20/10/2025
Updated post 4pm Tuesday 21 October:
A final message from our Hydrology team as rainfall in the ranges has eased and all the upper river catchment gauges have peaked and are now starting to fall.
This will still take time for the flows to work their way down the main Motueka River, with the gauge at Woodstock just sitting at its peak now, and anticipated to start dropping shortly.
For the lower Motueka, the river will continue to rise for the next hour or so, peak anticipated at about 5pm with a flow of 1150 cumecs, which is an annual flood flow.
In Golden Bay, the Upper Tākaka still remains high, but is sitting below an annual flood level and not anticipated to rise further, so we wouldn’t have any expectation of issues there.
Large amounts of rain fell in the headwaters of the Wangapeka River and catchments further south, 280mm was recorded in the Council’s gauge at Biggs Tops in the Wangapeka catchment. This led to significant flows in both the Wangapeka and Motupiko rivers with peaks estimated as at or about 10-year return period flood flows.
Further south, there have been reports of high flows coming from the Owen River catchment, and the Buller River at Longford reached a 5-year flood flow.
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Updated post 10am Tuesday 21 October:
An update on yesterday's weather forecast from our Hydrology team:
Metservice has issued an update on the Heavy Rain Warning, which shows forecast rain continuing through to 2pm. This 40-60mm forecast will be mainly confined to the western ranges, and is in line with previous forecasts.
But there is now also mention of thunderstorms which could be quite problematic, especially if they occur over any of these upper Motueka catchments that are already at high levels. Being thunderstorms they are by nature unpredictable so should consider that they could occur anywhere through the Motueka catchment, with potential to cause additional surface flooding with streams and rivers rising quickly.
In terms of the major rivers, both the Baton and Wangapeka have risen quickly this morning and are already above annual flood flows. Expectation is that they will reach 5-year flood flows, with peaks from midday. These sorts of flows will likely see low-lying berm areas immediately adjacent to the rivers with water on them for short periods.
The Motupiko river is also starting to rise, with flows likely to get to and potentially above the 5-year flood level. The Rainy is a sub-catchment of the Motupiko and is also likely to experience high flows with this westerly rain event.
Both of these areas were hard hit during the June/July floods, and normally, a 5-year flow would be quite manageable in these catchments. But with the damage that has occurred, these flows might lead to greater impacts than normal, and we will be expecting them to be covering low-lying paddocks adjacent to the river at times.
The good news is that the timing of the sub-catchment flows should mean that there is a lower risk of high flood flows through the main branch of the Motueka River from Tapawera down through to Woodstock and on towards Motueka. Therefore we would not be expecting flows in the main river akin to July 2021 as had been previously suggested as the upper possibility, though it will still be highest flows since July occurring on the main Motueka River.
We will continue to monitor throughout the day and provide updates if the situation changes.
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Original post 12pm Monday 20 October:
MetService has issued an Orange Heavy Rain Warning affecting parts of the Tasman District from 9pm tonight, Monday, through to 1pm tomorrow, Tuesday.
While the image makes it look like the weather will miss us in the top of the South, the impacts will still be seen in some of our river catchments, so our Hydrology team has an update below with what they are expecting.
This rainfall event is coming in from a north-westerly direction and therefore will be impactful mainly in the most western-facing catchments of the Tasman District. Eastern catchments of Tasman and Nelson are not likely to get large rainfall totals.
So areas such as the Maitai and Wairoa/Wai-iti catchments are not expected to reach high flood flows. This expectation would also extend through the Moutere and Lower Motueka catchments, such as Brooklyn/Riuwaka where only minor river flows are expected.
Golden Bay main rivers, such as the Aorere and Tākaka will receive rainfall into their upper catchments, but only low flood flows are expected, with flows below an annual flood level most likely.
With rainfall concentrated in western areas, this will also fall across the upper catchments of the Buller River. However at the rainfall totals forecast, we would not be expecting large floods in the Buller River or Murchison areas.
This leaves the Upper Motueka river area including the Wangapeka/Tadmor/Motupiko rivers where there is heightened concern due to the potential for high flood flows to eventuate. Given the state of the river system in this area, there is a high likelihood that flows could be impactful in vulnerable sections of these rivers.
For the main Motueka River, high flood levels are expected in and about Tapawera and down through to the middle sections around Woodstock. In the lower Motueka River, flows will still be high but not to such high levels, yet still potential for elevated flood flows in the lower reaches at Motueka.
For these upper Motueka rivers, it is likely that flows will be the highest seen since the large winter floods in June/July - however, we are not expecting it to be anywhere near that extent of flows. At the top end of the forecast range could be flows approaching those seen in July 2021 in the upper sections of the Motueka River through to around the Woodstock area. At the lower end of the Motueka River, closer to Motueka, expectations are that it would not reach July 2021 levels due to low flood inputs in these lower catchment areas.
Rain will build overnight with the heaviest falls around dawn on Tuesday. This will lead to flood peaks in the upper Motueka area through the early afternoon, with lower Motueka peaks likely late afternoon/early evening.
Links for more information:
• MetService warnings: https://www.metservice.com/warnings/home -south
• Road closures across the region: https://rebrand.ly/httfpkm
• River flow reports: https://www.tasman.govt.nz/flow-report/
• Rainfall reports: https://www.tasman.govt.nz/report/
There may still be people needing help following the winter flood events earlier this year. If you need assistance, there’s still plenty of free help, and a wealth of knowledge and resources available with our Navigators. They can point you in the right direction. Get in touch by phoning 03 543 8400 or emailing [email protected].
