The coast protects millions of Dutch residents against flooding from the sea. The coastal zone is home to over a million residents and businesses, and attracts many tourists and visitors. The Preferential Strategy for flood risk management along the coast is aimed at keeping the coastal area safe, attractive, and economically strong in the future. In the years ahead, the focus will be on fleshing out the strategy. The region is exploring opportunities for integrated solutions, such as multi-functional dune zones or dykes. The Delta Decisions that have been set down for the entire country and the Decision on Sand constitute the framework in this regard.
Along the coast, taskings in terms of flood risk management may arise from soil subsidence and the rising sea level , as a result of climate change. Major interventions will probably not be needed before 2050, apart from regular sand replenishment, and management and maintenance of flood defences. In the long run, depending on the rate at which the sea level rises, measures may be required at a number of locations in order to maintain the desired protection level.
Preferential strategy for flood risk management
The Preferential Strategy for Flood Risk Management along the coast ensues from the National Coastal Vision: a safe, attractive and economically strong coast. The Preferential Strategy outlines methods to link up the flood protection tasking and spatial developments, tailored to each individual location. In many cases, spatial developments outpace the flood protection tasking.
Several locations are open to sustainable economic and spatial development in combination with flood risk management, thus presenting linkage opportunities.
For each situation, the parties involved determine whether linking the flood protection tasking and the spatial ambition would be advisable and feasible, and within what timeframe. If the issues are not linked, the parties take one another’s tasking or ambition into consideration when implementing management or maintenance. If linking would be advisable, the parties jointly set down the tasking along with potential solution strategies.
Governments, nature organisations, the recreational sector, and drinking water companies have drawn up a “Coastal Pact”, outlining the coastal values that underpin their views of the future development of the coast. Under this Pact, the parties are collectively working on, e.g., a zoning plan regarding the use (e.g., nature, leisure activities) of the coastal zone. Each province will set down the agreements in provincial regulations. The province of Noord-Holland has completed this process; under the auspices of the province, 27 partners have collaborated on the establishment of the regulations. All the parties involved are satisfied with the result achieved. The balance between the protection of nature and landscape values and the development of leisure facilities has been secured through beach zoning plans, the existing dune protections, and agreements on further collaboration regarding the dune borders.
The coast mainly consists of sand which is moved by the water currents. The Dutch coast requires regular replenishment. This is necessary to preserve the coastal surface area and sustain coastal functions, such as the safety of areas inside and outside the dykes, nature, leisure activities, and water collection. Furthermore, beach replenishment allows the coast to gradually keep pace with the rise in sea level. The Coastline Care programme initiated by Rijkswaterstaat (Ministry of Infrastructure and Water Management) is responsible for drawing up and implementing the beach replenishment schedule.
More sand will be required if the sea level rises. Studies into future sand requirements and the effects of sand replenishment are being conducted under the multi-year knowledge programme Coastal Genesis 2.0.
Coastal Genesis 2.0
The Coastal Genesis 2.0 research programme is aimed at generating knowledge in order to enable well-founded decisions on the policy regarding, and maintenance of, the Dutch sandy coast system by 2020. Coastal Genesis 2.0 ensues from the Delta Programme Decision on Sand. Between 2015 and 2028, the Coastal Genesis 2.0 programme will explore the long-term sand requirements, where and when sand deposits are required, and how we can add these sand volumes to the coast. A policy recommendation will be presented by 2020, by way of an interim result. The studies are structured as follows:
- Long-term coastal research: additional monitoring and model development in order to gain more insight into factors determining the required replenishment volumes. In 2017, a large-scale measuring campaign produced additional data;
- Replenishment pilot in the ebb-tide delta of the Ameland Inlet: a pilot replenishment to gain information on the construction, morphology, and ecology of tidal inlets;
- Ecological monitoring: insight into the environmental impact and opportunities of changing replenishment volumes and replenishment locations.
Data management plays a key role in the substantiation of the focus areas. The goal is for the data to be publicly available in the future. The studies feature a “learning while working” approach, i.e., learning by gaining experience, as is the case in the Ameland Inlet replenishment pilot.
Replenishment pilot in the ebb-tide delta of the Ameland Inlet
Rijkswaterstaat has initiated the Ameland Inlet replenishment pilot in collaboration with research institutes in order to gain more knowledge on the operation of tidal inlets. As yet, little information is available on this topic. Measurements before, during, and after the sand deposits will provide insight into sediment transport and (benthic) life in the tidal inlet. Thus, the parties involved are exploring whether tidal inlets make suitable locations for future sand replenishment.
The sand replenishment project was completed in early 2019. In the tidal inlet between the islands of Terschelling and Ameland, some 5 million cubic metres of sand were deposited under water. The project involved collaboration with several other Rijkswaterstaat programmes and the SEAWAD research programme, which explores the options for a type of sand engine to protect the coastline along the Wadden islands. The evaluation report outlines the initial experience gained in the pilot during the preparation and implementation phases. The morphological and ecological measurements will continue up to and including 2021, as a minimum. The learning experience gained up to and including 2020 will be incorporated into the Coastal Genesis 2.0 policy recommendations.
Potential amendment of Decision on Sand and Preferential Strategy
Annual coastal measurements provide a picture of the coastal sand budget. Should the signs regarding a potentially accelerated rise in sea level (cf. Sea Level Rise Knowledge Programme) dictate an amendment of the Delta Scenarios, the annual requirements in terms of sand replenishment will change. In 2020, this issue will be addressed in the policy recommendations to be presented by Coastal Genesis 2.0.
Currently, coastal flood risk management is up to par; there is no reason to interconnect flood protection with spatial taskings. For the time being, the Coastal Pearls and the Linked Growth Concept will, therefore, only be substantiated on the basis of spatial development taskings. A point for attention is the manner in which governments are addressing spatial developments that may affect long-term flood protection. For example, the municipality of The Hague is working on the development of the Scheveningen port. Currently, flood risk management is not an issue at this location. The municipality and the district water control board are exploring ways to secure long-term flood protection by elaborating options and continued growth concepts.
The North Sea is subject to a range of spatial claims for purposes such as sand extraction, wind parks, fishing grounds, and nature parks. This limits the opportunities for sand extraction in the purview of the coastal replenishments required to safeguard flood protection. Consequently, it would seem wise to, on the one hand, to further elaborate the Preferential Strategy for the Coast and the Decision on Sand, based on a comprehensive analysis of sand extraction opportunities, and on the other, to analyse the admissibility of various functional uses of the North Sea. The guiding principle in this could be the perception of the coast serving as a climate buffer. The IPCC (Intergovernmental Panel on Climate Change) and KNMI (Royal Netherlands Meteorological Institute) data on an (accelerated) rise in sea level must be taken into consideration in this respect.
Delta Programme 2020
Read about the progress made in the Coastal area in Delta Programme 2020.