A coastal cliff erosion risk assessment of Taranaki under projected sea level rise scenarios.
- Author
- Garg L
- Year
- 2024
- Journal / Source
- MSc in Geography
- Publisher / Organisation
- University of Auckland
- Pages
- 148 pp
- Summary
- Coastal communities within New Zealand are already experiencing the effects of climate change. Coastal hazards such as coastal inundation and erosion are expected to increase due to rising sea levels and severe storms. On rock coasts, cliff erosion risk assessments are required to quantify what is and could be threatened by future erosion. Approaches are required that combine data from historic cliff recession measurements, models that anticipate possible acceleration in future erosion rates under different sea level rise (SLR) scenarios, and quantitative risk assessment software. Taranaki is exposed to high cliff erosion rates with longterm rates between 0.05 m/yr and 1.89 m/yr. However, future cliff top positions and the assets threatened by cliff erosion have not been assessed. This research uses historic cliff top position data, four future climate-change driven SLR scenarios projected from global socioeconomic pathways (SSPs), and four cliff erosion numerical models to make cliff top projections for Taranaki for the year 2100. RiskScape, a risk assessment software, was used to assess quantitative exposure values of coastal assets threatened by future cliff erosion. The Taranaki cliffs are eroding rapidly, and the model projections indicate that these rates will increase under accelerating future SLR. Median and maximum projected cliff erosion distances were 35 m and 123 m under SSP 4.5 (p50), and 52 m and 192 m under SSP 8.5 (p83). The negative feedback model produced the most variable retreat values and a modified Bruun Rule model produced the highest average cliff retreat distances under all SSP scenarios. Risk assessment modelling suggests that between 91 and 339 buildings are at risk of coastal cliff retreat. In addition, 371-399 archaeological sites, 10-27 km of roads, 10-17 km2 of land area, and 30-51$M of land value is projected to be exposed to cliff erosion under different numerical models and SLR scenarios. This research presents a new methodology that utilises historical coastal cliff erosion data and a numerical model ensemble to produce projections of future coastal cliff erosion, which are then used by a risk assessment software. This represents the first quantitative coastal cliff erosion risk assessment for Taranaki and RiskScape.