by Tony Harvie
Forty years back as chairman of Te Karaka Federated Farmers, I made a public statement that TK was living on borrowed time and relocation was a growing threat.
City engineers at the time labelled this alarmist but it has eventuated, with relocation of the township being considered after
it was flooded during Cyclone Gabrielle.
What we witnessed with the cyclone is a forerunning glimpse of what’s further to come.
Waipaoa sediment build-up is compounding continually and it’s a bigger threat to our district and its economy than many appreciate.
Contained rivers do have their problems. Ours now has to cope with millions of tonnes of sediment and aggregate from uncontrolled erosion continually feeding the build-up.
As designed by the original engineers, the western stopbank middle reaches are our flood safety valve. As a consequence, a very large area of the western Poverty Bay Flats is destined to bear the brunt and cost of that decision — but there is no alternative.
In reality, the Te Karaka relocation dilemma is only an indication of what’s to come and it is not primarily from occasional flooding. The compounding siltation of aggregate build-up is a permanent catalyst for drainage and access problems along the entire length of the Waipaoa.
Knowing this, I believe that comments by Willy Te Aho to our Regional Development Minister on relocation sites are short-sighted.
Without a major review into river aggradation and its effects, I am sure that inappropriate decisions will be made.
As already expressed, it is river aggradation that is creating the flooding risk and over-topping of the stopbanks will continue even after they have been raised.
Our ignored and still uncontrolled erosion is fuelling this threat, to the point of us now witnessing it and wearing the cost.
For the engineers and administrators responsible, I make this plea: for the region’s sake, broaden your view, look outside your stoic mindset, draw up and publicise long-term goals and objectives, and initiate appropriate measures.
How can insurance companies, government departments, planners and developers make decisions without sound local knowledge and assurance?
The current dilemma for the TK community is a case in point.
Do I relocate or rebuild and stay? Can I insure my property? Will anyone buy it? What’s it worth? Is it going to flood again?
Without knowledge, who knows.
Although we will never remedy the problem, we can significantly mitigate the aggradation.
Controlled spillways in the western stopbank would be a positive start, eliminating the need to keep raising the stopbanks. Spillways are controllable overflows that remove the deleterious consequences from over-topping stopbanks or manually induced breaching.
They can be structurally installed in several locations and self-operate. A published land-use warning in all spillway areas should be mandatory.
Retaining aggregates and silt in the mid to upper reaches could be the next focus.
Flooding is mainly controllable and recoverable; aggradation isn’t and has the potential to permanently destroy our region’s economy.
Unless regional erosion is remedied, we are headed for big trouble.
