Monitoring of Expansive Clays over Drought-Rewetting Cycles Using Satellite Remote Sensing

Abstract

New capabilities for measuring and monitoring are needed to prevent the shrink-swell risk caused by drought-rewetting cycles. A clayey soil in the Loire Valley at Chaingy (France) has been instrumented with two extensometers and several soil moisture sensors. Here we show by direct comparison between remote and in situ data that the vertical ground displacements due to clay expansion are well-captured by the Multi-Temporal Synthetic Aperture Radar Interferometry (MT-InSAR) technique. In addition to the one-year period, two sub-annual periods that reflect both average ground shrinking and swelling timeframes are unraveled by a wavelet-based analysis. Moreover, the relative phase difference between the vertical displacement and surface soil moisture show local variations that are interpreted in terms of depth and thickness of the clay layer, as visualized by an electrical resistivity tomography. With regard to future works, a similar treatment relying fully on remote sensing observations may be scaled up to map larger areas in order to better assess the shrink-swell risk.

Interpretation and Attribution of Coastal Land Subsidence: An InSAR and Machine Learning Perspective

“…Similarly, activities like mining and construction can induce land subsidence with increased structure loading or weakened mining support [15]- [17]. Also, natural processes can instigate land motion including phenomena like thawing permafrost [18], shrinkage and swelling of clay soils [19], and glacial isostatic adjustment (GIA) [20]. Additionally, the spatial patterns of subsidence velocity can be influenced or controlled by growth faults [21], further complicating the practical analysis of subsidence drivers.…”

Disentangling Shallow Subsidence Sources by Data Assimilation in a Reclaimed Urbanized Coastal Plain, South Flevoland Polder, the Netherlands

“…However, in other countries, subsidence by clay shrinkage is considered as a major issue. In France and Great Britain for example, potential damage to the built environment inflicted by clay shrinkage as a result of drought and climate change has been studied in terms of cost per annum in the light of the insurance industry for decades (e.g., Burnol et al., 2021; Charpentier et al., 2021; Pritchard et al., 2015). In addition, in Sweden, locally increased subsidence rates in an urban area were linked to the presence of clay, with the aid of Interferometric Synthetic Aperture Radar (InSAR) (Fryksten & Nilfouroushan, 2019).…”