Ian L. Turner | Geology Reports

USGS2026

Measurements of wave runup on an atoll island using LiDAR

Coral atoll islands are highly susceptible to flooding and overwash due to their low-lying nature and the impacts of climate change. This study presents the first long-term, high-resolution field dataset of wave runup on a coral atoll island, collected over 6 weeks using a shore-mounted LiDAR scanner. The LiDAR data captured swash dynamics on a steep coral rubble beach fronted by a conglomerate platform. Results demonstrate the limitations of depth-based swash extraction methods, particularly for thin swash events, where depth thresholds lead to significant underprediction. Further analyses show that low-frequency oscillations (infragravity and very-low-frequency bands) and high-frequency components (transitional bores) dominate the spectra on the reef platform and are reflected in the swash signal. The displayed swash spectra highlight the critical role of low-frequency oscillations in extreme runup events, emphasizing their contribution to island flooding and overwash.

Conference Paper↗

USGS2015

Coastal vulnerability across the Pacific dominated by El Niño-Southern Oscillation

To predict future coastal hazards, it is important to quantify any links between climate drivers and spatial patterns of coastal change. However, most studies of future coastal vulnerability do not account for the dynamic components of coastal water levels during storms, notably wave-driven processes, storm surges and seasonal water level anomalies, although these components can add metres to water levels during extreme events. Here we synthesize multi-decadal, co-located data assimilated between 1979 and 2012 that describe wave climate, local water levels and coastal change for 48 beaches throughout the Pacific Ocean basin. We find that observed coastal erosion across the Pacific varies most closely with El Niño/Southern Oscillation, with a smaller influence from the Southern Annular Mode and the Pacific North American pattern. In the northern and southern Pacific Ocean, regional wave and water level anomalies are significantly correlated to a suite of climate indices, particularly during boreal winter; conditions in the northeast Pacific Ocean are often opposite to those in the western and southern Pacific. We conclude that, if projections for an increasing frequency of extreme El Niño and La Niña events over the twenty-first century are confirmed, then populated regions on opposite sides of the Pacific Ocean basin could be alternately exposed to extreme coastal erosion and flooding, independent of sea-level rise.

Pacific Ocean↗