Marker Wadden

The deeper story

From the shore, Markermeer appears to be a vast open body of water, yet beneath the surface the lake suffered from a persistent problem. After completion of the Houtribdijk in 1976, Markermeer was separated from IJsselmeer. The natural movement of water and sediment changed dramatically. Fine silt remained suspended in the lake and was repeatedly stirred from the bottom by strong winds. The water became turbid, aquatic plants received little light and gradual transitions between deep water, shallows, shores and marshes were largely absent.

Marker Wadden emerged as a response to this ecological decline. Its principle was unusual: rather than protecting only existing nature, hydraulic engineering would create new conditions in which nature could develop. In 2016, Natuurmonumenten, Rijkswaterstaat and Boskalis began constructing the first islands. The project eventually produced an archipelago of seven islands. Together with the surrounding underwater landscape, the first phase covers approximately 1,300 hectares.

The islands were built mainly from material taken from Markermeer itself. Sand formed firm outer edges, beaches and submerged dams. Finer clay and large quantities of silt were placed within these boundaries. Approximately 35.6 million cubic metres of silt received a new purpose. Material that had previously formed a thick layer across the lake bed became the building material for mudflats, channels, shallows, marshes and islands.

Not every edge was designed as an equally hard barrier. Sandy rims and beaches protect the wet interior on the sides most exposed to wind and waves. Behind them lie sheltered basins, channels and shallow zones where the water is calmer and suspended silt can settle. The islands also shorten the distance across which waves can build. They therefore created not only land above water, but a more varied landscape immediately beneath and around the surface.

That underwater landscape is the heart of Marker Wadden. Many fish require shallow and relatively warm water for spawning or nursery grounds. Aquatic plants establish themselves more easily where sufficient light reaches the bottom. Shellfish, insect larvae and small aquatic organisms benefit from silty and sheltered zones. They in turn provide food for fish and birds. The visible islands are therefore only the uppermost part of a much larger ecological system.

Natural development began rapidly in many places. Reeds, marsh fleabane and other pioneer plants established themselves on the fresh sediment. Common terns, avocets, spoonbills and many other water and marsh birds found food, resting places and breeding habitat. Not every part develops in the same manner, however. Some areas remain open and muddy, while other zones become densely covered with reeds or other vegetation.

The landscape also remains physically dynamic. Silt compacts and slowly subsides. Wind and storm waves can damage sandy edges. Channels change shape and water levels determine which areas emerge or flood. Maintenance and repair are therefore not signs that the design has failed. They are part of a project in which ecological development and hydraulic engineering were conceived from the beginning as a single changing system.

The harbour island forms the accessible side of the archipelago. A small harbour allows arrival by ferry, private boat or charter. Walking routes lead from the harbour past a sandy beach, low dunes, reed beds, silt fields and wet hollows. Bird hides and screens allow animals to be observed without entering the undisturbed areas.

The Steltloper observation tower provides the clearest overview. From the tower, the separate islands, water channels and winding boundaries between sand, reeds, mud and open water become visible. From ground level, these zones can appear to be separate fragments. From above, it becomes clear that together they form a pattern of transitions.

Buildings and visitor facilities were deliberately concentrated around the harbour and walking routes. The principal structure is not the visitor pavilion or observation tower, but the complete combination of sand dams, silt fields, channels, shores and shallows. The boundary between constructed and spontaneous development is difficult to define. People determined the initial form, but water, wind, plants and animals continually alter it.

Marker Wadden is not a reclamation project in the traditional sense. There is no ring dike behind which water was pumped away. No fields, roads or permanent residential areas were created. Wet, muddy, mobile and periodically flooded zones are considered valuable. The new land need not remain entirely dry or unchanged, but may continue to develop under the influence of sediment and water.

From the Steltloper, pay particular attention to the sequence of elevations. Open water gradually becomes shallower, followed by mudflat, marsh vegetation, reeds and higher sand. Such transitions were missing along much of Markermeer. Marker Wadden therefore shows that new land need not be built merely to push water back. Here land was created to give aquatic nature more room.