Uses of sea level rise information by local government: Hawke's Bay case study

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Potter, S.H.; Grace, E.S.; Payne, B.; Levy, R.H. 2018 Uses of sea level rise information by local government : Hawke's Bay case study. Lower Hutt, N.Z.: GNS Science. GNS Science report 2018/32. 19 p.; doi: 10.21420/GE9F-1K76

Abstract: The uses of Sea Level Rise (SLR) information at a regional level were investigated between 2015 and 2017, using the Hawkes Bay Region of New Zealand as a case study. This work was carried out as part of the wider ‘Our Rising Tide’ GNS Science Strategic Development Fund project. Workshops were held to find out what information about SLR would be useful for key stakeholders (particularly in terms of impacts), what format would be most useful to receive that information in, and how that information would be used. We found that SLR information is used for a variety of purposes by local government, including to improve community resilience to hazards such as flooding, storm surge and tsunami using risk analysis, and developing effective mitigation methods including land-use zoning and policy development. SLR information is also used to manage impacts on freshwater, coastal, terrestrial and estuarine environments, and to manage council infrastructure. Impacts from SLR that are important for local government to understand include changes to liquefaction zones for hazard and land use mapping; salt water intrusion into groundwater aquifers for planning and water allocation; changes to the groundwater level for planning changes to consents and groundwater flooding management; changes to the tidal prism, which may impact estuary ecology, river models, sediment transport, coastal erosion, salt water intrusion and water quality; and changes to wave periods for inundation modelling, wave energy influence, and coastal erosion. We recommend that SLR information be developed and communicated based on the needs of the users. This is particularly important for determining timeframes for model outputs, as different local government functions have different information needs. SLR information could be communicated as probabilities for technical users, and as scenarios with explanations for more general users. More in-depth research should be conducted on which Representative Concentration Pathways (RCP) scenarios are most useful for local government needs, and to assist local government with ascertaining impact thresholds of SLR. There is also an opportunity to incorporate Mātauranga Māori into further investigations into SLR impacts. More effective communication of the science is needed to increase trust about SLR projections. (auth)