Does SL9 flood?

Yes — parts of the SL9 district carry real flood risk: 1 of its 28 at-risk postcodes reach the Environment Agency's High likelihood band. The SL9 postcode district covers Chalfont St Peter, Gerrards Cross & Denham, close to Denham, Rickmansworth, Uxbridge, and surrounding villages in parts of England and Buckinghamshire.

28 postcodes in the SL9 district appear in the Environment Agency's rivers-and-sea flood-risk dataset — worst bands: 1 high, 4 medium, 23 low. A postcode not listed here has no properties in any recorded risk band (which is good news, but never proof it cannot flood).

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Which SL9 postcodes are at risk?

Rivers and flooding history near SL9

The rivers that matter here, each monitored live on FloodRadar:

Denham Colne on the River Colne — 6.5 km away, highest on record 0.61m
Uxbridge, Fountains Mill on the Frays River — 7.9 km away, highest on record 2.06m
Howletts Lane, Ruislip on the Cannon Brook — 8.3 km away, highest on record 1.10m
Ickenham, Swakeleys Road on the River Pinn — 8.3 km away, highest on record 2.01m

145 official flood warnings and alerts have been raised within ~10 km of the district's centre since 2006 (5 at warning level or above), most recently 27 August 2026. Warnings cover flood areas, not individual addresses.

Recorded flood extents near the district (Environment Agency record):

EA06MarchSpring2024 (2024) — about 0.1 km from the centre
February 2014 flooding — about 0.2 km from the centre
January 2014 flooding — about 0.3 km from the centre
Winter 2013/2014 (2013) — about 22.7 km from the centre

Records, not floods: no outline on the record is not evidence a place has not flooded.

🏠 Buying or renting in SL9? The full property flood-risk report covers any postcode here — the official likelihood band, every recorded flood nearby with distances, warning history year by year, how the local rivers behave, and an insurance outlook, print-ready for £19. See what's in the report →

Flood risk in nearby postcode districts

SL8 SL7 SL6 SL5 SL4 SL3 SL2 SL1

Band = the worst likelihood band of any property in that postcode (EA Risk of Flooding from Rivers & Sea, defence-adjusted, area-level). Check any postcode in detail — or get the full £19 property report — at the property flood-risk report. © Environment Agency copyright and/or database right 2025. All rights reserved. Some features of this map are based on digital spatial data from the Centre for Ecology & Hydrology, © NERC (CEH). © Crown Copyright and Database Rights 2025 OS AC0000807064. This product is produced in part from PAF® and Multiple Residence Data, the copyright in which is owned by Royal Mail Group Limited and/or Royal Mail Group plc. All rights reserved. Licence number AC0000807064.