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More than 5000 landslides have been identified in the Three Gorges Reservoir (TGR) area since the impoundment in 2003, which posed great threats to the residential houses, transportation on the Yangtze, and dam stability. This paper focuses on the evaluation of the coupled influence of rainfall and reservoir water on deformation characteristics and failure evolution of the Outang landslide (in China) based on field investigations, a statistical Pearson cross-correlation coefficient analysis, multi-technique monitoring data, and a numerical model. This instability is a reactivated ancient landslide with a volume of approximately 90 Mm3 located in the Three Gorges Reservoir. The slope behavior is featured with a short period of fast displacement and a relatively long period of semi-constant displacement rates per hydrological year, and displacements velocities quicken gradually upslope. Rainfall and reservoir water level are the main triggering factors of slope movement existing in the upper and the lower parts of the landslide, respectively. Based on the numerical results, the failure evolution of this landslide is a compounded push-retrogression-type failure process involving: a) a first rupture at the toe caused by the reservoir water level that will rapidly mobilize a second and subsequent collapses upwards (retrogression type); and b) the rock mass at the upper part will be pushed out and failed downslope (push type) due to precipitation. These results provide a comprehensive analysis of the Outang landslide, which is critical for its management, as well as for disaster prevention and mitigation of analogous reservoir-induced landslides. • About 6-year monitoring data of deformations and hydrological factors were analyzed. • The slope deformation characteristics were addressed. • The primarily hydrological factors for the landslide movement were revealed. • A possible slope instability evolution was proposed. [ABSTRACT FROM AUTHOR]

• Ill-considered urban planning around Niwan gully may multiply the human and economic losses caused by debris flows. • A depth-integrated model was adopted to determine the hazard zones of debris flows with different recurrence intervals. • The debris flow inundation and evolutionary trajectory are shown to be reasonably comparable with historical debris flows. • This study established a relatively complete system to implement hazard and risk assessment in the study area. The highly geologically active, structurally complex Bailongjiang river basin, Longnan City, Gansu Province hosts many debris-flow gullies. The recent Wenchuan and Jiuzhaigou earthquakes have increased the amount of source material available in these debris flow gullies, and the disturbed nature of the slopes makes them prone to failure under high rainfall, increasing the risk of large-scale debris flows. Moreover, poor urban planning in the region may multiply the human and economic losses caused by debris flows. Therefore, it is necessary to determine the potential hazard zones associated with such debris flows and to implement debris flow hazard and risk assessment. In this paper, Niwan gully is chosen as the study object, as it is characterized by repeated debris flow outbreaks and an ill-considered urban planning at the outlet of the gully. A depth-integrated continuum method is adopted to determine the potential hazard zones of debris flows with different recurrence intervals. The debris flow inundation and evolutionary trajectory are shown to be reasonably comparable with historical debris flows. A two-factor model that couples maximum flow depth with momentum is used to better classify the hazard zones. This study also provides a complete and efficient means to determine the values of debris flow parameters and to implement a hazard and risk assessment based on the solid material reserve method and a probabilistic method. This proposed approach efficiently generated a debris flow risk distribution map that can be used for effective disaster prevention in the Bailongjiang River basin. [ABSTRACT FROM AUTHOR]

The Datong Basin is part of the regionally extensive Fenwei Graben System, a major tectonic zone impacted by active tectonics and the resulting damage to life and infrastructure. The basin also contains the Shizhuang ground fissure system. In this study, the likely origin, surface extent, and fissure subsurface characteristics are explored by traditional methods: surveying, mapping, trenching, drilling, and seismic exploration. The Shizhuang ground fissure is located at the intersection of the Xiaoshikou fault and the southern Liuleng margin fault in Yingxian County. It has a length of 2.1 km, excellent continuity, and semi-elliptical surface morphology. The dislocation of strata induced by the fissure increases significantly as the depth increases. The strata bend downward and form typical traction structures near the fissure plane, indicating that the fissure has prominent synsedimentary fault characteristics. The fissure causes serious damage to houses, farmlands, roads, and public facilities, featuring large tensile cracks and vertical dislocations. The resulting data and interpretations indicate that: (1) the ground fissures connect to two major subsurface active faults, which lay the tectonic foundation for the fissure; (2) accelerated groundwater extraction has reactivated the underlying faults and exacerbated fissure development; and (3) mitigation is best achieved by cessation of excessive groundwater pumping, appropriate engineering design, and local avoidance for placement of critical structures. This paper provides a heretofore generally unknown example, promotes research on the mechanisms of fissures, and has guiding significance for disaster prevention and reduction in this area. • Various characteristics of the Shizhuang ground fissure were determined. • Trenching, drilling, and geophysical prospecting were used to examine the fissure. • Tectonic and non-tectonic factors were used to analyze the formation mechanisms. • Regional stress and fault activity controlled the development of the fissure. • Groundwater pumping and a settlement funnel accelerated the fissure extension. [ABSTRACT FROM AUTHOR]