SANS ON FORESHORE

Evening Star, Issue 22722, 9 August 1937, Page 16

SANS ON FORESHORE

ITS REMOVAL LINKED WITH EROSION That the removal of sand and gravel Irom the beaches between Oauiaru and Moeraki is a matter very closely connected with the erosion that has been taking place along the coast, but more especially in. regard to the serious erosion in front of the town of Oarnnrn, is the essence of a report received by the Rev. A. H. Nordmeycr, M.P., from the Minister of Marine (Hon. P. Fraser). The report was issued as the result of a decision made by the Marine Department some months ago prohibiting the removal of sand and shingle from the foreshore between Oamaru and Moeraki. From Oamaru to Moeraki in the south, .states' the report, considerable quantities of sand and shingle have been removed over the past (35 years by the surrounding local bodies and by the Railways Department'. In North Otago especially and the east coast of the South Island generally, the littoral drift is from the south to the north. The coast runs from southwest in a north-easterly direction, and the prevailing heavy seas are mainly between a south and a south-easterly direction, and therefore, intensify the littoral drift. Impinging on the shore in an oblique direction, these seas have , the effect of cutting out any movable

material in a similar manner to a hose played obliquely on a loose face of earth. While littoral drift will not in itself cause much movement of sand and shingle, it will, however, where the breaking waves are from the same direction, cause the erosion to be more speedy., The report describes the action of the waves on the shingle, which travel along the beach in a zigzag- path, moving along the shore in the north-easterly direction, and giving rise to tHe term “ travelling beaches ” along the coast near Oamaru. Consideration is given to the geological formation of the Land bordering the sea, as apart from Cape Wanbrow there exists of stratum of gravel or shingle at varying depths below the surface. To the southward of where the Waitaki River now enters the sea there are no shingle-bearing rivers, so the only source of shingle supply for Oamaru beaches is what in the main comes from the eroded cliffs, and possibly negligible quantities from erosion of the outlying reefs, together with an insufficient quantity of fine shingle from the Kakanui. The earliest information of the original condition of the beach at Oamaru is for the year 1864, when the coast carried a considerable quantity of shingle extending backwards on to the land. This deposit was so great that the top of the shingle bank was level- with the surrounding country. The report goes on to quote Mr John Carruthers (engineer in chief), who stated on October 30, 1871, that a contributing factor to the erosion has been the removal of sand from the beaches to the south of Oamaru. For many years these beaches have .been the source of supply of fine grave] for roads all over the district. When one considers the enormous quantities of sand and shingle removed by the Railways Department, together with the quantities removed annually for very many years by the local bodies, and the dredging carried out by the Oamaru Harbour Board (which prevents accretion that would otherwise take place on a travelling beach), it seems questionable whether the efforts of man will prevail against the attacks of Nature, when those attacks have in reality been facilitated by man’s operations over such a wide front. Man’s efforts at protection will certainly not prevail until the removal of sand and shingle by local bodies and others over the 50 miles of foreshore to the south of Oamaru is terminated. For the Marine Department to permit these removals to continue is only involving the department on the side of those who are responsible for the serious erosion taking place and the expenditure that will be involved in the attempts to save the railway line and the property along the coast.