The Origin and Use of the "100-Year Flood Protection Standard" in New Zealand
- Mar 2
- 2 min read
Updated: Jul 1
The abstract for the paper I presented at Water New Zealand's Stormwater Conference 2026 in Auckland in May can be found here on the Water NZ website. The full paper will be uploaded by Water New Zealand to their website sometime in the future but in the meantime contact me if you'd like a copy, or to discuss any aspect of the paper.
The paper is titled The Origin and Use of the "100-Year Flood Protection Standard" in New Zealand and answers the questions:
When was the 100-year flood protection standard first used for a publicly funded flood scheme in New Zealand?
What influence did central government part-funding have on the selection of design standards for schemes?
How did the standard become to be used as a reference scenario in floodplain mapping, and in urban settings?
It is commonly understood amongst water professionals in New Zealand that the 100-year flood protection standard had its origins in fluvial flood protection schemes. More specifically, investment decision-making for government part-funding of schemes, through subsidies and loans. However less is known about why and when it originated and whether it was mandatory. Further, the commonly understood origin doesn’t explain how it came to also be used in pluvial, urban settings for stormwater, and for floodplain mapping. It also does not explain why it has endured, despite the cessation of government subsidies for flood schemes in the late 1980s.
My paper addresses these matters based on research I have done over the past year or so, compiling and reviewing documents from Archives New Zealand, the National Library, regional councils and unitary authorities and various public libraries, along with journals of professional bodies. This includes documents of the former Soil Conservation and Rivers Control Council dating back to the 1940s and the former National Water and Soil Conservation Authority (NWASCA).
