How to create a city island

Located in the eastern part of the Netherlands lies the oldest city of the Netherlands, Nijmegen. In a bend of the river Waal a lot is happening: a city island is under construction, new bridges are being built and an ancillary channel will be created. From all over the world representatives from governments and companies are visiting this city to learn more about this unique and price-winning Room for the Waal-project.

The activities in Nijmegen, or actually Nijmegen-North, are part of the nationwide Room for the River-project, organised and coordinated by Rijkswaterstaat. In this programme, which was approved by the Dutch government in 2007, much needed action is taken to create space for the rivers, which are likely to flood now or in the near future because of the increasing melt water.

The programme has three objectives: by 2015 the branches of the Rhine should be able to handle a discharge capacity of 16,000 cubic metres of water per second without flooding; the overall environmental performance of the river region should be improved by the taken measures and lastly, the possibility to create additional space for the rivers in the coming decades if needed will remain permanently available.

Fundamental changes

In Nijmegen the municipality took matters into her own hands and decided that, in contrast to other Room for the River-projects, they would be the executers. Karsten Schipperheijn, area manager at the municipality of Nijmegen, explains why: ”The municipality is closer to the environment and the inhabitants of the area, in which the changes are made. Because of the fundamental character of the project and because of the interfaces with other major municipal projects the decision was made that the municipality would take over the direction from Rijkswaterstaat.”

A public tender was set up to give contractors a change to apply for the job, onto which the municipality received eight entries. Schipperheijn: ”There were two main selection criteria: expected costs, and the quality of the project. Consortium i-Lent, consisting of building company Dura Vermeer and earth moving company Ploegam, scored the most points.”

The project consists of seven subprojects: the construction of city island Veur-Lent, an ancillary channel and accompanied floodplains, the Promenadebridge, the Citadelbridge and the extended Waalbridge, a new quay and the area on the embankment. Rody Kusters, project leader landscapes at i-Lent says: ”There are still a lot of designs to be completed, although we are in the final stage. Furthermore, we have started the first proceedings in the area and our planning is to finish August 2016 although our goal is to finish on 31 December 2015.”

creating a ancillary channel

In order to create the city island a 150 to 200 metres wide ancillary channel has to be dredged. Kusters: “The dredging has started on the west side of the project and is now one third on its way. First we started excavating the upper layer of clay with traditional hydraulic excavators; the clay is loaded onto inland shipping vessels of Dutch Van Oord Handel & Transport to be reused in our project or sold. Due to the size of the project we use ships, which are better able to handle the large amount of clay, and in order to reduce the traffic obstruction. Then, we use a sand dredger from the Dutch company K3 Delta to remove a total of three million cubic metres of sand and gravel, of which 300,000 cubic metres has already been reused at the eastern side of the project.”

At this moment a dike called Bemmelsedike lies at the east side of the project, which will be excavated in May 2014 and turned into a threshold between the ancillary channel and the Waal. A couple of openings will be made in the dike, creating a constant flow of water from the Waal into the ancillary channel. During high water the threshold will flood, creating more space for the Waal and making full use of the capacities of the ancillary channel.

Fighting seepage water

On the mainland a new hard quay is under construction that will consist of an aboveground L-shaped quay and an underground seepage barrier made of cement-bentonite up to 20 metres deep. Schipperheijn: ”For the residents on the mainland it was very important to have something that would protect them against seepage water, therefore an underground barrier was designed. This subproject has already been finished.”

Besides this quay, a new green dike consisting of a sand and clay core will be constructed, and will join the underground barrier. After the green dike is completed in May 2014 the Bemmelsedike can be excavated, as stated above. The quay and the dike will protect the inhabited mainland area behind it against high water if necessary.

Three bridges

Before the sand dredger can continue its way eastwards to dig the ancillary channel, on the other side of the hard quay and the green dike, the extended Waalbridge, which will connect Nijmegen with Nijmegen-North, needs to be constructed. Currently the bridge rests on mainland, in the near future this will be the ancillary channel, and therefore new pillars need to be constructed. This extended Waalbridge will consist of three parts: the extended part of the bridge, the Parmasingelbridge which will connect Nijmegen-North and the extended Waalbridgde, and the Bastion, the abutment pier on the city island. Kusters: “At this moment the three pillars are constructed, in April we will start the construction of the roadway and we expect to be finished with the extension in May 2015.” Schipperheijn: ”In the construction of this bridge you can also clearly see the attention we pay to the environment: an ecologist advised us to design a resting place for bats under the bridge. Furthermore, we also created incubators for screech owls and swamps for the great crested newt.”

The second bridge is the Promenadebridge, which was designed to maintain the traffic between the island and the mainland and will become the main access point to the city island. Kusters: ”For this bridge four cofferdams and two abutment piers will be constructed. We hope to finish this bridge at the same time as the extended Waalbridge in May 2015.”

The last bridge that will be constructed is the Citadelbridge, which will connect the western part of the island with the floodplains on the upper side in Nijmegen-North. The five metres wide bridge is only accessible for pedestrians and cyclists. Kusters: ”The work will be carried out from April to October, when the probability of high water is the lowest, and we will be finished in October 2015. We already started working on the Citadelbridge, because of better weather than expected. This bridge will have six cofferdams, two abutment piers and a lot of the bridge will be prefabricated. We will leave one part of the bridge open during the project, in order to enable the shipping industry to continue the sand discharge.”

Involving the environment

About 50 houses or companies had to move out as they were living on the land were the ancillary channel is going to be created. The residents that are living in the area that is going to be island Veur-Lent, will not longer live on mainland, but on an island that is surrounded by water. As their environment is going to change fundamentally contact with the residents is crucial, according to Schipperheijn: ”There was and still is a lot of contact, we have set up a soundboard with the residents association of Nijmegen-North, information evenings take place every several weeks and there is the possibility for one-on-one contact twice a week.” Kusters adds: “Furthermore, i-Lent has developed a website with a lot of information, an application for smartphones and tablets, we sent out a newsletter, there is a weekly walk-in-hour on Friday, and we organise excursions in the area. We also use the facilities of the neighbourhood, like the local café, and the bike shop delivered 20 new bikes for excursions. This way, we are not only an inconvenience, but we also enable them to profit from our presence. We think 98 per cent of the people are enthusiastic about and concerned in the project.”

Matching the city

Kusters: “There are not many city islands in the world, let alone city islands that are being created, and therefore we have a lot of international attention. Delegates from, among others, China, Mexico, the United States of America and Germany have visited the project in order to learn what we are doing and how. Next to all this attention, the project received the prestigious New York Waterfront Center Award in 2011, thanks to the innovative combination between flood management and area development among other things.”

Schipperheijn continues: “The project does not only consist of these subprojects that need to be constructed separately, but there is a lot of attention for the qualitative consistency between them: the Citadelbridge for example, winds over the ancillary channel, making it naturally blend in with the floodplains. And when finished a lot of recreational activities are planned on the island by the municipality of Nijmegen. There will be an area for festivals, spots for food service industries, walking and cycling routes and on the ancillary channel there are water sports possibilities. This way the area will become an addition to and match with the city of Nijmegen.”

Anne Kregting