Environmental Seismology as a Complementary Tool for Groundwater and Hydrological Landscape Functioning in Upland Headwater Catchments

Extreme hydrological events such as pluvial floods are increasing in magnitude and frequency due to environmental change, causing severe impacts on critical infrastructure and inhabited areas. However, it remains uncertain how extreme floods alter subsurface flow paths and sediment dynamics—and vice versa. Groundwater and the critical zone may play a key role in buffering the landscape response to such events. This study investigates subsurface responses to rainfall and flooding using passive seismic techniques, which use ambient seismic noise to non-invasively monitor subsurface water dynamics over time.

A network of ten seismic stations has been deployed across two sub-catchments in the upper Ahr Valley to measure relative seismic velocity changes (dv/v). These signals are used to infer temporal variations in subsurface water content, including groundwater fluctuations and vadose zone saturation. Seismic data are analyzed alongside environmental drivers such as rainfall intensity, soil moisture, river discharge, and groundwater levels. We focus on continuous data from May 2024 to June 2025, aiming to present dv/v responses to seasonal groundwater dynamics and to a 5-year flood event in January 2025, when the landscape was fully saturated.

This approach offers insight into the role of subsurface water pathways in shaping the hydrological and erosional response of upland headwater catchments. It supports the long-term monitoring of critical zone processes and erosion risk, and highlights the value of environmental seismology as a spatially integrative tool in hydrological research.