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Increasing   resilience to floods in the city of Leuven

The flooding of the Dyle River in the city of Leuven has   always been an issue as the naturally-occurring steep slopes and historical   deforestation upstream of Leuven easily lead to rapid increases in flow rate   and water level during high precipitation. These floods occurred after heavy   rainfall or after sudden thaws following cold winters, resulting in the   rivers overflowing. The most extreme flooding event in its recorded history   took place in 1891, which led to a third of the city being flooded, and it   remains a reference point for the river’s destructive potential. Since then,   flooding events (e.g. in March 1947 leading to extensive flooding in the   upstream municipality) have remained a regular occurrence and prompted a   number of interventions.

In the 1970s, the idea to   protect the city of Leuven began with the design of traditional hydraulic   solutions, in particular a large flood reservoir in Neerijse valley upstream   of Leuven. The poor water quality and the agricultural land use (still very   important in that period) made it a requirement that the flood reservoir   would not take up more space than was absolutely necessary. During the design   period of this traditional hydraulic solution, growing environmental   awareness led Leuven to explore more nature-based solutions that take the   ecological health and landscape value of the river valley into consideration   (La Rivière 2014).

Using new modelling   software and taking into account the ecological requirements, the protection   measures were tested, yielding successful results. The tested measures   included a controlled flood reservoir in Egenhoven and natural, uncontrolled   flood zones in the Neerijse valley (La Rivière 2014.).

In this new approach, instead implementing a hard   engineered solution with artificial flood reservoirs, the natural processes   has been restored resulting in “wet” valley floors along the River Dyle   upstream of Leuven. Infrastructure works are kept to a minimum and are   intended to 'guide' the river rather than contain it (La Rivière 2014).

In addition to the provision of areas to store water   upstream of Leuven, it may be possible to slowly enhance the capacity of the   channel network within the city over the years, providing that there is   sufficient support within Leuven. Although the capacity enhancements will be   relatively small, when these are coupled with flood resistant and resilient   constructions, they will help to reduce the amount of storage required upstream.   In the EU project Flood Resilient City (FRC), the Flanders Environment Agency   implemented a number of measures to enhance the capacity of the channel   network within the city. The existing quay-walls were improved to maintain   the discharge capacity in the city centre. This was done in close contact   with the riparian owners. In that way they became more aware of the river   flowing next to or close to their houses. At one location it was possible to   build a terrace alongside the river and a small park for people to enjoy.   During high water the steps can flood. This increases the capacity for the   river in the city centre. Additionally the terrace helps to make more people   in Leuven aware that the Dijle is a living river, and that there is an   ongoing threat of flooding (Source: http://www.floodresiliencity.eu).         

Terraces alongside the River Dyle in the city of Leuven. Photo:   @Flemish Environment Agency

Previous comments

  • Annelies Haesevoets (invited by kristpet (disabled)) 31 Aug 2016 13:46:37

    Flemish Environment Agency should be Flanders Environment Agency

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