Flood protection systems stand up well to inundation

South Canterbury’s flood protection works mostly coped very well with the heavy rain that drenched the region on Monday and Tuesday, resulting in serious flooding.

Environment Canterbury’s Timaru-based Flood Controller, Phil Lees said today that inspection teams had been checking on stop banks and other flood protection structures. They had reported finding very little damage and were happy with the way the river systems stood up to the floods.

“Up to 240mm of rain fell in the foothills over a 36-hour period – it was a very significant amount of rain,” Mr Lees said.

Environment Canterbury staff had been out from first light today (Wednesday) inspecting river protection works, including carrying out an aerial reconnaissance.

“There is a lot of debris, especially trees jammed up against bridges and some bridge approaches have been damaged. Several of our river level recorders have also been damaged and staff are now working to get them operational again as soon as possible, Mr Lees said.

River levels throughout the region had been dropping back all day and since midnight only about 10mm more of rain had fallen.

Analysis of rainfall and river flow data indicated that the flow in the Te Ngawai River was a one in 50-year event and was a 10-15 year event in the other major foothills rivers.

The heaviest rainfall occurred in the Mackenzie Pass which received 240mm of rain in 36 hours, a one in 100-year rainfall event.

Mr Lees said no significant rain was forecast for the next few days but Environment Canterbury staff would be reassessing the situation on Friday.

“We are remaining vigilant because the whole district is well and truly saturated.”

Residents of the Pareora Huts, who were evacuated as a precautionary measure early on Tuesday evening returned home today. About eight or nine households were evacuated with two other residents opting to stay in their homes overnight.