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Geographic Coverage 

This report covers the Wellington region, including Wellington Harbour, Kāpiti Coast, Wairarapa coast, and parts of the upper South Island. 

Summary 

This report updates the analysis of relative sea-level rise (RSLR) and vertical land motion (VLM) in the Wellington region, building on previous work from 2012. It incorporates sea-level and GPS data up to the end of 2017. The Wellington Harbour tide gauge shows that mean sea level (MSL) has risen at a rate of 2.74 mm/year since 1960, with an overall trend of 2.28 mm/year since 1900. The highest annual MSL was recorded in 2016, followed by a decrease in 2017 due to post-earthquake uplift from the 2016 Kaikoura earthquake. 
 
Vertical land motion is a significant factor in local sea-level rise. The Wellington region experiences subsidence due to tectonic plate subduction, with rates between 2–5 mm/year. However, this is offset by uplift from slow-slip events (SSEs) and postseismic deformation. The Kaikoura earthquake caused subsidence of up to 40 mm, but subsequent postseismic uplift has reached up to 50 mm in some areas. The net effect over the past decade has been a mix of uplift and subsidence across the region. 
 
The report highlights the complexity of VLM and its impact on sea-level trends. It recommends continued monitoring of both MSL and VLM, especially in tectonically active or subsiding areas. The dynamic adaptive pathways planning (DAPP) approach is suggested to manage future uncertainties, allowing for flexible adaptation strategies based on monitored triggers. The report supports updating RSLR and VLM analyses every five years, with a more rigorous review every ten years.