution of water at the IJsselkop for dammed conditions (discharges lower than 2350 m3/s at Lobith). A minimum discharge of 285 m3/s has to be diverted into the IJssel by weir Driel for the fresh water supply of the northern part of the Netherlands (the section of the Netherlands which is located above the fictive line Amsterdam-Nijmegen) and for generating sufficient draught for commercial shipping. The weirs Amerongen and Hagestein regulate the upstream water levels for commercial shipping; minimum levels of +6.0 m NAP respectively +3.0 m NAP are maintained by these weirs. The water levels of the IJssel decrease to 1 metre or lower when weir Driel fails in dry summers which results in an obstructed waterway for commercial shipping and an insufficient fresh water supply to the northern part of the Netherlands. ARCADIS made an assessment for the reliability and availability of the weirs in the framework of the project RINK-SSC (Risico Inventarisatie Natte Kunstwerken Sluis Stuw Complexen). The assessment indicated that the weirs do not meet the reliability and availability norms for the present situation and that structural parts of the weirs have exceeded their technical life span. Therefore, the weirs need to be renovated or replaced within ten years from now. Furthermore, a secondary problem statement is present which concerns the application of Systems Engineering for large scale design projects. Presently, a major ‘transition’ of the substantiation of design choices made in the political domain and design choices which are made by engineering firms, which are based on the Systems Engineering methodology, is present. Design choices made before the ‘transition’ are not well traceable and results in ambiguities during the design process. This graduation research is focused on the replacement of the existing weirs. The weirs could be replaced at the same location, but a broader scope is chosen within the graduation research. The aim of the graduation research is providing an alternative design for the present canalization taking into account the changed environment and use of the waterway. This goal is reached by designing an alternative for canalization using a design methodology based on Systems Engineering (SE). Therefore, a methodology for the application of SE for large scale hydraulic projects is developed and tested for the design of the recanalization. The developed methodology is also applied at large scale design choices for interventions in the present ‘wet infrastructure’ which are, in fact, normally made in the political domain. A toolset is composed from the toolbox of SE methods for the development of the alternative design. The design is elaborated in five sequential design levels. The first design level starts at delta level, the second continues at Nederrijn-Lek level, the third proceeds at the weir location level, the fourth considers the weir build-up, and the structural design of the gates is made for design level five. The gates are designed using fibre reinforced polymers (FRP) which is a self-imposed secondary goal for the graduation research. A small requirement set is developed for each design level in order to obtain a well-structured and clear design method which is applicable for large scale hydraulic design projects. The result of the research is an alternative design of the present canalization. The Nederrijn and Lek are chosen for recanalization due to the lowest impact for the implementation of the recanalization with respect to the other rivers. It is possible to canalize the Nederrijn and Lek using two weirs when the reach located in between the Amsterdam Rijnkanaal and the Lekkanaal is downgraded to a recreational river. The upstream weir is located near the village of Driel and has to maintain the present dam regime to reduce the implementation works and time. The downstream weir is located at a floodplain near the village of Culemborg and has to regulate a minimum upstream level of +5.0 m NAP. The weir is subdivided in three gaps of 41 metres wide each. Three FRP submerged segment gates have to control the discharge and the upstream water levels of which an impression is given in Figure 1. The gates are composed of sandwich panels and four shear webs which are located in between the panels. The application of separate design levels with a limited set of requirements each turned out to be applicable for large scale hydraulic design projects for the first four design levels. So, the SE methodology could also be applied for decision making on a large scale which are normally made in the political domain. A well-structured and clear design methodology is obtained, which performed well for these levels. The method had to be adjusted for the structural design level (level five) because the set of requirements exponentially expands which results in a non-clear design method. Furthermore, using a functional analysis for the structural design results in a non-meaningful definition of the functions of the elements.Hydraulic StructuresHydraulic EngineeringCivil Engineering and Geoscience