The impact of storm sequences on coastal erosion: a Case Study on Tairua Beach, New Zealand

Abstract

Under climate change, storms are projected to increase in frequency and magnitude, leading to a possible increase in the occurrence of sequences of storms. This thesis aims to investigate the impact of storms and storm sequences on shoreline change and to understand which storm characteristics “drive” shoreline change. Using Tairua Beach as a case study, hindcast wave characteristics were used to identify and analyse individual storms and storm sequences. Linear regressions were used to test the relationships between shoreline change and wave characteristics, revealing that storm power had a statistically significant relationship to shoreline change during individual storms. This relationship was also reflected in storm sequences; furthermore, a statistically significant relationship between initial shoreline position and the tidal range of the first storm and shoreline change was also seen for storm sequences. Additionally, a multiple linear regression showed that shoreline change during a storm sequence can be predicted based on the initial shoreline position and the sum of storm power. Findings also revealed temporal elements to the occurrence of storm sequences: seasonal variability and phases of the El Niño Southern Oscillation (ENSO). Results show that the most intense storm sequences are more likely to occur during the La Niña phase of ENSO. These insights provide a further understanding of how storm and storm sequences influence shoreline change and the drivers behind these changes. The findings highlight the importance of including the impacts of storm sequences in future coastal management strategies, especially considering current climate projections.