Protection for coastal cliffs

Press, 26 November 1987, Page 2

Protection for coastal cliffs

Any shoreline erosion protection work being considered to prevent cliff-top properties in Motunau crumbling into the sea, will have to gain the approval of the Conservation Department. The department’s contract technician with special responsibilities for marine and coastal issues, Mr Bruce Fraser, said in Christchurch yesterday that any reclamation, shore protection work or commercial removal of shingle from coastlines had to have the approval of the newly-formed department. The department’s mandate was to protect the country’s national and historic resources and to watch out for the public interest. That included making sure that the national value of an area was not “compromised,”

he said. Ironically, as a result of reorganisation of Government departments, the Conservation Department has inherited the soil erosion problems at Motunau from the Ministry of Transport’s Marine Division.

It used to have responsibility for the coastal foreshores, but that is now looked after by the department, although the division retains its navigational coastal interests.

In 1971, the division originally gave approval for several tons of rock under the cliff to be removed, said Mr Fraser. The rocks were transported round the corner to the mouth of the Motunau River, which was also suffering from erosion.

The work was done by

the Hurunui County Council with assistance from the North Canterbury Catchment Board and a subsidy from the National Water and Soil Board. Some residents believe that removal of the rocks has accelerated the erosion and the potential threat to their homes, because the rocks formed a protective barrier from the sea.

The occupants of one house, dangerously close to the 30-metre drop, had been advised to leave as there would be “no warning” if the cliff gave way, said the County Engineer, Mr Bruce Yates.

About 16 properties and parts of two others are threatened by the erosion on the hill subdivision, which was created by the former Waipara County Council in the late 1940 s

or early 19505. A recommendation in a draft report on the problem that a “wave trip” wall be built to stop the erosion, would have to be fully investigated before any work went ahead, said Mr Yates.

The report was jointly commissioned from the Christchurch consulting engineers, R. W. Morris, by the council anti the Catchment Board, and a final copy was expected early next week, he said. Whether any of the recommendations in the report would be adopted was uncertain, although the council had acknowledged there was a problem and would “certainly be wanting to take some steps” to correct it, said Mr Yates. One of the advisers to the report, a senior lecturer in geography at the

University of Canterbury, Dr Bob Kirk, said he agreed the erosion had been accelerated by the removal of the rocks, but he was “quite confident” that it was not the only factor involved. Erosion had been taking place throughout the whole coastline over a number of years, particularly along Christchurch coastlines after heavy storms in the late 19705. The Catchment Board’s river and drainage engineer, Mr Bob Reid, also agreed that in hindsight removing the rocks had “not been a good idea,” but that the problem was a “total geological process.”

He said the residents would like to see more haste, but there was no point in “rushing in upsetting a very delicately balanced system.”