Story · Environment map · about 4 min
Where could England flood?
The Environment Agency maps the land that rivers and the sea could flood, and Natural Resources Wales does the same for Wales. This story reads both maps council by council: where the risk covers the most land, why it sits where it does, and how London and Wales stand apart.
England’s flood map
Dark blue is Flood Zone 3, land with at least a 1% chance of flooding from a river in any year, or 0.5% from the sea. It covers 10.2% of England’s land, and the lighter Zone 2, down to a 0.1% chance, adds 2.0%. The zones are drawn as if there were no flood defences, and they leave out surface water, the rain that floods a street before it ever reaches a river.
The Fens: nine-tenths in a flood zone
In Boston 94% of the land is in Zone 2 or 3, in South Holland 91% and in Fenland 83%, the highest shares of any council in England. Much of the Fens was drained from the 17th century and now lies at or below sea level, kept dry by banks, drains and pumps. Without them the rivers and the sea would take this land back, and that is what the map shows.
Hull, a city in the flood zone
Hull is the only city near the top of the list: 90% of its land is in a flood zone. It sits on the low north bank of the Humber estuary, where the River Hull meets the tide, so it is open to both the river and the sea.
London, behind the Barrier
Across Greater London 13% of the land is in a flood zone, and along the Thames far more: 59% of Hammersmith and Fulham, 52% of Newham and 46% of Southwark. Since 1984 the Thames Barrier has closed against dangerous tides from the sea. The zones leave defences out, so the land the Barrier protects still shows: the map is what the river and the tide could reach without them.
The Somerset Levels
The Levels are low, flat moors between the Quantock and Mendip hills, drained and farmed for centuries. 32% of North Somerset’s land is in a flood zone, and 17% of Somerset’s. In the wet winter of 2013 to 2014 much of the Levels lay under water for weeks, and the village of Muchelney was cut off and supplied by boat.
Wales maps the future too
Wales draws its flood zones with an allowance for the higher rivers and seas that climate change is expected to bring, while England’s show today’s risk, so read the border as a change of method as well as of country. In Wales 6.2% of the land is in Zone 3. Newport has the largest share in a flood zone, 45%, then Cardiff with 24%, both on the low coast of the Severn estuary.
For classrooms and curious minds
Questions to talk about, alone or in a group.
- The zones leave out flood defences. Why would a planner want to see what a river could do without them?
- Two councils have the same share of land in a flood zone. Why might one still face much more harm than the other?
Try it on the map: Find your own town. Is any of it in Zone 3, and is that the old centre or the newer edges?
The figures above are calculated from the datasets listed on Data & sources and are approximate: many map layers are modelled or interpolated. Read each layer’s caveats on the map.