Ashburton District Council staff are closely monitoring the Rangitata River after the MetService issued the orange heavy rain warning.
ECan says the situation is still developing and it's too early to determine expected flows for the Rangitata River.
But all adjacent landowners and people using the riverbed should carefully monitor their situation and prepare for high river flows and the possibility of flooding on Thursday and into Friday.
The river mouth is located in a central position and there is no elevated risk of flooding at the mouth.
The warning is in place from 10am Wednesday until 9am on Thursday, with forecasts of 300 to 450mm of rain about the divide, with 130 to 180mm within 15km east of the divide. Peak rates of 25 to 45mm/h are expected about the divide, with thunderstorms.
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.
The Metservice says further rain is likely after this period, and the warning could be extended.
The MetService website currently forecasts rain for the district continuing from Wednesday through until Sunday.
While the rain is not currently expected to have a serious impact on the District like last year’s May flooding, Civil Defence are taking a precautious approach and asking residents to be stay up to date with MetService warnings.
Elsewhere in the South Island, a rare Red Heavy Rain Warning has been issued for Westland with dangerous conditions and significant flooding likely for the area.
Check for the latest river flood warnings on the ECan website.
Canterbury alpine river warnings
Heavy rain is currently falling along the main divide and is expected to remain heavy throughout the day. Further rain is expected to continue through until the weekend. Environment Canterbury staff are monitoring rainfall totals, river flows, and forecasts.
Likely impacts based on the current MetService forecast are outlined below:
Rangitata River
As the situation is still developing, it is too early to determine expected flows for the river. All adjacent landowners and people using the riverbed should carefully monitor their situation and prepare for high river flows and the possibility of flooding on Thursday and into Friday. The river mouth is located in a central position and there is no elevated risk of flooding at the mouth.
Tekapō River
Increased flows are expected in the Tekapo River over the next week or more due to the heavy rain forecast, the high level of Lake Tekapo, and a planned maintenance upgrade on part of the Lake Tekapo dam. While these flows are not expected to cause out of river flooding, any recreationalists, contractors, or campers using the riverbed should monitor their own situation and be wary of changing flows and river flow patterns. This is a continuation of the varied flows that have occurred on this river over the last two months.
Ashburton River/Hakatere
Some rain is likely in the top of the Ashburton River catchment, but significantly less than will be falling along the main divide. While significant flood flows are not anticipated based on the current forecast, it is possible that flows could get high enough to test some areas of recently repaired flood protection works on the river if the rain extends further east. Landowners adjacent to the river should therefore keep an eye on river levels and areas of vulnerable protection works.
Waimakariri and Rakaia rivers
We expect to see moderate flood flows in both of these rivers, with water levels peaking in the lower reaches during the day tomorrow. At this stage, out of river flooding is not anticipated, however recreationalists or contractors using these riverbeds should monitor their own situation and remain wary of rising water levels.
Hurunui and Waiau Uwha rivers
Some rain will likely spill over into the upper catchments of these rivers, but significantly less than is expected further south. High flood flows are therefore not anticipated, but recreationalists or contractors using these riverbeds should still monitor their own situation and remain wary of rising water levels.
Other rivers
At this stage we don’t believe there will be significant flood flows in any other major rivers across the region, although some may rise a little. Some rain is also forecast for the Canterbury Plains over the weekend as the airflow turns south-west, however this is unlikely to be enough to cause any significant river flows.
