Southwest Delta

The Southwest Delta encompasses Zeeland, the Zuid-Holland islands, and the northwestern 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 interconnection in terms of safety, the economy, and ecology. The area has drawn up a preferential strategy to that 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 National Framework Vision for the development of Grevelingen and Volkerak-Zoommeer has been drafted, featuring plans for restoring limited tidal movement in the Grevelingen lake, and re-salinising the Volkerak-Zoommeer lake with a limited tidal movement. The adoption of this Vision is contingent upon the availability of sufficient funding.

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 Grevelingen 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. According to the draft National Framework Vision for the Grevelingen and Volkerak-Zoommeer lakes, keeping this option open is not necessary. Dyke improvements turn out to be a more cost-efficient solution than additional water storage in the Grevelingen lake. Any decision by a new Cabinet to restore tidal movement in the Grevelingen lake will be taken into account in the assessment of the dykes around the 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. With respect to the Oosterschelde, a MIRT study into Integrated Flood Protection has been launched to map out potential bottlenecks in the areas of flood risk management, spatial planning, and nature in the period 2050-2100.

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 sand replenishment pilot has been launched 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 2018-2019, and a potential sediment pilot to be 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) 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 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 involving water and air bubble screens at sluices. A pilot to this effect has been carried out at the Krammer locks yacht lock. At the end of 2017, a decision will be made regarding the introduction of the innovative freshwater-saltwater separation systems at the commercial shipping locks, which Rijkswaterstaat prefers over major repairs to the current freshwater-saltwater separation system, because of the social benefit of several millions of euros per annum (due to shorter passage times), lower annual maintenance costs, and energy cost savings that new systems would yield. The major repairs encompassing the introduction of the new freshwater-saltwater separation system could be completed in 2021.

The Roode Vaart project that will be completed in 2018 combines a sustainable freshwater supply with a quality boost in Zevenbergen city centre. A decision to re-salinise the Volkerak-Zoommeer and restore limited tidal movement 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 the self-sufficiency of freshwater users.

Climate adaptation in Zeeland and Zuid-Holland

The province of Zeeland is working on the Zeeland Climate Adaptation programme within a comprehensive coalition. The parties are developing, inter alia, a climate test for flood risk management, waterlogging, 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. In the period from 2016 to 2020, all the municipalities in the province of Zeeland will be subjected to a climate test. The first test was conducted in the municipality of Noord-Beveland in the autumn of 2016.

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 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 2018

To view the progress made in this area, click here: Southwest Delta in Delta Programme 2018.