The Great Flood of 1968: causes, the towns it hit, and the risk today

What caused the Great Flood of 1968?

The trigger was a textbook piece of bad luck in the weather. A band of warm, very moist air drifting up from the Mediterranean ran into cooler air sitting over the South East, and the front between them more or less parked over the region for around 48 hours. Rain fell, and kept falling. In places close to 150mm came down in two days, getting on for three months' worth of rain in a single weekend.

What made it so destructive was the ground underneath. The summer of 1968 had already been a wet one, so the soil was saturated before the storm even arrived. With nowhere to soak away, the rain ran straight off fields and streets and into the rivers, which rose far faster than anyone could manage. This is what we now call fluvial, or river, flooding, and it remains one of the main sources of flood risk in England. The 1968 event is one of the clearest examples of how quickly it can take hold.

The towns and regions that were hit

Although Lewisham became the best-known casualty, the flood was a regional event. The worst-hit towns stretched right across the South East: Crawley, East Grinstead, Horley, Redhill, Tonbridge, Tunbridge Wells, Petersfield and Tilbury all flooded badly, along with Lewisham itself. More than 14,000 properties were inundated across Surrey, Kent and Essex.

Some of those names sit right on Unda's doorstep. Crawley, Horley and Redhill are a short drive from our Sussex office, and they flooded again in 2000, which we wrote about in the 2000 Crawley and Gatwick floods. In Beckenham, the River Ravensbourne came over its banks and put the High Street under water, the kind of localised river flooding that still generates questions today. The River Mole, further west, saw something close to a 1-in-200-year storm, a useful reminder of how flood return periods and annual probability actually work in practice.

The disruption reached well beyond flooded homes. On the morning of 15 September the 9:50 from Charing Cross to Hastings was diverted and then stranded by floodwater at Edenbridge, leaving 150 passengers stuck on board for twelve hours. It is worth noting that an earlier bout of flooding in the South West in July 1968, around Chew Stoke and Bristol, had been the deadlier of the two events. The September flood, for all its scale, claimed no lives in the South East.

Lewisham under water

In Lewisham the rain did not fall hardest, but the geography did the damage. The borough sits at the meeting point of three rivers, the Ravensbourne, the Quaggy and the Pool, and all three burst their banks at once. The Quaggy, normally a modest channel only about six inches deep, rose to something like fifteen feet in places.

People woke on the 15th to boats drifting down the High Street, shopfronts submerged and parks turned into lakes. The water lingered for the better part of a week. Thousands of homes and businesses were damaged, and getting to work or school was simply impossible for days. Much of that river network is made up of main rivers and ordinary watercourses running through dense housing, where riparian ownership and maintenance still matter a great deal to how water behaves in a storm.

How 1968 changed the way we treat rivers

For a long time the official answer to flooding like this was to fight the rivers. Channels were straightened, lined with concrete and, in places, buried underground out of sight. That reactive approach held until the mid-1990s, when thinking began to change.

In Lewisham much of that change was driven from the ground up. The Quaggy Waterways Action Group, formed in 1990, argued that the best way to reduce flooding was to let rivers behave like rivers again, with soil and gravel beds acting as natural sponges rather than concrete pipes. Their restoration work has since become a well-known example of natural flood management, and it has given the borough some genuinely pleasant green spaces in the bargain.

The flood also stayed in local memory. The In Living Memory project, run through Goldsmiths under the name Lewisham Underwater, gathered residents' stories of 1968 and even produced a commemorative flood beer. That programme drew to a close in autumn 2025 with a new public artwork, Street Waders, installed beside the River Quaggy at Plough Bridge Gardens, linking the memory of the flood to the climate questions we face now.

Are these areas still at risk today?

The short answer is yes. Parts of Lewisham, and stretches of the Sussex and Surrey towns hit in 1968, still fall within the Environment Agency's higher-risk flood zones. If you want to understand what those bands mean, our guide to Flood Zones 1, 2 and 3 sets it out, and you can see how a site is classified on the Flood Map for Planning.

The risk is not standing still either. Rising rainfall intensity means the kind of downpour that overwhelmed these rivers in 1968 is modelled very differently now, with climate allowances built in. For anyone buying, selling or building in one of these catchments, that history is not just a curiosity. It is a reason to look closely at the evidence before committing.

That is where a proper assessment earns its keep. A flood risk assessment for planning shows a local authority that a development can go ahead safely, flood modelling can quantify depths and flows where the standard maps fall short, and a flood risk survey for a property purchase gives a homebuyer a clear, site-specific read on the actual risk rather than a broad screening colour. You can see the full range on our flood risk assessment services page.

1968 in the bigger picture

The Great Flood of 1968 belongs to a long line of serious British floods, and the pattern of lessons learned and then half-forgotten repeats with uncomfortable regularity. The year 2000 alone brought major flooding to Lewes, York and the River Ouse and the Severn valley, and four years later Boscastle was almost washed away in a matter of hours. Each one tells a version of the same story: water finds its old paths, and the places that flooded before tend to flood again.