Wednesday, June 28, 2017
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Edgecumbe should have been protected


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Utter despair – the the feeling when in the blink of an eye your whole life, plans and progress are turned upside down! I live in Hamilton now but the news of the flooding in my hometown of Edgecumbe struck an emotional cord. We have been there.

Our family farm was just across the Rangitaiki River from Edgecumbe and in 2004, under similar weather conditions, the river’s stopbank blew out on the opposite side upstream from the town and flooded reportedly 17,000 hectares of farmland. Our farm of 162ha was in the middle of it.

Widespread heavy rain fell after an already wet winter, during three days from July 15 with 284mm being recorded in Edgecumbe.

Calving was underway and it wasn’t long before surface water was creating havoc on farms throughout the district.

On the morning of the July 18 we walked up the stopbank to view the height of the Rangitaiki River. Our house was 50m from the river and the banks were 2.5m above the surrounding land.

Higher in the middle

We nearly fell over to see the river raging about 150mm from the top of the banks. Because of the friction of the water on the banks, the river runs higher in the middle and when I lay down and looked across the river I couldn’t see the other side. Shortly after this there was an urgent call to help stack sandbags on the opposite bank of the Rangitaiki River about 4.5km downstream from Edgecumbe on the way to Thornton.

It seemed like a pointless excercise because the river was rising faster than we could stop it going over. There were plenty of helpers so a couple of us raced back through Edgecumbe to see what the rest of the river was doing.

We stopped at that concrete wall on College Rd, which failed in this April’s flood, and the water was lapping the top. The concrete was quivering.

Because of repeated flooding throughout history, particularly in the 1960s, there was a plan put in place by Bay of Plenty Regional Council to protect Edgecumbe and the lower Rangitaiki River from flooding.

Reid Central Floodway

The Reid Central Floodway, which runs parallel to the Rangitaiki River about 1-2km east, was set up as a second bypass river with stopbanks creating a 200m wide channel to take the pressure off the river banks in Edgecumbe town. This channel returns back to the river just before the sea at Thornton.

This work was completed in 1972 and since then the weather cycle has changed and 25 years have passed with lower incidence of heavy rain, so not causing major floods. Consequently, the Reid Central Floodway has never been used. There is a spillway upstream from Edgecumbe where the east bank of Rangataiki River has a lower section, which is about 300m long. This spillway is about one metre below the rest of the bank. When water from the river overflows, it follows the contour of the land and is channelled into the Reid Central Floodway.

It was this spillway we were racing to see. There was an air of urgency as we could feel something bad was about to happen.

Burst its bank

When we arrived the river was just starting to trickle over. Obviously, if the river was already running over 6km downstream, the spillway needed to be at least one metre deeper.

Within 10 minutes the river burst its bank about 1km downstream from the spillway on the eastern side, which was 3km before the town of Edgecumbe.

Of course this immediately dropped the river significantly and the rest of the river was safe. The general opinion afterwards was that if the river hadn’t breached when and where it did, it would have breached the bank at College Rd within Edgecumbe with devastating consequenses for the town.

Most of that breached water ended up in the floodway but with at least three times the design capacity. Within a couple of hours the uncontrolled water was topping the banks of the Reid Central and flooding farmland as it went.

A blowout occurred some seven kilometres down the canal where it narrowed to only 40m and could no longer contain the flow. The subsequent damage from silt was devastating to the farmers affected

It took three weeks of continual pumping, along with the innovative use of shipping containers as floodgates placed in the river bank of the Rangataki River, to clear the water. About 20 tractor-driven pumps were involved.

Millions of dollars were spent to repair damage and millions more on lost production throughout the Rangataiki plains from that 2004 flood.

Fix weakness

Since the 2004 flood investigative discussions have taken place. A plan was put into action and finance attained to fix weakness in the drainage and flood mitigation system, including the Reid Central Floodway to protect Edgecumbe.

A great deal of the work was underway but not completed. The lowering of the river bank to activate the floodway into the Reid Central Canal was part of the unfinished business.

On April 5, 2017, at 7.24pm Bay of Plenty Regional Council announced an urgent warning stating: ”Due to steady rainfall the Rangitaiki Floodway and Reid Central canal are likely to start operating as part of the flood protection scheme….”

This action was not implemented until after the breach of the stopbank into Edgecumbe town. After the flooding into Edgecumbe and the threat of the second storm – Cyclone Cook – and more rain, action was then taken.

The Matahina Dam was lowered further to be able to contain more water and subsequently reduce the impact on the river. The bank of the Rangataiki River was lowered about two metres to activate the floodway automatically, if the water rose too high again.

This was the action needed to avoid the flooding of Edgecumbe so was a little bit late.

I drove through Edgecumbe on Easter Sunday and out to the farmland, which was being pumped by tractors just like we did in 2004 on the other side.

Totally avoidable

The devastation was overwhelming and totally avoidable. The plan to mitigate the flooding was excellent but totally useless without any decision to implement it at the right time.

Ratepayers have paid for the flood protection, now those same people will pay again for the flood cleanup.

Failure to proceed with the flood protection plan is disrecpectful to the work and people involved in the making of it.

And the unnecessary emotional cost of those affected? Utter despair.

For more background on flood mitigation see: www.waternz.org.nz/Attachment?Action=Download&Attachment_id=1174


 
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