Significant anthropogenic land subsidence within the Port Adelaide estuary of up to 0.7 metres is inferred from the Holocene stratigraphy and associated radiocarbon dates on materials that act as palaeo-sea level indicators. Principal contributing factors are reclamation of Holocene wetlands and groundwater extraction from Tertiary aquifers. Wetland reclamation has caused surficial soil compaction as a result of artificial lowering of the water table, oxidation of peat and pyrite, and leaching of the substrate by soil acidification. Land settlement at a rate of 10 mm / yr has occurred in reclaimed mangrove woodlands as a result of these processes. Extraction of groundwater from deeper aquifers over the past 50 years has created a potentiometric cone of depression in excess of 20 metres beneath the Port Adelaide estuary. Land subsidence estimated at 2.8 mm / yr is associated with the central zone of depressed groundwater levels. Tide gauge data from Port Adelaide and Outer Harbour have been used in global sea level rise calculations without adequate local neotectonic correction. Although outside the zone of greatest land subsidence, three-quarters of the secular rise in mean sea level of 2.5 - 2.9 mm / yr indicated by the tide gauge records is attributed to land level changes. The neotectonically corrected local sea level trend is a rise of 0.7 mm / yr. This highlights the necessity of applying local neotectonic corrections to all tide gauge data before drawing any conclusions regarding global or local eustatic sea level change.