OCEAN BEACH

Evening Star, Issue 17159, 27 September 1919, Page 8

OCEAN BEACH

ENGINEER'S REPORT ON

EROSION.

GROYNE EXTENSIONS ADVOCATED.

[From Orra Pabuamkotarx Bkpobtek.]

WELLINGTON, September 27. A report on the erosion at St. Clair beach, containing proposals for its protection, has been prepared by Mr F. W. Farkert, Assistant Engineer-in-chief, Public Works Department. Mr Furkert points out that as a result of the erection of groynes between 1903 and 1906 erosion, which was then very active, immediately stopped, but of late years a considerable number of piles were washed oat, and some taken out purposely, and lately a fair amount of erosion has taken place. A prolonged spell of southwesterly weather must result in some denudation ; but groynes will delay this process, arid assist in building up in favorable weather. It would be possible to protect the foreshore by continuous rif-raf work; but very heavy stone would be required, that at "present being entirely inadequate. Its expense would be unwan-anted, and the presence of heavy rock would not tend to make the beach beautiful. No doubt the same could be said of groynes, but not as regards expense. The protection of the foreshore by a continuous wall such as exists at St. Clair Esplanade is still less justified, as a vertical wall is very destructive of the foreshore. PROPOSED REMEDIES.

Mr Furkert suggests that the first thing to do is to repair the neglected groynes, and extend them both in height and length. Experience in other parts of New Zealand shows that a few feet at the outer Mid of a groyne has the greatest amount fif effect. What should be aimed at is a flat, even beach on which the waves can spend themselves before reaching the foot di the sandhills. Very good work has been done by the Domain Board ?n fixing the sandhills, particularly in the vicinity of St. Kilda; but as these sandhills formed a reservoir from which a considerable amount of sand would be drawn for making up the St. Clair beach during easterly weather, it will be recognised that this source of supply will not now be available that is St. JKilda has been improved to some extent at the expense of St. Clair. In addition to repairing the existing groynes, at least three more groynes should be erected at intervals of 250 to 300 feet to the eastward of the present ones. The most easterly one should be erected first. If erosion becomes acute still further east it will be necessary to erect further groynes, but probably not to any great extent. If New Zealand timber is used and the piles put down by the water-jet method, obtaining the water from the City Council mains, the cost will not exceed £6OO to £7OO.

Mr Furkert opposes the suggestion to erect a breakwater near the baths, as it would only render it more difficult for Fand particles to get on to the beach in the vicinity of St. Clair, and would lead to denudation rather than accretion On this point he quotes Mr Blair Mason's report m 1901, which states that the method of promoting sand accumulation by means of groynes extending out beyond high condi lions prevailing at Ocean Beach, water mark is peculiarly adapted to the while the method opposing further sea encroachment by means of a sea wall should only be resorted to when conditions are such as admit of no other alternative, which is not the ease at Ocean Beach.