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 Building with Nature Guideline > Projects > Rich Revetment for coastal protection - Eastern Scheldt, NL

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Rich Revetment for coastal protection - Eastern Scheldt, NL

Location: Zeelandbrug close to Zierikzee, The Netherlands,

Date: 2008 - 2013
Involved parties
: Deltares, WINN, Ministry of Infrastructure and the Environment (Rijkswaterstaat), Project Agency Zeeweringen, Waterschap Scheldestromen
Technology Readiness Level
: 7 (successful pilot case)

Environment: Estuaries

Keywords: Habitat enrichment, Ecology, Fish/Shellfish

Building with Nature designTraditional design


The additional cost of introducing water retaining pools, additional types of limestone and additional sorting in the berm is marginal in the total cost of dike upgrade. In the eco-engineering design, this berm is engineered to produce variable profiles (in slope, material and sorting) in perpendicular and alongshore directions. Monitoring has shown that water retaining pools with additional sorting of limestone increases the biodiversity dramatically in the intertidal zone. The pools function as sheltering habitat for many shrimp and smaller fish species. Algae productivity is increased in the pools.


In a standard design, the required safety level is maintained by parts of dike construction situated above the average high water mark. Lower zones, such as the intertidal berm are not crucial to safety and allow degrees of freedom in the design process. In the traditional design this berm is engineered to produce monotonous profiles (in slope, material and sorting) in both perpendicular and alongshore directions.

 

 

Abstract

Structural works like dikes are mostly designed purely from a safety point of view. Optimization for enhancing ecological functions is not often considered in the design phase. In Natura 2000 area Oosterschelde, the dike upgrades should result in zero net change of nature value of each dike section compared to the original situation. The objective of ecobasins is to contribute to the ecological value of a dike and create a net positive contribution to natural value of the dike section. Construction of Ecobasins along dikes will improve biodiversity and bio-productivityOther objectives are to create educational opportunities and to raise awareness of designers, constructors, students and visitors. 

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Initiation

An analysis of the planned works and the ambient ecosystem is needed in the first step of the design process. On the basis of a set of conceptual designs, a feasible technical design has been realized and budgeted. A scan has been performed with the Project Agency to identify dike transects suitable for ecobasins.

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Planning and design

In view of the influence of the envisaged ecobasins on the functioning of the flood defence system and the local environment, calling in physical and biological expertise on the local environment was important in order to have an effective design.

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Construction

The first pilot of the rich revetment ecobasin was delivered in 2008 on the dike section between Wemeldinge and Yerseke. The second set of ecobasins was delivered in 2010, on the dike section between Wemeldinge and Kattendijke.

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Operation and Maintenance

After construction the ecobasins have been monitored for a period of three years.

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Cost and benefits

For an overview of the costs and benefits of ecobasins, the following indicators should be quantified:

  • Costs: Investment costs (stones, asphalt etc.); Maintenance costs (inspection for leakage, repair costs); Project management costs (permits, process, contracts etc.).
  • Benefits: Increased biodiversity; Education/raising awareness; Creating opportunities for nature mitigation and compensation.

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Lessons Learned

The following lessons were learned from this project:

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 References

 

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