2/1/2024 0 Comments Call of the sea water levelThere was a trend away from the steep structures to a long and much lower gradient, so that the storm-flood wave energy could gradually run out over a longer distance. 4.17 > Through time, the profile of dikes on the North Sea coast of Schleswig-Holstein changed. In contrast to past centuries, when it was sufficient for engineers to design structures that were suitable for the existing conditions, precisely this question arises now in the face of climate change: What conditions will exist in the future? Coastal protection will have to account for diverse probabilities and consider the various scenarios of the IPCC (Intergovernmental Panel on Climate Change) in the planning and construction of protection systems. No one knows, however, how strongly or rapidly climate change and sea-level rise will progress. They will have to be upgraded in many places. If sea level should rise by one metre by the end of the century, and even by several metres thereafter, today’s tried and tested coastal protection systems will no longer be adequate. Climate change as a new challenge to coastal protection These were repeatedly damaged during heavy storm surges. – Stackdeiche) to protect the region around Amsterdam, as shown in this illustration of the Zuiderzee in 1702. 4.16 > For several centuries the people in the Netherlands relied on “stack dikes” (Ger. But with climate change and its accompanying rise of sea level, coastal inhabitants are facing new challenges. These can withstand even high storm-flood surges. They have low slope ratios of at most 1: 6, and are around 100 metres wide at the base. Today, the large sea dikes in northwest Europe have heights of around nine metres. The trend thus developed toward the construction of increasingly higher dikes with even flatter slopes. This would wash out material on the back side until the dam collapsed. Although the gradually sloping profile proved to be effective, water would still spill over the top during high-surging floods. ![]() In the mid-eighteenth century, these dikes often had a height of around five metres. ![]() But because these kinds of dikes were heavily battered by the surf, the vertical form was soon abandoned in favour of an elongated slope and flatter profile, where the wave energy of the storm floods could be absorbed more gradually. In the early sixteenth century the dikes in many places consisted of two-metre-high walls of timbers, backed and stabilized by an earthen wall. Through time, the design of dikes changed. As early as the twelveth century, ring dikes were already being built in northwest Europe for the protection of individual settlements. In some countries buildings were built on stilts, so that water could flow freely underneath, while in other places houses were built on man-made earthen hills. Although fairly helpless against such events at first, over time they learned to build protective structures against storm floods. Coastal populations have always been threatened by flooding.
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