How aerodynamic roughness elements control sand movements
- Author
- Lyles, L.; Schrandt, R.; Schneidler, N.
- Year
- 1974
- Volume
- 17
- Pages
- 134-139
- Summary
- Matakana Island, in the western Bay of Plenty, is a barrier island which encloses Tauranga Harbour. It comprises two distinct parts: an older area of tephracovered Pleistocene terraces and, to seaward, a large Holocene sand barrier. Vestiges of shore-parallel relict foredunes indicate that the lowest Pleistocene terrace originated as a prograding coastal plain, The Holocene sand barrier initially formed in at least two separate parts about 6000 cal (calendar years) BP. Its environmental history was determined by means of geomorphological, sedimentological, tephrochronological, pedological and palynological techniques, together with radiocarbon dating. The northwestern part of the Holocene barrier originated as a migrating washover ridge, whereas the southeastern part abutted the cliffed edge of the lowest Pleistocene terrace. The barrier grew by means of southeasterly spit extension, the accretion of successive foredune ridges along the ocean shoreline, and progradation along the harbour shoreline. By about 3500 cal BP the tidal inlet which separated the two parts had closed. During the past 600 years the ends of the Holocene barrier adjacent to the present tidal inlets have been particularly dynamic features which extended rapidly as the harbour entrances narrowed. The Holocene barrier has undergone major environmental change throughout its history. Parts of the relict foredune topography of the Holocene barrier were modified by migrating dunes. Parabolic and blowout dunes developed prior to human settlement and a variety of dunes has developed since. Since 600 cal BP natural changes have been augmented by human impact, including modification of the vegetation and soil by Maori and, more recently, farming and plantation forestry. Future planning and management decisions should take into account the dynamic nature of the island.
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