The impact of long-term changes in ocean waves and storm surge on coastal shoreline change: a case study of Bass Strait and south-east Australia

Abstract

Numerous studies have demonstrated that significant global changes in wave and storm surge conditions have occurred over recent decades and are expected to continue out to at least 2100. This raises the question of whether the observed and projected changes in waves and storm surges will impact coastlines in the future. Previous global-scale analyses of these issues have been inconclusive. This study investigates the south-east coast of Australia over a period of 26 years (1988–2013). Over this period, this area has experienced some of the largest changes in wave climate of any coastal region globally. The analysis uses high-resolution hindcast data of waves and storm surge together with satellite observations of shoreline change. All datasets have been previously extensively validated against in situ measurements. The data are analysed to determine trends in each of these quantities over this period. The coastline is partitioned into regions and spatial consistency between trends in each of the quantities investigated. The results show that beaches along this region appear to have responded to the increases in wave energy flux and changes in wave direction. This has enhanced non-equilibrium longshore drift. Long sections of the coastline show small but measurable recession before sediment transported along the coast is intercepted by prominent headlands. The recession is largest where there are strong trends in increasing wave energy flux and/or changes in wave direction, with recession rates of up to 1 m yr−1. Although this is a regional study, this finding has global implications for shoreline stability in a changing climate.