When the water came
Christchurch was built on a swamp and the record keeps proving it, 20 named surveys and storm events in the council’s flood layer, 12,195 mapped patches of ground that went under, 1934 to 2022. The Heathcote’s banks, the Avon’s margins, the low east, the same ground every time.
Every recorded flood, drawn
All 12,195 patches over the suburb outlines: hover for the event that drew each. The biggest record is the quake-era taskforce’s: the ground that dropped in the shakes ponded afterward.
The record, oldest first
Where the water went, by suburb
By share of each suburb’s outline under the recorded patches, the wettest of its ground first.
- Ferrymead, 63% of its outline under the record · 156 ha · 1 event
- Bromley, 57% of its outline under the record · 437 ha · 2 events
- Avonside, 48% of its outline under the record · 57 ha · 1 event
- Redcliffs, 47% of its outline under the record · 89 ha · 2 events
- Spencerville, 46% of its outline under the record · 130 ha · 2 events
- Westmorland, 44% of its outline under the record · 110 ha · 1 event
- Burwood, 43% of its outline under the record · 254 ha · 2 events
- Ouruhia, 42% of its outline under the record · 315 ha · 1 event
- Duvauchelle, 41% of its outline under the record · 1,821 ha · 2 events
- Moncks Bay, 40% of its outline under the record · 15 ha · 2 events
Each flood patch files under the suburb its exterior’s middle sits in: hectares net of holes, with the count of distinct events. A patch is one event’s observation, not a live hazard finding for an address.
Questions, answered briefly
The council’s historic-flooding layer holds 20 named surveys and storm events, 12,195 mapped patches of ground that went under, from 1934's Waimea Terrace mapping to the 2022 wet-weather response. The two biggest records are the quake-era Mayoral Flood Taskforce (2011–14) and the 2008 Akaroa harbour-settlements study.
The same ground every time, the Heathcote’s banks (surveyed 1977–81, again 1992, again 2017), the Ōtākaro Avon corridor, St Albans' Frees Creek, the estuary margins, and the low eastern suburbs. The map draws every recorded patch; a point’s own record answers at /before.
Yes, the largest record in the layer is the 2011–14 Mayoral Flood Taskforce: ground that dropped in the shakes ponded afterward, and the taskforce mapped thousands of patches that had never flooded before. The dropped ground itself is drawn at /liquefaction and /redzone.
No, each patch is the record of where water was observed or surveyed in one named event. Ground that flooded in 1934 may be behind stopbanks now; ground the record missed may still flood. The layer is history kept for LIMs, not a live hazard map.
The record behind this
Christchurch City Council’s open land layers, the HistoricFlooding layer of OpenData/LandCharacteristic, kept for LIMs. A flood patch is where water was observed or surveyed in a named event, not a prediction or a hazard-zone finding for an address today. Ask a point’s own record at /before; the ground that dropped is at /liquefaction; the land the Crown wrote off is at /redzone; the ground the city tipped into is at /landfills; the ground it made is at /fill.
This page as markdown: /floods.md · the record as data: /floods.json · /floods.geojson · /suburb-floods.json · on the live map: /map?layer=floods.