Achieving Natura 2000 by Building with Nature in the Eastern Scheldt

Abstract

Historically, hard engineering projects, such as the construction of dikes and surge barriers, have been the ultimate solution to protect coastal zones from flood disasters. However, there is an increasing awareness about the impacts that these traditional solutions have in valuable natural habitats and species. After the tragic consequences caused by the storm event occurred in 1953 in The Netherlands, the Deltaworks plan and the compartmentalization of the Eastern Scheldt by a storm surge barrier and secondary dams began. The finalization of this compartmentalization was considered an enormous success. However, changes produced in the hydrodynamics and geomorphology of the Eastern Scheldt, such the reduction in tidal prism, tidal range and maximum flow velocities, have influenced the equilibrium of the ecosystem. The Eastern Scheldt is in need of a high volume of sand so that the main channels can adapt and reach a new equilibrium. Since the storm surge barrier and secondary dams are blocking sediments from the North Sea and rivers, the channels are filling at the expense of the tidal flats and salt marshes. These tidal flats and salt marshes are suffering a net erosion, reducing their elevation and surface, and affecting other habitats and species that depend on them. This degradation process is called sand demand, and its degradation will accelerate as sea level rises.

Several habitats and species located Eastern Scheldt are protected by Natura 2000 goals, the largest network of protected areas in the world. In order to preserve and protect these valuable areas and species, strategies based in Building with Nature (BwN) approach were executed. Solutions based in BwN approach emerged to simultaneously guarantee safety standards and protect nature at the same time. The aim of this study is to investigate whether these strategies mitigate the effects of sand demand while contributing to Natura 2000 goals in relation to habitat conservation and species protection now and in the future (2050-2100). To achieve this, monitoring data with regard to two nourishment projects were collected and evaluated. These projects are the Galgeplaat nourishment and the Oesterdam nourishment.

Results showed that both nourishments are mitigating the degradation process of sand demand by increasing the bed elevation at both locations, by improving the surroundings through sedimentation processes, and by protecting valuable areas from erosion. Moreover, these strategies proved to restore to some extent the quality of the habitats and their closest surroundings, influencing the availability of benthic animals and the time birds spend in these areas foraging for food. However, this research can not conclude whether these strategies are benefiting the protection of the species affected by sand demand in the Eastern Scheldt due to the lack of information in this respect.

In the Eastern Scheldt, sand nourishments proved to be suitable strategies to maintain valuable areas in the short term (horizon 2050). However, they do not solve the problem of sand demand. Moreover, other causes of degradations, such as sea level rise, will have an impact on the effectiveness of these measures over the years. According to experts interviewed during this research, if habitats and species are to be preserved and protected in the long term (horizon 2100) in the Eastern Scheldt, the best solution is recovering the former hydrodynamics and geomorphology of the basin.