Mimmshall Brook at Warrengate Road
The Mimmshall Brook at Warrengate Road including Water End
Mimmshall Brook Hertfordshire
Postcode district
Flood risk in AL9
How exposed the AL9 postcode district (East Hertfordshire and Welwyn Hatfield) is to flooding from rivers, the sea and surface water, from a sample of points checked against the Environment Agency maps.
0%in Flood Zone 2 or 3
0%in Flood Zone 3
0%medium or high river and sea risk
0%some surface water risk
Based on 5 points spread across the district. An indication of the area, not a count of properties.
What the maps show around AL9
Most of the points we checked are outside the flood zones, but flood risk is local: a single street, underpass or stream can be the exception. We checked 5 points spread across the district: the centre and four points about 900 m away.
0% of the sample points are in Flood Zone 2 or 3 · 0% have some surface water risk
Overall: mostly lower risk. This describes the district as a whole, not your street.
Flood zone: 0 of 5 points in Zone 3 and 0 in Zone 2.
Flood warning areas near AL9
The Environment Agency issues flood alerts and warnings for these named areas within about six kilometres of the district centre.
River Colne at Colney Heath
The River Colne at Colney Heath including North Mymms
River Colne Hertfordshire
River Lee from Lemsford to Hertford
River Lee from Lemsford to Hertford including Welwyn Garden City, Hatfield and Mill Green
River Lee Hertfordshire
Mimmshall Brook
The Mimmshall Brook at Warrengate Road including South Mimms, Potters Bar, Brookmans Park and Welham Green
Mimmshall Brook Barnet, Greater London, Hertfordshire
Upper River Colne and Radlett Brook
The Upper River Colne and Radlett Brook at Colney Heath, London Colney, Borehamwood and Radlett
River Colne Hertfordshire
River Colne at London Colney
The River Colne at London Colney including Colney Street and Broad Colney
River Colne Hertfordshire
You can sign up for free flood warnings for your own address on GOV.UK.
Check your own AL9 postcode
The figures above describe the district. Your home is one point in it, and that point is what the check reads.
This district spans East Hertfordshire and Welwyn Hatfield.
Will your address flood, and can you get it insured and mortgaged?
Enter an English postcode and see free of charge its flood zone and the risk bands for rivers, the sea and surface water. What the numbers mean, which past floods were recorded around the property, which warning areas cover it and what to ask your insurer, surveyor and solicitor is in the report for that one point.
A flood is the most expensive thing that can happen to a home, and a flood zone or a surface water flow path can change the insurance terms, the mortgage offer and the resale price. The report gathers the Environment Agency data for your address before you commit; it is not a substitute for a flood search from your conveyancer.
- The flood zone and all three risk maps at your point: rivers and sea, surface water, with the annual chance in plain figures and a map of the ground around it
- Every recorded past flood and the flood warning areas that cover the address, with dates, sources and causes where the Environment Agency has them
- What it means for insurance, a mortgage and the building itself: Flood Re, questions for the surveyor and practical flood resilience measures, as a PDF you can share
England only. The short answer is free.
🔒 Card or PayPal via Mollie · download straight after payment, emailed as well · no subscription
Source: Environment Agency under the Open Government Licence · not a substitute for a flood search
Nearby postcode districts
Questions
Frequently asked questions
Is AL9 in a flood zone?
None of the 5 sample points we checked across the AL9 postcode district fall in Flood Zone 2 or 3. That does not rule out a zone elsewhere in the district, because the sample is a handful of points and flood zones can be narrow. Check your full postcode to be sure.
Is surface water flooding a risk in AL9?
None of the 5 sample points rate above very low for surface water flooding. Surface water risk is highly local, so check your own postcode.
Which flood warning areas cover AL9?
The Environment Agency issues flood alerts and warnings for named areas. Within about six kilometres of the centre of AL9 these include Mimmshall Brook at Warrengate Road, River Colne at Colney Heath and River Lee from Lemsford to Hertford. You can sign up for free flood warnings for your address on GOV.UK.
How accurate is a postcode district summary?
It is an indication, not a verdict on any single home. We checked 5 points around the centre of the district against the Environment Agency maps. A district can hold many streets and a flood zone can be a few metres wide. The free check on a full postcode, with a pin you can move onto your plot, is the precise answer.