FLOOD PROTECTION WORK IN THE OTAKI RIVER

Chronicle (Levin), 3 September 1947, Page 2

FLOOD PROTECTION WORK IN THE OTAKI RIVER

(Contributed) ( Otaki , is the scene of our story i today. This litUe town, situateu j on the banks of the Otaki River, has some of the most fertile and highly productive land to be fou'nd ] anywhere in the country. The ; Otaki River, commonly knowri as , a hungry river, and like many more of our New Zeaiand rivers, \ has been feeding itseif on this ; good fertile land for so many years tnat tne situation has now become alarmmg. ■ Early .settlers in Otaki worxea hard to stop the river taking their land, but no matcer wnat eiiorts were made the river conbinued eating into it. With the advent of the machine age, farmers and local bodies attacked these erosion problems with bulldozers and smail draglines, making stop banks and putting. in cuts to divert the river, but in flood time even these works were not a guarantee against the raging waters of our fast flowing rivers.. The problem of how to save our good land from the ravages of these rivers has iong been a ma,j or one, but not until our present Minister of Works, Mr. R. Semple, decided on a plan of attack had anything been done in a big way to keep the rivers in check. Our problem was so serious that, when oifered certain machinery that had been worked by the Americans and was rtbt in first class order, Mr. Semple had to deeide whether to take a chanee and spend public money on something that might prove a failure. Our engineers were men of vision and had faith in themselves, and with the backing and courage of our Minister of Works specuiated and brought to New Zeaiand what is known as the Ducyrus Erie super dragline. This machine was used in America for buiiding up the stop banks of some of that countrys biggest rivers, and had already done years of work. The mechod used in America was t« drag up all the surrounding country near the river and form it into a big stop bank to arrest the flow of the river when in fiood. This method could not be used successf'uiiy in New Zeaiand, "oecause our best land lies along the banks of our rivers, and to clrag up a strip 1000 teet wide- along the length of the river on each bank would take away too much valuable land, and would not have the eiiect of deepening Jthe river. It is here that Mr. Semple and our engineers had to take a chance. Would this machinery dig up the hard shingle and boulders oi our rivers without wrecking the machine at a cost that could be compared with other methods that had alreaay been tried with only moderate success. Otaki and its river was the site decided on to try out this huge machine. This river was handy to Wellington, the port where the sections of this big dragline were landed and suited also as a testing ground for this type of work. The sections of this machine are so big and cumbersome that many delays were experienced by the Public Works Department when it tackled the job of putting them together. Electrical equipment was the most aifficult problem, as a world shortage existed at the time, but aicer many delays the machine was at last erected. Would It Work? The ' people of Otaki , who -ill knew how their land had been affected by the river, and who had also seen it wash away all previous forms of protective works, were anxious to see what this monster could do in the way of fighting the river. Any faith the Otaki people had in this machine and the work ?t was to do was.badly shaken when their present Member of Parliament openly stated at .a public meeting in Otaki that the buying of the machine was a very bad move. He knew that it would never do the work here and would be such a failure that the money para for it was a complete loss. I-Iis very words were that it "wouldn't even scrape the gravy off the side of a plat of Irish stew." But that did not shake Mr. Semple's faith, neither did it-affect the engineers of the Public Works Department, nor did it change the minds of the men who had the difficult job of assembling and working the machine. Today the scene has changed and just as the river took big mouthfuls

of our land ayay this dragline is taking it back again, not as the good fertile land we once knew but shingle from the bed of the river, so d'eep that the river will take a Long time' to get out again. The big bucket used on the dragline is dragging otit !2 cubic yards on each haul, and piling it up to form a protection bank between the river and the good land along the banks. Twelve cubic yards every one and a-half minutes aeross a span of river 650 feet wide, leaving a deep channel for the - river to flow in and a.good solid bank to keep the river from taking more of our good land. In Otaki today history is being made in that this is the first attack on river control and land conservation. History, too, in the moving of earth and shingle in such quantities as was never thought possible even by mechanical means a few years ago. This dragline now has the record for earth and shingle moving from under water for the distance travelled. The amount for one morith's digging is 90,000 yards. ' This machine has not worked on this method before, nor has it dragged in such hard metal. A trip down to the Otaki River. will show what a big undertaking this job has been, and even if the work was a' bit slow at the start the job has prcived worthwhile. A huge channel approximately 300 feet wide, with plenty of depth, and over a mile long, has already been carved out of the surrounding country. This cut is nearly straight and has the effect of letting the flood waters away much more rapidly. The success of this cut has already proved itseif, for during the last heavy flood that did so much damage in the Wairarapa the water level above the cut was as high as any previous flood in the Otaki River, and had the water level not dropped a? it did when it reached the entrance of the big cut, damage such as took place in the Wairarapa might also have affected the lower country between the bridge and the sea. The work of completing this big undertaking has still a long- way to go. Something like a mile and aquarter stands between the dragline and the outlet of the river at the sea, and the cut has to be put through the centre of the river bed where the ground is high and covered.with vegetation. To every chain of distance on the remain'--der of this cut something between 4000 and 5000 yards of shingle will have to be moved to get the depth of channel required to take the volumne of flood waters down to the sea. The most remarkable feature of this machine is that it was built in 1929. and yet has all the features of a modern machine. The dragline is driven by its own electric power generated on the job by six Diesel motor generators. The operator is housed comfortably on the tower, where he can see right over the river. On the deck of the machine is housed all the winches and motors, and it is very much like the engine room of a ship with the engineer always on watch. These men seem to take a pride in their work, too.