EA Flood Zones (NaFRA2)
What it is
The Environment Agency's Flood Zones map England's probability of flooding from rivers and the sea. WildStack uses Flood Zone 2 and Flood Zone 3, derived from the EA's National Assessment of Flood Risk (NaFRA2) — the second-generation national flood-risk modelling:
- Flood Zone 3 — higher probability (broadly ≥1% annual chance from rivers, or ≥0.5% from the sea).
- Flood Zone 2 — medium probability (broadly between the Zone 3 threshold and 0.1% annual chance).
They are primarily a planning and flood-risk dataset, but they matter to nature because floodplains and their habitats are ecologically distinctive.
How it's produced
NaFRA2 is a national modelled assessment combining terrain, defences, and hydrological/hydraulic modelling. Like any national model, it is authoritative at strategic scale and generalised at the parcel — it is not a substitute for a site-specific Flood Risk Assessment.
Update frequency & currency
The EA's flood-risk products have moved to updated national modelling (NaFRA2) and are refreshed periodically. Confirm the current edition/vintage when citing zones.
Spatial resolution / precision
National-model resolution: good for "is this site in a flood zone?", not for precise on-site flood depths or defence-adjusted risk. Treat zone edges as strategic, not surveyed.
Known limitations
- Probability, not certainty. Zones express modelled likelihood, not a forecast for any given event.
- Rivers and sea only (this product). Surface-water and groundwater flooding are assessed separately.
- Strategic scale. Not a replacement for a site-level FRA.
Role in BNG assessment
In WildStack's stack, Flood Zone 2/3 is a constraint overlay that fires a floodplain-habitat signal: a site intersecting a flood zone flags the potential presence of ecologically significant floodplain habitat (grazing marsh, wet grassland, functional floodplain) worth attention in the assessment. It contributes context and a trigger, not habitat parcels.
Flood zones are usually read purely as a development risk layer — can we build here, and at what cost? — and their ecological signal gets missed. A floodplain is not just a hazard; it is often where the more distinctive wet habitats live, and where nature recovery has real leverage. We use the flood-zone intersection as a prompt to look harder at floodplain habitats, not just as a planning constraint. The two readings aren't in tension: the same wet ground that complicates development is frequently the most ecologically interesting part of a site.
Official source
Last reviewed
5 July 2026. Revisit as the EA rolls out and updates NaFRA2-based products, or if the flood-zone probability definitions change. Confirm current dataset URLs and thresholds at review.