ST. CLAIR GROYNES

Evening Star, Issue 17605, 9 March 1921, Page 8

ST. CLAIR GROYNES

TO THE EDITOR. Sir,—ls it not a fact that every bay, harbor, or inlet on the east coast is cut into by the sea on the south side of the bay? The inlets of Waikouaiti, Waitati, Purakanui, Otago Harbor, Gatlins River, etc., all have their outlet on the south side of tlie bay. This clearly shows that the tendency of the sea is to make ai\ opening at that part. It therefore seems superfluous to attempt to save the beach at St. Clair without causing erosion further cast. If, as was suggested, a mole was ran out from the second beach, the sand would probably remain at St, Clair, but the scour would strike across to about (Moreau street, and cut in there. At tho meeting held at St. Clair Mr Edgar expressed the opinion that a continuation of the esplanade would cause erosion whene it. ended, I do not think that would be the case. The tendency of the sea is only to attack St. Clair; and if its ravages were stopped by a sloping wall forming part of a useful esplanade, the matter of the beach disappearing at St. Clair would bo of little importance so long as the sand remains at St. Kilda. which beach is large enough to accommodate all. The continuation of the esplanade to Moreau stared, faced with ferro-concrete piles, would be a permanent, and useful asset to St, Chur and the city, and must eventually be carried cut.—l am, etc., J.A-P. March 8. TO THE EDITOR. Sir, —1 was one of many who predicted that the groynes would prove a failure. How can a row nr two rows of piles placed end on to the seas make any effective resistance? It is simply ridiculous. Had those groynes been placed at an angle of 45deg from the shore, and pointing towards Lawyer's Head, or north-east, they would certainly have caused more resistance to the incoming seas, and probably have stopped the scour into the sandhills; but they would have been a poor job, anyway. Sticking rows of piles in a beautiful beach, such as St. Glair used to be, merely tends to make an ugly outlook. I havo watched this beach for years, and I am of the opinion that the cause of the whole trouble is the deepening of the sea bed at St. Clair, while it is making up at St. Kilda and towards Lawyers Head. This deepening gives the seas a greater battering force on a gradually steepening shore, thereby causing a very strong undertow, which scoops out the sand. To counteract this the plan would be. to build up that part of the sea floor which can be readied at low tide with a rubble wall, about 4ft high, with a slope of 1 in 4, exposed to the seas. This wall should start from the reef near the end of the, hatha (shore end), and curve in to within 40ft of tho centre of the esplanade wall, then gradually curve out until it was about opposite the shore end of the baths at the Forbury road ond. This curve would, in bad weather from tho south, curl the swift undertow away from the land—in other words, give the scour a lead seaward instead of in toward tho sandhills as at present. The present rocky state of tho beach at St. Clair would make a good foundation for this buffer rubble wail. Tho wall itself should be made up of round bounders, cemented together to form a solid mass, leaving round tops to help to break up the waves. This scheme would, in my opinion, be the most economical. A mole would be too costly, and to do any good would have to be run out from tho reef at the oea end of tho baths for at least 1,500 ft. A mole run nut from tho second beach would not be' much good to Rt„ Oair unless it joined up with White Island.—l am, etc., March 8. R. Waiaser.