Sustainable Risk Assessment of Loess Landslides: Distribution and Failure Modes in the South Jingyang Tableland, North of Xi’an, China

Loess landslides represent a severe geohazard in the Loess Plateau, posing significant challenges to sustainable development and regional safety. This study analyzed 111 landslides (1976–2018) and 529 marginal fissures in the South Jingyang Tableland (SJT) to reveal the distribution and failure modes of the landslide cluster. Preparation factors, including stratigraphic lithology, geomorphic features, and discontinuity systems (vertical/tectonic joints, unloading fissures, weak layers, and marginal fissures), were evaluated alongside triggering factors such as precipitation, irrigation, and river erosion. The main takeaways of this study are as follows. (1) A comprehensive database of 111 loess landslides (1976–2018) and 529 marginal fissures was constructed for the SJT, representing the longest and most complete chronological record available for this region. (2) Landslide activity within the Jiangliu landslide cluster (LC) exhibits an approximately decadal clustering pattern, with a temporal spacing of 9.6 ± 2.8 years between successive active periods, providing a basis for medium-term hazard forecasting in comparable settings. (3) The evolution of marginal fissures is controlled by the margin’s geometry and their interaction with slope failure processes, and the strong correlation between fissure development and landslide initiation enables the use of fissure monitoring as an early warning indicator. (4) The evolutionary mechanism follows a sequence of initial tectonic activity → rising groundwater → formation of the critical slide structure → water accumulation in fissures → single landslide → subsequent clustering. This process, termed a “water-induced loess catastrophe” (WILC), provides a conceptual framework for understanding landslide clustering on loess tablelands. (5) The database construction methodology, the decadal clustering analysis, and the WILC model collectively offer transferable tools for medium-term hazard forecasting, fissure-based early warning, and sustainable land-use planning on loess tablelands, not only in the SJT, but also in other loess regions with similar geological and hydrological settings.