THE HARBOR WORKS AND THE NORTH BEACH.

Timaru Herald, Volume XXX, Issue 1481, 20 June 1879, Page 3

THE HARBOR WORKS AND THE NORTH BEACH.

TO THE EDITOR OF TIIE TIMABU BBBALS. Sib,— ln a letter published iv your issue of Monday last I drew attention to the d inger menacing the railway viaduct at Le Cren's Gully from the action of the sea, and with your permission I will resume the subject, looking a little further ahead than wben writing my former letter. From observations made since writing that letter, I find that I magnified the imminence, of the danger threatening the viaduct mentioned. This was probably due to my not having visited that point for a week or more previous to the day on which I wrote, during which time the change produced m the beach was so great as to surprise even me, who had expected such a change m the course of no long period, and under the influence of that surprise I wrote as I did. The danger, however, is no less (real, though it may be less imminent than I I hen urged, and this must be patent to anyone who will watch the change produced day by day, and consider what a continuance of the present process must imply. There cannot be the slightest doubt that this process will be continued, though probably at a slowly-diminishing rate, and that, therefore, some steps must be taken to secure the safety of the viaduct. It may not be bo apparent, but it is nevertheless equally true, that tho danger which now threatens the fir»t viaduct will m the course of a short lime also thrtaten the railway structures spanning the second and the third hollows to the northward of Le Cren's Gully, and, at some later time or times, the rest of the lino between that point and WooHcombe's flu!!;. The beacli nloug the whole western shore of the buy, from the head of the bay to the Dashing Rocks, is being narrowed more or less rapidly, and m tho courto of a comparatively short time, the beach from LeCren's gully to the Waimatuitai Lagoon will be as bare of shingle as is that between the first-named point and the Breakwater. That is, unless the clay bluffs aro cut back more rapidly than the shingle spit at the lagoon is shifted m the manner ti presently described. The clay of which the lower portions of tho;e bluffs are composed is certainly of a very tough character, but it would be absurd to expect it to withstand the direct beat of the surf. The bed of clay into which the pilrß supporting the Government ■Service shed are driven, is aleo of a tough kind, yet, broken and weakened as are the waves that reach it, their effect is plainly perceptible week by week. I have no doubt that if the clay sub-beach ou the western shore of Iho bay were exposed to the direot action of tho surf, they would be eroded at a rate that would produce results more picturesque than profitable to the holders of the fee simple of the soil above. There is one fact which, from a practical point of view, must be considered a very favorable one, as tending to postpone the commencement of such destructive action on (he clay banks. This is, that the soaward projection of tho Dashing Rocks will render the northward transport of shingle more and moto difficult as the quantity immediately to tho southward diminishes. This conserving action is even already apparent, little or no shingle having been carried round the rocks during the last few day?, notwithstanding the heavy eeas that have prevailed. Supposing, however, that no more shingle is carried northward round the ro-ks, the final result will be the same ; it will only be delayed. Attrition alone will rapidly lessen the quantity of material now on the beach, and after this process of diminution has been continued for a time, another process will be initiated, which will deprive the clay banks of their shingly protection. The whole of the beach having been somewhat narrowed, tbe wash of the sea will overlap the summit of the spit at the Waimataitai lagoon, and carry the shingle over and landwards, and the effect of this will be to draw the shingle from the rest of the western shore of the beach— unless, as said above, tho clay banks are cut awuy as rapidly as this overlapping process goes on. I would not pretend to be able to form an estimate of the time when serious destruction of the land will commence, but 1 think that m making such an estimate, one would bo as likely to err iv one direction as the other. That suoh a destruction will follow, unless the shingle stream be allowed to resume its normal flow, iB as certain as that a change m the aspect of the beach hns already been brought about by the arrest of that stream. I should think that the Harbor Board, and whoever thought with them, already regret that they did not consider with a little more patience, and with some desire to understand them, Sir John Coodo'e objections to the construction of a breakwater solid with the shore. 1 do not say that Sir John Cootie's plan should have been, or could have been adopted. I merely wish to point out the unwisdom sf entirely ignoring the well-matured opinion of a man who has made himself famous m his profession. Sir John Coorle said plainly that it would not be advisable to stop the shingle, and mentioned m his report that the slight and temporary arrest caused by Mr Balfour's experimental blocks, affected the beach at the head of the bay. Mr Carruthers, before him, expressed the tame opinion, stating that the removal of the beach to the northwards would assuredly result. These opinions were ignored by the Board, nnd, it is but fair to the Board to say, by most people, and even tho fact upon which they were based— the northward movement of the shingle— was denied by a great many, including some members of the Board. Denial of the fact of the northward movement is now impossible, even by the most obtuse, and the inadvisability of arresting that movement without counting the cost will be demonstrated very soon, and is being very praotically intimated even now. I tbink.itis well worth considering whethei-it would not be cheaper, m the long run, to allow the shingle to resume its former course, by removing the present Breakwater, and adopting Sir John Coode'a plan or some modification of it, for, expensive as that plan wouli be to carry out, it may be questioned whether its cost would equal that of carrying oul the present plan and paying for all damage accruing from the arrest of the shingle it necessitates. I have said nothing of any damage likely to accrue to the northward of Caroline Bay — northward of Dashing Bocks — but it is plain that tbe shingle spit now protecting the Washdyke Lagoon muet be carried away, and the sea encroach on the land there also. In fact, owing to the conserving action of the Dashing Rooks upon the beach to the southward, before referred to, it is not impossible that the arreßt of Ihe shingle may produce strongly marked effects north of the bay, sooner than within the bay itself. Within the pnst four days the width of the beach immediately north of the Dashing Rooks has been perceptibly lessened. I am, &c., A. M.