Findlay & Kirk--Post-1847 changes, Avon-Heathcote Estuary

New Zealand Journal of Marine and Freshwater Research abstracts

Post-1847 changes in the Avon-Heathcote Estuary, Christchurch: a study of the effect of urban development around a tidal estuary

R. H. FINDLAY1* R. M. KIRK2

1.Christchurch City Council (City Engineer's Department) P.O. Box 237, Christchurch, New Zealand 2.Department of Geography Canterbury University Christchurch, New Zealand Abstract A detailed, previously undescribed, history of changes to the Avon-Heathcote Estuary mouth at Christchurch, New Zealand, is presented. Between 1847 and 1911 the estuary inlet was dominated by a tidal bypassing regime. Between 1911 and 1938 this changed to a mixed tidal and bar bypassing regime, with consequent erosion of the tip of the South Brighton Spit, probably permanent loss of sand from Sumner Beach, and increased vulnerability to erosion of properties in the suburb of Redcliffs. The change is thought to be related to changes in estuarine tidal compartment owing to the pre-1920-40 urbanisation of the Christchurch area. The change in estuary inlet regime, especially in the context of the post-1946 residential development of Brighton Spit, has important implications for town planning.

Keywords Avon-Heathcote Estuary; spit tip; estuary inlet changes; urban growth; inlet regime; tidal bypassing; bar bypassing

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