BOARD OF CONSERVATORS.

Globe, Volume XXI, Issue 1710, 13 August 1879, Page 3

BOARD OF CONSERVATORS.

The usual monthly meeting of the Board of Conservators for the South Waimakariri took place yesterday at noon. Present— Messrs R. J. S. Harman (chairman), P. A. O’Callaghan, A. Duncan, J. N. Tosswill, and the Mayor of Christchurch. The minutes of the last ordinary and special meetings were read and confirmed. The Chairman said that the principal business which they had to transact arose out of the complaints which had been made by the members of the Avon Road Board of the encroachments of the Waimakariri on the south bank, near Chainey’s corner. These encroachments had become so serious as to necessitate some immediate action being taken to check them for the future. By his (the chairman’s) and Mr Duncan’s instructions the overseer, Mr Potts, had made a thorough examination at both sides of the river, and the following was his report:— Waimakariri Works, August 11th, 1879. R. J. S. Harman, Esq., Chairman of the Board of Conservators. Sir, —In obedience to the instructions of the Board I have examined the river from Chainey’s Corner to the railway bridge with the view to see if anything can be done to prevent the overflow and the encroachment of the river on the North road. But before making any suggestions as to what I think may be done to prevent the evil complained of, I may state that there can be no doubt that this trouble has barn caused by the cutting that was made some years ago by Mr Coutts for a mill race. This has increased to immense dimensions, being now at the northern end not less than a mile wide, and at the southern end about 400 yards wide. The south branch of the river having been the lowest channel this cutting has acted as an immense drain to the north branch, and is now receiving nearly the whole of the water which should go down the northern channel. Thus in time of flood nearly the whole of the water is drawn into the south branch which comes rushing out of the cutting with great force at right angles with the south channel which is not nearly of sufficient capacity to contain it. The consequence is that it is scouring away its banks and overflowing in all directions.

Although it is out of the Beard’s jurisdiction I examined the north channel to see if anything could be done to reduce the quantity of water passing through the cutting. But I find it would be quite useless to attempt any works there, if there was any hope of success, which there is not, as it would only increase the tendency which already exists of causing the water to overflow and cut channels across the upper end of Kaiapoi Island. Returning to the south bank of the river, about half a mile above the traffic bridge is tbe greatest bend, the effects of water rushing out of the cutting which has eaten more than half of the North road away, and if it continues to scour away at the present rate in another flood the road will be quite gone, and nothing that we can do will prevent the necessity of a new road being made. Our usual plan to protect such a bend as this would be to put out a groyne at A and B, as shown on the accompanying sketch. But in this case we dare not place our work so that it would in any way obstruct the water way, ns the least obstruction thus placed would force the water into the bend C, and cause the overflow to be much greater than it has over been before. I would therefore suggest that the safest way to prevent the bank from further scour would be by facing the foot of the block of concrete or rock up to about half way between high and low water, above that to slope the bank d own and plant willows thickly. I estimate such work as this would cost, done with concrete, about .£3OO per chain. It would perhaps not bo necessary to do the whole length of the bend at once, but it is difficult to see where a finish could he made, as the scour is about the same all the way round the bend. There is no doubt that if the river does not make a change that the whole length from Chainey’s to the traffic bridge must at sometime be protected; at present there is about twenty chains being badly scouted.

To prevent the overflow at Chainey’s, it would bo necessary to construct an embankment about one and a half miles in length, and averaging about four feet high. The whole of this would h»va to be erected on private land, and would be altogether a very expensive work; but, apart from the expense, it would not bo expedient to stop the overflow for the reasons I have stated. Above that, the south channel is not large enough to carry the whole of the water that ia now being forced into it. Lven with the overflow channel open, it can bo seen that the water has risen half way up the post and rail fences on the island and south sides of the river, and nearly up to the floor of the bridge, so that it would not do to close this escape channel. Prom the traffic bridge down to the railway bridge the water is close under the no th bank, except at one point, about three quarters of a mile above the railway, it strikes the south bank, but does not appear to 1 # scouring to any extent. The water being well away from the bank between the two bridges offers a splendid opportunity for planting willows, and I should strongly urge the Board to undertake this work on the first opportunity.

Since the la t meeting of the Board, 1 found it necessary to put two timber gabions in a few chains above the two and a half chain groyne at No. 5, as the water was likely to get behind some old gabions and soonr out a quantity willows. This, and sundry cdd jobs of repairs and planting is the only work that has been done during the month. There have been no floods,

and the works are all in a good state of repair, and ready for the coming season. I have the honor to be, sir, Your obedient servant, Potts.

The Chairman said he had full confidence in the overseer’s report, as although not an engineer his experience was to great and his judgment so good as to render his opinion very valuable. Mr Tosawill expressed a similar opinion. The Board went into committee to consider the report. On resuming the Board reported the following resolution, moved by Mr A. Duncan, and seconded by Mr J. N. Tosawill —“ That the Board having had the report of Mr Potts on the river at Chainey’s corner before it, is of opinion that the cutting across the island is the chief cause of the damage to the North road ; and further, that any protective works would be of such a costly nature as to bo entirely beyond the means at the command of the Board. The Board is also of opinion that the Selwyn County Council should be asked to take steps to purchase a new line of road as being the most inexpensive plan that can be adopted under the circumstances.” The resolution being put was carried. It was resolved—“ That copies of the resolution should be forwarded to the Selwyn County Council and to the Avon Hoad Board.” DEPUTATION. Mr Monro waited on the Borurd as a deputation from the Avon Road Board to bring the matter which had just been discussed under their notice. The Chairman explained to Mr Monro what the Board had done, and read over to him a copy of the resolution wbioh had been passed. finance. The Chairman said he had received £I3CO at 9 per cent, for six months, and £1950 at 8 per cent, for six months. He asked that the debentures for these amounts should be be sealed with the seal of the Board. This was agreed to, and the Board having passed sundry accounts for payment adjourned.