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Press, 20 October 1978, Page 2

Written by

D. W. ROONEY,

of “The Press”

staff and prepared before the journalists’ strike began on October 9.

Recent articles about the history of the Rakaia Gorge bridges and ferry (“The Press,” Sept 16 and 23) prompted a retired Christchurch surveyor, Mr Frank Parnham, to recall the origin of another construction that puzzled many people: the flying fox across the river, upstream from the bridges. The flying fox is no longer there: it broke, was carried away by a rockslide, or was cut down several years ago. A farmer who has lived all his life at the gorge says that he and his brother often played near the flying fox when they were young, but they were never able to release the cage for a ride across the river “because it had a

very good padlock.” After the cable broke, he says, the steel rope lay in the riverebed for years, sometimes creating a hazrd for jet boats negotiating the river. But he has not seen it recently; and he thinks it has probably been carried away by a flood.

With the farmer, I walked up the riverbed from the bridge one misty afternoon last week, and on the south bank, 10 minutes walk up from the bridge, we found a galvanised steel rope trailing down a bank — just where his memory had placed it. But it was not broken; the end had been cut. The rope trailed about 12ft down a clay face, and the end lay on a shelf that might once have been a small cave cut from the clay to provide a landing place for the cradle. The road is almost directly above the face at this point, and massive slips have come down below it. A small area round the cable is the only area that is unharmed. Just a few yards away a huge slip has spread sticky clay and a tangle of uprooted coroki a s , pittosporums, broom, and other wild shrubs well out into the riverbed.

The flying fox was built for the Ministry of Works, then the Public Works Department, in 1933, when irrigation surveys were being made throughout Canterbury, so there is no mystery about its origin. But its end proved less easy to establish. ■ Local residents recall that the flying fox was used at one time by some Ashburton men, who were mining a rare type of blue pottery clay on the north bank. There is some speculation that these men might have taken it with them when they worked cut the deposit.

The Ministry of Works in Christchurch does not know. There have been staff changes and retirements in recent years, and if any of them knew of the flying fox’s fate, he has taken the knowledge with him.

According to Mr Parnham, the flying fox was put up in 1933, when three parties of engineers and surveyors employed by the Public Works Department were measuring river flows in Canterbury in preparation for a major irrigation scheme.

Their researches ultimately led to the construction of the Rangitata River diversion, in which a giant channel carved, for 42 miles across the plains

takes from one-third to one-half the average winter flow of the Rangitata River and discharges it into the Rakaia through the Highbank power station.

Mr Pamham’s party, which camped at Pudding Hill, beneath Mt Hutt, and other parties based at Temuka and Oxford, worked under the direction of the architect of the scheme, Mr T. G. Beck, who, by the time it was completed, was assistant engineer-in-chief of the department. The engineering students in the party put the flying fox above the river where it narrowed and ran through a single channel,

make measurement of the flow easier.

Depth gauges and velocity meters were lowered into the river at different points across its width. These measurements provided a contour map of the river bottom, and enabled the area of a cross-section to be calculated. This area, multiplied by the average velocity, gave the flow, Mr Parnham says. The party’s main job, however, was out on the plains, taking contour levels so that a system of irrigation races could be designed. They spent nearly two years at Pudding Hill, from early 1933 to late 1934, and even though most of the time was spent under canvas and the winters were bitter, Mr Parnham found it a very enjoyable period. “It was depression time, and jobs were scarce,” he says. “We considered ourselves jolly lucky to be working at all, and especially lucky to be paid for being out in the open air.” Mr Parnham did not

stay to see the project through. As soon as his initial task was completed, he left for another job in the open air — doing survey work for the Railways Department at Parnassus. Later, he entered private practic in Greymouth, then returned to Canterbury to do survey work for local bodies, first in Ashburton and finally in Rangiora. He was in Rangiora when he retired 12 years ago to live on Mt Pleasant and raise early jonquils for sale on the market in Christchurch. Though he no longer grows flowers (his daughter does that now), he is still fit and active, and he keeps his hand in by doing occasional private surveying jobs. He recalls that in its early stages the Rangitata diversion project met bitter opposition from some Mid-Canterbury farmers, and members of his work party sometimes had a hostile reception. But most people realised that the surveyors were just doing their job, and co-operated with them.

Most of the opposition to the scheme was based on fears — later dispelled — of seepage from • the huge water race, 25ft wide at the bottom and 9ft Sin deep. Some, according to newspaper reports of the time, simply objected to its going through their land, destroying “tangible assets for a problematical benefit.”

The Highbank power station, says Mr Parnham, was Mr Beck’s idea. The initial scheme was for irrigation only, but with the backing of the chief electrical engineer (Mr F. T. M. Kissel), Mr Beck persuaded the department in 1938 to extend the race to Highbank to make power generation possible. When the Highbank station was opened by the Minister of Works (Mr Bob Semple) on June 17, 1945, it was the largest single generating unit in the country, and one of the early examples of multiple use of natural assets — 30 years before the phrase became a popular one.

As originally conceived, the project called for the water to irrigate the plains in summer, and drive the power station in winter, when no irrigation was needed.

Work began in April, 1937, when nine concrete caissons, the largest weighing 850 tons, were sunk in the river at the intake at “Klondyke,” at the mouth of the Rangitata Gorge. The scheduled date for completion was 1941, but delays caused by floods in the Rangitata, landslips in the

Surrey Hills, and war-time shortages of equipment and manpower caused work to drag on until 1945. The contract for the plant was let in June, 1939, delivery to be in 1940, but the generator stator was lost at sea and the war delayed the delivery of other equipment until 1944. The first power was generated in November, 1944, seven months before the official opening. The flying fox put up by Mr Parnham’s party was not the only one across the Rakaia Gorge. Halfway through the gorge a water tower (now replaced by the telemetered tower at the bridge) was once used to measure the river flow, and mj' farmer friend recalls that there had been a flying fox above the river at this point, too, to provide access to the tower. . This flying fox was nearly the cause of a serious accident some years ago, he says. Two low-flying aircraft went through the gorge, and the pilots were unaware of the cable until they were nearly upon it. One of the small planes went underneath the cable.