Backing on to the Waimatā River, this Gisborne home was flooded during Cyclone Gabrielle. Photo / Ben Cowper, Gisborne Herald, File
Backing on to the Waimatā River, this Gisborne home was flooded during Cyclone Gabrielle. Photo / Ben Cowper, Gisborne Herald, File
Opinion by Neil Ericksen
OPINION
University of Auckland associate professor Nic Brooks recently, and rightly, sang the praises (NZ Herald, July 25) of earthquake engineers “making buildings quake-proof from the floor up”.
He highlights engineers attending seminars to see results from four years of research on quake-proofing buildings. The research was supportedby private and public agencies, including BRANZ (Building Research Association of New Zealand) and EQC (Earthquake Commission).
While all this is highly commendable, it is concerning that civil engineering departments in universities seem not to carry out research and teaching on “making buildings flood-proof from the floor up”. This is extraordinary, given the frequency of flooding in New Zealand.
Since 1920, floods have occurred several times in every decade in all regions. Of 136 communities with over 1000 people in 1956, two-thirds had had one or more damaging flood. In the next 30 years, there were 117 damaging floods, despite river protection works in many places. In 20 years to 2005, 30 floods occurred affecting most regions at least once and impacting over 10,000 people, including 18 deaths.
Since then, there have been 10 flood-inducing cyclonic events ending in the disasters of 2023.
Many, many billions of dollars have been lost to flood-damaged buildings and utilities over the past 100 years. Yet, no effort has been made to flood-proof them. That is, to make them resilient or resistant to flooding.
Illustration / Rod Emmerson
I first became aware of flood-proofing buildings in North America more than 50 years ago. Upon returning home in 1974, I continued researching flood-loss reduction measures for New Zealand. Periodically, I searched libraries in vain for flood-proofing manuals such as those seen in the US.
Nearly 40 years ago, the Water and Soil Directorate published the results of my nationwide research in a book titled “Creating Flood Disasters? New Zealand’s need for a new approach to urban flood problems” (1986). The final chapter included 22 recommendations for change.
The recommendation for flood-proofing buildings and utilities was prefaced with the following: “In areas without protection and in others where there remains a residual threat with ‘protection’, many buildings and utilities would benefit from flood-proofing, that is, making them waterproof. This is particularly so in areas of moderate flooding, where flood height is low and duration short. Flood-proofing is also appropriate in areas that have no ‘protection’ or where it is not feasible; and where a community prefers measures other than traditional flood control… Apart from raising floor levels, flood-proofing has not been a formally recognised option in New Zealand.”
Thus, recommendation number nine was: “A programme to collect, prepare, and disseminate information and to provide assistance and advice on flood-proofing should be undertaken by the Building and Property Management Directorate of the MWD in conjunction with the Water and Soil Directorate of MWD. A detailed study of the architectural and engineering viability of flood-proofing buildings should be done immediately…”
Like most of my recommendations, this was lost in the neoliberal economic and government bureaucracy reforms of the late 1980s and early 1990s.
Neil Ericksen.
Nowadays, the USA requires any new developments on the 100-year floodplain to be flood-proofed; that is, made water-tight and/or raised above flood levels.
By doing so people can reduce their flood insurance premiums.
In Australia, research on flood-resilient new and existing homes in Queensland shows it’s technically and economically viable for events up to and including the 1 per cent (100-year) flood. That is a flood having around 10 per cent chance of being equalled or exceeded in a 10-year period.
Although flood-proofing manuals have been available overseas for many decades, there are none in New Zealand, although BRANZ recently signalled the need for one.
Since the 1970s, governments have rightly funnelled many millions of dollars into research agencies, including universities, aimed at making buildings resilient to earthquakes. But nothing has gone towards research aimed at making buildings resilient to flooding.
It is extraordinary that in such a flood-prone country as New Zealand, government regulations do not require buildings to be made flood-resilient in the same way that its regulations require buildings to be made earthquake-resilient.
- Neil Ericksen retired from The University of Waikato in 2006, where his research focussed on human response to natural hazards and environmental planning and governance.
