Adaptive dikes

MOTIVE

The adaptive dike requires a new approach and forms of social interaction. Consequently, the role of the water board, which will manage the spatial and functional connection between foreland and hinterland, also changes. Dike managers and the authorities are making agreements with third parties, as a result of which the contractor will be responsible for reinforcing and maintaining the dike for a considerable periode of time. New strategies and techniques are implemented and optimalised. Low-tech solutions involving sand distribution, sand irrigation and (autonomous) robotised building will be applied to reinforce the dike.
But these solutions also contribute to the quality of the environment and local support for this continuing execution phase, due to opportunities for small scale and social initiatives.

GUIDELINES

1.    DEVELOPMENT INSTEAD OF EXPROPRIATION

Stop the expropration of land for dike improvements and maintenance. Residents and companies can contribute to this in exchange for development space. Example: extra GFA (Gross Floor Area) on an increased verge.

2.    RESPOND TO THE RHYTHM OF ADJACENT LAND USE

Connect the dike and landscape by expanding land use to the verge of the dike. Example: orchard on a slope.

3.     USE LOCAL SEDIMENT

Create extraction sites in appropriate channels in floodplains. Explore the possibilities for the use of sediment in the area on the short and the long term.

4.    FOCUS ON CYCLICAL LIVING

Do not build for eternity but build temporary houses that can be moved, upgraded and adapted. Ensure that buildings are able to expand.

5.    ENSURE MULTIFUNCTIONAL PROGRAMMING OF THE DIKE ZONE

The dike should respond to the surrounding area and vice versa. Example: create gardens in the area outside the dike as a result of which the area inside the dike, the dike and the floodplain are turned into areas where people can live, work and recreate.

6.    INCREASE LOCAL SUPPORT

Stimulate light building and maintenance techniques combined with a contribution to the maintenance of buildings.

CYCLICAL HOUSING

Cyclical housing has a temporary character: houses should make way for dike reinforcement after a period of 15 to 30 years. This can be realised according to the cradle to cradle principle. A different implementation of cyclical housing is formed by the approach that buildings should be adaptable, meaning houses should be moved and upgraded. In this way it will be easy to build houses on the dike and the dike can be programmed multifunctionally.

THE DIKE AS A WORKING LANDSCAPE

Near IJzendoorn the river dynamics, sedimentary deposition and land use of the hinterland are deployed for the new dike management method. By transferring the management of the entire dike zone, new types of use are created. Sediment depots, nature development, recreation, agriculture and other activities are part of a single strategy. By dredging, storing and ripening various types of sediments for dike reinforcement, the landscape will change in a 5 – 15 year cycle. The rapidly changing storage of sediment has a 5 year cycle and offers space for nature, temporary recreation and orchards. The locations close to the main residential area will change less frequent. On these locations sediment will be stored for a longer 15 year period. This area could be used as a golf course or recreational area.

FROM DIKE TO DIKE ZONE

As a continuing process, the adaptive dike and the area inside and outside the dike will provide for the required flood protection. In order to achieve this, a number of site-specific solutions have been explored between Tiel and Oosterhout. These solutions are:

• a  multiple dike zone
• landward reinforcement / increased tolerance with regard to incidental flooding
• reinforcement by means of a smart sediment strategy and creation of new levees
• dike reinforcement on a ‘second line’, behind the existing dike
• implementation of reinforcement over a longer period of time
• development of a dike zone with a temporary soil depot