Heavy flows from the Dome Burn have contributed to a larger flood on the Mataura River than first thought, but the overall extent of the flooding on the river is not expected to be significantly higher than predicted earlier today.
The flood peak is travelling faster than earlier calculated as it moves downstream and is now expected to be about 2.5 metres above normal at Pyramid about 8pm tonight, peaking at Gore about 3.5 metres above normal between 4-5am on Tuesday – the earlier predicted peak was 3.1 metres at Gore, arriving at about 6am.
The peak will increase in size as it travels downstream, bringing in water from other tributaries, and is now expected to be about 3.8 metres above normal at Wyndham at 11am tomorrow, reaching Seaward Downs about 2pm at a height of 3.5 metres above normal.
The Waikaia River peaked at Piano Flat at 2.5 metres above normal at 3.40pm and was expected to reach about 2.3 metres above normal at the Waikaia township, Environment Southland duty floodwarning officer Rachel Webster said.
Senior Technical Officer Chris Jenkins described the flood on the Mataura River as “the most unpredictable I’ve seen in a long time” because of the irregular intensity and location of the rainfall in the catchment. Environment Southland does not have rain gauges in all the minor tributaries, and some of these had received heavy falls yesterday.
He said the extent of the flooding in the Lower Mataura was likely to be similar to that experienced in May 2009 and February 1994.
The Makarewa River is now predicted to peak at Tussock Creek between 8-11pm tonight at a level of about 4.2 metres above normal, reaching Counsell Road near State Highway 6 about 5am at a level of about 4.3 metres above normal. Mr Jenkins said that level was unlikely to cause flooding on the main road.
However, motorists are urged to be aware of the risk that some roads could be affected by surface flooding, particularly overnight.
Full information about the state of the river levels and rainfall at each site is on Environment Southland’s website www.es.govt.nz and is also on the Council’s automated phone information service 03 2115010.
Farmers and anyone living close to a river in Southland should keep an eye on the website and make their own decisions about moving livestock to higher ground. The Met Service is forecasting another front to reach Southland tomorrow, bringing more rain.
– Environment Southland