Southwest Delta

The Southwest Delta encompasses Zeeland, the Zuid-Holland islands, and the western part of Noord-Brabant. Since the catastrophic flood in 1953, the Delta Works have offered protection and good infrastructure links. Yet they also present a number of challenges in terms of their impact on Nature, water quality, and the economy. 

With respect to future flood risk management and freshwater supply solutions, the focus of the authorities in the Southwest Delta is on safety, the economy, and ecology. The area has drawn up a preferential strategy to effect. In the years ahead, emphasis will be placed on its elaboration. The region is exploring opportunities for an integrated approach to the measures. The Delta Decisions constitute the framework for the approach.



Realising integral ambitions

Climate change and socio-economic developments present the region with challenges in terms of flood risk management and the freshwater supply. In other areas too, work on the Southwest Delta is far from finished: most of the delta’s waters are ecologically unhealthy and the use of the waters in the economy is under pressure. The region is arguing for restoring tidal movements in the Grevelingen, and a saline Volkerak-Zoommeer lake.

Fortunately, there are good opportunities for safeguarding flood protection and the freshwater supply in the Southwest Delta. The majority of these do not involve any major modifications to the current design of the water systems. The approach adopted in the region is characterised by innovative, integrated solutions. Examples include: doing more with dykes (multi-functional dykes), and generating sustainable energy using tidal power. This offers significant opportunities for the region’s economy which is strongly tied to water. A decision on the development of Grevelingen and Volkerak-Zoommeer, and the National Framework Vision for these waters is expected by the end of 2016.

Preferential strategy for flood risk management

Pursuant to the new standards for flood defences, various dyke sections in the Southwest Delta need improvement. At each location, innovative dyke concepts are being explored which could also offer opportunities for Nature, recreation, and habitation. The preferential strategy for the Oosterschelde involves a future-proof approach to flood risk management which also contributes to reducing demand for sand. The storm surge barrier is currently disrupting the natural sand deposits on flats and foreshores because of the reduced tidal flows, whereas alluvion continues to wash sand away.

In the Westerschelde, dredged sludge can be deposited to allow the dyke foreshores to rise along with the sea level. This also offers opportunities for restoring the natural environment. In addition, long-term measures will be needed to mitigate increasing tidal ranges in the basin. The Netherlands and Flanders are working together to this end. The sand replenishment programme is being continued along the coast.

No water storage in Grevelingenmeer lake

The central government and the region have investigated whether water storage in the Grevelingen lake is an option for keeping flood protection up to par in the long run. The conclusion is that it is not necessary to keep this option open. Dyke improvement turns out to be a more cost-efficient solution than additional water storage in the Grevelingen lake.

Sand and rising sea level

A rising sea level may necessitate increasing sand replenishment in order to maintain flood protection. This requires insight into sand movements. This knowledge is gained in various ways, including by drawing up integrated visions for the Westerschelde, Oosterschelde, Grevelingen and Haringvliet estuaries. A study into the optimum combination of flood defence, dykes, and sand replenishment in the Oosterschelde estuary is expected to be completed by the end of 2016.

In addition, pilots are also providing us with knowledge regarding sand replenishment; for example, the pilots involving underwater channel margin replenishment (Southwest Walcheren) and the Galgeplaat (Oosterschelde). These underwater replenishments turn out to have a positive impact.

At the Brouwersdam beach, a pilot is underway involving sand replenishment. New knowledge will be generated by the Roggenplaat (Oosterschelde) sand replenishment that is expected to be carried out in 2017-2018, and a sediment pilot carried out in the Scheldt estuary, together with Flanders. This knowledge can be used for new innovations. Flood protection can thus be realised in an increasingly more effective and more efficient manner. And if the costs are borne collectively by the stakeholders, sand replenishment can also be used for the benefit of, e.g., Nature and the economy.

Preferential strategy regarding freshwater supply

Determining water availability is an important element of the preferential strategy regarding the freshwater supply. If the climate changes, measures will be needed regarding the main water system, regional water systems, and among consumers of freshwater (such as the agricultural sector, industry, and drinking water companies).

The islands of Zuid-Holland, West-Brabant, Tholen, Sint Philipsland and the Reigersbergsepolder receive freshwater via the major freshwaters, such as Biesbosch, Hollandsch Diep, Haringvliet and Volkerak-Zoommeer lake. For these areas, it is important that the freshwater supply and stocks are maintained, and that salinisation is tackled, for example using innovative freshwater-saltwater separation systems at sluices. A pilot to this effect is underway at the Krammer locks. The Roode Vaart project that will be realised by no later than 2018 combines a sustainable freshwater supply with a quality boost in Zevenbergen city centre. A decision to salinise the Volkerak-Zoommeer will necessitate additional freshwater supply measures. Zeeuws-Vlaanderen, Walcheren, Noord-Beveland, Zuid-Beveland and Schouwen-Duiveland do not receive any freshwater from the main water system. A more economic use of freshwater demands innovations here, for example water conservation in the soil, a more efficient use of rainwater and freshwater lenses, and the reuse of freshwater. The Freshwater testing ground in Zeeland is aimed at increasing freshwater self-sufficiency.

Climate adaptation in Zeeland

The province of Zeeland is working on the Zeeland Climate Adaptation programme within a comprehensive coalition. One of the goals of the project is to develop a climate test for flood risk management, pluvial flooding, drought, and heat stress, using the existing tools. The aim is to come up with a simple test that is widely supported by the authorities involved. The test will also be suitable for mapping out climate adaptation taskings in spatial plans and visions at an early stage, and for taking climate adaptation into account in new construction and restructuring projects. During the period 2016 to 2020, all the municipalities in the province of Zeeland will be subjected to a climate test.

Vital and vulnerable functions in Zeeland

A component of the approach adopted in Zeeland is raising flood awareness among vital and vulnerable functions. To this end, meetings have been held with representatives of such companies. A next step involves determining which spatial planning measures could reduce the impact of a flood (layer 2). Making more efficient use of secondary dykes appears promising in this regard. In the years ahead, the province of Zeeland will be updating the regional flood defence systems and the associated standards for each dyke ring.

Zeeuws-Vlaanderen resilient water system

This impact project is aimed at developing a sustainable and climate-resilient water system that is optimally subservient to the infrastructure in the region and that enhances the vitality of the area. To this end, the participating parties intend to share knowledge and experience. To facilitate this exchange, they have developed a wiki that connects information on the Internet and thus generates new insights. The wiki went online in mid-2016.

Delta Programme 2017

To view the progress made in this area, click here: Southwest Delta in Delta Programme 2017.