Witteveen+Bos to design preferred alternative for Noordelijke Randmeerdijk

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At the request of Vallei & Veluwe Water Board, engineering and consultancy firm Witteveen+Bos has started an exploratory study this week to find a broadly supported preferred alternative for the dike called Noordelijke Randmeerdijk. This primary flood defence between Doornspijk and Reevedam (a new dam yet to be constructed) was rejected after being assessed, and is one of the dikes that require improvement over the next couple of years as part of the flood defence programme. A unique aspect of Witteveen+Bos’ approach is that the dike is not being regarded on its own, but that they are taking the entire system of bordering lakes referred to as Veluwerandmeren into consideration. In this way it may be possible to reduce the impact of the dike reinforcement on the surrounding area.

The recommendation for a broadly supported preferred alternative is set to be offered in October 2018, after which the Vallei & Veluwe and Drents-Overijsselse Delta water authorities can evaluate and adopt the alternative. After February 2019 a start will be made on the plan specification for the preferred alternative. The Noordelijke Randmeerdijk is a very old dike that dates back to the time of the Zuiderzee, and as such has great cultural and historical value. Even though the dike may not be located along a river or sea, it still serves a purpose as a primary flood defence. Under the Dutch Water Act, dikes in the Netherlands are assessed once every twelve years. At present the Noordelijke Randmeerdijk does not meet the flood protection requirements.

Vallei & Veluwe Water Board has awarded this contract (which is part of the framework contract for general engineering services) to Witteveen+Bos because it offered the best price/quality ratio. What is new about the approach of Witteveen+Bos is that when deciding on a preferred variant we are not just considering the dike on its own but we are looking at the system of Veluwerandmeren as a whole as well. This means that account is also given to the water levels that the dike must protect against in case of heavy south-westerly storm, when the water is pushed to a high level, and to the connection between this dike and the Reevedam that is being constructed in the Drontermeer as part of the ‘Room for the River’ works in the IJssel delta. In the exploration study several options will be considered to see which variant will best solve the water safety problem.

For Rivierenland Water Authority, Witteveen+Bos has been working with Bureau Stroom on a similar assignment since May 2017: an integrated preferred alternative for the dike on the north side of the river Waal between Wolferen and Sprok, near Nijmegen. In this project the emphasis is on investigating safety measures to be realised on the dike, and possible dike relocation at Oosterhout.