Too much water pressure
Water has the natural tendency to flow to the lowest possible point. As a result, the high water in dikes that serve as a dam flows from one side to the lower water on the other side. This results in a diagonal flow of water through the dike, as shown on the drawing below.
The current dikes are often constructed in such a way that, at a normal water level, there is little to no pressure on the dike walls. The water flow runs underneath the dike wall.
However, if the water level rises, the water flow increases as well. As a result, there is pressure on the dike walls. Long-term pressure can make the dike unstable.
Use of the HDDW
By placing an HDDW in the dike, superfluous water can be extracted in the event of a rise in the water level. This brings the water flow back to the desired level, as a result of which the pressure on the dike walls disappears.
There are a large number of peat dikes in the Netherlands. The humidity level of the peat determines the sturdiness and stability of such a dike. If a peat dike is too wet, it can collapse under its own weight. In a peat dike that is too dry, there is a risk of erosion and soil compaction. If the peat dries out completely, it even becomes water resistant and does not absorb water anymore at all.
The climate changes mean that the humidity level leaves a lot to be desired. This decreases the stability of the peat dikes.
Use of the HDDW
By placing an HDDW in a peat dike, water can be extracted or infiltrated. This makes it possible to stabilise the humidity level.