Four flood events in recent years have prompted Selwyn to spend about $220,000 on 50 reusable water-filled barriers to help protect the district from future flooding.
Two of those floods involved states of emergency, highlighting the need for a faster and more practical response when floodwaters threaten communities.
The 14.5m-long PVC barriers can be rapidly deployed and connected to form temporary walls, containing or diverting floodwater away from vulnerable areas. Unlike thousands of sandbags, they can be emptied and packed away once the water recedes.
Selwyn Civil Defence controller Al Lawn said the emergency management team had been looking at practical ways to increase the district's resilience.
"We believe these temporary barriers give us another tool to reduce the risk of flooding from overland flow and storm water flooding."
The barriers can be filled from fire hydrants, tankers or other water sources using a pump and hose, with the water itself providing the weight needed to hold them in place.
Lawn said traditional sandbags were time-consuming and labour-intensive to fill. They could also become contaminated with sewage during a flood, meaning the sand could not simply be emptied out afterwards.
Lawn also said that putting up barriers without planning could simply shift floodwater and the damage elsewhere.
Council executive director infrastructure and property Tim Mason said almost every area of Selwyn had experienced different levels of flooding in recent times, describing flooding as the "most common and frequent threat" in the district.
"Our water engineers now have a better understanding where the water wants to go and have created maps, so all the local volunteers know in advance where to put the barriers."
Fire and Emergency New Zealand, the council's New Zealand response team and contractors will work together on training and deployment.
Despite buying 50 barriers, the council acknowledged the barriers will not be enough to protect the entire district during a major flood. Lawn described the initiative as a "proof of concept" rather than a silver bullet.
"In a large flood event involving many parts of the district there will simply not be enough barriers to divert all the flood waters."
The barriers are intended to help bridge the gap between areas where flood modelling has identified a risk and permanent infrastructure that could provide a longer-term solution, he said.
The purchase comes as Selwyn reviews its wider emergency management capability as part of its long-term plan process, looking at what resources, training and personnel it may need to be better prepared for future emergencies as the district continues to grow.
Chief executive Steve Gibling said the flood barriers were another practical tool for when severe weather struck.
"Good preparation and early action can make a real difference when communities are under pressure."
