ST. CLAIR BEACH

Evening Star, Issue 23332, 31 July 1939, Page 12

ST. CLAIR BEACH

M: Protection of Sandhills EROSION OF LONG STANDING History of Restoration Efforts The ravages of heavy seas on the beach and sandhills at St. Clair are once again causing anxiety to residents. Articles and photographs in recent issues of the ‘ Star * have shown the position, and it would seem to be serious enough. That it is not irreparable would appear from the fact that there-is hardly a resident of long standing in St. Clair who cannot remember other occasions in the past when the sea made as great, or even greater, inroads. At the same time it has been emphasised by many that the position can and ought to be rectified.

THEORY OF EROSION There is no beach in this country that, in its natural state, is not constantly changing. It has been pointed out by a St. Clair resident, who has deeply interested himself in the welfare of the beach, that where the sea breaks directly on the sand and the receding water "travels back on its former path there is no erosion. The damage is caused when wave after wave breaks on an angle to the level sand, and, as must follow if this is the case, the water takes a different track on its escape back to the sea. To put the case more clearly, if the beach ran straight in a north-easterly direction and "the seas came from the southeast—that is, at right angles—even though they broke against the line of the sandhills, these would bo_ unimpaired. If, however, the sea in this instance came out of the south, the sweeping motion at the foot of the sandhills would soon undermine them. Like most beaches, Oceau Beach takes roughly the shape of a half-moon. Therefore, according to this theory the seas that erode the beach at one end will have an opposite effect at the other. This is the case, St. Clair losing sand while St. Kilda is building up. This actually has been the case from time immemorial probably, but there is another aspect of it to-day. REDISTRIBUTION OF SAND. During the violence of the southerly gales there is little or no windblown sand. It is in the summer time then that sand is shifted, mostly by dry northerly winds. Consequentlyother days the sand that was lost to St. Clair and added to St. Kilda in the winter came back via air transport in the summer. A more or less constant lev el was maintained, varying in each year according to the quality of the weather. BREAKING THE CYCLE. However, when man and his pleasures enter into the picture flying sand in the summer time has very few desirable aspects. Also it is disturbing if the seaward boundaries of a city are to shift about, as is the habit of a sand dune left in the way that Nature leaves it. So the very necessary work of building the sandhills with marram «rass and lupine was engaged upon, and m these days it is only a very determined warm breeze that has any effect on the stability of the dunes. In fact, so successful has this work become that the amount of sand shifted to-day is infinitesimal. - There is still the problem of the sand shifting northward in the winter time, and this has never been satisfactorily tackled. It is true that by the use of brush fences and groynes the work of the sea has been slowed up, and the damage would probably be far greater to-day had it not been for the work of the Domain Board, which is responsible for them. But St. Clair residents who have watched the beach for many years claim that the low-water mark could be pushed further out to sea by, to a certain extent, harnessing the waves to bring in the sand. UTILISATION OF GROYNES. While the utility of brush fences is generally admitted, the feeling of those interested is against the groynes as they stand. Were they boarded up for their entire length it is claimed that, by training the waves directly against the “ lie ” of the beach, and minimising the side-slew of the wave that is nearly spent they would prevent erosion of the beach. It is the end of a wave that does the damage. On a long sandy stretch, straight-running billows will build up a beach rather than break it down. It seems feasible, therefore, that boarded-up groynes, set to straighten the run of the waves, would have an ameliatory effect. As they stand to-day, the groynes cannot to any appreciable extent alter the direction "of the waves. In fact it is claimed that they help the process of erosion on account of the receding water swirling at the foot of each pile. In illustration of this point, it is only necessary to point out that most of the small river mouths in Otago used as harbours, have a rock in the entrance, and that in cases where this condition does not obtain, the river enters the sea by a cliffside, although it may run some distance at the back of a long, sandy beach. This is not coincidence. Receding water, swirling by the cliffside on the rock made it the weakest spot in the beach, and there the river first found the sea. In the same way, there is often, or nearly always, a depression in the beach adjacent to the vows of piles. It is not surprising that there is a strong feeling that the groynes should be either removed or hoarded up, and that representations have been made to the Domain Board to this eff€Ct. One adverse criticism to the boarding up of the groynes has been made that the probability is that the beach on either side of any groyne would probablv be on’ different levels, and, even though space was left in the boarding for strollers on the beach, the vary in"' heights would constitute a difficulty 0 for many people. It is not,

however, anticipated that this would be a very serious matter. CONSTRUCTION OF BREAKWATER. One other suggestion has been the construction of a breakwater near the baths, running in an easterly direction. It is difficult to anticipate the results of this move, ■ although it would probably assist in the building up of the beach. In some quarters, it is thought that it could be built from the end of the cliff at the southern side of Second Beach, where the quarry is operating. If this were done, it would have the effect of increasing the amenities of St. Clair with a boat harbour for pleasure craft, and with the freedom from heavy weather that the seas adjacent to Ocean Beach enjoy for the greater part of the summer (exemplified by the constant use of canoes), it would make St. Clair one of the more popular summer resorts ■of the South Island.

No 'great depth of water obtains near the cliff, or, for that matter, in any part of the hay, and there is an absence of strong tides. Concentration on this beach would also make it an ideal spot for the establishment of an aquarium, if some shelter existed towards the south-east. The removal of the Marine Hatchery to Wellington will leave Dunedin without aiiy amenity of this sort. However, as far as the erosion of sand is concerned, it is a matter for an engineer’s report as to whether a breakwater would be successful. In a report to the Engjneer-in-chief, Mr F. W. Furkert. public works engineer, in August 1919 gave it as his opinion that the breakwater would do no good whatsoever. Mr Furkert advocated the groynes then in use,, althoughit is only fair to add that he encountered no little opposition in so doing. EARLY INTEREST, Since the early ’nineties the condition of the beach and . its maintenance have been the subjects of much argument, sometimes vituperant. In 1888, or thereabouts, the Domain Board sponsored a by-law making it illegal to bathe after the hour of 7 a.m. In ensuing years some enthusiasts used to walk to Tomahawk for their afternoon swim, until the day when a guardian of the law was stationed there to prevent these illegal proceedings. _ In 1910 a good deal of public indignation arose over the prosecution of three young men for bathing in defiance of the law. The magistrate dismissed' the case—costs were not allowed—and arrangements were made with the Domain Board whereby there would be no prosecutions “ providing suitable costumes > were worn.” From this time more interest began to be taken, and in the same year, on June 29, the “ St. Clair Society,” later known as _ the St. Clair Improvement Association was formed, the objects being the improvement of the beach. THE ESPLANADE PROPOSED. Even at that date, its denudation at the St. Clair end was a matter for auxietv, and the building up of the St. Kilda Beach at the same time was commented upon. Some idea of the extent of the ravages of the sea then can be gained from the fact that Air F W. Furkert, the district engineer of tho Public Works Department reported to the Ocean Beach Domain Board that “with a proper system of groynes it would be possible to drive the high water 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-- The prediction is triumphantly proved by the presence of the Esplanade. . , Mr Furkert went on to maintain that the extent to which accretion of the beach could be pushed was limited only bv the necessity of preventing silting up of the baths, and the undesirability ot creating a large extent of sand above high water mark. Considerable opposition was met with at the time, and for a while no move was made in any direction. Newspaper comment may be indicated by the one sentence : To look for a live policy from the present hoard is, we are afraid, to search for figs on thistles.” . . .. As a means of increasing‘the revenue of the tramways department, the City Corporation, in April, 1911, bought land for the Esplanade, and also for a wooden pavilion on the site of th® present brick structure. This building also raised a protest, this time from the team room proprietors at St. Clair, as it was thought that the council intended to enter into the catering business. Skating was also to be an attraction of the new building, as was dancing, and a band stand and other amenities' were planned for. However, as far. as the beach was concerned, tho Esplanade and the sea wall which fronted it were the next attempt to withstand sea erosion. It was very strongly made, and, although there was much opposition to its buildintr on the grounds that the straightness of the wall would accelerate erosion, it has not interfered in any way, harmful or otherwise, with the natural action of the sea. In some years the sand has been built up to. within a few feet of the footpath. It has probably never been as exposed as now, although it is maintained that this is solely on account of natural causes, and the security of the building which has

been provided for the sandhills further north. Four years after the wall wa« built the beach was in the finest'cpndition within memory, but in 1919 erosion was again serious. So it has gone on. Many reasons have been put forward for the erosion, and in most cases, the very attempts that have been made to combat it have been blamed,. A great deal has been done fay the trial and error method, and results of the work are often not obtainable. The natural cycle erosion at St. Clair, building up at St. Kilda, and the return of wind,?: blown sand to St. Clair, has been interrupted, and only artificial mean* will now supply' the want. So much i* obvious. Just what means will be successful is hard to say, although StClair residents maintain that boarding up of the present groynes will be efficacious, It is certain that no patriotic resident of the beach suburb will r be. completely satisfied until he, or she,. ia disporting once again on -a paragon among beaches. ■_