Dikes are inseparable from the Dutch landscape. Their original function of safeguarding the country from floods, like those of 1953, is combined today with landscape integration, recreation and conservation. This makes the task of the Netherlands' 23 water boards, responsible for the maintenance of the hundreds of kilometres of dikes, all the more meaningful. In 2013 the Rivierenland water board - responsible for dikes in the provinces of Gelderland, South Holland, North Brabant and Utrecht - reinforced the Lekdijk to meet safety requirements.
Traditionally dikes are reinforced with local material. In some places the soil is too weak for this, and the deeper sand layers shift under the pressure of the water. In Streefkerk this caused a displacement of the dike in the 80s at high tide, with houses at the foot of the embankment pushed backwards several metres.
To ensure safety at high water levels, BESIX integrated bored piles and diaphragm walls into the lower layers of the dike. If the dike itself were to collapse, the diaphragm wall would still withstand the water.
Given the novelty of this dike strengthening technique, the design was also carefully examined by a team of external experts, bearing in mind that the renovated dike needs to be able to discharge its duty without problems for a hundred years. The BESIX design succeeded with flying colours.
The biggest concern when building the dike reinforcement was the danger of damage to neighbouring homes. The vulnerability of the environment, combined with the gigantic size of the machines to be used, required enormous precision and care from the contractor.
To safeguard the houses as far as possible, BESIX subsidiary Franki Foundations placed vibration-free bored piles and diaphragm walls. The placing also took place in several phases spread over a year, so as to minimize the stress on the soft subsoil. In this way the dike wall was placed without damaging the surrounding homes.
'Collaboration with the water board’s experts was very constructive,' says dikes expert Christophe Bauduin (BESIX). 'The experts posed open and honest questions about the design. Strengthening a dike in this way was new to them and BESIX was recognized as an expert here.'
'The experts posed open and honest questions about the design. Strengthening a dike in this way was new to them and BESIX was recognized as an expert here.
In its own ranks too, BESIX reaped the fruits of this project. 'We started with a single dikes expert in the company', says Bauduin. 'In the course of the project he was able to share his knowledge with colleagues.' BESIX has since specialized further in dike reinforcement with various reinforcement technologies.
'To ensure sufficient public support for the dike reinforcement, we made a priority of our conversations with residents on and around the Lekdijk. We tried as far as possible to fulfil everyone's wishes and desires in the project', says Bram De Fockert, project leader at the Rivierenland water board.
At the request of local residents the strengthening of the dike was combined with the redevelopment of the marina. Space is also provided on the dike for new homes.
Project name
Dike reinforcement Kinderdijk Schoonhovenseveer (KIS)
Category
Shore Protection, Quay Walls
Contract type
Design & Build
Location
Zuid-Holland, The Netherlands
Stakeholder(s)
BESIX Nederland
Building Period
2014 - 2017
Total value
€ 59.4 million