FLOODS IN THE WAIMAKARIRI

Press, Volume LXXVII, Issue 23299, 8 April 1941, Page 6

FLOODS IN THE WAIMAKARIRI

New Protection For City

WIDENING OF THE MAIN STOP-BANK

Stronger protection for the city against possible flooding‘from the Waimakariri river will be afforded by improvements being made to the vitally important, mile-long stop-bank erected many years ago above Harewood. It is at this point that the Waimakariri. flowing across the Canterbury plains, takes a direct line for the city, towards Papanui. The stop-bank was breached slightly in the last big flood, in February, but it is now being raised considerably and given a stronger and more durable form. It was at this point that the great flood of last century broke through and inundated parts of the city and urban surroundings. And even in the February, floods of this year, the break through the stop-bank wiped out in an hour construction which had previously taken 120 to 130 men at least two months to complete. This big stop-bank, situated above the Harewood aerodrome and golf-course, extends for nearly a mile and a half, and is 80ft wide at its base. There it has been raised in height and levelled off—its original form was a bankette with a step—and now it is wide enough at the top for a motor-car to pass along its surface with ease. Yesterday members of the Waimakariri River Trust and officials made an inspection of the whole area involved in the work of the trust, and the motor-cars used were able to pass along a considerable stretch of the newly strengthened stop-bank. . This work is nearly completed. It will provide an adequate protection, presumably, against the worst floods to be expected and keep the river from overflowing'in any dangerous quantity into the old south channel. It is this channel that leads down on to the city. The trust has also been able, in recent months, to see how successful has been its operations in keeping the bed of the river as clear as possible of willow and scrub growth. At the stopbank above Harewood, there is now a clear expanse of river-bed of at least 3000 ft across. This is the. cleanest condition in which the river has ever been and the unobstructed flow of the river at this point has assisted in clearing our other islands of scrub further down. The trust has recently had the services of a bulldozer. This powerful unit of its plant, crossing the channels of the river at low water, has been able to scour off big areas of scrub (even including fairly advanced willows). The floods have then carried on the cleaning process, with the result that in some parts of the river, particularly opposite Stewart’s Gully, what appeared to be permanently established islands of willow, gorse and scrub have now been sv/ept clear to only a low height above high water. This clearing out of the river-bed has become an important and successful part of the control scheme for the trust.

* Big Problem One of the major problems the trust faces in its task of keeping the protection banks safe and the river in a more or less straight course until it reaches the pilot channel at White’s bridge is at a spot known as Englebrechts, on Coutts Island. There, towards the river from Belfast, the Waimakariri comes across its bed in great force, strikes the bank and travels along it for some chains. In the last big floods part of the bank was eroded at this spot, but hard work by the trust’s staff saved a break. The trust will erect a groyne at this spot, when the opportunity offers, deflecting the current into its proper channel. On the opposite side of the river from this point, a bulldozer will be' got across and used to reduce the level of an island, the point of which is deflecting the river on to the protection bank. A little further down, the trust is soon to be engaged in another vital job, considered to be the culmination of its extensive programme of stop-bank construction. This is near the dotting bridge, at the top of the pilot channel cut a mile below the Waimakariri river bridge on the main- highway. There some chains of protection bank will be constructed to link up the main banking system, The road which runs below the miles of stop-bank will be continued, making available to landowners a considerable area of country adjacent to the stopbanks and linking the trust’s road with the South Island road. This new section of stbpbank will parallel the weir which was constructed to break the run of the river when, in .flood, it spilled over into the old channel to flow under the Cutting Bridge. The banks along this old channel are being reinforced to prevent flooding from the old channel of a big area of highly productive land, lying between the main stop-bank and White’s bridge.