Strengthening of Piako flood protection assets underway near Ngatea
Saturday 19 February 2011, 6:24AM
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Every minute an eight metre pole is being driven into the banks of the Piako River at Ngatea in the first stage of a multi-million dollar project for the area.
Environment Waikato project manager Dan du Toit said the 10-year programme of flood protection work aims to extend the width of the berm, a flat area of land between the river and stopbanks, to 15 metres.
“This work ensures the flood protection system’s integrity is maintained by reducing the risk of the stopbank slipping into the river.
“Ngatea and the surrounding area on the Piako River is vulnerable to flooding and this project is vital to providing continued protection to land and property as part of the Piako flood protection scheme,” said Mr du Toit.
The existing comprehensive Piako flood protection scheme was developed by the Hauraki Catchment Board in 1959 and constructed between 1962 and 1979. The scheme provides vital river and coastal flood protection for a significant portion of the Hauraki Plains.
Environment Waikato’s River and Catchment Service (RCS) group now manages and maintains the scheme to ensure it continues to provide effective protection and security to the communities into the future.
EW works supervisor Ian Sara said, “Downstream of Ngatea a machine is driving between 50 and 60 poles at an angle into muddy berms every hour.
“Once the poles are in place, we are filling the space between the poles with brushwood. In areas where the existing berm is less than six metres wide the risk of it eroding is higher, so the berm is initially strengthened with rock and gravel which is supported by poles. Additional poles and brushwood would then be installed in following years.
“Over time, sediment will naturally build up through tidal movement and the berms will increase in width.
”Gumpoles, similar to those being used in the project, have still looked like new when pulled from the mud 40 years later, so we know the mud and sediment does not cause deterioration,” Mr Sara said.
Planning for the work, which has been underway for several weeks and is expected to continue into April, began after a piece of stopbank at Rawerawe slipped into the Piako River about seven years ago.