THE TIMARU HARBOR.

Temuka Leader, Issue 2611, 23 January 1894, Page 3

THE TIMARU HARBOR.

REPORT OF THE ROYAL COMMISSION.

The Shingle Question. ( Continued.) a Mr Marchant’s plan has this advantage, that he is using a method of dredging over the mole which by trial has been found successful, and the storage of shingle as he proposes in still water presents no difficulties; also the cost of constructing the requisite storage bins should not be very great. The method has the further advantage that any abnormal advance of the shingle can be followed up, but it labors under the disadvantage of having to life the shingle twice from the sea bottom. Should the board be unable to see its way to adopt a method of direct lifting by the machinery of the dredge, Mr Marchant’s plan seems a simple and certain method of procedure. “ The present state of the shingle accumulation is shown by the survey executed last mouth by Mr Merchant for the board at our request, and the total quantity of shingle accumulation is given in his report. Copies both of plans and reports are hereunto appended. Mr Merchant finds the average annual rate of accumulation of shingle for the last years to be 67,000 cubic yards, and this he takes to be the quantity that will have to be dredged annually to prevent the advance of the shingle along the breakwater. Should Mr Marchant’s estimate of the quantity of shingle to be removed prove correct, i.e., should dredging when begun have no effect on the accumulation south of the Rock island, about two months’ continuous working of the new dredge should be sufficient to remove the average annual average accumulation. From the present position of the toe of the shingle bank and its possible rapid advance clear that the board has now to face within a period of a few months the perfecting of some scheme for finally checking any further

accumulation of shingle. « A letter from Mr W. Balfour to the Hon. the Minister of Marine regarding the encroachment of the sea on the land northward of the harbor of Titnaru having ' been referred to us, we accordingly examined the coast from the south end of the Wnihdyke lagoon to the north of the Opihi river. . From landmarks given to us by Mr Hardball® it would appear that the shingle bank separating the lagoon from the sea has been shifted landward over a considerable portion of its length J the shift has been the greatest at the south end, amounting to some chains, but gradually diminishes towards the north end. The sea evidently washes ~ver the greater portion of the shingle bank in heavy weather, but there were no breaches in it at the time of our visit. There are evidences that the bank rests on a stratum of loamy clay, which is . being cut away and the shingle thrown further back as the sea encroaches on the clay beneath. For a distance of about II to 2 miles north of the lagoon, the sea is apparently wearing the beach away, as throughout this distance a strip of an old forest area is now exposed to view just aoove low water mark, and the roots are being cut out and thrown upon the beach in quantities by the waves. Between Tidal Creek and Milford Lagoon the sea now appears to be cutting the beach away, iu a face 2 to 6 feet high ; also a number of sand dunes which formerly existed along part of this portion of the coast are fast disappearing, and the rr id, together with some shingle, is being carried back on the adjacent grass laud by the action of the wind and waves. Sim ’ar destruction of grass land appears to be taking place between the Washdyke lagoon and Tidal Creek. There appears to have been, as yet, little destruction of private land, and no injury except the covering up of portions of grass by the sand and shingle. As tho boundaries of private land are some distance back from rue H.Wj mark, jt is the strip of laud between the section boundaries and the sea only that has suffered up to date, It appears, however, that the sea has cleared si way tho protecting shingle beach, and h s now nothing oppose! to its ac!T n except the friable sub-strata, consequently future encroachments may be expected to be much more rapid than they have been iu the past. We undaistand from Mr Marchant, that there are surveys under tho Land Transfer Act, which will enable the exact area of laud destroyed by tho •sea being determined whenever it may bo desired to do so, by another survey, but that no special surveys have ever been made that would enable tho relative rates of encroachment before and after the construction of the breakwater, nor the rate after the disappearance of the protecting shingle beach, to bo now ascertained. It wiT now no doubt take many yo: rs deposit of dredgings on tho Washdyke beach to restore the shingle beach between there and tho Opihi to its former condition, but it is possible that rapid erosion may bo prevented, or at any rate the erosion that is now taking pi: :o be much diminished, by a thinner coating sUipgls on the beach than formerly

existed. In the experiments with shifting the shingle carried out by the board, Mr Merchant was convinced that the shingle then deposited on the sea bottom was all , carried ashore by wave action. The average distance from the shore at which the shingle was then deposited, was given to ua at about 200 feet. With the draught of the new dredge a much greater distance will be necessary, especially at low water. Whether or not there will be a loss of shingle for restoration of the beaches it is impossible to say. Further, there have been no soundings taken that would enable the probable distances of unloading at low and high water for the new dredge to be determined with any accuracy. The total amount of damage done to agricultural land between Washdyke and the Opihi is as yet very small; without, however, a special survey to determine the exact area washed away, it is needless hazarding a guess as to its value. “After carefully balancing the advantages that would accrue to the harbor of Timaru —the increased shelter to the outer berth at the breakwater wharf, the slight projection to the harbor itself, the three years’ probable delay in having to provide for the removal of the shingle, the possible value of the extra land that would be reclaimed, and the other advantages expected to be derived from the construction of the proposed works — against their great probable cost, the delay in restoring to the northern beach some of its original protection, and the benefits that might be derived from the same sums brother ways in internal imwe are unable to recommend that your Excellency’s approval for the construction for the proposed works be granted, for it appears to us that the board should be able to deal with the shingle accumulation by either of the methods above described, or by similar methods, much more economically than by any method requiring an extension of the south mole as an indispensable part; also the funds necessary for the construction of an extension of the south mole if spent in internal dredging and in increased wharfage accommodation, would greatly relieve the port from the inconvenience experienced during S.B. gales and seas, and be otherwise beneficial, “We have to sincerely thank the chairman and officials of the Harbour Board for the cordial mander in which they assisted us by furnishing all information askedfor, andalso the other gentlemen previously mentioned in this report.” “ (Signed)E .R. Usshbr,M. Inst, O.E. P. S. Hay, M.A., M. Inst. O.E. Mr W. Parr sent in the following remarks on the Commissioners’ report:— «To the Chairman Timaru Harbour Board. “Sir, —I have looked over the report of the .Royal Commission appointed to report on the extension of the breakwater, and in the interest of the Board, as well as in justice to myself, desire to make a few remarks thereon. “After specifying the points which appear to them to be those which have been urged in support of the extension, they go on to say that the structure is not sufficiently strong, and that enough has not been allowed for the cost. A great deal might be said against these contentions, but 1 think it quite unnecessary, and 1 will show that, taking their own figures as correct (which, however, I do not admit) my scheme is cheaper and better than the alternative they offer. I will also prove it from their own report, I think, to the satisfaction of the Board. “ I will now proceed to examine their

contentious on the proposal. They say on page 6— e If the idea of being able to utilise the proposed works as part of a possible extension of the harbour into deeper water were given up, the object the Board has now in view—the construction of a groyne to retain the shingle could be attained more cheaply by building such a groyne at right angles to the breakwater. As only about 80 feet in length would be saved we do not think this of sufficient importance to justify its adoption.’ A groyne at right angles to the breakwater would not answer the purpose intended by the original proposal, that is putting the shingle through or over the breakwater, as the groyne at right angles would have a very different action on both the waves and the shingle, and made in the same manner would be more expensive to construct as it would probably necessitate a turn-table. “ On page 6 they say, ‘lt may be replied that the proposed works are only necessary if it can be shown that there is no other method of dealing with the shingle without their aid. The board has made no attempt to prove this,’ I think the facts scarcely warrant this assertion. I beg to refer the board to Messrs O’Conner and Goodall’s report on that subject, where there are nine suggestions of different proposals besides their own, and also Mr Merchant’s reply to their report, and also to the board’s practical and costly experiment with the Priestman crane and hopper—node of which were a complete success, that of the 1801 Commissioners least of all. That would not work at all, whereas the other would work at a price. So 1 scarcely think they can say the board have made no attempt. “ ‘ The question really at issue in their authorisation is :—Are they necessry for the most efficient working of the plant for shingle removal now at the disposal of the board 1’ What do the Commissioners mean by ‘ most efficient ’ 'I What I should mean is the most certain and least costly. The cost is a serious item, and I contend my plan is the only one which fulfils those conditions. (To he continued).