Shoring up Europe’s flood defences

Tuesday, 6 January, 2015
From Pakistan to the Balkans and from Mozambique to Western Europe – images of the misery caused by flooding are a regular feature in the media. While eliminating all risk is impossible, understanding it and adapting buildings, infrastructure and flood defences can save lives and money. EU-funded researchers have developed the tools needed to do just that, and have passed them on to Europe’s policymakers.
Flooding in Warsaw, Poland, in 2010

The EU alone spends more than €40 billion every year on flood mitigation, recovery and compensation, while 75% of all damage occurs in urban areas. “With climate change and increasing urbanisation, there is a higher risk of loss of life and damage,” says coordinator of the FloodProBE project, Derk van Ree of Deltares in the Netherlands.

The project developed the technologies, methods and tools for flood risk assessment, and for the adaptation of new and existing buildings, critical infrastructure and flood defences. The results will help decision-makers implement the EU directive on flood control and prevention, which requires all EU countries to assess and reduce the risk of flooding.

Understanding failure

Most of the regions at risk of flooding already have some defences in place, but they are sometimes very old and in need of repair and upgrading. Understanding how these defences could fail allows authorities to better assess the risks and to start improving them, but collecting data from thousands of kilometres of defences is no mean feat.

The team found techniques such as high-density LIDAR – a remote sensing technology that measures distance by illuminating a target with a laser and then analysing the reflected light – to be effective for assessing long stretches of flood defence.

The FloodProBE team also looked at the full impact of flooding, which goes way beyond the area under water. If an electricity plant is flooded, for example, this could affect people and services – some of them critical – many kilometres away. These consequential effects can be costly for communities, impacting humans and finances.

Accepting risk, minimising damage

Where space is limited, particularly in urban areas, it is not always possible to build new defences. But town planners need not despair – it is possible to minimise damage and disruption. “It’s not only about defence, but also about accepting that there will be water and looking at how to recover quickly,” says van Ree.

Using tools developed within FloodProBE, it is possible to calculate the potential cost of flood damage to buildings. The result can be given as a percentage of the cost of building a new, more flood-resistant building. The calculations take into consideration that the building would be out of action for some time, and that some materials may have to be replaced.

These simulations can help public authorities to decide whether it’s best to build a new building, or to change something in an existing structure – for example the materials used for the flood-vulnerable areas of a building.

The analysis tool can be used anywhere – the building expert just needs data on local materials and costs.

Erosion-evading enzymes

One secret weapon in the fight against flooding, tested within FloodProBE, is BioGrout. This soil-strengthening technique uses microbes to create a chemical reaction to enhance the solidification of calcite (a mineral found in soil) to make the ground harder.

The strength can be altered as desired, but ultimately it can turn loose sand into sandstone, which is more resistant to flood-water-induced erosion. It is particularly helpful in avoiding internal erosion through embankments, which can weaken flood defences.

The team found BioGrout to be effective, but in need of further development.

FloodProBE ended in October 2013 with comprehensive advice for decision-makers on aspects of flood risk. This ranges from how to assess whether certain technologies can be used to reinforce flood defences, to the importance of considering transitions between flood defence structures, which are often ignored, says van Ree.

Van Ree would also like to see decision-makers referring to the FloodProBE guidance early on in discussions on where and how certain buildings will be built. For example, it is clear that if the risk is low, flooding will not be taken into account when deciding where to build a new hospital. Equally, it makes little sense to redesign an existing hospital to address a low risk. “We need to find a way to include flood risk in the list of topics assessed before decisions on building design are taken,” says van Ree.

Additional work is still needed to implement all of these recommendations, but in the meantime several EU countries are looking into how best to ensure the knowledge gained through FloodProBE is used.

One option could be the creation of a network of flood risk management experts to share good practice and collaborate on new and evolving solutions. The team has already submitted a proposal for funding under Horizon 2020.

“A kick-start is needed. The community should ultimately be self-sustaining, but it needs a catalyst to define the structure and priority topics,” says van Ree.

Technologies for the cost-effective flood protection of the built environment
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