Preliminary findings on last year's Whanganui floods have found the city may have to reconsider its flood protection systems.
The Whanganui Manawatu regional council's group manager for river management, Ramon Strong, says the June flood is estimated to have been a one in 130 years' event, with a peak flow of 5150 cubic metres per second.
Flows measured on the Whanganui River were the highest ever recorded there.
It was also the second biggest flood in the North Island after the Mohaka flood in 1938.
Mr Stong said the findings mean the current standard of flood protection for Whanganui needs to be reconsidered.
The report also found that flooding of Taupo Quay, in the CBD, will start to occur as a one in 20-year event.