We try to stop the water in the Rhine getting too high or too low. But we don’t always succeed.
We try to retain water so that there is enough during a dry spell. There are various ways of doing this, such as setting aside special areas to hold water. Basins, called retention basins, are built for this purpose. When water levels in the river are high, water can be stored here. As a result, the river does not have to carry as much water at that time. This means that we can control the water better and release it into the Rhine when we can and when we need to.
We also try to make sure that high water does not cause too much damage. This can be done by protecting areas and blocking the water.
Dikes run alongside the river, protecting the area behind them against water from the river. There are various types and sizes of dikes. Grass often grows on them, and sometimes there is also a path running along the top.
A retaining wall is a straight wall that blocks the river water. They are usually made of concrete, and take up less space than a dike. There are also walls which are used only at high water, especially in towns and villages.
Dams also block river water by keeping it behind the dam wall. This creates a type of lake called a reservoir.
These solutions block the water up to a certain height. But it may rise higher, and will then flood over the dike.
This often causes more damage, for instance because people who live behind a dike feel safe and don’t usually think about a flood!
And blocking water only works at the place where it is blocked. If water is blocked by a retaining wall at a particular point, the high water will flow more quickly to the next place. This means that the Rhine can flood in places where there is no retaining wall or dike!
Many old dikes are not as strong as they used to be. They need reinforcement, but maintaining and reinforcing dikes is very expensive.