Effects of heterogeneity distribution on hillslope stability during rainfalls

The objective of this study was to investigate the spatial relationship between the most likely distribution of saturated hydraulic conductivity ( ) and the observed pressure head (P) distribution within a hillslope. The cross-correlation analysis method was used to investigate the effects of the variance of  , spatial structure anisotropy of  , and normalized vertical infiltration flux (q) on P at some selected locations within the hillslope. The cross-correlation analysis shows that, in the unsaturated region with a uniform flux boundary, the dominant correlation between P and   is negative and mainly occurs around the observation location of P. A relatively high P value is located in a relatively low   zone, while a relatively low P value is located in a relatively high   zone. Generally speaking, P is positively correlated with   at the same location in the unsaturated region. In the saturated region, the spatial distribution of   can significantly affect the position and shape of the phreatic surface. We therefore conclude that heterogeneity can cause some parts of the hillslope to be sensitive to external hydraulic stimuli (e.g., rainfall and reservoir level change), and other parts of the hillslope to be insensitive. This is crucial to explaining why slopes with similar geometries would show different responses to the same hydraulic stimuli, which is significant to hillslope stability analysis.