Flood prevention: is the UK prepared for the worst?

Plans for a milestone £150 million flood alleviation scheme in Oxford have been submitted by the Environment Agency (EA) – the latest flood prevention measure put forward by the government. 

The project, which awaits approval from Oxfordshire County Council, will introduce a new stream, with a wetland wildlife corridor, to divert overspill from the River Thames, away from the city’s homes, businesses and transport links. 

It was one of nine government-backed measures announced by the EA in March 2022 alongside a £42 million upgrade of tidal flood defences along the River Humber, a 180-metre flood defence wall in York, and a refurbished pumping station in Doncaster. 

The Oxford project is part of a £5.2 billion government initiative that aims to better protect 336,000 homes and non-residential properties from flooding and is one of the programme’s 2,000 defensive schemes. 

However, the question is: will these measures be enough? 

What actions has the government proposed to reduce the UK flood risk? 

According to a progress report published in 2021 by the Climate Change Committee (CCC), there are five goals outlined in the government’s Flood Policy Statement: 

1. Upgrading and expanding national flood defences and infrastructure. 
2. Managing the flow of water more effectively. 
3. Harnessing the power of nature to reduce flood and coastal erosion and achieve multi-benefits.
4. Better preparing communities.
5. Enabling more resilient places through a catchment-based approach. 

These policies will be bolstered by more than 40 actions, one of which is the £5.2 billion programme. These were established in 2019 and work with the EA’s Flood and Coastal Erosion Risk Management (FCERM) Strategy and Action Plan. 

It is imperative these protective policies are carried out. However, the CCC has stressed that “even with ambitious global efforts to reduce greenhouse gas emissions, further climate change is inevitable”. 

In its progress report, the CCC warns that flash floods and flooding are projected to rise considerably by 2050 because of increased intensity of rainfall during winter and summer. 

Sea levels are also predicted to rise by 10-30cm, which will compound coastal flooding and negatively impact coastal infrastructure. 

Without the completion of defensive infrastructure, two million people in the UK will have a 1 in 75 or greater chance of flood risk by the 2050s, a figure that will increase as the global temperature continues to rise.  

What type of flood defences are used in the UK? 

Flood defences are identified as either temporary or permanent. 

During periods of flooding, temporary defences are erected quickly in areas that do not have permanent structures in place or where it is impractical to build such structures. 

These are constructed from timber, steel, aluminium, plastic and combinations of these materials. There are four types of temporary or demountable flood defences:  

• Dams made from tubes of prefabricated membrane, which are filled with air or water.
• Cellular containers constructed from a wire frame or impermeable plastic, and filled on-site with water or aggregate.
• Self-supporting barriers formed from impermeable, free-standing sections joined together.
• Barriers that implement a system of metal frames, which support impermeable sections  between them.

Permanent flood defences are built into the existing landscape and can be modern barriers, such as canals, reservoirs and sea walls, or natural structures, such as channels, retention ponds, and planted vegetation. 

Whether a temporary or permanent defence is used  is down to the suitability of the specific area.

For example, the EA’s plans to reinforce flood defences in Shrewsbury and the surrounding area this summer will not implement permanent flood barriers at Ironbridge’s Wharfage due to its “historic setting and environment”. 

Which areas in the UK are most vulnerable to flooding? 

Ignoring the presence of existing flood defences, the EA has devised a map that highlights the probability of flooding across the UK. These are distinguished by three, colour-coordinated zones. 

• Flood zone 1: Land in this area has a low probability – less than 1 in 1000 chance – of being flooded by river or sea.  
• Flood zone 2: Land in this area (highlighted in light blue) has a medium probability of flooding – the likelihood of river flooding happening per year is between 1 in 100 and 1 in 1,000 or between 1 in 200 and 1 in 1,000 for sea flooding. 
• Flood zone 3a: Land in this area (shown in dark blue) has a high probability of flooding – the chances of  river flooding is between 1 in 100 or greater and 1 in 200 for sea flooding. 
• Flood zone 3b: Land in this area (also shown in dark blue) is where water is stored and then flows to during periods of flooding. 

Why are flood risk assessments vital preparation? 

The not-for-profit organisation Climate Central has projected that by 2050 parts of London, Blackpool, Cardiff, Bristol and much of the UK’s east coast will sit below the annual flood level. 

Where present and future developments are concerned, flood risk assessments (FRA) are a crucial tool for predicting the probability of a site being in the UK’s floodplain. 

An FRA is a detailed analysis of an existing or proposed development that demonstrates how a building will be affected by potential flooding. It also analyses how this can be mitigated and what impact the development in question would have on flooding in the surrounding area. 

FRAs are required for any planning applications where the site of the proposed development is located within Flood zones 2 or 3.  

These assessments are an integral part of the development process as they outline flood risk possibilities from all sources – the ground, estuaries, the coast, sewers, rivers and surface water from rainfall. 

They also take into account climate change, the topography surrounding the site and the vulnerability of the proposed development. 

Builders and developers, architects, mortgage providers and insurance companies, as well as private individuals, all recognise the importance of FRAs when it comes to assessing either individual properties or larger developments. 

GeoSmart Information produces a range of FRAs to support planning applications, property transactions and insurance for architects, planning consultants and developers, plus the legal market. 

Find out more here or contact us below to speak to one of our experts. 

Tags: climate change, flood barrier, Flood Resilience, flood zones, Flooding