COUNTRY IN FOCUS
The Netherlands – Living with floods



 

Climate change is now a fact and its impacts threaten water supply in all parts of the planet. While some countries (e.g. Morocco) are expected to suffer severe water scarcity, others will observe an increase in rainfall and flooding events. The Netherlands, one of the most densely populated countries of the world, is particularly vulnerable to floods, both from the sea and from intense rainfall in the upstream catchment areas of the Rhine-Meuse-Scheldt river systems.
 
This low-lying country has been fighting back water for centuries, and has become a global reference for water management in terms of ensuring protection from flooding. A sophisticated system of more than 3,500 km of primary flood defences has been built, from coastal dikes and sand dunes to major hydraulic structures, accompanied by more than 14,000 km of polders and channels to protect its land area below sea level.
 
However, for the past decade, the Netherlands has been embracing a different approach to flood risk management, switching from these hard-engineered defences to more flexible management. Up next, we are going to review the new Dutch approach to flooding and the different organisations involved in it.

 

A. What is the new Dutch approach to flooding? 

 

Over time, the Dutch have been fighting against water and building higher and higher defence structures, but realized after flooding in the 1990’s that infrastructure alone was no longer an adequate solution. Consequently, the approach changed from fighting the water to living with it. This new solution consisted in searching the optimum harmony between water and space, and the idea resided in re-imagining the current landscape to make ‘Room for the River’.
 
At the end of 2005, the Dutch government gave green light for the development of a national adaptation strategy based on this approach and invested significant funds into it (in total, €2.3 billion in more than 30 crucial river locations).
 
The new Dutch approach for flood protection and mitigation consists in different measures, all with the main idea of returning the natural floodplains to the rivers and allowing superior volumes of water to flow safely through the country. This is key to face a future where storms are predicted to cause more rapid and extreme rainfalls. The projects along the Dutch waterways include various measures:

 




 

 

Riverbed excavation – riverbeds can be dredged to deepen their beds, increase their capacity and giving more room for water to flow in the channel.

 

 

 



 

 

 


Dike relocation – dikes can be moved back from the river to increase the width of the floodplains and give more room for the river.





Dike reinforcement – dikes can also been strengthened in those areas where dike relocation is not possible (e.g. in higher-density areas or locations with iconic buildings).






Floodplain lowering – floodplains can be excavated to remove the silt deposited in them during seasonal floods and create more room for the river when the water level rises.
 

 


 



Groynes lowering – groynes (i.e. structures that ensure that the river does not alter its course or lose depth) can be lowered to avoid slowing down the flow of the water during flood events.

 

 


 

 



Depoldering – polders (i.e. sub-river tracts of land surrounded by dikes) can be relocated further away from the river to allow water from the river to flood this area at times with high water.

 

 


 

 




Obstacles removal – barriers (e.g. bridges with large abutments) can be removed or modified to increase the flow rate of the water in the river.





High-water channels – secondary channels can be created between two dikes to divert the excess water from the main river to separate routes at times of high water.






Water storage – lakes can be used as a temporary water storage area to hold back fast-flowing water.





The implementation of this strategy is ambitious: it started in 2007 and is scheduled for completion in this year, 2015. Most of the project are already finished or at a very advanced state, such as:
 
Removal of obstacle Machinistenschool Elst – the project consists in removing an old brick factory and its excavation site near the Rhine River at Elst to eliminate the bottleneck effect.

Dike relocation Lent – the project consists in relocating the dike along the Waal River at Lent 350 meters inland to create space for a new channel in the river’s floodplain.

Groynes reduction Waalbochten – the project consists in reducing a total of 450 groynes in the Waal River at Gorinchem and Nijmegen, ranging from 0.5 to 1.5 meters below.

High-water channel Veesen-Wapenveld – the project consists in constructing two 8-kilometre long channel dikes through agricultural land for the IJssel River at Veesen-Wapenveld to create an additional 713 hectares area for its floodplains.

Water storage Volkerak-Zoommeer – the project consists in transforming the Volderak into a suitable water storage unit in case of closing of the barriers in the New Waterway and the Hartelkanaal simultaneously as high river discharge.






This new Dutch strategy is being considered by many experts the most impressive flood management project since the completion of the notorious Delta Works in 1997. It shows, once again, that the Netherlands is constantly looking to the future and developing innovative strategies to secure it.

 

B. What are the organisations involved?


The “Room for the River” strategy is a collective process and a clear example of cooperation, with several partners of government bodies as well as private companies, engineering firms and research universities.
 
Government and public administrative bodies are involved at various levels: national (3 ministries), provincial (5 provinces), regional (5 water boards) and municipal (between 30 and 40 municipalities). In addition, a special body, known as the “Room for the River Directorate”, was created to coordinate the various stakeholders, monitor consistency between the different measures and promote exchange of expertise across the numerous projects.
 
The private sector also plays an important role in the strategy by helping develop the solutions and implementing the projects (e.g. dredging and relocation of dikes). Besides, universities (e.g. Radboud University and TU Delft) are involved and carry out important research and monitoring of the projects to study the interventions and their long-term effects.





By Fatine Ezbakhe
Civil Engineer specialized in Water

 

Published on 2015-07-12 12:48:02

 
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