THE WAIMAKARIRI.

Star (Christchurch), Issue 6309, 6 August 1888, Page 3

THE WAIMAKARIRI.

Mv Lambert's Report. The following is Mr Lambert's report on the Waimakariri River Protective Works, near Ho. 14 embankment, a3 read at the meeting of the Board of Conservators on Tuesday : — N I visited the upper protective work 3 yesterday, in company with Mr Jeal, who expressed himself as being pleased with my coining, aa I would see the effect of the flood on Friday last on the new (or Jubilee) groin. The wattr ou that occasion rose only three feet, but it did considerable damage to this work, as ifc had tcoured ! under the la&t placed concrete blocks, and consequently they had fallen into the ; torrent, and the remaining ones were ! gradually being prepared to foliow them, 1 as they are inclining considerably over from the vertical. The scout under, and : the embankment behind, will soon * accomplish the rest. The bank has also ; been scoured away for six feet behind I where the laßt concrete wa3 placed. I i much fear we shall not be able to Ircep this point, on account of the enormous volume oi: water-impinging atjainet it at au tfngle of about seventy degrees, and the i consequent erosion of the friable bank, which is lower than the shingle in the bed o£ the river, & few chains distant, ;at right-angles. I was much surprised at the altered appearance from the time I last it, when a member of the Board about four years ago. The torrent now setting in being almost the entire stream, has, during that period, scoured away to a width of ten chains, at the said groin, and about fifteen chaius lower down, at the weakest point, in all about an average of, say, six ehaius for more than a mile, or, say, about fifty acres. Mr Jeal agrees with these measurements. The worst feature of it is that less than a chain further from the water's edge are the old gullies, leading into the head waters of the Avon, at the point where it overflowed on Dec. 25, 1865, which the shingle bank of No. 14 will not intercept. Referring to the proposed cutting, I find the river has commenced to make a channel in the direction I have suggested. A bank of Bhingle, formed apparently by the embankment at No. 14 checking the velocity of the river, has gradual ly com menced to form a fan mo viny !in a South-west direction. The cutting I ! propase is intended to try to break up this : fan, by making a channel through it in the I original line the river took until a few years ago. The decline at this part would be very considerable, as I estimated with the appliances at hand that the fall from where the water leaves the comparatively level bed several chains North, to rush in a South-east direction on the before mentioned groin down to No. 14 is over 30f b, and I would also suggest that an anchored spar should be placed in the stream to wear the water into the cutting to give it a start. I am thoroughly convinced that if such a cutting were made as shown on the accompanying plan, although it is tentative, still I think the experiment is worth trying, as ifc would, if successful relieve the water from the weak point, and would enable the necessary groin of a permanent character to be placed in position to meet such a contingency on a future occasion. I would further suggest that the shingle dyke from No. 14 should also be j continued up in a South-west direction for some distance, to intercept tha gullets j above referred to, so as to form dead water and return it again into the stream at No. 14. These two works, in my opinion, ought to precede any permanent works that will undoubtedly have to bo taken in hand at this point at an early date, as ifc is useless to diuguise the fact that this weak point is a source of real danger, and must be attended to. According to Mr Jeal's statement on the occasion of the Jubilee flood, the water rose to within ft few inches ot' the top of the shingle dyke referred to. If. it had made a breach it is impossible to say what damage would have resulted, as it is about 400 feet above Christchurch ; and, inasmuch as the volume of water was to the full capacity of the wall, if the current could be directed through the fan referred to it would go past instead oi lodging behind and endangering this valuable and expensive piece of work. Mr Jeal admits that more than 6uffc of No. 14 embankment, composed of enormous blocks of concrete of triangular section, costing more than jSIOOO, have gradually been swept away and buried out of sight an unknown depth. In arriving at the ' above conclusions, 1 have consulted the various maps of the river by Messrs Doyne and Cameron in 1865, and other subsequent ones as to datum, and ttpy till materially agree. With regard to tbe cuttings that were tried come years ago afc Chaney's, the conditions were totally different, as I saw them on several occasions, as also works on other rivers. Butl have considered this on the altered general appearances, and the environment of this undisputably weak point. Before coming to a conclusion on the matter, 1 would suggest that the members should see and judge for themselves, and I have little doubt but that they will generally agree with me as to the importance of immediate action at this the most suitable eeaEon of the year, when there is the greatest immunity from floods, and labour is plentiful and cheap. Idr Jeal's estimate of Is per yard for shif iin«the shingle with a Yankee scoop a few i yards, is, to my mind, about double what it ought to cost, or would if tendered for. I