Fast Flood Risk Assessments and Reports

Everything You Need to Know About Flood Risk

Rising Levels of Rainfall

Climate change causes the atmosphere to warm, so it holds more water which is released as rainfall. Record-breaking rain is more likely in the future, according to Met Office climate research which also reveals that summers and winters are getting wetter. Since 1998 the UK has seen six of the 10 wettest years on record. Instances of river and sea flooding are increasing accordingly, putting many parts of the UK in flood risk zones.

Our summers are heating up and if heavy rainstorms follow a time of drought, the ground is too baked to allow the water to absorb, resulting in flooding of the surrounding area. Surface water drains fail to cope leading to critical drainage problems and increasing flood risk. Flooding from rivers happens when water drains into the water course rather than into the ground. Reservoir flooding is another issue.

Susceptible areas

While flood defences will help, critical drainage work needs to be carried out to help systems cope. The Met Office says that one of the impacts of climate change will be localised flooding. Low-lying land and coastlines are at the highest risk; rising sea levels result in long-term coastal change. In urban areas, the problem is worse due to the amount of area that is concreted over, which prevents water from sinking into the soil easily.

Met Office UK climate projections in August 2022 found that winters in the UK between 2009-2018 have been on average 5% wetter than 1981-2010, and 12% wetter than 1961-1990. Summers have also been wetter; by 11% and 13% respectively.

More intense heavy summer rainfall is predicted following thunderstorms, which in urban areas will lead to frequent and severe surface water flooding. Heavier autumn rain is also predicted, and more winter rain.

Rapidly Heating Climate

An independent assessment of UK Climate Risk prepared by the Climate Change Committee found that the chances of experiencing a hot summer have doubled in recent decades and are now about 10-25% per year. This is expected to rise to 50% by 2050.  

The Committee states that dwelling houses may need to be retrofitted to incorporate flood resilience measures: improving building regulations to take a whole-building approach is the best option to reduce potential flood risk in any new development type.

Building houses in Environment Agency ea flood zones has not helped the situation: while planning permission can be granted for homes in areas at risk of flooding provided that resilience measures are incorporated, more evidence that this is carried out is needed.

Extreme Weather Events to Become the Norm

Jess Neumann, associate professor of hydrology at the University of Reading said:

There is ever-increasing evidence that the UK climate is changing and for many of us, we are seeing more unpredictable and extreme weather including floods, droughts, and heatwaves. The average temperature (2009-2018) has been around 0.3°C warmer than what we experienced in the 1981-2010 period, and nearly 1°C warmer than 1961-1990. Coupled with this rise in temperature, a warmer atmosphere can hold more moisture, so we are also seeing an increase in rainfall.

On average, UK winters are around 12% wetter than they were in 1961-1990, and extreme rainfall events which can lead to flooding are now commonplace, both in terms of their frequency and areas of the UK affected. Flooding incidents in the future will continue to come from multiple sources. These include river flooding where river flows exceed the capacity of the channel and riverbanks inundating the floodplain; flash flooding from heavy rainfall often associated with summer thunderstorms; groundwater flooding from persistent heavy rain where the rising water table emerges at permeable surfaces; and coastal flooding driven by storm surges, high tides, and low-pressure weather systems.

As the UK weather becomes more unpredictable, the chance for multiple flood events to occur in tandem increases, placing more of the population at risk. Whilst all four of these flood conditions are concerning, it is flash flooding that is often taking people by surprise and having huge detrimental impacts in urban areas.

Be Prepared: the Steps to Take

For property owners or renters living in flood risk areas, signing up to the Government’s free sign up for flood warnings service is recommended. Preparing in advance an emergency flood kit and putting in place a communication plan with family members and neighbours can help save lives.

For those living at high risk of flooding, purchasing flood insurance from a reputable provider and investing in flood defences and retrofitting reinforcements in your home can reduce the worst impacts.

For those who do not own their properties, get support and advice from landlords, councils, and housing associations. If flood risk is imminent, heed warnings and move belongings and valuables upstairs, onto furniture or shelving where possible, turn off gas and electricity supplies, put in place any flood defences you might have, and check on vulnerable neighbours. Move to an area of safety and call 999 if you are in immediate danger.

How should Local Planning Authorities and Developers be reacting?

How we manage the land is critical for helping to slow water down at a catchment or landscape level – trees, cover crops, and soil and land management (so-called ‘Nature-Based Solutions’) all have a role to play in absorbing water. Impermeable surfaces such as concrete and asphalt, on the other hand, force water to run off the land surface rather than soak away increasing the risk of flooding in urban areas.

The planning and development of housing in flood zones, including floodplains, has also placed thousands at increased risk.

When considering proposed development, local planning authorities and developers need to consult flood risk data and identify areas and communities that are at flood risk in a flood map for planning. Environment Agency advice and guidance must be followed; this lays out a framework for approving proposed development in susceptible areas. Flood risk information is available from bodies such as the Scottish Environment Protection Agency, Natural Resources Wales and the lead local flood authority.

Steps to Mitigate Flood Risk in Flood Zones

It is possible, where no feasible alternative solution can be found, to build safely in flood risk areas but this requires the correct resources and for planners to investigate and work with different designs: building on raised banks, houses on stilts, floating foundations, and dry floodproofing with waterproof membranes are examples of `hard engineering’.

Bringing Nature-Based Solutions into urban areas in the form of `sponge cities’ with in-built sustainable urban drainage is also an attractive option. A surface water drainage strategy is crucial for a proposed development site: flood modelling is a useful tool for future development especially where a critical drainage area poses problems or the site is within flood zones.

Careful placement of retention ponds, wetlands, rain gardens, and the protection and expansion of blue-green infrastructure e.g., parks in urban areas will have a cumulative impact on reducing flood risk, whilst also benefitting nature and society.   

Protect your Home and make a Flood Risk Assessment

You can check your long term flood risk by entering your postcode into a government website and signing up for free flood warnings.  Met Office advice to protect your property from flooding includes preparing a flood plan.

You can download a flood plan template from your local planning office or the lead local flood authority. To create your own, it should include:

• A list of useful contact numbers including your local council, utility providers, and insurance company.
• Instructions for turning the gas and electricity supply off.
• Where to move valuables to a safe place.
• Key things to move – pets, car, furniture.
• Who to ask for help.
• Vulnerable people you could help.

Prepare a flood kit to include:

• Insurance documents and key contact numbers.
• Torch and spare batteries.
• First aid kit and prescription medicines.
• Warm waterproof clothing and blankets.
• Bottled water and snacks.
• Battery or wind-up radio.
• Baby or pet supplies.

Flood risk mitigation measures

If your property is in a flood zone, make it as resilient to flooding as possible.

• Lay tiles rather than carpets.
• Move electrical sockets higher up the wall.
• Fit non-return valves.

Install flood protection products such as:

• Flood boards to fix to doors and windows.
• Plastic covers to seal airbricks.
• Sandbags.

Recovering after a Flood: Flood Consequence Assessment

• Contact your insurance company. Find out if they offer the Build Back Better scheme, which may help you make your home more flood resistant in the future.
• If you have had to leave your home, check with the emergency services before returning: there may be residual risks.
• Take professional advice before starting to clean your home after it’s been flooded: your insurer may insist on using an approved cleaner.
• Be aware that flood water can contain sewage and take precautions when in contact with it.
• Contact your local flood warden or flood action group. Recovery events may be coordinated from a central location in the case of a severe flood.

Planning permission and flood risk assessment

If you want to apply for planning permission, firstly, find out if your area is at risk by consulting the Environment Agency flood map. Flood zones were created by the Environment Agency to demonstrate flood risk and help councils and developers to understand the risks.

There are four flood zones: Flood Zone 1 covers areas with a low probability of flooding (shown as clear on the flood zone map). Flood Zone 2 indicates a medium probability of flooding, while Flood Zones 3a and 3b indicate a high probability.

The National Planning Policy Framework states that some plans for development in Flood Zone 1 should be accompanied by a specific flood risk assessment, while all applications to develop in Flood Zone 2 or 3 require a site specific flood risk assessment.

Flood Zones 2 and 3 usually include land at risk of sea or river flooding, or areas where a strategic flood risk assessment shows the possibility of future flooding. Areas of Flood Zone 1 can be at risk if the Environment Agency has notified the local planning authority about drainage issues.

Flood risk assessments can be carried out by a flood risk consultant, however, for permitted development, minor development or a simple application such as a house extension, you may want to submit your own flood risk assessment.

Flood risk is increasing

Protect your property

Maintain your property and if you feel you are at risk of flooding, there are steps that you can take, commented John Alexander, managing director of Aquobex, a company that designs and engineers world-class flood protection solutions. He said:

The Met Office and the Climate Change Committee have recently published their projections for increased rainfall, and these should come as no surprise to people who follow weather events at home and abroad. The intensity and duration of these rainfall events are what make them so damaging, as we often hear reports of “a month’s rain in a day” or “300mm have fallen in a matter of hours”.

These impacts are widespread too, and it is no longer safe to assume you won’t flood because you don’t live near a water course. We continue to pave over the world so these intense rainfall events can impact any property regardless of location – flash flooding can even impact you if you live on a hill and are in the way of the flow. There is much property owners can do to protect their buildings though.

Property maintenance

Firstly, keep on top of the maintenance of the fabric – repair damaged bricks and mortar and seal all pipe and cable penetrations. If the building has air bricks, consider changing these for Smart ones that close automatically when a flood hits.

There are good quality flood doors and barriers on the market that carry the British Standard Kitemark certification – don’t be misled by products that are cheaper without this essential accreditation. This is not an item to go for the cheapest option.

Local authorities hoping to benefit from any grants to make their social housing stock warmer should be aware that these flood doors and windows also provide improved thermal qualities and should be very careful about what cavity wall insulation is used if this housing stock is in a flood zone. Closed cell foam insulation will provide warmth and act as a layer of flood mitigation as well – doubling the grant benefit.

If you live in a highly vulnerable flood zone you should already be aware of the Flood Re insurance scheme that helps to reduce the costs of flood insurance, but also look out for their new Build Back Better campaign which now allows for ‘betterment’ or flood resilient repair, as the industry calls it. Basically, insurers will be enabling property owners to make their homes more resilient to flooding following future flood events.

Need a flood risk report?

Engage a consultancy with extensive experience of flood risk assessment and managing flood risk. A flood risk specialist will be able to identify different sources of flooding and by using detailed hydraulic modelling, advise you on optimal flood prevention strategies. If required, planning consultants can guide your planning application through the planning process.