West Sussex floods: ‘Deadly’ flooding is getting worse with climate change. We must prepare for the new norm

England is known for its rain. But the last 18 months have left us soggier than ever – and experts are blaming horrendous floods on climate change.

Some 1,695.9mm of rain fell from October 2022 to March 2024 – the highest level recorded since 1836.

The unprecedented drenching has flooded key transport networks and left farmers struggling to plant crops in water-saturated fields.

Meanwhile, dramatic downpours are sweeping across South West England, as a combination of gale-force winds, rain and high tides prompts the Environment Agency to issue several extreme flood alerts.

According to experts, it’s just a taste of what we can expect in the future.

• Here are the supermarket staples at risk from climate change
• How to find out if your home is likely to flood – and what help you can get

“We are already experiencing heavier rainfall in the UK due to climate change,” said Ben Clarke, a researcher at the Grantham Institute for Climate Change and the Environment. 

“Most countries in the world are not well prepared for the impacts of climate change. Flooding events can be incredibly deadly and costly events, so it is important that countries and cities prepare.”

Here’s how climate change will make the future wetter – and how we can be ready for it.

How is climate change making flooding more likely?

When you think of global warming, it’s natural to think of sweltering summer sun.

But as the atmosphere warms, it holds more moisture – roughly 7% more for each degree of warming – which means more rain.

“Climate projections indicate that on average, winters will continue to become wetter and summers drier, though natural variability will mean we will continue to see individual years that don’t follow this trend,” a Met Office spokesperson said.

“[A warming atmosphere] can lead to more intense and frequent downpours. In autumn, the UK will likely see more days with rainfall totals over 50mm, particularly for western areas of the UK. For summer, despite an overall drying trend, there will likely be future increases in the intensity of heavy summer rainfall events.”

The Met did not directly attribute the UK’s current spell of wet and windy weather – including the devastating Storm Kathleen – to a warming climate, pointing out that individual weather events are caused by a variety of complex atmospheric processes.

But it is clear that the overall trend tends towards increased rainfall and flooding. 

“In the future, rainfall events exceeding 20mm/h, which can cause flash flooding, are expected to be four times as frequent by the 2070s compared to 1980s, under a high emissions scenario,” the Met spokesperson said.

“Changes are not projected to happen gradually, but instead extreme years with lots of events could tend to cluster.”

Why do we still have water shortages if it is raining so much?

It is raining a lot – yet we are still likely to face drought this summer.

This is because the water that drenches the UK in winter is not being stored properly for the hotter, drier months. Our water infrastructure is insufficient: Britain has built no new reservoirs for 30 years, while our water distribution pipes leak around a fifth of the water they carry.

Last month, the EA released a report predicting that we will have a deficit of 5bn litres of water a day by 2050.

In a slightly counter-intuitive twist, drought also makes flooding more likely.

When rains do come, the impermeable, sun-baked earth is unable to absorb the downpour, causing flash flooding. The University of Reading illustrated this with a simple experiment, embedded below. 

Wetlands used to act like ‘giant sponges’ in periods of heavy rain. But Britain has drained most of its marshes and dug up most of its peatland, losing 90% of its wetlands over the past 500 years.

Building settlements on floodplains hasn’t helped, adds Clarke.

“While heavy rainfall is often the primary cause of flooding, human factors can make it more severe,” he said. “For example, settlements and infrastructure on low lying land near rivers are at higher risk of flooding.”

Finally, as sea levels rise, coastal areas will be more prone to storm surges. According to the UK Climate Risk Assessment, Current projections for the UK show the likely change in sea level to be between 0.27 and 1.12 metres by the end of the century.

EA estimates that, in 2022-23, approximately 5.7 million properties in England were at risk from flooding. This figure increased by around 500,000 between 2021-22 and 2022-23.

Friends of the Earth have created this map to show which areas are most at risk.

Who will be most impacted by flooding?

The impacts of flooding will not be felt evenly, says Sarah Lindley, professor of Geography at the University of Manchester.

“There are several ways that being on a low income affects the extent to which people are impacted from floods,” she says.

“Top of the list is home insurance, people are less likely to be able to afford insurance for their homes and may not have as much ability to prepare homes for floods, eg. to obtain property protection. People living in poorer quality housing, mobile homes or who are homeless are often more exposed to flooding, including from pluvial flooding (which is rainfall related).”

More than 95,000 homes in the most deprived one-fifth of English neighbourhoods are currently at medium or high risk of flooding, Resolution Foundation analysis suggests.

How can we adapt to climate change-induced flooding?

Reducing emissions is the most vital protection for such households, Clarke explained.

“The warming of the climate will only stabilise when global emissions are reduced to net zero,” he said. “To do this, the world needs to replace oil, coal and gas with renewable forms of energy.”

But adaptation is also vital. Part of the answer will be improving infrastructure like levees and stormwater drainage systems.

But these don’t go far enough, warns Friends of the Earth.

“Not enough emphasis has been placed on restoring nature as part of reducing flood risk,” a spokesperson said.

“Such measures include the full restoration of peatlands and sea marshes, tree planting, reintroduction of beavers in upper catchments, and increasing green spaces and water storage areas in urban areas, including the removal of hard surfacing to enhance drainage.”

It’s a call that Clarke echoes, stressing the importance of rewilding and green space. But for some communities, he adds, it won’t be sufficient.

“Nature based solutions that increase green and blue spaces in cities can help to drain floodwaters more efficiently during bouts of heavy rainfall.

“Some communities at high risk of flooding will need to consider ‘managed retreat’ to safer areas.”