Hydrogeological insights from UAS thermal remote sensing. Case study at Sant'Angelo (Ischia, Italy)

Thermal Infrared (TIR) remote sensing from Unmanned Aerial Systems (UAS) has revolutionized the monitoring of volcanic and hydrothermal environments, providing a critical link between ground-based observations and satellite data. In coastal volcanic settings, the identification of hydrothermal discharge points—such as hot springs and fumaroles—is often challenged by their intermittent nature and the dynamic interface between the terrestrial and marine domains.

This study presents a high-resolution thermal mapping survey conducted along the Sant'Angelo beach on the island of Ischia (Gulf of Naples, Italy). By leveraging the flexibility and high spatial resolution of UAS-mounted TIR sensors, we successfully identified and characterized localized thermal anomalies that are otherwise undetectable through conventional field surveys or lower-resolution satellite imagery. A key finding of this work is the detection of a distinctive submarine-to-intertidal fumarolic vent that emerges on the shoreline exclusively during low-tide conditions.

From a hydrogeological perspective, the ability to precisely map these "transient" thermal signatures provides crucial insights into the structural control of fluid migration and the spatial distribution of the hydrothermal system’s discharge zones. These thermal features act as preferential pathways for pressurized fluids, and their characterization is fundamental for refining the hydrogeological conceptual model of the Ischia volcanic system. Our research indicates that UAS-TIR mapping has the potential to enhance coastal hydrogeology in volcanic regions by detecting ephemeral thermal targets and enhancing the assessment of geothermal potential and volcanic unrest indicators. This approach offers a cost-effective and non-invasive methodology for monitoring hydrothermal activity at the land-sea interface, with significant implications for both environmental management and geohazard mitigation.