THE OCEAN BEACH

Evening Star, Issue 17155, 23 September 1919, Page 8

THE OCEAN BEACH

SE'A ECS CROACHMBNT. In view of to-night's meeting at tit. Kilda, the following report will be read with interest. It .is dated October 18, 1910, and was forwarded by Mr F. W. Furkerl, then district engineer for Otago, to the Engineer-in-Chief (Mr Holmes) : In replv to the Under-Secretary's memo of August 18, I have to report as follows : 1 have examined the protective works, and also the beach at interval* ever since. I ■havo purposely delayed replying to this latter so as to give me a certain amount of time, both to observe the natural phenomena and to obtain information from persons interested, and who have been keeping watch 'for some time. In my opinion the scheme of protective works carried out is on the right lines, though in certain details I consider it might have been improved upon. As ] undeistand their purpose was to prevent erosion of the sandhills and the private property in the vicinity of St. Clair, it appeals that they havo effectively served the purpose for which they were erected, as no further erosion has taken place since they were constructed. As to whether it is desirable to build additional groins, tins depends on whether or not it is desired to attempt to drive the sea back with the object of gaining the ground which was lost prior to 1901. With a proper system of groins it would be possible to drive the highwater mark seaward as far as necessary to regain ground for a street on the seaward side of the block between Forbury road and Beach street. While making inquiries I found that sonic of the local people are in favor of buying a portion of this block so that a. street and esplanade, might be formed above tho present high-water mark, in which cu-se the present grains would not require much extension. Others, however, wish la erect a .sea. wall so that the esplanade might be renewed on the lin.es which it occupied some years ago. Soma of tho residents consider that if this gea wall were erected the groins would then not be necessary. On this point I entirely disagree, with them, and I. consider that to build a sea wall on tho line of " Smith's Wall" (boundary of old esplanade) without first extending and protecting the beach by means of groins would bo courting disaster, and the wall would be. extremely expensive to construct, and would have the effect of denuding the beach of sand. If the old esplanade is to be rtstired tho groins must be extended and strengthened and the high-water mark driven_ sufficiently seaward to enable a comparatively cheap esplanade wall to be constructed, or even to a.llow of an esplanade being constructed without, any sea wall. The records show that the sand level has fluctuated very considerably, even since the erection tif the groins, and I consider that it was a great pity that when- the aand_ was these groins were not raised slid lengthened, thereby securing the advantage which had heen gained. At tho present time, too, the high tide passes behind two ;of the groins, which is a very undesirable state of affairs. I believe that some of the landward piles of one of the groins were removed by the Domain Board under a. mistaken idea that it v >iild be beneficial to allow the waves to ; m round the end. I forward herewith 'wo tracings showing the position of hi' .ater mark at different dates, and alr-o e configuration of tho coast line adjacent to the groina, the second of which indicates tho reason for the scarcity of the sand in the bight. Tho general <"' : -ect <n of the current is paa-allel to tlv average ran of the shore, while the breakers coming ashore use roughly at right angles to that direction, consequently the sand, which comes from the rivers flowing into the owan further south, approaches the beach in a ■diagonal direction, and owing to the points just west of Kt. Clair very little can be carried into the bight u: ' ;s the breakers have a certain amount of w...-terly sot. As for many months the set ■;.* the waves has been easterly, duo to the extreme prevalence of winds from the opposite direction, the tendency has been for the beach to be denuded of sand, and probably, had there been no groins there, there would have been a further attack by the sea on the sandhills. In addition to bringing the sand in, the breakers are constantly carrying it. along the beach in the direction of the main current, and it is to prevent this tendency and to ar.use the sand which is brought into this bight to remain there that the groins were originally placed. The extent to which _it would" be desirable to extend the groins and cause accretion of the beach is limited i by the necessity of preventing ailting up of the baths, and by the undesirability of creating a large extent of eand above high-water mark, which, when dry, would blow about, causing great annoyance unless it were fixed by the planting of sandbinding ;grasses or other plants or covered with clay. ________