Characterising landscape and sea level dynamics to predict shoreline responses over the next 100+ years in a high energy tectonic setting, Kaikoura, New Zealand
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
This thesis examines local scale landscape dynamics and coastal responses to climate change along the tectonically active, high energy Kaikoura coastline, South Island, New Zealand.
In New Zealand, the majority of urban infrastructure is built along low-lying coastal plains. As a result, expanding coastal communities face increasing exposure to coastal hazards, which will potentially be exacerbated by climate change-induced adjustments in sediment supply, wave climates and sea levels, amongst other factors. Sea level around New Zealand has been predicted to rise between 0.8 m and 1.0 m by 2115 as a response to increasing global temperatures. In Kaikoura, local relative sea levels may vary from regional projections based on local sediment dynamics in response to; local tectonic uplift and co-seismic sediment delivery, increased rainfall and storm intensity, ocean climate and tides.
Local sediment dynamics are important to consider when managing relative sea-level variations, in terms of assessing erosion response affected by sediment supply. New Zealand Coastal Policy Statement (NZCPS, 2010) Policy 24 states that the effects of climate change on coastal sediment dynamics should be factored into 100 year hazard risk assessments. To this date there has been no combined assessment on tectonic, climatic, and anthropogenic controls on local sediment dynamics, to predict mixed sand and gravel morphology response to future climate change and sea level variation along the Kaikoura coastline.
The main objective of the research is to predict how coastal geomorphology in Kaikoura is likely to respond to local tectonic and climate change- induced adjustments in landscape and sea level dynamics over the next 100+ years. In order to fulfil the research objective, the primary focus of this research was developing a conceptual framework for the preliminary assessment of local sediment dynamics as part of a sea-level rise response matrix. The methodology was developed using a Kaikoura area case study, including the coast between the Hapuku and Kahutara Rivers, Kaikoura Peninsula and the adjacent coastal progradation plain, and Seaward Kaikoura Ranges. This area encompasses key coastal sediment processes and controls in a small well-constrained region that produced findings that can be scalable to other areas in New Zealand and elsewhere.
Tectonics, climate, and human interventions were identified as the main controls on local sediment dynamics in Kaikoura. Key physical (faults, watersheds, landforms) and anthropogenic (hard/soft engineering structures, regulatory frameworks) factors influencing the sediment dynamics were assessed at different temporal and spatial scales. Various climate, river gauge, and beach survey data alongside local tectonic assessments were used to characterise and assess each control.
Determining how each control influences local scale sediment dynamics proved challenging in a relatively sparse data context. Rainfall, ocean climate, and beach profile data analyses provided sufficient information to construct a conceptual model for the preliminary assessment of local sediment dynamics, how tectonic and climate change-induced adjustments could affect sediment supply and how future relative sea level may manifest in the Kaikoura region.