Geophysical monitoring of soil moisture response to re-establishing river flow in an Agricultural setting

We present initial results from a three-month-long geophysical monitoring campaign in an agricultural setting in Cumbria, NW England, aimed at assessing subsurface moisture response to the re-establishment of river flow.

Over the last five years the study area experienced persistent flooding and associated soil degradation, caused by a blocked outflow channel of the River Winster where it flows into Morecambe Bay. In September 2025, the river channel was cleared with the aim of re-establishing flow and reducing future flood events. To assess the impact of this intervention in the subsurface, seismic and electrical geophysical monitoring across four agricultural fields was carried out, spanning two weeks prior to 2.5 months post re-establishment of river flow.

This known hydrological change to the system provided a unique opportunity to explore the effectiveness of high-frequency ambient noise seismic interferometry at measuring changes in soil moisture content. A total of 180 seismic nodes were deployed in densely spaced (5 - 20 m) grids, across four fields with variable soil type and at varying distance along the river course. The project aimed to explore: 1) optimal network configurations, 2) consistency of a previously observed 50 Hz noise source thought to be generated by the national electrical grid, and 3) the effectiveness of the technique in various soil types.

Seismic results are compared to time-lapse electrical resistivity tomography (ERT) profiles repeated at monthly intervals, and bench-marked against continuous soil temperature data, water-table loggers, precipitation, river-level and tidal data, and point measurements of soil moisture content.