Flooding in Napier

November 2020 Napier Flood Report 

Executive Summary 

Read the full report here.

On 9 November 2020, Napier received an extreme level of rain in a short period of time over a small geographic area. Due to the speed and intensity of the weather event, many parts of the City and environs were flooded.

The stormwater system worked as it was designed to do, although the specifications of the system are rated below the rating of this storm, which was described as a ‘1 in 250 year’ event, one of the highest rainfalls on record. As the climate changes these return periods or Annual Exceedance Probabilities are less relevant with such events returning more often than the rating suggests. As population, and resulting housing stock, grows, the built environment includes a greater number of houses, and a greater number of impermeable surfaces such as concrete and roofs, meaning water sheets off exacerbating flooding issues.

The priority is to mitigate the damage caused by flooding. This will take a multi-pronged approach with councils, partner agencies and community working together to ensure the city can withstand such events. Building a resilient community that understands the nature and effects of flood, and can take proactive measures to minimise damage, is as important as ensuring council-led strategies and operational processes are effective.
Post flood reports on the incident have been reviewed to help inform operational and strategic approaches to managing flood in the future. As much as reviewing the incident, response and recovery of the November flood, reviewing such reports is a valuable element in taking a forward-facing view to prepare community, assets and infrastructure to best meet the impacts of any future events.