The southern part of Dunedin City, New Zealand, is built over an estuarine marsh, close to sea level and is vulnerable to increased flooding from raised groundwater levels, which will only worsen with predicted sea level rise. Limited data indicate that this area may also be subsiding via either sediment consolidation or tectonism. The underlying sediments amplify seismic waves with the potential to liquefy during strong earthquake shaking. Dunedin is a hazardous place to live and about 2,600 homes are less than 50 cm above mean sea level. Past mining of a dune barrier led to inundation of parts of the city and without the re-established dune barrier, this community would be unprotected. In June 2015, a moderate rainfall event caused NZD 26 million damage through flooding, primarily related to deteriorating and poorly maintained drainage infrastructure. However, the groundwater level here is near the surface (0–1 m depth) and shows tidal fluctuations, which influence the degree of flooding. Reduced storm water storage, related to the increased groundwater levels due to sea level rise, will result in more frequent flooding and of greater magnitude over time. Engineering solutions such as increased pumping capacity and creation of storage areas will be required at considerable cost and disruption to the city. There are difficult decisions to be made about the sustainability of this low-lying coastal community in terms of investment and protection or abandonment of this area. While fundamentally social and economic issues, such decisions should be informed by rigorous technical assessments and investigation and more extensive monitoring systems.
flooding, groundwater, New Zealand, sea level rise, South Dunedin
 Parliamentary Commissioner for the Environment (PCE), Preparing New Zealand for Rising Seas: Certainty and Uncertainty, Wellington, New Zealand: Parliamentary Commissioner for the Environment, November 2015.
 Ministry for the Environment (MfE), Preparing for Coastal Change. A Guide for Local Government in New Zealand. Wellington, New Zealand: Ministry for the Environment, 2009.
 Department of Conservation (DoC), New Zealand Coastal Policy Statement. Wellington, New Zealand: Department of Conservation, November 2010.
 Goldsmith, M. & Hornblow, S., The Natural Hazards of South Dunedin. Dunedin, New Zealand: Otago Regional Council Report, Otago Regional Council, July 2016.
 Rekker, J., The South Dunedin Coastal Aquifer & Effect of Sea Level Fluctuations. Dunedin, New Zealand: Otago Regional Council, October 2012.
 Fordyce, E., Groundwater Dynamics of a Shallow Coastal Aquifer. Unpublished MSc thesis, Dunedin, New Zealand: Geography Department, University of Otago, December 2013.
 Beca Ltd., Assessment of Options of Protecting Harbourside and South City from Direct Impacts of Sea Level Rise. Auckland, New Zealand: Report prepared for Dunedin City Council. 2014.