Erosion a risk for Mataura stop bank
Media Release - 20 December 2022
Erosion a risk for Mataura stop bank
A geophysical report has found that there is no obvious structural damage to the stop banks on the Mataura River as a result of the 2020 flood event, however, river engineers have raised concerns about a 600m section of riverbank along the Mataura township that is at risk of erosion.
Environment Southland commissioned the geophysical report in September following on-site observations by specialist engineers who had concerns about their condition. The report has been reviewed by a technical advisory group of experienced river engineers, who also raised concerns about erosion risks to the riverbank in the Mataura township.
High river flows could create erosion leading to failure of the stop bank and flooding of the township on the true left bank– upstream of the old Mataura paper mill.
Environment Southland general manager integrated catchment management Paul Hulse said the Council was immediately procuring 27,000 tonne of rock for a permanent solution for the Mataura township and the work will begin as soon as possible in the new year. In the meantime, an active monitoring programme has been put in place.
“Engineers are monitoring the stop banks weekly, and will move to daily monitoring if river levels and weather forecasts change.
“It is reassuring to know that the stop banks are sound, but our immediate concern is the risk of erosion. Our message to the Mataura community is the same as it has been since we first identified a potential issue, earlier this year: ‘Be prepared to evacuate your homes at lower river flows than you might have in the past, and at short notice’.”
Emergency Management Southland would make any decisions about when and if to evacuate and will lead any evacuation. Each situation will be assessed on a case-by-case basis, as it is not possible to predict conditions for every situation.
River levels are monitored 24/7 by the Environment Southland hydrology team who notify Emergency Management Southland of rising river levels/flows.
All Mataura residents on both sides of the river should be prepared to evacuate. Residents are advised to have a plan, gather supplies and to get connected online (go to cdsouthland.nz). Being prepared will help to make any evacuation easier and less stressful.
Environment Southland, this morning, delivered supporting information to letterboxes in the Mataura community on the left bank, and will be hosting community drop-in sessions in February to discuss the issue and solutions.
