Weather Event update - 1000hrs 5 May 2023
The Tasman District Council - Te Kaunihera o te tai o Aorere Hydrology team has provided an update on the forecast weather (below).
As we remain under a weather warning we are still encouraging people to be prepared for a wet weekend ahead, as the situation can change quickly.
Our region remains under Orange Heavy Rain Warning as of 1000hrs Friday morning, although the potential for heavy rain has lessened. The warning remains in two parts, one for the north-west corner of our District, and the other for the Eastern side closer to Nelson and Richmond.
The nature of the event is for ongoing rain of moderate to a lesser intensity, but with the potential for heavy rain to occur in specific areas, mostly overnight Friday. There is uncertainty about where the exact location of heavy rain might be, but it is most likely to be in the general area of Riwaka through Golden Bay including Abel Tasman. There is less likelihood of heavy ongoing rain in the eastern side of the District, in particular the hills behind Richmond and Nelson.
As before, the focus is on the potential for land slips to occur in two broad areas: the erosion prone granite soils of Lower Motueka River and Riwaka, lower Tākaka Hill, and North of Tākaka to Totaranui; plus the slopes from Nelson City through to Cable Bay. There is potential that travel could be disrupted in these areas, but the likelihood is moderate at best.
The potential for flooding is reduced from previous advice. The most likely scenario is flooding of a nature expected on an annual basis across the northern parts of our District. As with any severe weather event however, there may be more extreme flooding in certain areas depending on how the storm plays and bands of heavier rain develop. Therefore, given the wet nature of catchments and the ongoing uncertainty of the forecasts, it is prudent to plan for at least 5-year floods across any of these rivers in the northern parts of Nelson and Tasman. Localised heavy rain may result in more significant flooding in small streams.
Travel disruptions are possible, in particular the State Highways of Tākaka Hill, Motueka Valley and between Nelson and Marlborough. You can stay up to date with road closures here: https://bit.ly/3GB5v0x - we have a map with local road conditions and also Waka Kotahi's map of state highway conditions.
Stay up to date with the MetService warnings here: https://www.metservice.com/warnings/home#upper-south.