Lessons from the past : a history of coastal hazards at South Brighton Spit, Christchurch. (1995)
AuthorsComfort, Julie Anneshow all
This thesis provides a history of coastal hazards at South Brighton Spit, Christchurch, through the description and documentation of past coastal hazard events. South Brighton Spit is one of the most intensively developed coastal landforms in New Zealand. Together with the natural fluctuations associated with spit landforms, this provides a useful base for an examination of coastal hazards in a dynamic and high intensity-use coastal environment. The study period is from the establishment of the Southshore Ratepayers' Association in 1946 to 1995, and was delineated as such due to the lack of residential development prior to 1946. Conceptually this thesis is based on the small amount of literature on the interaction between dynamic spit environments and the human use system. It is this interaction between the physical and human systems which creates the potential coastal hazards. There is a popular belief that erosion of the open coast side of South Brighton Spit is the only major coastal hazard to occur there. This is not true. Erosion of the Avon-Heathcote Estuary margin, flooding from the estuary, and tsunami all present major hazards to residents of the spit. The assets at risk include 650 houses valued at $75.6 million. Within the study period there have been five coastal or estuary erosion events, four flooding events, and one tsunami. In total over the last 140 years there has been 38 different coastal hazard events, including 18 coastal or estuary erosion events, nine flooding events, and seven tsunamis - four of which had an impact on the spit. In addition there have been two prolonged periods of erosion - one on the coast and the other on the estuary foreshore. Prior to the construction of stormwater drains in the late 1970s, the area was prone to prolonged periods of flooding. Such a dynamic and hazardous environment requires co-operative and integrated management of the spit between the Regional and City Councils. This thesis provides the first step in managing hazards by identifying those occurring in the area.