Reduction Barrier: A cost effective solution for safety, shipping and the environment? Case Study for the Western Scheldt
De Boom, L. (2013). Reduction Barrier: A cost effective solution for safety, shipping and the environment? Case Study for the Western Scheldt. Civil Engineering and Geosciences: Delft. xx, 90 + appendices pp.
Flood protection of the land around an estuary has been important for the Netherlands since the floodings of 1953. There are several types of possible solutions. For example; levee heightening, construction of a dam or a storm surge barrier. All these solutions have certain disadvantages, like costs or environmental impact.Another option is a reduction barrier. This was one of the options for the Eastern Scheldt barrier, but at that time a storm surge barrier turned out to be better. A reduction barrier can provide safety by introducing additional resistance in the estuary. This can reduce the amplitude of the tide in the estuary. The reduction barrier itself can be described as a dam with some openings in it. Water can still flow in and out of the estuary which is important for both the environment and shipping traffic.The design water level consists of a combination of regular tide and a storm surge. The tidal wave has a smaller timescale than a storm surge wave. This makes the tidal wave much easier to reduce than the storm surge wave, since slow motions are more difficult to dampen. The reduction barrier is more effective on reducing the tidal wave in estuaries where this wave is amplified due to the shape of the estuary. The tidal wave reduction means that the reduction of the water level maximum is limited, since the storm surge wave is not reduced.The analysis revealed that the Western Scheldt is a suitable location for a reduction barrier. The Western Scheldt requires a relatively small reduction in water level maximum, due to the relatively high quality of the levees. Belgium requires a reduction of the water level maximum of 0.5 metre in the current situation near Antwerp. The reduction barrier can be adapted for up to 1 metre sea level rise by installing moveable gates.The shipping traffic through the barrier is an important aspect for the feasibility of the barrier, since there are four ports located along the Western Scheldt. The barrier is located just east of the line Vlissingen - Breskens. The reduction barrier has two shipping channels. The main shipping channel is located near Vlissingen and the secondary shipping channel is located near Breskens. Vessels are able to pass through the barrier during normal conditions.It is assumed that the environment is not harmed since 80% of the original tidal prism can be maintained.The barrier is mainly composed of concrete caissons and rubble mound. The construction costs of the reduction barrier are an estimated 4 billion euros, this is comparable with the costs of the Eastern Scheldt barrier and also comparable with the costs of levee heightening.A reduction barrier in the Western Scheldt is technically feasible. For further research is recommended to make models of the water motion and sediment transport in 3-D. Fast and real-time shipping simulations can be used to optimize the shipping openings.
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