Landscape erosion is generally considered to take place vertically downward. Here, by writing gradient-driven erosion in Hamiltonian form, we show this is not true. Instead, we find it takes place in two directions simultaneously: (i) normal to the surface and (ii) along rays pointing upstream and either up or down depending on how erosion rate scales with slope. The rays follow the shortest time paths that determine how long it takes for a landscape to respond to changes in external conditions.

Arctic rivers erode into permafrost and mobilize organic carbon, which can react to form greenhouse gasses or be re-buried in floodplain deposits. We collected samples on a permafrost floodplain in Alaska to determine if more carbon is eroded or deposited by river meandering. The floodplain contained a mixture of young carbon fixed by the biosphere and old, re-deposited carbon. Thus, sediment storage may allow Arctic river floodplains to retain aged organic carbon even when permafrost thaws.

River valleys are important components of mountain systems: they are the most fertile part of landscapes and store sediment which is transported from mountains to surrounding basins. Our knowledge of the location and shape of valleys is hindered by our ability to measure them over large areas. We present a new method for measuring the width of mountain valleys continuously along river channels from digital topography and show that our method can be used to test common models of river widening.

Our work is focused on describing how and why the terrace levels of central Amazonia were formed during the last 100 000 years. We propose to address this question through a landscape evolution numerical model. Our results show that terrace levels at lower elevation were established in response to dry–wet climate changes and the older terrace levels at higher elevations most likely formed in response to a previously higher elevation of the regional base level.

Landscape evolution is highly dependent on climatic parameters, and the occurrence of intense precipitation events is considered to be an important driver of river incision. We compare the rate of erosion with the variability of river discharge in a mountainous landscape of SE France where high-magnitude floods regularly occur. Our study highlights the importance of the hypotheses made regarding the threshold that river discharge needs to exceed in order to effectively cut down into the bedrock.

Alpine landscapes are transformed by several erosion processes. ¹⁰Be concentrations measured in river sediments at the outlet of a basin represent a powerful tool to quantify how fast the catchment erodes. We measured erosion rates within the Dora Baltea catchments (western Italian Alps). Our results show that erosion is governed by topography, bedrock resistance and glacial imprint. The Mont Blanc massif has the highest erosion and therefore dominates the sediment flux of the Dora Baltea river.

Erosion modulates Earth's carbon cycle by exposing a variety of lithologies to chemical weathering. We measured water chemistry in streams on the eastern Tibetan Plateau that drain either metasedimentary or granitoid rocks. With increasing erosion, weathering shifts from being a CO₂ sink to being a CO₂ source for both lithologies. However, metasedimentary rocks typically weather 2–10 times faster than granitoids, with implications for the role of lithology in modulating the carbon cycle.

There is an increasing demand for tidal-marsh restoration around the world. We have developed a new modeling approach to reduce the uncertainty associated with this development. Its application to a real tidal-marsh restoration project in northwestern Europe illustrates how the rate of landscape development can be steered by restoration design, with important consequences for restored tidal-marsh resilience to increasing sea level rise and decreasing sediment supply.

River avulsions (rivers suddenly changing course) redirect water and sediment. These floods can harm people and control how some landscapes evolve. We model how abandoned channels from older avulsions affect where, when, and why future avulsions occur in mountain-front areas. We show that abandoned channels can push and pull avulsions, and the way they heal controls landscapes. Avulsion models should include abandoned channels; we also highlight opportunities for future field workers.

To study channel network development following continental glaciation, we ran small physical experiments where networks slowly expanded into flat surfaces. By changing substrate and rainfall, we altered flow pathways between surface and subsurface. Initially, most channels grew by overland flow. As relief increased, erosion through groundwater sapping occurred, especially in runs with high infiltration and low cohesion, highlighting the importance of groundwater in channel network evolution.

Rock glaciers are some of the most frequently occurring landforms containing ice in mountain environments. Here, we use field observations, analysis of aerial and satellite images, and dating methods to investigate the activity of the rock glacier of the Vallon de la Route in the French Alps. Our results suggest that the rock glacier is characterized by two major episodes of activity and that the rock glacier system promotes the maintenance of mountain erosion.

During the late Pleistocene, the incision of the Trinity River valley left behind terraces. Elevation data and measurements of abandoned channels preserved on terraces are used to evaluate how terraces formed. We find a transition in the style of terraces with age from those associated with external environmental forcings to those produced by internal river migration changes. This result shows the importance of several indicators (i.e., channel bends, elevations) in determining terrace form.

Climate change fundamentally alters glaciated high-alpine areas, but it is unclear how this affects riverine sediment transport. As a first step, we aimed to identify the most important processes and source areas in three nested catchments in the Ötztal, Austria, in the past 15 years. We found that areas above 2500 m were crucial and that summer rainstorms were less influential than glacier melt. These findings provide a baseline for studies on future changes in high-alpine sediment dynamics.