Floods, explained
While floods and other extreme weather events such as droughts aren’t exactly new, their frequency and intensity have been increasing in the past years due to climate change. Unfortunately, these destructive natural phenomena are causes of concern almost everywhere in the world.
Storm Chandra, which happened earlier this year in January, brought exceptionally wet weather to parts of south-west England, north-east Scotland and the east of Northern Ireland and was responsible for flooding events in Devon, Cornwall and Dorset.
Summer 2026 was the country’s hottest summer on record, according to the Met Office, with July 2026 being recorded the driest for England and Wales since records began. Unusually warm temperatures this year have led to sea-surface temperatures rising, contributing to the strengthening of El Niño. El Niño is a climate phenomenon that happens roughly every two to seven years, when sea temperatures are persistently 0.5C above average in the central and eastern tropical Pacific Ocean. The 2026–2027 El Niño is expected to trigger some of the most severe extreme weather events in decades.
Floods happen when water soaks land that’s usually dry. Heavy storms might be the most common cause behind them but ruptures in dams or levees, rapid melting of snow or ice and even tsunamis can lead to flooding. Urbanisation also contributes to increasing the flood risk in cities. As the population grows, more buildings and roads are built, adding pressure on drainage systems, and leaving less space for water to soak. Rivers and waterways have also been modified, straightened, and culverted, making them overflow more easily than if they were in their natural states.
Usually, floods can take hours or days to develop, giving residents and businesses time to prepare for potential damage and evacuate if there’s a need. However, they can also evolve quickly and without warning – what we call flash floods. Roads become rivers, and brooks become dangerous fast-moving streams able to sweep anything in their way.
There can be many devastating impacts of severe floods. They can destroy homes and businesses, disrupt transport links leaving people isolated, overload sewage and drainage systems leading to spills and the spread of diseases, and ultimately, cause deaths. The aftermath can be equally harmful: power cuts, lack of drinking water, and silt and mud areas contaminated with toxic substances, not to mention the economic toll.
The Thames Barrier is an important tool to protect London from tidal flooding and storm surges. It became operational in 1982 and is one of the largest movable flood barriers globally. Since its opening, it’s been closed 221 times – 119 to protect against tidal flooding and 91 to protect against combined tidal-fluvial flooding.
However, there are also simple and natural ways to mitigate flood risks. Nature-based solutions address societal challenges, such as climate change, and human health while protecting the environment and helping us build resilience to extreme weather events. Natural flood management and sustainable urban drainage systems (SuDS) are examples of effective strategies to do so.
At Thames21, we use both methods mentioned above in our projects. Besides enhancing the natural landscape’s ability to cut down water overflow, absorb pollution and improve biodiversity, these also provide blue and green spaces for people to enjoy. Natural flood management techniques include building wetlands and storage ponds, planting trees and reducing soil compacting. Some of the common SuDS are rainwater harvesting with a water butt, rain gardens, swapping hard paving for permeable surfaces, and green roofs.
Action for Silk Stream, Greenwich Natural Flood Management Project, and Glassmill Pond are examples of some of our projects that make use of nature-based solutions.
While these can’t solve the problem, they can play an important role in helping both people and the environment cope with a changing climate.
On the ‘Prepare for Flooding’ gov.uk page, you can check your flood risk, sign up for flooding warnings, and find important information on how to protect yourself from future flooding.
Header image by Michael Elliott Photography