High-resolution temperature observations to monitor soil thermal properties as a proxy for soil moisture condition in clay-shale landslide

The heterogeneity of hillslope material and variations in its hydrological characteristics affect the spatial and temporal fluctuation of soil moisture patterns within a landslide. Moisture conditions of the unsaturated zone influence the distribution, intensity and time delay of groundwater recharge from precipitation. High-resolution monitoring of hydrological features of the near-surface soil layer is necessary to advance understanding of the temporal behaviour of complex landslides and their displacement dynamics. This paper aims to show the potential of high temporal and spatial resolution temperature sensing for hydrological analysis of unstable slopes. The main focus of this research is to detect the spatial and temporal variation in soil moisture conditions through the monitoring of soil thermal properties. We present qualitative and quantitative analyses of soil temperature data collected during three field campaigns in the black marls mudslide of Super-Sauze (France). The temperature data are used to determine soil thermal parameters that are affected by bulk density and soil moisture content. On the basis of the spatial and temporal variation of the soil thermal parameters, the information about soil moisture content fluctuations could be obtained. Promising empirical relationships between apparent thermal diffusivity and soil moisture content have been obtained when accounting for local heterogeneities in soil characteristics. Furthermore, the requirements and limitation of the proposed methodology for clay shale material is elaborated. Copyright (c) 2011 John Wiley & Sons, Ltd.