With an increasing amount of surface water on the rivers, there is a great need to investigate how we can transport that surface water to the sea in a way that is safe for humans and animals.

This can be done in a number of ways:

  • Weirs
  • Removing obstacles in the river
  • Extending floodplains
  • Constructing side channels

Weir Driel

The north of the Netherlands has to rely on the IJsselmeer for fresh water. In order to provide for this, the weir in Driel was built. The function of the Driel weir was also to increase the navigability of the IJssel with little discharge from the surface. To this end, water will be extracted from the Lower Rhine and the river Lek, and the water from the IJssel head will be pushed up as a result, causing more water to flow into the IJssel.

Figure 18: Weir Driel

Removing obstacles in the river

Obstacles such as traffic and railway bridges slow down the course of the river at high water levels. It is not possible to remove these engineering structures. However, plants and shrubs can be removed. It is also possible to remove the summer quays. These quays stop the water, to keep the floodplains dry for agriculture. The agricultural function is now often discontinued in the floodplains, so that they can get wet again. By removing the summer quays, the floodplains will flood faster, keeping the water in the river lower and limiting the flow velocities.

Extending floodplains

By constructing the dikes inland, the floodplains become wider and the river has more space. Of course, this is not possible in towns and villages, but it is possible in many places. This is a very effective measure that can bring about a water level drop of up to 40 centimetres.

Construction of side channels

A side channel is a flowing channel along the river. You can compare side channels with old river arms, which are now being restored to their former glory. At high tide, such a trench can drain extra water. Moreover, new nature can develop in and around the side channel, because many plants and animals are fond of this marshy environment.

Figure 19: Effect of a side channel