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, provided good infrastructure links, and ensured the availability of fresh water. Yet now and in the future, they also present a number of challenges in terms of their impact on nature, water quality, and the economy. Furthermore, the area is under pressure on account of the rising sea level and future higher river discharges. In addition, in the long run, a sufficient supply of fresh water cannot be taken for granted.

The authorities in the Southwest Delta have acknowledged this and are focusing on the interconnectivity in flood protection, the economy, and ecology, especially with respect to future solutions for flood protection and the availability of fresh water. Ensuring a climate-proof, safe, ecologically resilient, and economically vital Southwest Delta: that is the ambition. In the years ahead, the emphasis will be on the elaboration of the collective Preferential Strategy for the Southwest Delta, whilst the region will be 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 water is ecologically unhealthy and the use of the water in the economy is under pressure. For the Grevelingen and Volkerak-Zoommeer lakes, a National Framework Vision has been drafted; its development perspective is the restoration of limited tidal movements in the Grevelingen and Volkerak-Zoommeer lakes. The Volkerak-Zoommeer lake can become saline again, once the alternative freshwater supply has been realised. The final adoption of the National Framework Vision is contingent upon the availability of sufficient funding.

Funding for the restoration of tidal movements in the Grevelingen has meanwhile been secured through an additional grant from the Nature and Water Quality Budget of the Rutte-III Cabinet, in addition to the grants already allocated by the Ministry of Infrastructure and Water Management, the provinces of Zuid-Holland and Zeeland, and the municipalities of Goeree-Overflakkee and Schouwen-Duiveland. In 2018, the focus will be on the completion of the exploration phase and the preparation of the plan elaboration. In this context, the authorities will explore, in concert with the regional parties, whether the Brouwersdam sluice that is required to restore tidal movement can be combined with a tidal plant.

The central and regional governments will continue their consultations regarding the funding of the measures pertaining to the restoration of limited tidal movement in the Volkerak-Zoommeer lake, its resalinisation, and the required alternative freshwater supply. This is in line with the agreements set down in the Administrative Agreement regarding the Development of Grevelingen and Volkerak-Zoommeer and in the Administrative Agreement on Freshwater Supply (2015).

Good options exist for safeguarding flood protection and freshwater supply in the Southwest Delta. In most cases, large-scale modifications in the current water system structure will not be needed. The regional approach is characterised by innovative, integrated solutions. Cases in point are: alternative freshwater supply via the Roode Vaart, multi-functional dykes, and the generation of sustainable energy. This offers significant opportunities for the region’s economy which is strongly tied to water.

Preferential Strategy for flood risk management

The new standards for flood defences dictate dyke improvements at various locations in the Southwest Delta. Each dyke improvement involves the exploration of options for innovative dykes that open up opportunities for nature, leisure activities, and habitation. For the Oosterschelde, the Preferential Strategy sets out a future-proof approach to flood risk management that also contributes to the reduction of the effects of sand deficits. The storm surge barrier is 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 dyke improvements set out in the Flood Protection Programme are proceeding as scheduled. The projects on the island of Schouwen-Duiveland have been completed. Preparations for the Hansweert dyke improvement project are underway.

Sand and rising sea level

If the sea level continues to rise, increasing sand replenishment may be needed in order to maintain flood protection. The sand deposits along the coast are proceeding as planned in the period between the autumn of 2018 and the end of 2019. With respect to the Oosterschelde, a MIRT study into Integrated Flood Protection was launched in 2017 to map out potential bottlenecks in the areas of flood risk management, spatial planning, and nature in the period 2050-2100. The initial focus was on the Oosterschelde storm surge barrier. In 2018-2019, a follow-up study will be conducted into the impact of the rising sea level and sand deficits in the Oosterschelde. In this study, the sand deficit issue is addressed in interconnection with issues involving ecology, the landscape, and the economy.

At the Brouwersdam beach, a sand replenishment pilot was launched in 2016 in order to safeguard the economic use of the beach (beach sports such as kite surfing and sand yachting). New knowledge will be generated by the Roggenplaat (Oosterschelde) sand replenishment scheduled for 2019-2020, and a potential sediment pilot to be carried out in the Scheldt estuary. 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 for freshwater supply

Agreements regarding water availability constitute an important element of the preferential strategy for the freshwater supply. To this end, meetings are held between the governments and freshwater consumers. 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) in order to secure a sufficient supply.

The islands of Zuid-Holland, West-Brabant, Tholen, Sint Philipsland, and the Reigersbergsepolder receive freshwater via the major fresh water bodies, such as Biesbosch, Hollandsch Diep, Haringvliet, and Volkerak-Zoommeer lake. For these areas, it is important that the Biesbosch, Hollandsch Diep, and Haringvliet freshwater supply and stocks are maintained, and that salinisation is tackled, for example using innovative freshwater-saltwater separation systems involving water and air bubble screens at sluices. A pilot to this effect has been carried out at the Krammer locks yacht lock. Based on this pilot, it was decided to introduce such an innovative freshwater-saltwater separation system at the commercial shipping locks. In addition to more adequate freshwater-saltwater separation at the Krammer locks, these new systems will yield a social benefit of several millions of euros per annum (due to shorter passage times), cut back annual maintenance costs, and result in energy cost savings. The major repairs encompassing the introduction of the new freshwater-saltwater separation system is scheduled to be completed by 2025.

The Roode Vaart project combines a sustainable freshwater supply with a quality boost in Zevenbergen city centre. The project will be completed in 2019. If the authorities decide to re-salinise the Volkerak-Zoommeer and restore limited tidal movement, additional freshwater supply measures will first be implemented in the immediate vicinity. To this end, an alternative, climate-resilient freshwater supply has been designed. This set of measures has been incorporated into the Delta Decision on Freshwater Supply; it will be co-funded by the central and regional governments.

The islands of Zeeuws-Vlaanderen, Walcheren, Noord-Beveland, Zuid-Beveland, and Schouwen-Duiveland do not receive any fresh water from the main water system. The islands largely depend on precipitation. A more economic use of fresh water demands innovations here, such as water conservation in the soil, a more efficient use of rainwater and freshwater lenses, and the reuse of fresh water. The Freshwater Supply testing ground in Zeeland is aimed at increasing the self-sufficiency of freshwater users.

Spatial adaptation in Zeeland and Zuid-Holland

In Zeeland, the provincial authorities, the Scheldestromen district water board, and the municipalities have joined forces in a comprehensive coalition to work on the Zeeland Climate Adaptation programme.

In September 2017, the administrators decided on the substantiation of the Delta Plan on Spatial Adaptation in Zeeland. Three studies have been scheduled for 2018 and 2019:

  • Identification of regional flood defence systems and setting down flood protection standards;
  • Analysis of the potential impact of flooding;
  • Conducting climate stress tests.

The parties have jointly developed a manual for a climate stress test to map out the impact of flood risks, waterlogging, drought, and heat stress. All the municipalities in Zeeland will be conducting climate tests in the period 2018-2019. The municipalities of Noord-Beveland, Borsele, Reimerswaal, and Goes have already conducted such a test.

The parties are collectively conducting research into heat stress. A calculation model has been developed to identify locations prone to heat stress using the heat map in the Climate Impact Atlas. Five monitoring stations have been set up in several cities in Zeeland to collect and analyse data in the period 2017-2021. This data is used by the Cool Towns project launched by the municipality of Middelburg, which is developing solutions to combat the impact of heat.

The municipality of Borsele has rolled out the Nieuwdorp Climate Street project, in which the municipality is exploring, in concert with residents and entrepreneurs, climate-neutral and climate-adaptive designs for a street in the Nieuwdorp neighbourhood. This project generates knowledge on methods to develop a publicly supported strategy in collaboration with residents and entrepreneurs.

The comprehensive and complex spatial adaptation tasking facing Zeeland necessitates collaboration, because individual parties lack sufficient expertise, resources, knowledge, and networks. The authorities in Zeeland seek to reinforce administrative collaboration, to which end they intend to develop a governance structure. An administrative working group has developed a proposal to be discussed in the autumn of 2018.

In the spring of 2017, the Spatial Planning and Housing administrative platform hosted a meeting on spatial adaptation, attended by delegates from the province of Zuid-Holland, the municipality of Goeree-Overflakkee, and the Hollandse Delta district water board. In the latter half of 2017, a follow-up meeting will be held, once the parties are embarking on the implementation of the agreements set down in the Delta Plan on Spatial Adaptation. Furthermore, the stakeholders in this area have joined forces in a regional programme to improve the quality of the living environment; boost recreation and tourism; encourage innovation in fisheries, agriculture, recreation, and healthcare; realise sustainable energy; serve as testing ground for innovations; and improve access and traffic safety.

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 functions 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 2019

Read about the progress made in the Southwest Delta region in Delta Programme 2019.


To contact the programme team working on the Delta Programme for the Southwest Delta, please send an email to For more information on the developments and projects in the Southwest Delta, go to