Flood defences: a challenge and opportunity for civil engineers

It is fair to say that the UK has a considerable share of rainfall. In 2021, the UK as a whole experienced the fourth-wettest May on record – and the wettest on record for Wales.

While flooding has been a persistent problem across the British Isles for millennia, the evidence shows that the frequency and intensity of extreme events such as heavy rainfall occurrences are increasing. The adverse effects of flooding are numerous, from immense damage to buildings to spoiled crops, transport disruption and overwhelmed drainage systems.

In some cases, it can even lead to loss of life and a devastating impact on the local community, as seen in the catastrophic 2009 Cumbrian floods and, more recently, Storm Christoph, which brought insurance claims of over £120m and hundreds of evacuations.

A 2020 report issued by the Met Office, State of the UK Climate, highlighted that the country has become distinctly wetter over the past few decades, with rainfall increasing by 9% between 2011 and 2020 compared with the previous half-century. The report cites a probable increase in extreme weather events as global warming accelerates. 

Last year, the UK government committed to investing £5.2bn in a six-year flood and coastal defence investment programme that will run until 2027.

While implementing adequate flood defence remains a challenging national priority, it represents a massive commercial opportunity for the civil engineering community. Furthermore, it represents a clear opportunity for my profession to play a prominent role in delivering substantial public benefit while mitigating the effects of climate change and demonstrating our evolving expertise in this field.

The pathway to establishing effective flood defences is not without its difficulties, and civil engineers often face a unique set of challenges when undertaking these projects. Currently, one of the most prominent pathways is to produce a scheme that is acceptable to the widest range of stakeholders within the decision-making process.

One of our most important steps is to allay fears around the proposed plan and develop a sympathetic solution that can overcome any NIMBYism

Competing interests are inevitable and must always be delicately handled. For example, consent-based concerns by environmental organisations will always be a crucial element when developing scheme options.

So, one of our most important steps is to allay fears around the proposed plan and develop a sympathetic solution that can overcome any NIMBYism (not in my back yard) we may confront. To overcome this barrier to development, we ensure all parties can have a voice in the scheme’s development through public consultations and transparent sharing of detailed information across all phases of development. This stage is one of the most crucial in scheme planning and approval.

Quality assurance and the implication of a design deviation or amendment to the original scheme can represent another issue. But, it is always our goal to avoid upset or unheard stakeholders who could challenge the planning process and delay operations.

Therefore, the use of diplomacy combined with clear communications helps stakeholders to understand the reasoning behind any deviations. It can also be used as an opportunity to educate those affected about any positive benefits. 

Technology has helped to grow our skillsets in flood management and increase our understanding of the behaviours of flooding events over the past decade

Advances in digital technology are enhancing flood management schemes to a considerable degree: digital software and hardware enable civil engineers to operate in a more efficient, intuitive and sensitive way.

Technology has helped to grow our skillsets in flood management and increase our understanding of the behaviours of flooding events over the past decade. Prominent among emerging platforms and devices is the use of computer mapping and modelling to identify where flooding occurs and to analyse the depth and flow rates in the past, present and future.

These tools help us to better understand the pattern and behaviour of the water, which informs the selection of the optimal scheme while also building in the potential to adapt over time, as flooding events increase in size and scale.

At a higher level, geospatial data technology software is helping us to visualise the whole expanse of the study catchments, offering even greater insight into how the land can be used to improve planning decisions.

This leap in digital capabilities is complemented by emerging operational approaches. Sometimes it is not just about pouring concrete or building an embankment but looking more closely at the landscape and seeing how it can be adapted with minimal intervention.

Natural flood management measures can slow the flow of water downstream, store floodwater and contribute to river restoration and coastal adaptation.

You may have heard this described with the phrase “slow the flow”, which is now a key deliverable when implementing a flood management scheme. This process describes the method of storing more water within the landscape upstream to slow its passage downstream, thus reducing the frequency and flow speed of future floods.

Even with advances in technology, designing flood prevention schemes is about respect for the heritage of the catchment area and landscape

It can be done sustainably, too. For example, in 2016, in the North Yorkshire towns of Pickering and Sinnington, flooding was mitigated by combining land management with flood storage. This represents a forward-thinking solution to a long-standing challenge, perfectly encapsulating our profession’s crucial, problem-solving role.

Even with advances in technology, designing flood prevention schemes is about respect for the heritage of the catchment area and landscape: recently, when designing a flood protection scheme at Springfield Clonlara in Co Clare, Ireland, the team found an archaeological feature on the site, which was determined to be a burnt spread, which we recorded and protected and ensured we incorporated into the design.

Burnt spreads/mounds are probably the most common prehistoric type of site in Ireland and Britain. Typically middle to late Bronze Age, the function of these sites has been much debated with the most commonly cited uses being cooking, steam baths/saunas, brewing, tanning or textile processing.

Of course, I have only dipped my toe into the water in this short article. Flooding events are driving innovative thinking in my peers in the civil engineering profession, and our services will be in demand more than ever.

By embracing the latest technology, methods and approaches, we can manage each project successfully, delivering the best service, addressing and easing stakeholder concerns to provide the optimum and most environmentally sympathetic solution that will serve the catchment far into the future.

Sean Harrington is technical director of ByrneLooby, an Ayesa company