Coastline change at Wanganui, New Zealand (1971)
AuthorsBurgess, J. S.show all
In the last 100 years the coastline adjacent to Wanganui River mouth has changed substantially. Construction of harbour moles at the mouth of Wanganui River initiated these changes. It is suggested that sediment reaches the mouth of the river in substantial quantities from the north via longshore currents and from the Wanganui catchment via Wanganui River. Interruption of natural by-passing processes resulted in progradation of updrift beaches and erosion of parts of the downdrift coast. The improved depths found at the entrance in the late 1920’s as a result of mole construction deteriorated rapidly in the 1930’s, facilitating more rapid by-passing of sediment. Consequently progradation of the updrift beaches and erosion of downdrift beaches slowed. At present conditions at the harbour entrance are not unlike those encountered by early settlers of the area. Most material reaching the coast is by-passed south of the entrance and present day changes are minimal.