A design of the Delta21 sea defence using the adaptive pathway approach

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Besides global warming, climate change is expected to result in (among others) an increased number of extreme precipitation events and a rising sea level. In the future, this can be the cause for an increased number of high river discharge events in combination with high water levels on the North Sea, which goes hand in hand with an increased risk of flooding in the Netherlands. However the rate of change in the future is hard to predict and therefore very uncertain.

One of the projects which seeks to be a (part of the) solution in climate change and flood prevention for the Netherlands is the Delta21 project. By combining a sea defence, energy storage lake, pumping station, overflow structure and storm surge barrier, the Delta21 project increases safety against flooding while providing a sustainable way for temporary energy storage.

In this thesis a design was created for the sea defence of the Delta21 project, during the design process the uncertainty of climate change was taken into account by the use of the adaptive pathway approach.

Three conceptual design variants are created which provide water safety until one meter of sea level rise occurs. When the sea level increases even more, the designs should be altered to the new circumstances. Various adaptation options are put together in the form of adaptive pathways which provide adaptation methods for up to five meters of sea level rise. The pathway schemes are evaluated on 4 evaluation criteria to select the preferred adaptation method for each of the three base design variants.

Using an analysis over the total lifetime of the sea defence measured in meters of sea level rise, the preferred conceptual design for the Delta21 sea defence is selected.

It turns out that the adaptive pathway approach can be used to integrate the uncertainty of climate change into the selection of a conceptual design variant for a sea defence. The use of the approach provides a methodological way of evaluating design options under uncertain circumstances.