Auckland’s recent intense rainfall was the largest rain event since 1869 (NIWA). The sheer amount was just too much for the city’s stormwater pipe network to cope with.
Auckland Council’s Healthy Waters Head of Planning Nick Vigar says, “A stormwater pipe network is never designed to take so much intense rainfall in such a short time. It is designed to cope with the majority of rainfall events but it is not possible, in any practical sense, to design a pipe network to cope with extreme events.”
When we experience such a downpour, capacity of the pipe network is exceeded, and overland flow paths are important to clear the water. “No amount of concrete can work in these circumstances; it is simply not possible. That’s where overland flow paths come into play; keeping these paths clear is vital so when the stormwater system does become overloaded, the water can drain away through these.”
Nick says once they’ve analysed where the flooding of houses has occurred around the city, he expects to find confirmation that water has flowed over known paths.
“We will be looking at how we can help people living in those areas for the future and use this latest experience to help with planning when it comes to development land.”
As these weather events may become more frequent, there are ways individuals can prepare. Information is available on the council website for people to find out where the flood hazards are.
Read Auckland Council’s guide to managing stormwater at your home.
