FloodMap.nz is a data product of SAE Ltd, Napier. The aim is straightforward: a consistent national overland flow path layer at the resolution councils, engineers and developers actually need — built on current LiDAR, with the methodology open to inspection.
The gap that needed filling. Every consent application for subdivision, multi-unit residential, or non-trivial earthworks needs an answer to one question: where does surface water flow across this site? In practice, the answer comes from a patchwork — old council GIS layers, district plan overlays, NIWA national products, and a lot of judgement.
The new National Flood Map (Earth Sciences NZ) is excellent at the regional scale, but it covers 256 major floodplains and explicitly excludes property-level detail. Most council overland flow layers were built on 2016 or older LiDAR, and many councils don't model overland flow at all — only big rivers. That's fine for public awareness. It's not enough for an engineer trying to screen a site quickly.
How it started. SAE Ltd does subdivision and stormwater engineering across Hawke's Bay, Manawatu and Auckland — 300+ projects across 15+ years. Every one of those projects starts with the same exercise: pull the LiDAR, look at where water flows, decide what the constraints are. That work was being done one site at a time. In late 2024, with LINZ publishing fresh nationwide 1m LiDAR and open-source geospatial tooling having matured (WhiteboxTools, GRASS, MapLibre, PMTiles), it became viable to do the analysis once, for the whole country, and publish the result.
The first region (Auckland) went live in early 2026 with 1.17 million flow paths derived from 2024 LiDAR. The rest of the country is rolling out as new survey blocks land. Methodology is published in full at /methodology — every step from DEM mosaic to vector tile is documented and reproducible.
What's published today. The public map shows Tier 3 (25–500 ha catchment), Tier 4 (2–25 ha) and Tier 5 (0.4–2 ha) overland flow paths — flow paths only, no depth or hazard category. It's a screening reference, not a regulatory hazard layer. Free to view, no login, because property-level overland flow visibility is, in our view, public information.
What's coming. Tier 1 and Tier 2 (large-catchment) coverage, Tier 6 (property-scale, <0.4 ha), and data partnerships with councils that want closer integration. Site-specific HEC-RAS 2D flood assessments (depth, velocity, hazard) are currently delivered as bespoke engineering through SAE Ltd — see /flood-report for what those typically cover.
Chartered Professional Engineer (registration 237893), Director of SAE Ltd, based in Napier. Previously Design Engineer at Hawke's Bay Regional Council on flood protection infrastructure — including the Taradale Stopbank, which was tested by Cyclone Gabrielle in 2023 and did not overtop. SAE Ltd specialises in subdivision engineering, stormwater design, flood assessment and three waters infrastructure across Hawke's Bay, Manawatu and Auckland.
Every step from LiDAR ingest to vector tile is documented at /methodology. No black-box derivations. If a council, peer reviewer or consultant disagrees with an output, they can read the method and challenge it.
Built against the latest LINZ composite. As new survey blocks are published, affected regions are reprocessed. No region runs on stale terrain longer than necessary.
The OFP layer is bare-earth-derived. It does not model culverts, stormwater pipes, or constructed drainage, and it does not include depth, velocity or hazard category. It is a screening reference, not a regulatory layer. The methodology page lists every limitation up front.
Tier thresholds align with NZS4404 and the AUP E36 4,000 m² trigger. Manning's n tables match SWCoP v4. The data is structured to drop cleanly into the workflow engineers already use.
The map view is and will remain free for public, professional and council use. Property-level flow visibility is too important to gate.
FloodMap.nz is built and maintained by SAE Ltd. SAE delivers civil engineering for subdivision, stormwater, flood assessment and three waters across New Zealand. Site-specific flood modelling that goes beyond the published OFP layer — HEC-RAS 2D, hydraulic neutrality assessments, consent-grade reports — is commissioned through SAE.
Methodology questions, data discrepancies, council partnership enquiries, media — direct line to Andre.
Get in touch → Read the methodology