Modern reactivations of a thick colluvial landslide reconstructed from dendrochronology: the example of the Xiakou landslide, China

Abstract

AbstractIn this study, we investigated two types of growth disturbance (GD) in tree‐ring sequences, namely, the abrupt growth reduction in annual tree‐ring width, and the formation of reaction wood, in tree stems growing on the thick colluvial Xiakou landslide in China. In total, 96 GDs were identified in 183 core samples that were acquired from the 81 trees on the Xiakou landslide, revealing nine reactivation phases of the landslide body over the past 30 years. These reactivations were found to have occurred in the years of 1987, 1988, 1989, 1992, 1993, 1995, 1997, 2006, and 2007. Further hazard analysis indicated that the probability of landslide reactivation in 20 years was highest in the upper body of the landslide and on the boundaries where the new and old landslides meet. In contrast, the most stable region was the lower landslide body. Under the circumstances of an extreme lack of historical data, this work demonstrated the usefulness of dendrochronology in reconstructing modern reactivations over the past 30 years for a giant, deep‐seated, colluvial landslide with a volume exceeding approximately 10 million m3. This study has broader impacts because landslides in colluvium are a globally common types of land degradation.