Conceptual model for reinforced grass on inner dike slopes

A desk study has been carried out in order to develop a conceptual model for the erosion of inner dike slopes with reinforced grass cover. Based on the results the following can be concluded: The presence of a geosynthetic in a grass slope can be taken into account in the EPM method by increasing the critical flow velocity. In particular, a factor Cgeo has been added to the Mirtskhoulava formula. The value of Cgeo in this formula is unknown. Prediction of the failure of a reinforced grass cover did not result in a failure as the erosion is less than the thickness of the layer on top of the geosynthetic. In summary, it is recommended to continue with the results obtained, because the elements for a prediction are available although a correct prediction is not possible yet. In this respect it is recommended to incorporate the failure mechanism of slope material underneath the geosynthetic which probably can be treated in a similar way as geosynthetics in erosion control applications. The Mirtskhoulava formula is valid for the stability of individual elements, but probably there exists a relation with the Edelman-Joustra method for the stability against sliding based on the Mohr-Coulombrelation. It is recommended to attempt to develop this relationship because it might link the stability of individual elements with the stability of soil layers. Furthermore, it is recommended to develop depth-dependant strength parameters in accordance with the observed strength as shown in Figure 4.2: high strength at the surface due to roots, then decreasing to a depth of about 10 cm due to decreasing number of roots, and then increasing again due to clay properties.Civil Engineering and Geoscience

Overtopping resistant dike, Sandy dike

An important element in the ComCoast concept is the overtopable sea defence (often a dike). In this concept the landward (inner) slope of the dike is adjusted in such a way that it can withstand higher overtopping rates. Two new concepts for covering the inner slope, sand cover and perforated mats, are discrebed in this report.Civil Engineering and Geoscience

Social, economic en ecological evaluation of the polder Breebaart

The aim of this evaluation is to gain insight in the social, economic en ecological impacts of an overtopping resistant dike compared to a traditional dike in combination with different forms of land use in the hinterland. At the same time this pilot study should provide support the decision makers of the province of Groningen to find solutions for the spatial development of their coastal zones. The coastal zones will have to deal with a rising sea level and a lowering ground level caused by the exploration of gas.Civil Engineering and Geoscience

Work package 2 socio economic evaluation. Water Assets: Summary

The Dutch coast carries a variety of values. With its diversity in dune areas, its shallows and the delta areas, the coastal area of the Netherlands has a high ecological value, forming a unique biotope for a great variety of plant and animal species, and providing an important foraging area for migrating birds. The economic importance of the Dutch coast is significant as well. The coastal waters provide a large area for the fishing industry and in the wide dunes drinking water has been extracted since the nineteenth century. The Dutch coast is the gateway to the ports of Rotterdam and Amsterdam and it also attracts millions of tourists every year. Furthermore, the coastal area is popular as a residential and as an agricultural area. Finally, the Dutch coast carries many socio-cultural values. For centuries, the coast has played an important role in securing the safety of the hinterland while the image of the coast with its dikes, dunes and water works is characteristic of Dutch cultural history. Against this backdrop, the Directorate-General for Public Works and Water Management (Rijkswaterstaat) has established the umbrella project Water Assets within the organisation for water exploration (WVK). The most important reason this project has been established is that in the past the costs were often a deciding factor in the specification of policies on water, while the assets of water management were often not considered in detail. Participants in the Water Assets project are, among others, the National Institute for Coast and Sea (RIKZ) and the National Institute for Inland Water Management and Wastewater Treatment (RIZA). In the context of salt water management, the RIKZ had two case studies1 carried out by the Institute for Environmental Issues (IVM) and Resource Analysis (RA). The first case study is aimed at an Integrated Coastal Zone policy, in which various options of coastal management of the Hondsbossche Zeewering are evaluated. The second case study investigates the idea of a Veluwe on Sea. In this case study, the effects of the introduction of a natural sea reserve in the Voordelta area are evaluated. The central question in the Water Assets project is how to make the benefits of integrated water management and policy visible. It is all about quantifying the benefits and disadvantage of certain actions, comparing the different dimensions of certain effects and balancing both against each other. It was decided to split the project three ways into ecological (Green issues), economic (Financial issues) and socio-cultural (Opinions) methods of evaluation. Management and legal issues in this study do not form separate aspects; they are tools or they are part of the three abovementioned topics.Civil Engineering and Geoscience