Council to undertake review into Clutha’s flooding event

Clutha District Council staff will undertake a full review into the flooding event that affected many areas around the district from October 3-7.

Deputy Chief Executive Jules Witt said the review would include looking into the whole flooding event including those properties at in Frances St, High St and James St, Balclutha that were affected by flooding.

“Concerns had been raised about the Hospital Creek Retention Embankment and we will investigate this and whether there were learnings that could be applied in future flooding events.” Mr Witt said.

Hospital Creek Retention Embankment was intended to slow stormwater flows from the upper rural catchment to reduce the strain on the lower hospital creek drainage system through the urban area.

The embankment captures flows from a very large upper rural catchment and only has a 450mm diameter outflow pipe. This does have a valve that can be closed to reduce flows.

“The valve was initially half closed at 8.30am and then then fully closed at 9.11am on Friday morning.”

Field staff were constantly monitoring the hospital creek pump station where debris can sometimes reduce inflows. This pump station operated throughout the rainfall event and is essential to remove stormwater from the lower catchment when the Clutha River is in flood, he said.

“Flooding in this issue was not just related to the stormwater retention pond.

“It is also related to rainfall in the catchment, Clutha River levels and the operation of the downstream Hospital Creek Pump Station. There is no way to know if a change in timing would have had a meaningful impact on flooding in the area.”

Fire and Emergency NZ also assisted by pumping water across to the Clutha River to clear the flooding.

Council is now moving to the recovery phase.

“Staff are also dealing with significantly damaged roads and water treatment plants as well returning wastewater treatment plants back to normal operations.”

He advised motorist to take care on the roads as there was more rainfall forecast expected and it could result in more slips.

“If you come across any damage that does not have warning signs please report on our Antenno App or phone 0800 801 350.”

To assist Council with the review of the event any videos or photos of stormwater flows and including the time and location of the media would be of assistance.