NEWS: Flood protection along watercourses has been a topic of general interest not only since the catastrophic floods in July this year. As settlements have often been built in the immediate vicinity of watercourses, measures against flooding have had to be taken for centuries. Until the end of the 18th century, measures were mainly implemented at specific points without considering how these measures might affect other areas. But even after that, many measures were implemented that did not improve the overall situation, but at best shifted it. The most common solution was to widen the watercourse with a trapezoidal profile, remove the vegetation and straighten the course of the watercourse. The aim of these measures was to increase the flow velocity and thus allow the water to flow away more quickly.

Even leaving aside the negative consequences for biodiversity, these measures have actually made the situation worse. The main problem is that watercourses today have much less space available than they would naturally need. For a lowland stream that is one metre wide today, it can be assumed that a 9 to 30 metre wide corridor was naturally available to it for development and flooding. At the same time, many areas are sealed, especially in residential areas. This means that less precipitation water can be stored in the soil and vegetation or evaporates slowly, but instead runs off quickly and is channelled into watercourses.

If the water level rises as a result of continuous rainfall, heavy rainfall events or melting snow, the watercourse cannot overflow its banks to slowly release the water into the floodplain. Instead, the flow velocity increases and the water is transported downstream. If too much water is added to the watercourse or the water is dammed up, especially by structures, the water masses quickly exceed the capacity of the flow cross-section. Severe flooding then occurs, especially at narrow points. Due to the greatly increased flow velocities compared to the natural state, the water has enormous forces at its disposal that can cause considerable damage.

The EU adopted the Water Framework Directive back in 2000. One of its aims is to minimise the effects of flooding. This is to be achieved by restoring watercourses to as near-natural a state as possible. This should have been achieved by 2015, but the renaturalisation of watercourses is often not a priority. As a result, only 8.2 % of German surface waters were in a good, i.e. natural or near-natural, state in 2015.

Various measures that successfully reduce the effects of flooding have already been implemented on watercourses with a history of frequent flooding. It is particularly important to give the watercourse space that can be flooded. On the one hand, these areas increase the capacity of the watercourse. On the other hand, water is retained in the area, which means that water is stored in the soil and vegetation and is therefore not directly discharged. One way of achieving this is to dismantle or relocate dykes. Another important point is that the flow velocity in the watercourses must be reduced again. This can be achieved by reconnecting old watercourse loops or constructing new ones. In addition, natural watercourse profiles and natural vegetation should be developed again.

The MuP-Group makes its contribution to a safe and natural future for our watercourses, particularly in the "Water Management" business unit. Engineering for a better tomorrow!

 Find out more about our work and projects and follow us:     

#mullandpartner #engineeringforabettertomorrow #news 1TP5Floods 1TP5River restoration