Multi-decadal spatiotemporal shoreline vulnerability assessment (1987–2025): integrating erosion-accretion dynamics for disaster risk reduction across 90 coastal transects
摘要
Coastal zones, vital for socio-economic activity, face escalating threats from climate change, including sea-level rise and intensifying storms. Accurate shoreline change assessments and vulnerability analyses are critical for resilience planning but are often constrained by methodological limitations that may not capture complex spatiotemporal dynamics. This study aims to address critical gaps related to temporal simplification, the methodological constraints of linear models, and spatial homogenization by developing and applying an integrated analytical framework to quantify multi-decadal trends and event-scale variability along a dynamic coastline. We analysed 38 years of Landsat-derived shoreline data (1987–2025) along the north section stretch of North Stradbroke Island, Australia, using 90 shore-normal transects. Our multi-method approach integrated ordinary least squares (OLS) regression, Sen slope, and annual Δ-chainage analysis (≈ 2100 transitions) to distinguish long-term trends from short-term variability. Transects were classified into behavioural groups and spatially zoned into regions (e.g., stable, volatile, erosion-dominant, and accretion-dominant) based on alongshore change patterns. The coastline exhibited a clear tripartite structure: Regions 1 and 3 (57 transects) showed chronic erosion (up to: − 3.73 m yr−1), while Region 2 (33 transects) functioned as a sediment sink with sustained accretion (up to + 1.90 m yr−1). Despite a near-equilibrium in annual erosion (52%) and accretion (47%) events, 61% of transects experienced net erosion, with a mean net shoreline displacement of − 35.47 m. Transect classification revealed four distinct behavioural groups: stable (17), volatile (24), erosion-dominant (27), and accretion-dominant (21). The Sen slope provided trend estimates in volatile zones where OLS was skewed by storm-driven outliers. This study demonstrates that integrating multi-temporal analytical techniques is essential to reveal the coexistence of dynamic equilibrium and directional change on contiguous coastlines. The framework identifies precise vulnerability gradients, sediment sources, sinks, and hotspots. These findings operationalise Sendai-aligned (Disaster Risk Reduction) DRR by converting 38-year shoreline dynamics into prioritised, place-based interventions, enabling targeted nature-based measures, sediment conservation strategies, and governance triggers that strengthen coastal resilience.