# When the water came

Christchurch was built on a swamp and the record keeps proving it, 20 named surveys and storm events, 12,195 mapped patches of ground that went under, 1934 to 2022.

## The record, oldest first

- **1934 Waimea Terrace Flood Mapping**, 16 patches · 0.8 ha · Flood Map
- **1968 Aranui Flood Mapping**, 31 patches · 2.5 ha · Flood Map
- **1977-1981 Heathcote River Flood Survey**, 848 patches · 52.4 ha · Resident Survey
- **1986 Storm Report (July)**, 899 patches · 52.5 ha · Post Event Summary
- **1986 Canon Street - Manchester Street Flood Survey**, 33 patches · 0.9 ha · Resident Survey
- **1986 St Albans and Frees Creeks Flood Survey**, 184 patches · 8.2 ha · Resident Survey
- **1987 Lower Styx Flood Survey**, 45 patches · 48.8 ha · Resident Survey
- **1989 Fendalton Riccarton Flood Survey**, 57 patches · 4.6 ha · Resident Survey
- **1991 Barrington Flood Survey**, 24 patches · 0.7 ha · Resident Survey
- **1991 Queensbury Street - Mascot Place Flood Survey**, 9 patches · 55.1 ha · Resident Survey
- **1991 Upper Wildnerness Drain Flood Survey**, 40 patches · 1.5 ha · Resident Survey
- **1992 Heathcote (Lower) Flood Survey**, 113 patches · 6.8 ha · Resident Survey
- **1992 Heathcote (Upper) Flood Survey**, 119 patches · 8.4 ha · Resident Survey
- **1993 St Johns Street - Hargood Street Flood Survey**, 183 patches · 11.3 ha · Resident Survey
- **2000 Sumner - Redcliffs Flood Event (October)**, 197 patches · 55.5 ha · Post Event Summary
- **2008 Akaroa Basin Harbour Settlements Study**, 1,978 patches · 7400.8 ha · Flood Assessment Report
- **2011-2014 Flooding - Mayoral Flood Taskforce**, 7,330 patches · 7951.0 ha · Flood Assessment Report
- **2017 Heathcote Flood Event (July)**, 50 patches · 2.7 ha · Resident Survey
- **2021 Le Bons Bay Flood Event**, 18 patches · 677.5 ha · Photograph
- **2022 Wet Weather Response (July)**, 21 patches · 8.4 ha · Post Event Summary

## Where the water went, by suburb
By share of each suburb’s outline under the recorded patches.

- Ferrymead: 63% of its outline · 156 ha · 1 event
- Bromley: 57% of its outline · 437 ha · 2 events
- Avonside: 48% of its outline · 57 ha · 1 event
- Redcliffs: 47% of its outline · 89 ha · 2 events
- Spencerville: 46% of its outline · 130 ha · 2 events
- Westmorland: 44% of its outline · 110 ha · 1 event
- Burwood: 43% of its outline · 254 ha · 2 events
- Ouruhia: 42% of its outline · 315 ha · 1 event
- Duvauchelle: 41% of its outline · 1,821 ha · 2 events
- Moncks Bay: 40% of its outline · 15 ha · 2 events
- Avondale: 40% of its outline · 85 ha · 1 event
- Mairehau: 39% of its outline · 176 ha · 2 events
- Bexley: 37% of its outline · 79 ha · 1 event
- Bottle Lake: 34% of its outline · 426 ha · 2 events
- Southshore: 33% of its outline · 37 ha · 1 event

_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._

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Christchurch City Council open data, the HistoricFlooding layer of OpenData/LandCharacteristic. A flood patch is where water was observed or surveyed in a named event, not a live hazard finding for an address today. A point’s own record: https://www.chch.live/before. The files: https://www.chch.live/floods.json · https://www.chch.live/floods.geojson · by suburb: https://www.chch.live/suburb-floods.json