The Puebla–Morelos earthquake (19 September 2017) was the most damaging event in central Mexico since 1985. The seismic shaking produced hundreds of shallow landslides on the slopes of Popocatépetl Volcano. The larger landslides transformed into large debris flows that travelled for kilometers. We describe this exceptional mass wasting cascade and its predisposing factors, which have important implications for both the evolution of the volcanic edifice and hazard assessment.

We measured the shear strength of marsh soils along an estuarine salinity gradient to determine salinity's influence on marsh erodibility. Our work is one of the first studies to directly examine the relationship between salinity and marsh erodibility. We find that an increase in salinity correlates with higher soil shear strength values, indicating that salt marshes may be more resistant to erosion. We also show that both belowground biomass and soil properties drive shear strength differences.

Despite the inherent difficulties in quantifying its value, sediment transport is essential to understanding fluvial systems. This study tries to improve the measurement by comparing several methods. Acoustic methods are compared to direct measurements with samplers. The hydrophone is well adapted to quantify sediment transport in mountain streams, but this study shows the potential and the efficiency of this device in large lowland rivers.

We investigated how shallow landslide occurrence is impacted by deforestation and rifting in the North Tanganyika–Kivu rift region (Africa). We developed a new approach to calculate landslide erosion rates based on an inventory compiled in biased © Google Earth imagery. We find that deforestation increases landslide erosion by a factor of 2–8 and for a period of roughly 15 years. However, the exact impact of deforestation depends on the geomorphic context of the landscape (rejuvenated/relict).

Ongoing deformation of the Himalaya is not constrained to its southern extremity. With morphometric analysis using a high-resolution digital elevation model, satellite image analysis, luminescence chronology of fluvial terraces and field observations, we identify a zone of rapid rock uplift in the interior of the Kashmir Himalaya. Our results suggest active tectonic and structural control on the growth of topography in the Himalayan interiors over multi-millennial timescales.

Seismic techniques applied in rock slope failure research do not provide rapid notifications, as for earthquakes, due to the lack of connections between seismic signals and events. We studied 10 known events in Taiwan and developed a GeoLoc scheme to locate rock slope failures, estimate the event volume, and understand their physical process using available videos. With real-time seismic data transmission, a rapid report can be created for the public within several minutes of the event.

Quantifying wood fluxes in rivers would improve our understanding of the key processes in river ecology and morphology. In this work, we introduce new software for the automatic detection of wood pieces in rivers. The results show 93.5 % and 86.5 % accuracy for piece number and volume, respectively.

Sediment particles skitter down steep hillslopes on Earth and Mars. Particles gain speed in going downhill but are slowed down and sometimes stop due to collisions with the rough surface. The likelihood of stopping depends on the energetics of speeding up (heating) versus slowing down (cooling). Statistical physics predicts that particle travel distances are described by a generalized Pareto distribution whose form varies with the Kirkby number – the ratio of heating to cooling.

The generalized Pareto distribution of particle travel distances on steep hillslopes, as described in a companion paper (Furbish et al., 2021a), is entirely consistent with measurements of travel distances obtained from laboratory and field-based experiments, supplemented with high-speed imaging and audio recordings that highlight the effects of bumpety-bump particle motions. Particle size and shape, in concert with surface roughness, strongly influence particle energetics and deposition.

The generalized Pareto distribution of particle travel distances on steep hillslopes, as described in two companion papers (Furbish et al., 2021a, 2021b), is a maximum entropy distribution. This simply represents the most probable way that a great number of particles become distributed into distance states, subject to a fixed total energetic cost due to frictional effects of particle–surface collisions. The maximum entropy criterion is equivalent to a formal application of Occam's razor.

Using analyses of particle motions on steep hillslopes in three companion papers (Furbish et al., 2021a, 2021b, 2021c), we offer philosophical perspective on the merits of a statistical mechanics framework for describing sediment particle motions and transport, and the implications of rarefied versus continuum transport conditions. We highlight the mechanistic yet probabilistic nature of the approach, and the importance of tailoring the style of thinking to the process and scale of interest.

The runout of rock avalanches scales with their volume but also shows a considerable variation for avalanches with similar volumes. Here we show that besides size-dependent weakening mechanisms, fragmentation can account for the observed variability in runout. We use laboratory-scale experimental avalanches to simulate and analyse the role of fragmentation. We find that fragmentation consumes energy but also increases avalanche mobility. It does so systematically and predictably.

We present a new technique for precisely monitoring water levels (e.g. sea level, rivers or lakes) using low-cost equipment (approximately USD 100–200) that is simple to build and install. The technique builds on previous work using antennas that were designed for navigation purposes. Multiple antennas in the same location are used to obtain more precise measurements than those obtained when using a single antenna. Software for analysis is provided with the article.