CPSL - Coastal Protection and Sea Level Rise

Background and Goals

At the 8th Trilateral Governmental Conference for the Environmental Protection of the Wadden Sea (Germany, 1997), it was decided to investigate the possible effects of an accelerated sea level rise. Proposals for future integrated coastal defence and nature conservation strategies were to be developed on the basis of this investigation. To this end, in 1998, the trilateral expert group "Coastal Protection and Sea Level Rise" (CPSL) was established, composed of representatives of the coastal defence and nature conservation management agencies of the three bordering countries of the Wadden Sea. The results were presented at the 9th Trilateral Governmental Conference for the Environmental Protection of the Wadden Sea in Esbjerg (Denmark) in 2001. Recognizing the high topicality and urgency of sustainable coastal defence strategies, the ministers decided to continue the work of the CPSL group. In this second stage (CPSL II: (2003 to 2005), the work focuses on the development of integrated solution strategies. The third phase was completed in 2010 with the third report: the focus of this study was the role of spatial planning and the management of sediment.

These integrated solution strategies will be examined on the following points:

  •  Safety standard;
  •  Environmental compatibility ("best environmental practice");
  •  Cost-benefit ratio;
  •  Public acceptance;
  •  Legal aspects;
  •  Conflicts with other interests in the Wadden Sea (e.g., tourism).

Furthermore, it should be guaranteed that the solutions developed for one part of the Wadden Sea would have no adverse effects on other areas. As the optimal solution strongly depends upon the future development of the Wadden Sea, two geomorphological scenarios will be developed and examined. The results of CPSL II serve as the basis for the 10th Trilateral Governmental Conference for the Environmental Protection of the Wadden Sea in 2005.

The first objective of the expert group is to develop a common understanding of the most important processes in the Wadden Sea regarding geomorphology, biology and coastal defence. Building on this, the effects on selected physical, biological and socio-economic parameters are studied, based on scenarios of sea level rise . Next, sustainable coastal defence measures (so-called "Best Environmental Practices") will be selected that can be used to ensure that the current safety standards can be guaranteed in the future.

Content time


Research area/region

  • Denmark
  • Germany
  • Netherlands
Region of implementation (all German federal states)
  • Lower Saxony
  • Schleswig-Holstein
Natural spatial classification
  • coasts: North Sea-/Baltic Sea coasts
  • North-West German lowland

Steps in the process of adaptation to climate change

Step 1: Understand and describe climate change

Approach and results 

Three scenarios are used for the sea level rise: +10 cms, +25 cms and +50 cms. Two geomorphological scenarios were devised for the future development of the Wadden Sea.

Parameter (climate signals)
  • Sea level rise und storm surges
Time horizon
  • medium term = to 2050

Step 2a: Identify and assess risks - climate effects and impact

Approach and results 

The climate change effects on selected physical, biological and socio-economic parameters of the Wadden Sea are analysed Characteristic elements of the Wadden sea system are the barrier islands, the tidal inlets, the ebb-tidal deltas, the tidal channels, the tidal flats and the salt marshes, and there is a constant sediment exchange between these elements.

For the scenario with +25cms of sea level rise by the year 2050 no significant changes in the Wadden Sea ecosystem (geomorphology and biology) are expected. However, the costs for coastal defence could rise by between 5 and 15%. For the scenario with +50cms of sea level rise by the year 2050, the capacity of the Wadden Sea to balance changes in the system through sediment distribution could be exceeded. Consequently, the tidal basins could evolve into coastal lagoons comprising large, permanently flooded areas. Such a geomorphological development would significantly affect and change the biological systems. Also, the costs for coastal defence could double in this scenario, if current safety standards were to be maintained.

Step 2b: Identify and assess risks - Vulnerability, risks and chances

Approach and results 

The vulnerability issue is limited to the (natural) resilience and adaptive capacity of the ecosystems in the Wadden Sea, the adaptive capacity of the resident population is not taken into account.

The Wadden Sea is characterized by a strong natural variability and has a high natural resilience to changes. However, because of this, developments away from the existing dynamic equilibrium are difficult to detect, and some uncertainties exist on the so-called "breakpoints" of Wadden Sea basins, above which new ecosystems and biotope changes may become established.

Adaptive capacity: The study expects that a breakpoint exists between the two scenarios for the sea level rise up to 2050 (+25cms and +50cms), above which the adaptive capacity of a tidal basin will fail. This breakpoint is, however, dependent on the rate at which the sea level rises, and will vary between the individual tidal basins.

Urgency and priorization of adaptation needs 

The urgency with which adaptation measures will be required mainly depends on the speed and extent of the sea level rise.

Step 3: Develop and compare measures

Measures and/or strategies 

Sustainable coastal defence measures (so-called "Best Environmental Practices") will be selected that are suitable for guaranteeing that the current safety standards can be maintained in the future. Since the measures considered differ strongly with respect to their technical effectiveness, it is obvious that there is cannot be one single solution that fits all the demands of the whole Wadden Sea. Therefore, the group will recommend particularly those measures that best suit the coastal defence purposes while taking account of the ecological consequences.

The following points should be observed in coastal protection measures and strategies:

  1. Spatial planning for coastal zones should include buffering and flood hazard areas (compliance with ICZM principles). Coastal defence and climate change should be duly considered in relation to each other. The feasibility of such plans should be investigated by a group of nature conservation, spatial planning and coastal defence experts.
  2. Sand nourishment should be applied, wherever feasible, to combat erosion along sandy coastlines.
  3. A study should be carried out on the extent to which sand nourishments will be able to balance the sediment deficit of the Wadden Sea tidal basins under an increased sea level rise.
  4. Regional salt marsh management plans should be established to harmonize the demands of coastal defence and nature conservation.
  5. An assessment the present-day coastal defence measures should be carried out to determine their suitability for guaranteeing that the current safety standards can be maintained in the future, with respect to their feasibility and ecological consequences.
Time horizon
  • 2011–2040 (near future)
  • 2021–2050 (near future)
Conflicts / synergies / sustainability 

Above all, conflicts exist between the interests of coastal defence, nature conservation and tourism. Sustainable coastal defence measures that comply with the ICZM principles can help reduce these conflicts.

Step 4: Plan and implement measures

Costs of the measures 

Costs of coastal defence measures for the preserving current safety standards


Funding / Financing 

Common Wadden Sea Secretariat (CWSS) with the three states of the Netherlands, Germany and Denmark

Project management 

Common Wadden Sea Secretariat (CWSS)


trilateral group of experts with representatives from coastal protection and nature conservation agencies of the three states bordering the Wadden Sea: the Netherlands, Germany and Denmark with the following institutions: Kystdirektoratet (Denmark), Sønderjyllands Amt (Denmark), Rijkswaterstaat - Directie Noord-Nederland (Netherlands), Rijksinstituut voor Kust en Zee (Netherlands), Expertisecentrum LNV (Netherlands), Wadden Sea National Park Authority of Lower Saxony (Germany), Lower Saxony Water Management and Coastal Defence Agency (Germany), Ministry of the Interior of the state of Schleswig-Holstein (Germany)


Common Wadden Sea Secretariat (CWSS) - Gemeinsames Wattenmeersekretariat
Virchowstrasse 1
D-26382 Wilhelmshaven

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Fields of action:
 biological diversity  coastal and marine protection  spatial, regional and urban land use planning  tourism industry