Make space for water by elevating flood-prone buildings

A new study shows that raising buildings is still largely overlooked as a viable strategy for adapting vulnerable locations to flooding in Europe.

Coastal regions are increasingly investing in flood defences or managed retreat from the sea. Elevating new or existing buildings could provide an additional option to increase the resilience of coastal communities.

Ulysse Pasquier at the Tyndall Centre for Climate Change Research, based at the University of East Anglia (UEA), examined how coastal policies in France, the UK and Ireland addressed flood accommodation. He reviewed local spatial planning documents along the coast of the three countries, creating the first database of flood accommodation at the municipal level.

His analysis shows that while national guidelines for raising floor levels of new developments in high-risk zones are available in all three countries, the implementation of standards for ground-floor elevation remains inconsistent.

Learnings from flood-prone buildings in the US

Elevation of flood-prone buildings is well-established in the United States and has been used around the world for millennia. In Europe, it is currently less common and faces several hurdles to implementation. Unlike other flood protection strategies, it typically places costs on individual landowners or developers. This lack of financial support makes elevating buildings a less appealing option.

In contrast, the US has longstanding mechanisms like the National Flood Insurance Program (NFIP) that provide detailed guidance to property owners on how to adopt flood-resilient measures and provide some funding to raise existing buildings, especially after floods. Timber-framed buildings, more common in the US than in Europe, are more easily elevated. New buildings in flood-prone areas must follow elevation guidelines to receive federal flood insurance in the US.

The researchers argue that Europe could also learn from the US experience to provide better guidelines on managing the constraints of elevated buildings. For instance, while basic elevation methods may be enough for some locations, areas impacted by waves call for more robust designs. This is the purpose of designated “V-Zones” in the US, where specific foundations that can withstand high velocity flood water are required. Introducing similar guidelines in Europe would help prevent maladaptation by ensuring elevated buildings remain safe and effective.

A “low-regret” option as sea levels rise

The study highlights that accommodation policies are evolving rapidly and that past storms have played a key role in France in accelerating their development. During the 2010 Cyclone Xynthia, many people were trapped in single-storey homes behind breached coastal defences, leading to many fatalities. This led the French government to strengthen flood accommodation standards, as well as to enforce the construction of raised refuge areas in exposed regions to provide shelter in case of another event. Other countries could use this experience to implement more pro-active accommodation policies of their own.

As sea levels continue to rise, coastal communities face a pressing need to adapt. Elevating buildings, under the right conditions, can provide a short to medium-term “low-regret” option with the potential to delay the need for managed retreat.

European coastal policies on flood adaptation can benefit from better integrating flood accommodation in building design, overlooked elevated buildings have a role to play.

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