New Zealand's stormwater and wastewater systems are particularly vulnerable to climate change, says a report citing Edgecumbe's experience as an example of the challenges.
In April, the Bay of Plenty town was swamped by flooding, leading to raw sewage floating through the streets and making the clean-up difficult.
Six months on, 500 houses remain unliveable and flood-proofing the town remains a distant goal, the report commissioned by the NIWA-led Deep South National Science Challenge says.
The country's stormwater and wastewater assets are valued at well over $20 billion.
However, the report says, much of it was not designed for climate change.
Adapting to the "increasingly severe risks" of extreme rainfall, storm surges, sea level rise and drought could require significant and expensive changes to networks.