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. Furthermore, a study will be conducted to gain a more detailed picture of how the potentially accelerating rise in sea level will impact the Preferential Strategy. Would you like to know more about the challenges in the Southwest Delta? Then view the film.


Realising integral ambitions

Climate change and socio-economic developments present the region with challenges in terms of climate adaptation, 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.

Several good options are available for safeguarding flood protection and the freshwater supply in the Southwest Delta. The strategy adopted in the area encompasses innovative, integrated solutions. Examples include: alternative supply of fresh water via the Roode Vaart, the construction of multi-functional dykes, and the generation of sustainable energy. This will also open up opportunities for the regional economy, which is strongly tied to water.

Grevelingen and Volkerak-Zoommeer

The Preferential Strategy for the Southwest Delta involves the restoration of limited tidal movements in Lake Grevelingen. This calls for a sluice in the Brouwersdam, possibly to be combined with sustainable energy generation through a tidal plant. In early 2019, the central government, the provinces of Zeeland and Zuid-Holland, the municipalities of Goeree-Overflakkee and Schouwen-Duiveland, and Staatsbosbeheer set down agreements regarding the completion of the exploration phase. In the period ahead, further research will be conducted into ways of factoring in the rise in sea level as caused by climate change, and into measures required to meet the Natura 2000 regulations.

The central and regional governments will continue their consultations regarding the further plan elaboration and 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).

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. Under this strategy, the Roggenplaat shoal is being reinforced.

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 have jointly drawn up the Agenda for the Future 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. In June 2019, a preferential alternative for the Hansweert dyke improvement project was set down, which is now being elaborated. The district water board is aiming for maximum involvement of stakeholders and local residents in the preparations and implementation. 

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 fresh water (such as the agricultural sector, industry, and drinking water companies) in order to secure a sufficient supply.

The Zuid-Holland islands, West-Brabant, Tholen, Sint Philipsland, and the Reigersbergsepolder receive fresh water via the major freshwater bodies, such as Biesbosch, Hollandsch Diep, Haringvliet, and Volkerak-Zoommeer lake. For these areas, preservation of the freshwater supply and stocks is imperative, as is the combat of salinisation.

The Roode Vaart project combines a sustainable freshwater supply with a quality boost in Zevenbergen city centre. Water transfer to West-Brabant via the Roode Vaart is now scheduled to be operational by the end of 2020. The parties involved have set down a collaborative agreement to that effect.

If the authorities decide to re-salinise the Volkerak-Zoommeer, additional freshwater supply measures will first be implemented in the immediate vicinity. To this end, an alternative, climate-resilient freshwater supply has been designed.

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

In 2019, all the governments in the province of Zeeland endorsed the Zeeland Climate Adaptation Strategy Action Plan. This sets out agreements on the substantiation of the seven ambitions featuring in the Delta Plan on Spatial Adaptation, including a timetable and the formulation of climate adaptation strategies at the provincial and local levels. The build-up to the action plan has raised awareness regarding the collective tasking. By the end of 2019, all the municipalities in Zeeland will have conducted comprehensive stress tests covering the entire province. At the provincial level, a comprehensive risk dialogue will have been conducted in preparation for the provincial climate adaptation strategy. In addition, some 30 per cent of the municipalities will have conducted risk dialogues.

In many projects underway in the province of Zeeland, climate adaptation is a key factor. For example, the Claverveld residential area in the municipality of Vlissingen has been constructed in a climate-adaptive manner. The IVN Natuureducatie organisation, the Zeeland Area Health Authority GGD, and the Zeeland University of Applied Sciences have initiated the Zeeland Schoolyards Green Revolution, which is co-funded by the province of Zeeland. This campaign is aimed at greening schoolyards, thus contributing to a climate-proof society. Furthermore, the province of Zeeland has set up a Green Rooftops grant scheme.

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 have developed a governance structure to this end.

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 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 road safety.

Spatial adaptation in West-Brabant and Zuid-Holland

The West-Brabant Working Region reports to the staff of the Delta Programme Commissioner via the collaborative alliance under the Zuid-Nederland Climate Adaptation Implementation Programme. The Goeree-Overflakkee Working Region conducted a comprehensive stress test covering the entire island in 2018, and is engaged in a risk dialogue with several stakeholders aimed at developing a climate adaptation strategy.

Potential amendment of Delta Decision and Preferential Strategy

If the rise in sea level remains limited to a maximum of 1 metre by 2100, the current Preferential Strategy can largely be preserved. However, Deltares studies have shown that some efforts need intensification, in particular, sand replenishment, minor interventions, and research development.

A 1 to 2 metre rise in sea level by 2100 dictates amendment of the strategy in several respects. In this event, depending on the pace at which the sea level rises, larger interventions could be required between 2050 and 2100, for which choices need to be made well before 2050. Being in a position to implement effective measures for the Southwest Delta in a timely and interconnected manner is essential. This calls for an integrated exploration of the long-term alternatives, focusing on safety, the freshwater supply, nature, and the economy. In the six years ahead, research will also need to be conducted into potential intervention points and effects in the event that the current Preferential Strategy continues to be pursued.
Solution strategies and choices will pertain to, inter alia, water level management; water and bed levels in closed-off basins rising apace with the sea; the use of pumps; the closure regimen of the Oosterschelde storm surge barrier; eventually, choosing between an open or closed Oosterschelde; and dyke improvement methods. The solutions and choices may differ from one Southwest Delta water system to the next: Bergsche Maas, Haringvliet, Hollandsch Diep, Grevelingen, Volkerak-Zoommeer, Binnenschelde, Markiezaatsmeer, Oosterschelde, Veerse Meer, and Westerschelde.
In addition, the seven ambitions of the Delta Plan on Spatial Adaptation will be accommodated in the Preferential Strategy for the Southwest Delta.

Delta Programme 2020

Read about the progress made in the Southwest Delta region in Delta Programme 2020.