The stopbanks were so crucial that engineers camped overnight the Sunday before last at a critical spot on the north branch just to make sure they were doing their job.
Raging floodwaters had washed away a flow recorder and the engineers took turns to be eyes on the ground at Jessop’s Bend, just west of Ashburton, to make sure the stopbanks were not overlapped.
Then, as floodwaters receded, they kept on inspecting the stopbanks to look for signs of erosion.
Ashburton district councillor Angus McKay was instrumental in the stopbanks project, as a councillor for Environment Canterbury in 2004. He said they were an affordable model, made of compacted gravel sown with grass, and paid for by ratepayers living alongside the Ashburton River.
Willows planted between the stopbank and the riverbed disrupted the force of the floodwaters and kept the water in the main channel.
Ashburton Mayor Neil Brown said the stopbanks had done a great job and more than paid for themselves.
Floodwaters that could potentially break out at Jessop’s Bend would flow down Racecourse Rd and affect 1700 homes from Allenton to Netherby.
Floodwaters that could potentially break out at Valetta would head towards Tinwald, affecting 2200 homes.
Mr Brown said it was too early to estimate the cost of the rain event to the district. It would likely be in the tens of millions and the Government had given $100,000 in early relief funds.
Ashburton District Council chief executive officer Hamish Riach said the estimated repair bill would be some weeks away as there was damage the council did not yet know about.
"It will take time to assess it all."
Council staff have been assessing roads and bridges and at one stage 19 roads in the district were closed, along with five bridges. Drinking water was being delivered by tanker to Mt Somers and Methven.
The council’s wastewater treatment pond at Wilkins Rd also flooded and potentially contaminated water mixed with floodwaters heading to Lake Hood, downstream of Tinwald.
Floodwaters have also receded at Hinds, where the residents of two houses were evacuated because of floodwater.
Mr Brown said farmers in the Greenstreet area had borne the brunt of the event but were being supported by the Rural Support Trust, which was working in the emergency operations centre.
New Zealand Defence Force personnel were in the district to help and helicopters had ferried in feed to some stock in isolated pockets.
- Linda Clarke
