Converting an estuary to Lake Grevelingen: Environmental review of a coastal engineering project

Abstract

/ To guarantee protection from storm floods in the southwestern part of the Netherlands, the length of exposed coastline is being greatly reduced by the construction of dams and a storm surge barrier. As part of the Delta Project, the mouth of the Grevelingen estuary was closed in 1971. Due to the closure, tidal movement was eliminated, which resulted in changes in environmental factors such as transparency and chloride and phosphate concentration. The number of plant and animal groups decreased. Large areas of sand flats and salt marshes, which were formerly exposed to the tides, were left "high and dry." This resulted in enormous changes for the communities living in these areas. The development of a new ecological system and the changed potential afforded by the water and land areas for human use, emphasized the need for physical planning. The potential uses (functions) of the new system are discussed in this article. Special attention is given to the demand for recreational facilities and nature conservation and to the balanced realization of these main functions. The methods applied in choosing between alternatives in physical planning are explained. Water quality and ecosystem management are discussed, One of the main management objectives is the prevention of a further decrease in the chloride concentration and the number of species. A sluice was, therefore, put into operation in 1978, by means of which water was exchanged between the North Sea and Lake Grevelingen. The responses observed are discussed here. In the near future, a crucial decision will have to be made: Will Lake Grevelingen remain a salt-water lake or will it become a fresh-water lake?

Presence and development of populations of the introduced brown alga Sargassum muticum in the southwest Netherlands

“…Gradual eutrophication of the lake necessitated opening (via a sluice) a connection with the North Sea ( Fig. 2; Saeijs & Stortelder, 1982). The sluice remained open briefly during the latter part of 1978 and for the whole of 1979.…”

Presence and development of populations of the introduced brown alga Sargassum muticum in the southwest Netherlands

“…2;Saeijs & Stortelder, 1982). The estuary was closed off from all riverine and North Sea influences in 1964 and 1971 respectively.…”

Damming deltas: A practice of the past? Towards nature-based flood defenses

“…There is extensive experience in adaptive management of exposed sandy coastlines through nourishment (Nordstrom, 2005). However, in complex estuarine systems, coastline shortening by damming estuaries is often chosen as a means to achieve desired safety levels (Saeijs and Stortelder, 1982;Pilarczyk, 2012). The Dutch Deltaworks illustrate that this approach disrupts natural sediment fluxes and may severely harm ecosystem health, which negatively affects ecosystem services such as freshwater availability due to algal growth and mussel and oyster farming due to reduced carrying capacity (Smaal and Nienhuis, 1992).…”