Drainage basins are bounded by water divides (divides) that define their shape and extent. Divides commonly coincide with high ridges, but in places that experienced extensive tectonic deformation, divides sometimes cross elongated valleys. Inspired by field observations and using simulations of landscape evolution, we study how side channels that drain to elongated valleys induce pulses of divide migration, affecting the distribution of water and erosion products across mountain ranges.

Particle motions and travel distances prior to deposition on hillslope surfaces depend on a balance of gravitational and frictional forces. We elaborate how particle energy is partitioned and dissipated during travel using measurements of particle travel distances supplemented with high-speed imaging of drop–impact–rebound experiments. Results show that particle shape plays a dominant role in how energy is partitioned during impact with a surface and how far particles travel in two dimensions.

A landscape's appearance reflects the properties of the underlying bedrock. For example, strong bedrock can lead to steep slopes. Recent work has shown, however, that in areas with mixed rock types the stronger bedrock can have lower slopes. In this study, we use numerical models of bedrock river erosion to show why this change in behavior occurs. We also present a new approach for estimating bedrock erodibility. This new approach can allow for new opportunities in the field of geomorphology.

We conducted experiments to investigate the mechanics of sediment attrition due to collisions with the channel bed during downstream transport. During this process, the grains become rounder and smaller, changing the overall distribution of sediment in the river. In this work we examine how material properties play a role in the breakdown of sediment due to energetic collisions and the fine particles that are produced when chipped off of larger grains.

The Klados River catchment contains seemingly overlarge, well-preserved alluvial terraces and fans. Unlike previous studies, we argue that the deposits formed in the Holocene based on their position relative to a paleoshoreline uplifted in 365 CE and seven radiocarbon dates. We also find that constant sediment supply from high-lying landslide deposits disconnected the valley from regional tectonics and climate controls, which resulted in fan and terrace formation guided by stochastic events.

The rise of a mountain affects the circulation of water, both in the atmosphere and over the land surface, thereby affecting the erosion of the land surface. We document how the rise of a mountain in central Guatemala has affected the erosion of an older range nearby. The new range intercepts precipitation formerly delivered to the older range. River response to the uplift of the new range has decreased incision across the older one. Both have reduced hillslope erosion over the old range.

In mountain ranges, earthquake-derived landslides mobilize large amounts of organic carbon (OC) by eroding soil from hillslopes. We propose a model to explore the role of different parameters in the post-seismic redistribution of soil OC controlled by fluvial export and heterotrophic respiration. Applied to the Southern Alps, our results suggest that efficient OC fluvial export during the first decade after an earthquake promotes carbon sequestration.

Glaciers are strong erosive agents, and they have created many unique landforms in mountain belts. Climate has been viewed as a primary control on glacial erosion, yet our understanding of the mechanism by which climate impacts glacial erosion remains limited. Using computer simulations, we find that climate controls glacial erosion by modulating the temperature of the basal ice. Our results suggest that a warm and/or wet climate can create warm basal ice and, therefore, enhance erosion.

Topographic effects on radioactive contamination in a forested area were quantitatively examined using soil core samples collected in a village in Fukushima, Japan. The results confirmed that local topography influences the contamination patterns in soils, and its effects vary depending on the combinations of the topographic parameters. This finding suggests that topographic characteristics should be considered carefully in future environmental radioactive risk assessments.

Elevated low-relief regions and major river knickpoints have for long been noticed and questioned in the emblematic Bhutan Himalaya. We document the morphology of this region using morphometric analyses and field observations, at a variety of spatial scales. Our findings reveal a highly unstable river network, with numerous non-coeval river captures, most probably related to a dynamic response to local tectonic uplift in the mountain hinterland.

Ancient Alpine glaciers have carved a fascinating landscape of piedmont lakes, glacial valleys, and mountain cirques. Using a previous supercomputer simulation of glacier flow, we show that glacier erosion has constantly evolved and moved to different parts of the Alps. Interestingly, larger glaciers do not always cause more rapid erosion. Instead, glacier erosion is modelled to slow down during glacier advance and peak during phases of retreat, such as the one the Earth is currently undergoing.

This paper presents a new approach to modeling glacial erosion on large scales. The formalism is similar to large-scale models of fluvial erosion, so glacial and fluvial processes can be easily combined. The model is simpler and numerically less demanding than established models based on a more detailed description of the ice flux. The numerical implementation almost achieves the efficiency of purely fluvial models, so that simulations over millions of years can be performed on standard PCs.

Increased salt intrusion jeopardizes freshwater supply to the Mekong Delta, and the current trends are often inaccurately associated with sea level rise. Using observations and models, we show that salinity is highly sensitive to ocean surge, tides, water demand, and upstream discharge. We show that anthropogenic riverbed incision has significantly amplified salt intrusion, exemplifying the importance of preserving sediment budget and riverbed levels to protect deltas against salt intrusion.

Alpine rockwalls are affected by weathering processes that result in rock and fracture deformation. This deformation decreases rockwall stability with time. I installed crackmeters along a topographic gradient to identify the spatial and temporal variation of weathering processes. My data show that elevation-dependent snow cover, topographic factors and fracture dipping control the frequency and magnitude of weathering processes and resulting rock kinematics.

The size of grains delivered to rivers is an essential parameter for understanding erosion and sediment transport and their related hazards. In mountains, landslides deliver these rock fragments, but few studies have analyzed the landslide properties that control the resulting sizes. We present measurements on 17 landslides from Taiwan and show that their grain sizes depend on rock strength, landslide depth and drop height, thereby validating and updating a previous theory on fragmentation.

Both landslide mapping and volume estimation accuracies are crucial to quantify landscape evolution and manage such a natural hazard. We developed a method to robustly detect landslides and measure their volume from repeat 3D point cloud lidar data. This method detects more landslides than classical 2D inventories and resolves known issues of indirect volume measurement. Our results also suggest that the number of small landslides classically detected from 2D imagery is underestimated.

We study effects of variable climate–vegetation with different uplift rates on erosion–sedimentation using a landscape evolution modeling approach. Results suggest that regardless of uplift rates, transients in precipitation–vegetation lead to transients in erosion rates in the same direction of change. Vegetation-dependent erosion and sedimentation are influenced by Milankovitch timescale changes in climate, but these transients are superimposed upon tectonically driven uplift rates.

River behavior depends on the size of rocks they carry. Rocks are born on hillslopes where erosion removes fragments from solid bedrock. To understand what controls the size of rock fragments, we measured the spacing between cracks exposed in 15 bare-rock cliffs and the size of rocks on the ground below. We found that, for each site, the average rock size could be predicted from the average distance between cracks, which varied with rock type. This shows how rock type can influence rivers.