Relocation of Dykes (Dikes)

Content Table

• Relocation of Dykes (Dikes)
  • General description
  • Pro and Co
  • Literature and Links
  • Case studies

General description

A new dike is build further away from the river bed after which the old dike is removed. This helps to increase the flood plain of the river. Although this can be an essential measure to remove bottlenecks in the river system, the measure is most often very unpopular. The reason is that land which has been cultivated for many years is transformed into low value river plain land. The unatractiveness of the measure increases when old buildings or gardens have to be demolished to realise the measure. An illustration can be found here.

Pro and Co

Pro:

• relocating dykes can be an essential measure to remove bottlenecks in the river system
• more room to the river
• improvement of  the land water connection (regarding the WFD (EU).

Co:

• The additional floodplain area often has been cultivated for many years and now is transformed into low value river plain land. Sometimes existing buildings or gardens have to be demolished to realise the measure. Adaption measures for farm land are often limited by several factors:
• higher prices of ecological feed purchase compared with the self production
• impossibility of purchase or rent of additional areas (tensed land market)
• intensification of land use is prevented ecological farming, nature protection guidelines and location conditions
•   (e.g. higher groundwater level)

Possible adaptation strategies regarding necessary changes in land use :

• reducing of livestock
• changing production methods (shorter animal fattening)
• staff reduction

Cost benefit aspects of dike relocation can be found exemplary for a case study (river Elbe). A cost benefit analysis has to be done separatly for each individual project. A possible procedure and the coast range for alternative solutions you will find here (link).

Literature and Links

• Room for the river- types of measures
• WFD Water Framework Directive (2006): Directive 2006/60/EC of the European Parliament and of the Council establishing a framework for the community action in the field of water policy
• DWA Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall (2005) Dezentrale Maßnahmen zur Hochwasserminderung,
• factsheet on the types of measures that are implemented for Room for the River
• project report of the room of the river project
• dike relocation Rosslauer Oberluch
• Economic valuation of dike relocation at the German Elbe

Case studies

Dyke relocation at Elbe tributaries, Germany

Within the SAWA project four variants of dyke relocations for the river Sude and Krainke (tributaries of lower Elbe) are discussed  in order to create more flood plain area and to safe the dyked landscape. an impact analysis comes to the conclusion that in case of forced dyke relocation and land losses a substitution of farmland is the most important point for a forward-looking development of the farm. Especially extensive and ecological working farms are due to their restricted management affected by measures like dyke relocation. full text

Room for the River (Netherland)

In the Netherlands, Room for the River is a well known term that relates to a large project with the goal to increase the flood plain of the main rivers in the Netherlands.
'The area available for the rivers has decreased continually during the past centuries. The rivers are confined between high dikes and more people live behind the dikes. At the same time the land behind the dikes has sunk due to soil subsidence. In addition, since it now rains harder and more frequently the rivers need to discharge more water to the sea. A flood in the current conditions would put the safety of 4 million people at risk.

Breaking the trend

The continued strengthening of the dikes is an option that would reduce the risk of flooding. However, any flood at nevertheless occurred would result in even greater damage since more water would flood to the sunken land behind the dikes. A trend has to be broken if the Netherlands is to be a safe, comfortable and pleasant country for its inhabitants. The answer is given by the 'Room for the River' plan. The Dutch government is taking action to improve safety and to protect the land and people living behind the dikes from floods. The river will be given more room at the total of 39 locations covered by the 'Room for the River' Programme. The main objectives of this programme are to complete the flood protection measures by 2015 and to improve the overall environmental quality in the river region.

Room for the River

The residents in the river region were confronted anxious times in 1993 and 1995. The water levels were extremely high and the dikes just managed to hold. A quarter of a million people had to be evacuated. Extremely high river discharges will occur more frequently in the future and for this reason it was decided to ensure that the rivers could discharge the forecast greater volumes of water without flooding. The Government approved the Room for the River Plan (Planologische Kernbeslissing Ruimte voor de Rivier) in 2007.

This Plan has three objectives:

• by 2015 the branches of the Rhine will cope with a discharge capacity of 16,000 cubic metres of water per second without flooding;
• the measures implemented to increase safety will also improve the overall environmental quality of the river region;
• the extra room the rivers will need in the coming decades to cope with higher discharges due to the forecast climate changes, will remain permanently available.

A range of measures is being implemented to create more room for the river and reduce high water levels, such as lowering the floodplains, relocating dikes further inland, lowering groynes in the rivers and deepening the summer beds. Strengthening dikes is a measure that will be implemented only when the alternatives are too expensive or inadequate.' room for the river