Inundation of unprotected areas due to flexible water level management around the IJsselmeer and Markermeer

By: Lisa Goossens

Since 2019 Rijkswaterstaat is applying a flexible water level management in the IJsselmeer and Markermeer. It offers the manager the opportunity to adjust for (extreme) weather conditions and the demand for drinking water. By maintaining an higher water level at the end of winter, an extra water buffer can be created of 390 million m3. During a dry summer the northern part of the Netherlands can be provided with fresh water from the buffer which can be used for agriculture, industry, drinking water and recreation. In addition, the water level will drop and rise in a more natural way with an higher water level in early spring and reaching lower water levels at the end of the summer. This can be seen in figure 1 in which the green line represents the flexible water level management.

However, at the end of winter/early spring, the chance of flooding of unprotected areas increases due to the higher water levels in the IJsselmeer and Markermeer as a consequence of the flexible water level management. What kind of areas will become inundated and what is the function of these areas? How much will they be flooded? These kind of questions will be answered during my research and I want to define the consequences of the flexible water level management regarding flood risk of unprotected areas.

Figure 1: Current and former water levels in the IJsselmeer.