During three winters (2022/23, 2023/24, and 2024/25), we monitored winter storm-driven boulder movement on Inishmaan, Ireland. We used drones to capture before-and-after imagery of entire sites, and iPhone LiDAR scans to create 3D boulder models and improve volume estimates. We installed motion sensors inside select boulders to log when and how they moved throughout the winter. We compared movement data to tide levels, and in the second year, to onshore water depths from pressure sensors drilled into the bedrock near the boulders.

We found that boulders moved during storms each year. Transport was linked to wave force, boulder size and shape, position on the coastline, and elevation above high tide. Importantly, we observed movement when boulders were fully and only partially submerged, challenging assumptions in existing interpretive models that require full submergence.

Altogether, this research improves our ability to interpret storm deposits in the geologic record and better assess future hazards along high-energy rocky coasts.