Nature-based bank design for the east side of Buiteneiland, IJburg, Amsterdam

The Engineering Office of the municipality of Amsterdam is developing six man-made islands in the IJmeer. One of the last islands will be Buiteneiland. The location and orientation of Buiteneiland is been agreed when IJburg was designed. The area of interest of this study is the land-water transition at the east side of the island. The IJmeer's morphology is storm driven and the prevailing waves in this low energy environment, have limited reshaping capacity. Therefore, the land-water transition needs to consist of erosion protection. At the same time, the east side of the island will contribute to the 'Boog om de Oost', a provincial arch that connects the province of Utrecht with North-Holland via outer dike reed fields. For the Engineering Office, this was the reason to ask for an approach to deal with a hybrid solution, that combines a nature-based foreshore with an erosion protection for the east side of Buiteneiland. Figure 2.a and Figure 2.b shows two possible land-water transitions, a traditional dike and a nature-based hybrid solution. This composed the research question for this study: What is a safe and nature-based hybrid solution for the case study: east side of Buiteneiland, IJburg?. Design of alternatives for the nature-based hybrid solutions is done according to the method of de Vries et al. [2016]. This Building with Nature method is developed for nature-based type of projects. The Building with Nature method contains the five clear steps that have been worked through iteratively. The most suited nature-based hybrid solution for the east side of Buiteneiland seemed the Hard Arch variant (see: Figure 3) When implementing a nature-based hybrid solution, components and concepts of this solution can be extracted and implemented individually. New build or restored land-water transitions at least consists of a vegetated foreshore. The dike of the Basic Concept (is a dike without a foreshore or vegetation), covered by grass requires a crest height of 2.27 m. The hybrid solution as the Hard Arch variant, the grass covered dike only requires a crest height of 1.61 m, while offering the same protection level. The costs estimate for the found hybrid solution is a factor 5.5 higher than for the Basic Concept. However, the hybrid solution does have a lot of extra benefits next to safety. A lot of natural capital is added to the IJmeer and for the citizens of Amsterdam, in terms of vegetation above and below the water surface. Furthermore, social value and inspirational values are added to the Markermeer, where other new islands or shore restorations can be inspired by this nature-based hybrid solution. Thus, this nature-based hybrid solution is more expansive, but a solution like this maximizes the benefits for local communities, nature and economy. Overall, the use of a nature-based hybrid solution is a way of combining the development of new nature and ecosystems with coastal protection providing safety and prosperity for local community.Civil Engineering | Hydraulic Engineerin