The full cost of the June 2015 flood on the Whanganui urban area may never be known but a Horizons Regional Council report has tried to put figures on the response, recovery and repair.
A report to councillors by project engineer Allan Cook and river management group manager Ramon Strong looked at the economic impact of the flood on Whanganui.
A "significant number" of houses along Anzac Parade and Putiki and approximately 28 businesses around the Taupo Quay area were affected by the flood.
The report said the true cost of the flood in many areas, such as additional staff time from emergency response organisations such as Police and Red Cross, was difficult to determine.
The greatest impact of the flood was on private residential and commercial property and neither insured or uninsured damage costs are available," the report said.
However the cost to New Zealand Insurance Council members was $41.5 million, but those figures includes Horowhenua, Wairarapa and Taranaki.
The cost of repairing damage to urban council infrastructure - Whanganui District Council and Horizons Regional Council - was $1.6million.
The majority of that was needed to repair water and wastewater infrastructure.
Horizons spent $364,000 on the initial recovery, including on staff, field observations and emergency measures.
Whanganui District Council spent an estimated $50,000 of extra staffing costs.
The costs on various emergency response organisations was difficult to determine.
NZ Police brought in an additional 55 staff while Red Cross deployed 12 teams which evacuated about 400 people.