The existing dikes along the river IJssel are crucial in protecting the hinterland between the cities of Deventer and Zwolle from possible floods. Despite the dike-reinforcement program ‘Ruimte voor de Rivier’, the dikes will not provide enough protection from the water on the long term. Especially the narrow and relatively low fundament of the dike is currently causing problems like instability and ‘piping’. The challenges regarding water safety and flood protection, combined with the multifunctional character of the dike in urbanized areas emphasize the need for a holistic vision on the safety and functionality of the IJssel-embankment both on the short and long term
The landscape of the river IJssel is of a very diverse and scenic nature. It offers a variety of both enclosed and open landscapes, and monumental river villages. The village of Olst is a representative example of a typical river IJssel historical settlement. Here the dike along the river does not only represent a technical solution for water safety but is also used as an infrastructural line surrounded by houses. This makes that the dike is ‘fixed’ by the program which is attached to it. Adjustments to the dike cannot be done without intervening in this program or by breaking down these monumental houses and buildings.
Based on the principle Building with Nature the natural sedimentation processes in the river are being used to develop a water-safe landscape zone situated along the existing dike. First, the top layer of the soil of the river banks are being excavated. By this, the water transport capacity of the river increases. Next, the yearly cycle of sediment suppletion by the river is used to form new river dunes. In winter, the sand is being deposited during high water levels. When the water level drops again to the average summer level, the sand is being dried out naturally and transported landwards by the wind.
This cycle repeats itself on a yearly base. By using this natural process a stable and robust system of river dunes can evolve protecting the hinterland and monumental villages from flooding. This new river dune landscape offers opportunities for nature development and new recreational use like hiking and cycling trails and summer sleeping cabins.
By integrally combining the objectives of water safety with nature development and recreational demands, a landscape is being developed showing the possibilities of the natural river system. The existing dike is not being changed, but a responsive river embankment is being developed according to natural processes. It is not a fixed plan but rather a proposal of using natural succession as a starting point for a safe and vibrant environment.
Type: research, landscape, leisure
Commissioner: Dutch Association of Architects, Groot-Salland Water Authority
Size: 33 km river embankment
Status: research project
In collaboration with IAA Stedenbouw en landschap, Grontmij