THE OCEAN BEACH MENACE

Otago Daily Times, Issue 17912, 17 April 1920, Page 6

THE OCEAN BEACH MENACE

SEA AND titLLiTING SANDS,

OAN THE! BE CONTROLLED ?

n. Thq dSaappuiniroenta, o£ 1898 wero followed by a period of apathetic rest —none but tho enthasufiia ' warned about tho menacing ocean- As was pointed l out in a previous article, tihe ratepayers could not bo persuaded to endorse the plans and find the money to give etfect to the Domain Board's programme of 1898. The effort was not altogether wasted, however, as a wider section of the puhlio became interested in the problem of beach, protoo 'In 1901 the Government District Engineer (Mr E. R. Ussher) and Mr J. Blair Mason tarnished reports on beach protection. Mr Mason's report ia tlte mo&t comprehensive yet presented, and oontainod a mass of information, as well as certain roooounendationa, which, have been acted on "with success. Mr Mason pointed out that all sand beaches fluctuated in form and contour. The strength and direction of tho wave forco, coastal currents, and meteorological changes all affected them in some torm or other. Hie increase of settlement along the coasts had thep, affected sandy shore formations. "Usually," wrote Mr Mason, state of practical equilibrium is attained ■when Nature ia left to herself." But Nature had been interfered with by man, and she set about making other changes, which did not always merit man's approval. Dealing with Ocean Beauh, Mr Mason ■considered tho unstabdlity of that timo duo t<>: (a) Alterations to natural conditions ' from the landward side by tho destruction of the original fringo of vegetation, especially at St. Clair. (b) Loosening and destruction of sand grasses by cattle and traffio. (o) Removal .from the boach of sea wrack, marine debris, dirftwood, etc. (Dobria of ovary kind aids materially in ' preventing the travel of dry sand.) . ? (d) Breaking of tho sand crust by traffiec ' (The saline crust formed in dry weather where sand is exposed to the ooean spray and the receding wave prevents drift to a considerable extent.) ; (e) Artificial removal of sand, especially at St.' Clair and Musselburgh. (f) "Variations from seawards in the original wave action, cnased by alterations and removal of rooks at St. Clair Baths, / Mr Mauon ecsprassed regret that the rooky shelf on whioh tho baths were formed had been interfered with. He was convinced that • in" heavy westerly and southerly weather the St. Clair rooks protected the beach. Tho wholo subject was covered in his report under two heads: (a); Protection and conservation of the sandhills and beooh;' (b) protection of St. Clair and reerection of sea-wall. The methods suggested for tho protection of the sandhills were:— (a) Arrest of wind-borne drift by means of wind-brakes inshore of high-water mark. ' ; (b) Arrest of sand travel generally by means of groins extending out beyond high-water mar*. (o) Protection of sandhills and flat by means of sea-walls or embankments, with or ,without protecting groins. • The problem to-day is the protection of the sacdhills; which have been fofmcd in part, as a result of the efforts of the Domain Board. It is unnecessary, therefore, to do more than acknowledge Mr Mason's proved advice as to the wisdom of trapping the sand and building up the sandhills. Mr Barr had pointed-out that "the proper principle was to endeavour to induce tho sandhills \o extend from the beach outVrards." Some considerable success has followed the practice of that principle. The question to-day ia one of opposing further sea: encroachments, "and consequently, public interest is centred in the various proposals ito resist the action of the sea. So far as the writer can discover, the proposals backed by engineering authority are limited to a sea-wall, groins, a sea mole, or a breakwater. Variations arid combinations of ifchese have been suggested, but the proposals deemed practicable fall under one or other of these heads, the major testimony strongly favouring groins. i .Tho sea-wall has had its supporters and vigorous opponents. Our first article gave faU 'evidenoe of that fact. Mr Mason was definite on the point: "A sea-wall . should only be resorted to when the conditions are such as to admit of no other alternative, whioh is not so in the case of tho Ocean Beach. . . . The tendency of a wall Would be to lower the beach, unless flanked by groins, which would, in turn, by encouraging sand deposit, pro- • faably lender such wall unnecessary. . . . !• am . . . not prepared to advocate ■walla or embankments us a defenco against (tea encroachments at the Ocean Boach, the effects of which may be serious and far-reaching." Dealing with the erection of a sea-wall at St. Clair proper, Mr Mason said thst "No doubt the comparatively sheltered position at St. Clair would be more favourable to the maintenance of a mil than at any other part of the beaoh." But even then, he held that the raising of the beach by the interception of sand drift or otlier mekns should precede the erection of the esplanade wall. To-day the beach at St. Clair has been lowered several feet, and a layman, who accepts Mr Mason's •view?, would naturally oonolude that tihe erection of the wall has been largely responsible for tie loss of sand in close proximity to the esplanade wall. Several of the engineers, Mr Mason included, champion groans as the best means pi influencing the sea. "I have not .the slightest doubt," Mr Mason "that the construction of gromi would, wherever placed on the outer beaoh, stop further encroachment and build it up by arresting the travel of drift eastwards. One may point to the efficient protection of portions of the Kentish coast, the coast of Sussex, Norfolk, and nocth of the Homber, brought about by analogous means. And in the same manner, no difficulty hoe been found in stopping sea encroachment in the State of Victoria. Swan Island at the entrance to Port Phillip, lost acres year by year until protected by groins, when accretion commenced, and ia still in progress where thus protected." In same cases unwelcome sand accumulations had' followed the erection of jetties and piei» run oat irom tho exposed sandy recast. .. They had acted as groins, and had farmed a teach, and so decreased £he depth of water close to the piers. The erection of a mole or a breakwater would be an undertaking of great magnitade, and it is questionable whether modern engineers woukl bo found to favour a breakwater from any point westward of the baths. Experience elsewhere would seem to suggest that if suah a work was undertaken St. Ckir would bo transformed. It is well, however, in this matter to keep near the beaten treusk blazed by the expert engineers. Tho issue is, therefore, clear, and. the immediate question is whether groibs are likely to effect the much-desired protection, of the beach. Groins were created between 1902 and 1906, and, despito the. fact that they were somewhat primitive, engineers regarded the experiment and the results with satisfaction. Mr F. W. Farkert, writing in 1910 as Government district engineer, said that the groins had effectively served their purpose, "as no additional enoeion had taken place since they ■wero constructed" Mr Furkert roported further in August of last year. 110 attributed the previous improvement of tho beach to tho influence of the groins, claiming that there was active erosion in progress before thei groins were erected, that the erosion stopped/ immediately the groins were erected, and that when tho groins fell into disrepair the erosion recommenced. . "In order to deal with the present position," Mr Furkert considered, "tho first thing to do- ia to repair the neglected gToins created 14 years ago: to extend them both in height and in length the first timo a favourable spell of weather, assisted by their action, causes sanding up of the beaoi*." In faoo of all thi3. only tho very confident layman, whoso faith is reposed' upon an flttsohite knowledge of all the oonditions, will oppose the present plan of erecting groins. The decision to put eight groins on the beach has hung fire because of. the difficulties of supplies. Tenders have boen culled for piles, and arrangements made fop the plant. Within a short timo, therefore, the work should be undertaken. It ia fitting that there fihonld be a word of recognition of tho work of the Domain Board in transforming the sandhill. There are now, roughly, ICO acres of sc/tled sand, planted with hrpin and marram gram. A portion of this ig level, and makes an ideal jAaygwund.. Not so many years ago a lagoon with 4ft to sft of writer covered a part of this area. Mr J. H. Hnnoocrk, charrnrnn of tho bonrvl has eared for tho flandhitlfl as one would rare for n. privato garden, and though vho menacing oronn ha« often defied its somewhat poverfystridcon efforts, the board has done mueh.io merit the thanks of citizens who appreciate