WANGANUI RIVER

Evening Post, Volume XCVIII, Issue 139, 10 December 1919, Page 15

WANGANUI RIVER

EROSION AT THE SOUTH SPIT

THE WORK AT CASTLECLIFF.

An article in the Wanganui Herald indicates that opinions differ considerably as to the ultimate success of the operations being carried, out at Castlecliff, at the mouth of the Wanganui River, with a view to preventing further erosion at the South Spit. The long succession of heavy gales has been a disturbing factor, iind the remarkable changes on tho sea beach, caused by wind and tide, have puzzled the Harbour Board authorities. One of the groins erected has done excellent work in holding the sand and building up the Spit, but the other two have been left high and dry. There is also a great body of sand on the move from the South Mole, which, it is hoped, will fill in the- danger holes which have been created by the scour. The pipes through which the spoil from the dredge is being depositedoii the Spit,' have been taken right across the Spit to the sea • shore, and the silt, which contains a good proportion of gravel, is resisting the power of the waves and settling down solidly. This is regarded by the Harbour Board officials as highly (satisfactory, and it is hoped to throw out a big tongue of river spoil, which will gradually spread right .along the Spit and materially strengthen the position. AN INTERESTING DISCOVERY. At one point there has been revealed portion of a vessel. This is presumed to be an old hulk which was used in the early days of tlje port for pulling up snags in the river. Forty-two or fortythree years ago, when tho river broke through the South Spit, and created a channel of from 10ft to 14ft in a single night, this vessel was placed in the gap with the hope that it would form a barrier, while sandbags and fascines were thrust down on either side. "Its pretty far down if it's got down to that," remarked a retired master mariner, who was closely connected with the port in the early days, to a Herald representative, He went on to explain that when further protection work was carried out on the Spit a year Or two later, the hulk had sunk out of sight, and the protective works were commenced about three feet below.tide level without disclosing any trace of the vessel. When these works were being carried out, they were pushed ahead with all speed, men working day and night, and including Sundays, to repair the breach. The method adopted was to first of all lay a solid foundation of sandbags, which was commenced about three feet below the then water level. _ Then brushwood and stakes were used inside this barrier to catch and hold the sand, and gradually the level was raised above highwater level. This scheme proved very effective and rapid, and large accumulations of sand were obtained, even after one tide. Since then erosion had been continually going on, but until late years the current from the northwards brought down sand'which acted as feed for the erosion. The extension of the moles cut off this supply ,_ so the reduction of the area of the Spit became a natural consequence. In the opinion of this master mariner, the repairing of the Spit will be a serious matter, and if more rapid progress is not made, he is pessimistic with regard to the consequences. He considers that the board should put every man available on to the work, as the authorities did in tho early days, and work till it is completed. He 'did not think it was of much use pumping spoil on to tho break until the bank was raised above high-tide level, for the material being light, the greater part of it was washed out to Ben.