LILA – Landezine International Landscape Award 2021

Area development Ooijen-Wanssum
In 1993 and 1995, the Dutch province of Limburg was startled by two major floods of the Meuse. Such highwater levels had not occurred since 1926 and the economic damage was enormous. Temporary measures were taken in 1996 to improve the water safety of the area in the short term: emergency dikes were constructed in various places and the old river course between Ooijen-Wanssum, the ‘Oude Maasarm’ was closed. In the long term, these temporary measures however are not sufficient.

With this project, the area is better protected against high water by a combination of dike construction and river widening. More than 20 km of new dikes are constructed and a 35 cm drop in water level is realized by lowering the ‘weerd’ (floodplain along the river) and by reactivating the ‘Oude Maasarm’. In addition more than 300 hectares of new, freely accessible nature is realized: with a sophisticated ground level design, the optimal conditions are offered for the development of special grasslands, sedge swamps and river forests. Finally, the quality of life in the town of Wanssum is increased by the construction of a new ring road and the redesign of the town center and space is created for new economic developments in the area. Both the spatial quality and the quality of life are boosted as a result of this project.

What is special about the project is the integrality of the plan, the close cooperation between all parties involved and the high degree of attention to spatial quality and innovations. Most striking and priceworthy part of the design is a new and unique approach to the dike reinforcement task.

Innovative dikes - area-specific, space-saving and sustainable
With the dike design a solution has been devised for water safety without affecting the traditional terraced landscape of the Meuse, that until the construction of the emergency dikes in 1996 never included dikes. To this result two new dike types were developed that merge into the landscape: the ‘steep-edge dike’ and the ‘high ground dike’.

The new dikes have a smaller net space requirement, more usage possibilities including arable farming and reforestation and a smaller management burden for the Water Board. The dikes are made with local soil that is released during the lowering of the floodplains. This makes it possible to achieve a virtually closed ground balance. Deep sand extraction with its negative environmental impact is avoided as well as large (CO2) emissions and costs of the removal of enormous amounts of soil from the floodplains and the supply of dike clay. In order to realize this innovation, we worked very closely with the water board and the dikes were tested in a hydrodynamic laboratory in Hamburg.

Steep-edge dike
The steep-edge dike has an a-symmetrical profile that fits in with the natural relief of the Meuse landscape, which only has gentle or steep relief transitions. The steep-edge dike is implemented at the transition from the upper middle terrace to the lower terrace, on the border of the new nature reserve. This boundary is shaped like a steep edge with a 2:1 slope. Natural erosion processes are allowed in this steep edge, creating an interesting, natural image with high ecological value. Vegetation with trees, grazing with large grazers and erosion are no problem. The entrances to the nature reserve are strikingly designed as incisions in the dike. To guarantee water safety, a strong ‘erosion buffer’ of local materials is built behind this 'natural buffer', replacing the clay layer and grass cover of a traditional flood defense. At the inside of the dike a slight slope is constructed at least 1:8, preferably 1:20 and enclosed lower areas are filled, which will improve agricultural conditions and the water system. The current land use can be continued on this slight slope.

New, modest yet iconic cross the Oude Maasarm. The bridges are cast in situ and are notable for their slender design, subordinate to the landscape. The bridge heads form distinctions on the dike as bastions.

High Ground dike
The high ground dike is an invisible dike, completely merging into the landscape which is rich in relief. With local soil from the lowering of the flood plains additional height and width are applied above the technically required profile of the flood defense. Due to this robust and future-proof profile, the high ground dike does not have to be maintained as a flood defense by the water board and there are no obstacles to its use. The dikes can remain in agricultural use with third parties and may even be overgrown by forest. An additional advantage is that no land needs to be purchased. The high ground dike is used on the sections where the dike runs straight across the middle terrace.
For the sake of cohesion, the dike types are applied consistently. In special places, such as the old castle ruins at Blitterswijck or where buildings are close to the dike, customized work is provided which enriches the view.

H+N+S have, in their very own Dutch way, invented a new dike typology – innovative terrain modelling for more efficient and sustainable land use and simpler maintenance.