Measures for the Southwest Delta

Milestones 2015-2025

Considerable progress has been made in the Southwest Delta in recent years. Milestones include:  

• The integrated Water Dunes project (Dutch) has been completed. It combined strengthening the coast, nature development and leisure.   
• The Roggenplaat sand nourishment project in the Eastern Scheldt has also been completed. It focused on nature and flood risk management (the mitigation of wave attack on the south coast of Schouwen). 
• The work on the Zevenbergen port was completed in 2020 in the Roode Vaart project.  
• The ‘Kop van Schouwen Smart Sand Use’ pilot project resulted in new dynamics and the improvement of the ecological and landscape values of the dunes. Sand nourishment also took place on the Brouwersdam beach, which is important for the regional economy.  
• In the context of the Zeeland Climate Adaptation Strategy (KASZ) (Dutch) , the climate stress tests have been completed and a risk dialogue has been conducted in the province. That resulted in 'Climate change: risks in Zeeland in the picture' (Dutch). In conjunction with this publication, a joint implementation programme was developed and a six-year implementation covenant was signed.  
• The Roode Vaart inlet facility was officially opened on 3 May 2022. This will allow West-Brabant to be supplied with extra fresh water from the Hollands Diep.   
• The Sea Level Rise Knowledge Programme organised three working sessions for the Southwest Delta in 2022. They produced more insights into future water and land use, such as the construction of nuclear power plants and new coastal landscape development combining flood risk management, nature and leisure. The Interim Report for the Knowledge Programme shows the long-term consequences of sea level rise for the region: the primary flood defences must be further raised and widened, the risk of salinisation pressures is increasing and the availability of fresh water in the summer is declining. The results make it more urgent to think in terms of Water and Soil as Leading Factors. 
• A large amount of fresh water is released, from the soil and from direct rainfall, at the foot of the Brabantse Wal. This water – about 30 million cubic metres per year – flows into the Western Scheldt without being used. The Brabantse Delta and Scheldestromen water authorities, the provincial authorities of Noord-Brabant and Zeeland, and water company Evides want to make use of the water. In 2023, studies showed that quality and availability were inadequate for the purposes of drinking water production. Nevertheless, agriculture, nature and industry will be able to benefit.  
• The Delta Programme for the Southwest Delta helps and encourages municipalities to find solutions in the overlap with the area-specific approaches of the provincial authorities. The Area Consultation Platform therefore called for local initiatives from municipalities and partners. In early 2023, the Area Consultation Platform approved five initiatives and projects. This means we have moved all five projects forward and shared the results of the interim milestone with one another. The Area Consultation Platform is now looking at how to move these projects forward together and how to disseminate the research findings.  
• In 2022, work began on the elaboration of the action perspectives in the 2015 Area Agenda for the Southwest Delta. That agenda combines the national agendas and the regional economy into inspiring action perspectives. In addition to the ongoing processes for the Veerse Meer Area Vision and the Volkerak-Zoommeer Area Process, work took place in 2025 on linking up area processes in the other sub-areas. 
• An exploratory system analysis of the Southwest Delta was drafted in 2024, focusing particularly on the interaction between water systems and specific areas (the islands). It identified the measures that can deliver realistic and robust freshwater supplies, and also looked at matters such as the long-term local effects of decisions made in line with Water and Soil as Leading Factors. The possibilities and opportunities from this system analysis constitute an important basis for the periodical evaluation of the preferred strategy. The conclusion is that the present preferred strategy for flood risk management and freshwater availability in the main water system throughout the Southwest Delta is tenable and that it can be made fit for purpose until 2050, and probably longer depending on the rate of climate change. However, additional measures will be required in the water systems to maintain their adequacy and flexibility. The long-term issues for the Southwest Delta depend primarily on supra-regional decisions in the Rhine-Meuse Delta. 
• The Volkerak-Zoommeer area process began in 2025. It involves the development of a long-term perspective.  
• The study of water quality in the Veerse Meer lake was completed in 2024. This study by Rijkswaterstaat and Deltares showed that the oxygen conditions in the lake have deteriorated. In addition, climate adaptation pathways were drawn up to look at which strategies with packages of measures contribute to a future-resilient lake. The research is part of the action programme in the Veerse Meer Area Vision for 2020-2030. The aim of this vision document is to safeguard and strengthen the qualities of the area. 

Grevelingenmeer - continuation of existing situation

A culvert in the Brouwers Dam to allow tidal action could improve water quality. The purpose of this additional culvert is to restore limited tides in order to improve underwater nature and maintain the natural conditions above the waterline.  

The sound ecological functioning of the Grevelingenmeer lake requires opening the Brouwers Dam in such a way that the dynamic system is restored. The tides are important for the ecology, and the difference between high and low water (the tidal range) for this purpose should be at least 40 centimetres.  

It is also important for there to be an adequate flow of water so that the salt water entering the lake can spread throughout the water column, rather than forming a saline tongue below the fresh water in the lake. There is a connection between the Eastern Scheldt and the Grevelingenmeer through the Flakkeese discharge sluice, which means there is also an exchange of water with the Eastern Scheldt. 

Eastern Scheldt - a range of measures

Various measures are being taken in and around the Eastern Scheldt in relation to flood risk management, ecology and water quality. One example is the Krammersluizen complex, which is located between the saline Eastern Scheldt and the fresh Volkerak-Zoommeer lake. Other measures relating to flood risk management are being implemented as part of the Flood Protection Programme. The Scheldestromen water authority and Rijkswaterstaat work together in that programme on dike upgrade operations. 

The study of the adequacy and flexibility of the Eastern Scheldt storm surge barrier under continued sea level rise was completed in 2025. It found that a range of effective measures are possible to continue to safeguard protection:  

• strengthening the barrier to cope with increasing loads; 
• raising the dike to accommodate higher water levels; 
• changes to the closure regime of the barrier to reduce the frequency of closure and allow for necessary maintenance. 

During the course of the second periodical evaluation, there will be an exploration of the measures required to think ahead in this respect and make it possible to develop smart designs to ensure future safety. 

Western Scheldt - periodical evaluation of long-term vision

Since the publication of the 2030 Long-Term Vision, new developments and challenges have emerged, such as climate change, the energy transition, a circular economy, updated nature and environmental regulations and new standards for flood risk management. The 2030 Long-Term Vision is therefore being evaluated by incorporating current knowledge about these developments and challenges in the scenario. The purpose of the periodical evaluation is to draw up a long-term vision that will allow Flanders and the Netherlands to once again establish trans-border decisions for policy and management in the Scheldt estuary. 

The periodic evaluation of the 2030 Long-Term Vision will consist of several phases. The first phase started in 2024. It involves drafting an approach that will describe a range of options for the initiation of the periodical evaluation. The approach will include a problem analysis based on current knowledge about the future of the Scheldt estuary. It also sets out the objectives for the periodical evaluation.  

The approach, including the problem analysis and objectives, will be drafted and coordinated with stakeholders and experts from the Flemish-Dutch Scheldt Commission (VNSC).  

Plans for 2026-2027

• Efforts are also being made to develop the action perspectives for the other subareas in the Southwest Delta in addition to the Veerse Meer and Volkerak-Zoommeer lakes. This involves working through area processes in the Area Agenda. Short-term (2030) and medium-term (2050) measures are being linked to the long-term perspective (after 2050).  
• A Veerse Meer Area Vision was produced in 2021. The aim of the 2020-2030 Area Vision is to safeguard and strengthen the qualities of the area, with flood risk management, nature, leisure activities, agriculture, fishing, habitability, the economy and the landscape being in equilibrium. The aim is to safeguard the accessibility and appeal of the area in terms of its range of functions and users until 2030 and well beyond.  
• For the Volkerak-Zoommeer lake, work is taking place on a concrete and feasible plan to improve water quality with the objective of making the area robust and healthy. This perspective will be incorporated in the Volkerak-Zoommeer Area Process. Important themes are: ecology and water quality, freshwater availability, and the economy and leisure. 
• One measure being worked on is improving the water quality of the Mark-Dintel-Vliet water system so that fewer nutrients are discharged into the Volkerak-Zoommeer and blue-green algae blooms are less prolonged. Lowering nutrient loads reduces the duration of blue-green algae blooms.  
• Another measure is to reduce the salt load from the Krammer locks by learning-by-doing about the innovative fresh-salt separation, so that less salt water enters the Volkerak-Zoommeer when ships pass through. 
• The Grevelingen Tide Restoration project is conducting an exploratory study looking at restoring limited tides here with the aim of reducing the area of the oxygen-depleted bed and improving the water quality and underwater nature. Water quality and underwater nature are suffering from the effects of the Delta Works. Sea level rise will make it more difficult in time to maintain the desired tidal range. The measure involves the construction of a culvert in the Brouwers Dam that makes tidal variations possible. A decision is currently awaiting approval from the Minister for the initiation of plan development. A study of the sustainability of the Eastern Scheldt barrier completed in 2025 showed that no changes are required to the current use of this barrier until 2050. The study shows that, at a sea level rise of up to 70 cm, the Eastern Scheldt barrier will continue to fulfil the major requirement, viz. control of the water levels in the Eastern Scheldt. The barrier dampens the effect of sea level rise considerably and protects the surrounding dikes. Together, they maintain the protection of the hinterland from flooding. The knowledge and insights from the EZZO study will be included in the course of the 2050 Southwest Delta Implementation Programme and they will be included in the 2050 Southwest Delta 2050 Integrated Preferred Strategy. Both will be completed in 2026. 
• The second periodical evaluation of the Delta Programme for the Southwest Delta is being linked to the concrete elaboration of the 2050 Southwest Delta Area Agenda. This will result in an Implementation Programme for the Southwest Delta in 2050. That programme describes the eight water and land areas with the associated area processes. In order to achieve the concrete implementation of the main agendas, pillars have been identified that add the details to the agendas in the Southwest Delta. They combine guiding principles from regional and national policy. The result: a connected delta in a mosaic of water and land use. 
• Knowledge and research continue to be important.  Knowledge questions about the effects of sea level rise have been given a place in the Sea Level Rise Knowledge Programme. Integrated knowledge questions are being elaborated in the Integrated Knowledge and Innovation Agenda for the Southwest Delta. This agenda provides a picture of the interaction and connections between the individual knowledge agendas. On the basis of an approach developed by Deltares, the parties will acquire an understanding of the complex integrated issues facing the area in the short, medium and long term. The plan is to implement this new approach in the work process by 2026.   
• The execution of ‘iconic projects’ as part of the Delta Issues Research Process is contributing to national and regional knowledge development. One example is the iconic Innovative Water Defence Landscapes project. 
• The Flood Risk Management Project Organisation (POW) (Dutch) is an alliance of the Scheldestromen water authority and Rijkswaterstaat Sea and Delta. The POW will be working on the Hansweert dike upgrade in the coming years. This is the first project in Zeeland to be executed in line with the latest safety standards. The project is also focusing as much as possible on sustainability and circularity. Residents were involved in discussions about a range of variants and they contributed wishes and ideas during residents’ evenings and dike excursions. The work is being done in phases and completion is expected in 2027.  
• The regional water system will be designed and managed more robustly to establish closer links with the main water system. The reuse of treated wastewater is being studied and taking shape in a few specific areas (in the Bath and Terneuzen region). The regional partners are working together as much as possible on the required knowledge development.  
• The Schouwen-Duiveland Living Lab network organisation is seeking new, innovative solutions to complex challenges in the areas of water, food, education and governance. That involves collaboration with educational institutions, business, government authorities, research institutes and local residents. They are testing innovative solutions in practice on the way to a circular economy in Schouwen-Duiveland.