Riverworks hold in Rangitata

Authorities hope damage to repair work in the Rangitata River will be minimal after heavy rain in its catchment caused a peak flow of more than 890 cubic metres per second (cumecs) on Tuesday night.

Mistake Flat in the Rangitata headwaters had recorded 185mm of rain on Tuesday, while the MetService monitoring station at Timaru airport recorded 16.8mm of rain over the same period.

In other parts of South Canterbury, Mt Cook recorded 227.5mm of rain and Twizel, 58.5mm.

By 10am yesterday, the Rangitata River had dropped to about 400 cumecs, with Environment Canterbury (ECan) monitoring the area.

ECan manager for river engineering Leigh Griffiths said staff have been closely monitoring rainfall and Rangitata River flows over the past 24 hours.

‘‘Staff have been on the ground since early this morning closely monitoring key areas of the river and how repair works were holding up,’’ Griffiths said.

‘‘Apart from a few minor areas where water is out of the river, there are currently no immediate areas of concern.

‘‘As things can change quickly when braids move as the river drops, staff will continue to monitor the river throughout the day.’’

Tuesday night’s high flow comes after ECan had done significant repair work in the riverbed in the wake of December’s flooding.

At its December peak, the river flowed at more than 2300 cumecs, causing significant damage to roading, power and farming infrastructure.

Initial repair work was completed in mid-January, but ECan has said further work, which will likely focus on reinstating banks and vegetated berms which are crucial in erosion reduction and provide some protection in flooding, could take one to two years.

MetService forecaster Thalia Crabtree said there should be a cold front making its way to Timaru this morning, which may lead to some showers in Timaru and further inland.