During the Late Holocene (1800 years BP to the present day) there have been three depositional episodes in coastal sand dune areas: Tamatean (1800 to 450 years BP), Ohuan (450 to 150 years BP) and Hoatan (150 years BP to the present day). Each episode comprised two phases: an unstable phase with a high rate of deposition, followed by a stable phase with a low rate of deposition and soil formation.
During the last 1800 years there have been eight periods of increased erosion and alluvial sedimentation in New Zealand, which have generally decreased in magnitude towards the present. Throughout New Zealand, alluvium of all erosion periods contains abundant remains of plants as evidence of widespread destruction of vegetation during erosion periods. Indices of the relative magnitude of alluviation, and estimates of the damage to vegetation in the current Waipawa Period (since 1950), are applied to estimate the impact of earlier erosion periods.
