South Hawke Bay beaches : sediments and morphology.

The beaches of south Hawke Bay extend from Tangoio to Te Awanga. These beaches are a separate feature to the material making up the Heretaunga plains. They are protected to the north and south by the promontories forming the Mahia Peninsula and Cape Kidnappers. There is a seasonal supply of material to the south beach which is related to seasonal variations in wave conditions. In summer a short period wave climate exists and superimposed on this is a locally generated wave system from the northeast. This causes erosion of the cliffs and beach ridge complex between Te Awanga and Cape Kidnappers. In the winter a longer period wave climate is found and this approaches mainly from an easterly or southeasterly direction. The presence of the breakwater prohibits movement of shingle from the south beach, north of this point so that the main source of material for the north beach is sand which is supplied by the Esk river, or moved northwards and shorewards from the offshore sand belt by wave action. The distribution of sediment along the beaches is a response to varying wave energy distributions associated with different wave approaches. Changes in sediments reflect the different energy conditions and these changes may take place over distances of approximately a mile. The morphological characteristics of the beaches are closely related to the grain size distribution of the sediments. Coarse material produces steep slopes while fine or sandy sediments result in more gentle slopes. Future developments on these beaches will include continued sedimentation between Port Napier and Westshore. The beach north of the breakwater will remain stable in a state of 'sub-equilibrium' and may develop a higher percentage of sand in the deposit. The beach to the south of Napier will continue to erode on its southern extremity until it has reoriented itself to the dominant wave direction and readjusted to the changes in elevation that took place in 1931