Flood risk methodology

Districts reports whether available mapped flood layers intersect or otherwise indicate exposure for the property location. That is a screen of official spatial overlays against the parcel Districts loaded. It is not an engineering flood study, a flood certificate, or an insurer quote.

When an official flood overlay intersects the parcel, Districts can show the layer name and the share of the official parcel that intersects, as a percentage. Split GIS tiles for the same layer are merged so they are not listed as separate tiny facts.

When the overlay only touches the boundary, Districts says so separately from a material intersection.

When the loaded overlay was queried and did not intersect the lot, Districts says no mapped flood exposure was identified in the datasets currently used — not that the property cannot flood.

When only a listing observation mentions flood and the official layer has not been queried, Districts treats that as listing evidence, not a government classification.

The dedicated official flood overlay currently catalogued for retrieval is Sunshine Coast Council’s Flood Hazard Overlay — Flood Risk Area. Other jurisdictions only contribute a flood result if a loaded planning overlay is classified as flood (for example a Victorian planning overlay whose name includes flood or inundation). There is no statewide New South Wales flood layer in the current catalog. An empty or missing New South Wales layer is not an all-clear; much flood mapping there is council-held.

The source line on the property page usually names the planning extract’s primary provider and dataset (often the zoning service) and the retrieval date. That label is not always the flood layer’s own dataset name.

Listing flood flags are public marketing observations, not official mapping.

Districts calculation: intersection of loaded flood overlay polygons with the official parcel geometry (area of intersection ÷ parcel area). The lot share is that ratio as a percentage, rounded to one decimal place, and capped at 100%. A hit is treated as boundary-only when the share is under 1% and the intersecting area is under 10 square metres; otherwise a positive intersection is treated as affecting the lot.

Overlays with the same name and category are collapsed before display so tiled fragments of one layer are not counted twice as independent facts. If those fragments look disjoint, their areas can be added; otherwise Districts keeps the larger fragment.

Classification used on research answers: mapped intersection (affects), boundary only, queried with no intersection, listing-only mention, or not enough evidence because the layer was not queried or failed.

Districts does not run a hydraulic model and does not assign an insurance flood category.

A supported mapped result requires a retrieved official layer. A listing mention without that layer is listing evidence only.

A completed query that finds no intersection is a queried-empty result for those layers, not a certificate the lot cannot flood.

If planning has not been retrieved, or the flood category was not queried, Districts leaves flood unknown. Missing is not “no.”