Matatā township has been largely spared from significant damage, thanks to the successful implementation of debris flow mitigation measures that protected homes from flooding and debris during a recent storm.
Earlier this month, intense rainfall of around 95 millimetres fell within two hours in a localised area of Matatā, causing flooding in the Awatarariki and Waitepuru streams. This resulted in approximately 7,000 to 8,000 cubic metres of silt being deposited in the Awatarariki sedimentation ponds.
The Awatarariki Stream area has been a key focus of extensive flood defence efforts due to its history of debris flows and flooding. General Manager of Planning, Regulatory and Infrastructure, David Bewley, explained that these measures were recently put to the test.
“Following the 2005 debris flow, we undertook significant works to enhance the Awatarariki Stream channel, including deepening and reinforcing it with raised stopbanks. Other debris flow mitigation measures were also implemented, such as the Waitepuru detention basin and the Awatarariki sedimentation ponds,” said Mr Bewley.
“While floodwater and silt were deposited at the front of several properties on Pioneer Place, these flood risk measures performed extremely well during this heavy rain event. They successfully contained most of the floodwater, preventing significant damage to residential areas,” he added.
“The Waitepuru detention basin functioned as intended, preventing floodwaters and silt from impacting the eastern end of Matatā township, including Matatā Primary School. Approximately 1,500 cubic metres of silt was deposited into the basin.”
As part of its broader flood resilience strategy, the Council is taking steps to reestablish the effectiveness of the debris flow risk management measures.
“Our contractors are currently working to restore the full design capacity of the Awatarariki sedimentation ponds and the Waitepuru detention basin. This includes the removal of 8,500 to 9,500 cubic metres of silt and debris deposited during this event, which will be relocated to a designated deposition area west of the Awatarariki Fanhead,” Mr Bewley added.
The Council is working closely with Ngāti Rangitihi representatives to ensure that appropriate tikanga is followed during the removal and relocation of the silt material.
ENDS