Juan Martinez was a third year Bachelor of Engineering Technology student in 2015 when he accepted a challenge by regional council to design a floodgate for Graham’s Creek in Tairua. He was supported by our staff and Wintec teachers, with specialist environmental and engineering consultancy Tonkin & Taylor providing free technical advice. The design even won the Todd Foundation Award for Excellence.
The people in Tairua were getting flooded, near Ocean Beach Rd. A stream runs along the back of some properties and when it rained too much it overflowed, the capacity of the channel wasn’t big enough, so water ended up in people’s backyards and houses. The people were not happy, it’d been happening for quite a while, and they approached the council.
One of the options was to forget about the channel, fill it up and build a high capacity new one to divert the flow. But the community was not happy in the sense that they liked to have the stream in their backyard. They really didn’t want to be invasive; they wanted to work with the environment; go with the fishes. There is a lot of marine life in the stream you don’t want to be a nuisance for. So, the decision was to keep the existing channel and when the water levels are nearing the safe limit, divert the flow before any flooding happens.
The challenge was to come up with a way to divert the water in a self-sufficient way, not relying on any source of power. It was very challenging, basically a learning curve. We looked at the world and trying to take ideas but nothing was like it. It’s quite unique.
I tried quite a lot of ideas: sketching, more sketching, have a think, think you have it, then everything crumbles. I started looking at this thing, hmmmm, no-no, but that one, maybe, and what if I mix this with that and come up with something, that might work. Actually, I got quite emotional about it, and anyhow, put some things together. I think we got it! I took it to the council engineer, “this is what I’m thinking of doing”, and they said “yes, that makes sense”.
We built a prototype, did the testing, and that took a lot of time. We actually have to recreate to scale the creek, the flow, the channel, to test the ideas. We used massive big timber bins, big bath tubs for wood, three to four metres long and one metre wide. Filling them up and creating the flow with a couple of pumps, to create the same flow as in the creek. The hydrologists gave us the data, so we know, or guess, how the channel can behave; recreate something tangible from all the data.
You don’t really size anything when you are in the middle of the thing but when you step out you go “oh yeah, that was amazing”. I’m pretty grateful for working alongside so many people, the time, the knowledge, the sharing of ideas together.
The Graham’s Creek scheme diverts water from the stream when it gets too high, without relying on power.
"There is a lot of marine life in the stream you don’t want to be a nuisance for. So, the decision was to keep the existing channel and … divert the flow before any flooding happens."
This innocuous creek would turn into giant lake during wet weather events, flooding people’s properties and homes.