REPORT ON THE BULLER RIVER PROTECTIVE WORKS.

Westport Times, Volume VII, Issue 1098, 15 August 1873, Page 2

REPORT ON THE BULLER RIVER PROTECTIVE WORKS.

In continuation of his report on the Ngakawhau Mino and Railway, Mr' Higginson reports as regards protection to the town of Westport and improvement of the navigation of the Buller river.

Having,. in company with Mr A. D. Dobson and Captain Leech, made a thorough examination of the river upas far as Snag Falls,- shortly after 1 the recent heavy flood, Mr Kigghi'sou formed the opinion that unless protective works are quickly undertaken, further damage to the banks and consequent loss of property must, ensue. The overflow channel conveying flood water from the Buller to the Ora'waiti undoubtedly requires first attention. The last flood left proof that a body ofi Water ten chains in width, and in places running twelve feet deep, had overflowed at this point, against which the dense bush and driftwood formed the only dam retaining the river in its proper place. " Should this bush be destroyed by accident nothing could prevent the river dividing. The town of Weatport would then be placed on a delta—'a very dangerous position." "From.the Snag Pall to■ the town the bush has hitherto been the sole protection to the river bank, and it is being from day to day destroyed, in many places cut down for feeding cattle." As protective measures Mr Higginson recommends that through the township a width of at least one chain of bush should be fenced oil* along the river bank, a width of five chains from the town to Snag Falls, and near the falls a total width of 20 chains, the bush to bo strictly preserved and willows planted to replace the bush destroyed. At the overflow channel, near Snag Fall,' a substantial bank to be constructed extending completely across the low ground through which the flood waters find their way, to be built from soil taken from .behind its position, raised well above the highest flood marks, the river slope to be flat, and protected by large river shiugle over the whole surface; the existiug piles of driftwood to be left, forming a shield from the force of the flood. This artificial bank to be four or five chains back from the bank of the river, which should also at this point be sloped and covered with stone. When comploted the bank to be planted with willows, as also the open ground between it and the river. To keep the river in its present central channel and if possible induce it to take to the other j

side completely, the snags on the south side to be cross sawn, but those near the north bank to be left in their present position. The estimated cost of these works is stated at £l-416. To protect the river bank through the township as far as the mouth of the riverj a serious matter both in point of cost and the probable effect on the river channel, Mr Higginson suggests that any works undertaken should hot only be designed for the protection of the town, but for* givlhg good wharf accommodation to works being of a design to deepen the entrance to the river, give the navigation a more fixed character, and to prevent the frequent changes occurring at the river mouth. A serious drawback to harbor works is the absence of good stone in the neighborhood of Westport, the town standing on a delta of alluvial deposit. Granite is obtainable at the Buller gorge some six miles distant, but the ■only means of transport being by boats. Five miles north of the town terraces exist covered to a depth of about 20 feet with loose blocks of quartzose sandstone, very hard and durable, and well suited for these works. The blocks are many of them large and angular, and could be quarried without blasting. The projected line of railway would pass within a mile of these terraces, and a branch line could reach them with little expense. At other points on the railvvaysuitablestonemightalso be found. The use of timber Mr Higginson considers out of the question firstly; because durable timber is impossible to •obtain on the West Coast, and secondly because it has been found that no •dependence can be placed on piles, even 60 feet in length driven 30 feet below the bed, the scour during floods releasing them from position.

The plan attached to the report indicates the natural protection to the river bank formed by the shingle spit extending above Wakefield street, which for some years past has shown no change 'beyond a slight increase in length. Below this a stone protection bank : should commence at M'Leod's wharf 'under tbe shelter of. the spit, following the present river bank with a gentle and liraform 'curve to the point. From the todhrt, the work to be continued for 1000 feet in a more solid form, and following she same curve, the effect of which, if ; as anticipated, would be that the deep water channel would follow this wall and 'comeq'uontry be thrown in a more direct •course over the bar, deepening the water •and straightening tbe channel.

The work should be commenced at 'the up stream end by first tipping in a 'rough stone bank from a little above the level of higli water, the bank forming a

[protection to the town by keeping off : the scouting action of floods. By •degrees the stone would find its proper bearing, and a face wall could be built from the level of low water, and backed ■up by surplus stone in the bank. The •extension of the'wall seaward for 1000 ieet of necessity taking a different form, being composed of heavy loose stone blocks, thrown in a't random, and

.•gradually 'extended outwards until the desired 'effect was produced. In the 'estimate provision is made for a further protection to the coast line for a few 'hundred feet, {shown on the plan as at Tight -"angles, along the present line of 11 olos'worth street), but this Mr Higgin:son hardly considers necessary, as the

training wall Would cause shingle to accumulate there, forming asure protection.

The estimated Cost of the works are thus stated'-: Stone bank, 2,700 feet, £22, : 500; quay wall, £5180; stone

tartdkiivg, £'9oo'; 'earthwork, £4000; training wall. 1(500 feet, £12,600; contingencies, £9216. Total, £55,296. In conclusion, Mr Higginson says it Would take but a fe~w months to construct the line up to the quarries, but should

the utmost despatch be used in pushing on this line, several months must elapse ' before the works 'could afford material protection. Temporary means should therefore be at once devised to prevent further encroachment. On the shore brushwood fascines well tied down would prevent the gradual melting away of the bank. On the bank of the river the bush reserves should be at once fenced off, and thd denuded places planted with willows. *' The bank across the overflow at Snag Fall should be constructed at once, •otherwise before the possible completion of the proposed works,, the port of ■entrance might be at the mouth of the Orawaiti."

Mr .Tobn Carruthers, as Engineer-in-Chief, appends a memorandum to these reports, wherein he recommends that Mr Higginson's suggestions should receive early consideration, and that a further expenditure of about £55,000 for harbor works, beyond immediate river protection, should be looked for. Ward to. His estimate of the financial position of the undertaking is as follows: —- EXPENDITURE The mines yielding 50,000 tons a year. Interest on £150,000 ... £7500 Working expenses ... ... 7000 Total annual charges ... £14,500 REYKNUE. 50,000 tons coal, 5s ... £12,500 Passengers, timber, goods 2000 £14,500 Showing that the railroad would pay interest on cost> but no sinking fund to repay capital. Assuming the output of coal to rise to 100,000 tons per year, with an increase in working expenses, making

total annual charges £21,000, the revenue Would theu be, From coal . ... ... £25,000 Passengers, &c. ... ~. 2500 £27,500 Amount anntialiy placed for refund of capital £6500 Thus, with compound interest, repaying the whole capital in sixteen years, and no loss oceufringj oven if the mine were worked out in that time. To produce these results 1,900,000 tons of coal would have to be procured, but the quantity the mi lie is estimated to contain being enormously greater than this no fear exists of its being worked out before the capital could be refunded. In conclusion Sir Carruthers says : "On the whole, it appears from the abovej that if the mines are worked with energy, the construction of a railway to the Buller, and .the necessary harbot works, would be a very good investment of money, independently of the advantage to the country which would be derived from the improvements to the Bullet river. Unless, however, an output of at least 50,000 tons a year Call be depended on, it would not pay to spend so large a sum as £150,000. I have above assumed that a charge of 3-jd per ton per 4 mile would be made for carriage aud wharf dues. I think this fair, and not higher than should be charged. I have also assumed the workLig expenses at 50 per cent of the receipts, which is very full where the charge per mile is so high, and where the traffic is regular and the speed low. The mines are not well situated for doing a medium business, as the Ngakawhau riyer is not large enough for accommodating more than a smail trade, and cannot be easily enlarged, as will be seen from Mr Higgiuson's report. The coast is also very ill-suited for a wharf such as is used at Bulli, in Australia, on account of the gradual slope of the bottom, which would require a wharf 50 chains long to get 16 feet depth at low water. There seems to be, therefore, no mean between the small trade which can be done with vessels small enough to enter the Ngakawhau and the large trade required to make it worth while carrying the coal to the Buller, as recommended by Mr Higginson." It will be observed that any auxiliary traffic to arise from the opening up of the Waimangaroa or other coal seams, or any other contingent mineral traffic along the line has not been taken into account.