Area development Ooijen-Wanssum

CAUSE

In 1993 and 1995, Limburg experienced two major floods of the river Meuse. Such high-water levels had not occurred since 1926 and therefore the economic damage was great. In 1996, temporary measures were taken to improve the safety of the area in the short term: temporary dikes were constructed in various places and the Oude Maasarm (the old branch of the Meuse) between Ooijen and Wanssum, which previously always flowed with high water, was closed.

However, these temporary measures are not sufficient for proper protection of the area in the long term. That is why the Ooijen-Wanssum Area Development is now being implemented. What is special about the project is how integrated the plan was for such a large-scale project, the intensive collaboration between all parties involved and the attention given to the spatial quality and innovation.

More than 20 km of new flood defenses will be constructed in the project. The developed dike concepts fit better into the originally undiked terraced landscape of the Meuse. They have a smaller net space requirement, more options for use, and a smaller management burden for the Water Board. The dikes are made with local soil that is released when the dike is lowered. This makes it possible to achieve a virtually closed land balance (gesloten grondbalans). Deep sand extraction has been avoided along with its associated environmental burden, and the costs of soil removal and the supply of dike clay have been saved.

To realize this innovation, we worked very closely with the Water Board. The dikes were tested in a hydraulic laboratory in Hamburg. The two new dike types were awarded the water innovation prize from the Union of Water Boards in the water safety category in 2019.

STEILRANDDIJK

The steep-sided dike is applied to the transition from the higher middle terrace to the so-called lower terrace, on the border of the new nature reserve. This border has a striking design as 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. Overgrowth with trees, grazing with large grazers and erosion are not a problem. To guarantee water safety, a strong erosion buffer made of area-specific material will be constructed behind this 'nature buffer', replacing the usual clay layer and grass cover of the flood defense. The entrances to the nature reserve are strikingly designed as incisions in the dike.

A gentle slope is constructed inside the dike (minimum 1:8, preferably 1:20) and enclosed depressions are replenished, which improves agricultural conditions and the water system. The current land use can be continued up to the crown of the construction, which significantly improves its integration into the landscape. An asymmetrical profile is created that matches the natural relief of the Meuse landscape, which only has sloping or steep relief transitions.

HIGH GROUND DIKE

The high ground dike is an invisible dike that completely blends in with the relief-rich landscape. Using soil from the local area, excess height and width are created in relation to the technically required profile of the flood defense in a robust and future-proof manner. Due to this excess, the high earth dike does not have to be maintained as a flood barrier by the Water Board and there are no obstacles to its use. The dikes can remain in agricultural use by third parties and may even be overgrown with forest. An additional advantage was that no land had to be purchased. The high soil dike is applied to the sections where the dike runs straight across the middle terrace.

GLASS DIKE CUSTOMIZED BROEKHOUSES

An innovative dike is also being applied at Broekhuizen. The residents themselves become owners of the flood defenses by protecting their homes with removable glass partitions, which can be placed if the Meuse water rises too much. With this customized solution, the view over the Meuse is preserved.

For the sake of coherence, the dike types are applied consistently. In special places, such as the old castle ruins near Blitterswijck or where buildings are close to the dike, customized work is provided that enriches the image.

NATURE DEVELOPMENT OLD MAASARM AND WEERDEN

The Oude Maasarm and the Weerden are being developed into one large, grazed nature reserve of approximately 540 hectares. To this end, the temporary dikes will be removed, parts of the ground level will be lowered, and gullies will be dug. What is special about the area is the seepage-fed nature. A sophisticated ground level design provides optimal conditions for the development of special grasslands, sedge marshes and swamp forests, despite the major river management task of addressing water drainage. The banks of the Meuse are de-lithified and natural processes are given free rein. A natural recreational path network with special water crossings, such as voordes (fords) make the area adventurous and the dynamics of the water able to be experienced.

NEW BRIDGES AND ROAD CONNECTIONS

New, modest yet iconic bridges are being constructed across the Oude Maasarm. The bridges at Blitterswijck and Wanssum were cast in situ and are striking because of their slender design in the landscape. This made it possible to span the bridges from dike to dike, without long abutments. The abutments, like bastions, form special features of the dike. The bridge over the Molenbeek near Wanssum forms a new meeting place in the village. The bridge that spans from the new ring road over the port is impressive because of the enormous length and height that is bridged in one gesture (with the largest prefab span in Europe).

Major quality gains have been achieved for the design of the Wanssum ring road by implementing a number of optimizations compared to the reference design. For example, the ring road and parallel structures have been unbundled, making the road more inconspicuous in the landscape. A lot of attention is also paid to ecology and the integration with local residents.

RENOVATION OF THE CENTER OF WANSSUM

The construction of the ring road has created opportunities for the redevelopment of the center of Wanssum. The new green-blue carrier (groenblauwe drager) is the Molenbeek, which is being greatly expanded and designed more naturally as a stream delta. The new bridge, a new water square and a walkway that is positioned low over the water make the stream in the heart of Wanssum an experience.

INTEGRATED PROCESS

To make the Ooijen-Wanssum area development possible, all parties have collaborated intensively. All authorities involved contributed financially and managed the project office with one joint budget. This serves many purposes and creates great added value. The environment is intensively involved and there is unprecedented support for a project with such an impact.

All assignments were requested together, making it possible to design the roads, bridges, dikes and nature in a coherent manner. What is special is the involvement of the contractor at an early stage and the continuous, intensive dialogue during the implementation phase. Consistently implemented and SMART-formulated quality frameworks in combination with extensive freedom in the design process for the contractor have created considerable added value to the spatial quality.

Within the contractor combination, a major role was reserved for the landscape architect. Due to the equal position within the 'decision-making team', spatial quality is just as decisive in decision-making as time and money.

The project was immediately put to the test during the high tide in July 2021. The dikes have held up and the water level upstream has been lowered. A confirmation that the project is working as intended.