New efforts are being made to protect crumbling cliffs on Lake Hawea’s foreshore.
The Queenstown Lakes District Council is investigating an engineering solution to reduce the amount of erosion taking place below Flora Dora Pde.
Lake Hawea Foreshore Working Group co-ordinator John Langley said the group made a submission to the council on its concerns about the impact of stormwater runoff.
Many sites on the reserve had experienced significant erosion caused by runoff.
“The stormwater comes on to the reserve and in some places it is not very well filtered, if you like, with plants.”
The working group, also called the “Thursday Group”, had a memorandum of understanding with the council to carry out native planting in the area.
The aim was to reduce the amount of runoff from roads that went straight into the lake.
“Stormwater comes off roads and it is full of crap from oil on the roads and tyres.”
Native planting could help reduce the runoff directly into the lake, but the scale of stormwater was undermining the group’s efforts to stabilise the reserve.
Corrugated iron channels directed stormwater down from the main thoroughfare of Capell Ave, but the amount of water overwhelmed these channels, causing a rush of water straight to the lake, and cutting large holes in the cliffs by the foreshore.
“It is really causing bad erosion,” Mr Langley said.
The group was pleased the council had agreed to look for alternative solutions.
Options could included sinkholes, or diverting the channels to run parallel to the lake shore, slowing the speed and volume of water runoff.
The corrugated iron channels “by today’s standards” would not be allowed as they were not effective enough to cope with the runoff, Mr Langley said.
Council media and channels adviser Jack Barlow said the council was looking at solutions to mitigate the impact of the stormwater discharge below Flora Dora Pde, which was accelerating the erosion of the cliff face.
“While we don’t have specific solutions or timeframes to share, it is something we are keen to address as a relative priority.”
The council was also providing native plants to support planting planned by the Lake Hawea Foreshore Working Group.
“The planting will help mitigate against erosion at a number of stormwater discharges along the Hawea foreshore.”
Specific numbers of plants would be confirmed in due course, Mr Barlow said.