Photo: Cyril Liebrand/Eureco.
With a third of the land below sea level, flood protection is the highest national priority in the Netherlands. Over the next thirty years, 1,300 km of dikes will be reinforced within the Flood Protection Programme. A traditional reinforcement usually means constructing higher and wider dikes. This is a extensive, time-consuming and costly undertaking. In addition, the dik reinforcement often leads to resistance from the surrounding area because of the impact on the living environment and the classical landscape. There is a need for knowledge about effective and safe, but less drastic reinforcement measures and a sustainable dikemanagement.
Biodiversity
The Future Dikes project investigates how we can strengthen Dutch dikes with a species-rich grass cover. Previous research has shown that a biodiverse vegetation is highly resistant to the erosive effect of water overflow. The variation of grasses and forbs results in a diverse and deep root mat that holds the soil layers together. Both above and below ground, a species-rich vegetation therefore offers an excellent first layer of protection.
In addition, species-rich grass cover can contribute to the restoration of biodiversity, offering opportunities for a variety of plant and insect species. Moreover, dikes meander through the Dutch landscape and form a corridor between different ecosystems. A species-rich dike cover is in line with the Green Deal Infranatuur that various water boards have signed to guarantee the biodiversity and environmentally friendly management of the dikes.
Research is needed to enable a large-scale application of species-rich grass cover in the Netherlands. More knowledge is needed about erosion resistance, the design, quality assessment and management of species-rich dikes.
Results
The following results are expected within the Future Dikes project:
Report theme 0: Current knowledge report (end of 2022)
- What are the relationships between vegetation composition, rooting, soil (as a result of dike improvements), drought and management of current dikes?
- What are the relationships between erosion parameters, vegetation and rooting as far as known from series of large-scale tests and tensile strength measurements that have been carried out before?
- This research is being carried out in close collaboration by Wageningen Environmental Research, EurecoAdvies, Lumbricus, Infram and Deltares.
Report theme 1: Dike vegetation parameters / civil engineering quality (end of 2023)
- Public database of revetment characteristics in relation to erosion resistance
- Version 2.0 of the Grass Cover Handbook (www.handreikinggrasbekleding.nl) (in Dutch)
- Protocols: overview of practically manageable parameters that provide reliable information about the erosion resistance of dike revetments
- Report and protocols: overview of which dikes are suitable for development into species-rich dikes
- Functional system of dike types in the Netherlands
- The research within Theme 1 is carried out in close collaboration by Radboud University Nijmegen, Wageningen Environmental Research, EurecoAdvies, Infram-Hydren and Lumbricus.
Report theme 2: Species-rich grass cover (2023/2024-2027)
- Proposals for seed mixes with high potential in terms of rapid establishment, turf closure, soil type, and drought resistance
- The research within Theme 2 is carried out in close collaboration by Radboud University Nijmegen, Wageningen Environmental Research, EurecoAdvies and Lumbricus.
Report theme 3: Strength of grass coverings (end of 2023)
- Report with the results of the large-scale erosion test and specifically the Uc values, the associated probability distribution and quality classes of species-rich grass cover;
- Analysis of the overtopping and tensile tests whether the Uc fall within the existing classes, or whether additional classes are required;
- Analysis of the applicability of the grass pull device for determining the strength of species-rich vegetation.
- The research within Theme 3 is carried out in close collaboration by the University of Twente (UT), Infram-Hydren, Radboud University Nijmegen, Wageningen Environmental Research, EurecoAdvies, Lumbricus and Deltares.
