Summary
Flood Zones and surface water maps are not the same thing. Flood Zones for Planning show broad river and sea probability bands used for planning, while long term flood risk and surface water layers help identify likely flood sources and local flow paths. A buyer should check both because a property can sit outside a high river flood zone but still have serious surface water risk.
Definition
Flood Zones are planning policy bands for river and sea flooding in England. Flood Zone 1 is lower probability, Flood Zone 2 is medium probability, and Flood Zone 3 is higher probability, with Flood Zone 3b used for functional floodplain in planning. Surface water risk maps estimate where rainfall may pond or flow over land when drainage cannot cope. These maps are screening tools and should be verified with long term risk services, flood history, insurance checks and site specific evidence.