Wijmeers is part of the extensive Sigmaproject Cluster Kalkense Meersen and is divided into two areas. Area 1 – the flood zone – was laid out so that it would only flood occasionally. For instance, there is an area for wetland, in the form of marshes and swamp forests. Rare and valuable sparse habitats have developed on the higher sandy ridges. Area 2 was depoldered, giving the water free rein again. As a result, a unique tidal habitat has arisen here with mudflats and salt marshes.
Herbosch-Kiere constructed an overflow dyke and compartment dyke, with the latter separating the northern and southern areas from Wijmeers 1. The works mainly consisted of demolition works, earthworks, protecting the foundations with a geotextile, applying a bound open covering with open stone asphalt (thickness E = 12 cm), building a dyke core for overflow earth dykes based on the Sigma profile and installing grass cover for overflow earth dykes as erosion protection.
How does a CFA work? In a demarcated area along the river, a high sturdy ring dyke is constructed inland. The existing river dyke is then lowered and reinforced. This is an overflow dyke and when the river level is high, the water can flow over the top of the dyke. The ring dyke protects residential areas behind it from flooding.