Homes in each flood zone, by London borough

Flood Zones (Flood Map for Planning – Flood Zones (NaFRA2)) show where flooding from rivers or the sea could happen, ignoring flood defences. Zone 3 is land with a 1% or greater chance of flooding from rivers, or 0.5% or greater from the sea, in any year; Zone 2 is land between that and 0.1%; Zone 1 is the rest.

Risk bands (Risk of Flooding from Rivers and Sea (NaFRA2)) account for the defences in place and their condition. High is a 3.3% or greater chance in any year, Medium 1% to 3.3%, Low 0.1% to 1%, and Very Low less than 0.1%.

That is why a home can be in Zone 3 and in the Very Low band: the land could flood without defences, and the defences there are taken into account in the band.

Outside the mapped area means there is no Risk of Flooding from Rivers and Sea (NaFRA2) cell at the home's point. It is counted as Very Low and kept in its own column. The Environment Agency's own property counts include only homes inside mapped cells.

What "homes" counts. A home is a London address with at least one domestic Energy Performance Certificate on the government register (2008 to 1 October 2026), placed at its Ordnance Survey address point. Homes with no EPC since 2008 are not counted, nor are certificates lodged without a UPRN or UPRNs absent from OS Open UPRN. Where several flats share one building UPRN on the register, they count as one home.

Coverage. London has 2,897,212 counted homes against 3,863,730 dwellings on the VOA Council Tax: stock of properties 2026, table CTSOP1.1 (dwellings at 31 March 2026, published 24 September 2026): 75.0%. By borough it runs from 70.0% (Bromley, Camden) to 82.8% (Newham). The two sources define a dwelling differently, so the ratio is context only, not a correction.

The reading. Each home is read at its OS Open UPRN point (September 2026 release), the same point the property tab uses. Zone: 3 if the point is inside any Zone 3 polygon, else 2 if inside any Zone 2 polygon, else 1. Band: the band of the Risk of Flooding from Rivers and Sea (NaFRA2) cell at the point; where a point touches cells of two bands, the higher band is taken. Borough: the Local Authority Districts (May 2026) Boundaries UK BFE boundary that holds the point. Camden and Islington have no counted homes in Zone 2 or Zone 3.

Editions. Flood Map for Planning – Flood Zones (NaFRA2): Published 25 March 2025; dataset revision 20 May 2026; national file posted 21 September 2026. Risk of Flooding from Rivers and Sea (NaFRA2): Published 28 January 2025; dataset modified 18 June 2026; area downloads taken 5 October 2026. Energy Performance of Buildings register, domestic certificates: Bulk file regenerated 1 October 2026; certificates lodged 2008 to 2026. OS Open UPRN: September 2026 release. Counted 5 October 2026.