Recent  

Monitoring sediment transport is relevant for flood safety and river restoration. However, the spatial and temporal variability of sediment transport processes makes their prediction challenging. We investigate the feasibility of a general calibration relationship between sediment transport rates and the impact signals recorded by metal plates installed in the channel bed. We present a new calibration method based on flume experiments and apply it to an extensive dataset of field measurements.

Glacial and non-glacial processes have left a strong imprint on the landscape of the European Alps, but further research is needed to better understand their long-term effects. We apply a new technique combining two methods for bedrock surface dating to calculate post-glacier erosion rates next to a Swiss glacier. Interestingly, the results suggest non-glacial erosion rates are higher than previously thought, but glacial erosion remains the most influential on landscape evolution.

Channel processes under flood conditions are important for river science and management as they involve high volumes of sediment transport and erosion. However, these processes remain poorly understood as the data are difficult to collect. Using a physical model of a river, we found that simple equations based on the mean shear stress and median grain size predicted sediment transport as accurately as ones that accounted for the full range of shear stresses.

Drainage reorganization redistributes drainage area across basins, resulting in channel and valley widths that may be unproportional to the new drainage area. We demonstrate scaling between valley width and drainage area in reorganized drainages that deviates from scaling in non-reorganized drainages. Further, deviation patterns are associated with different reorganization categories. Our findings are consequential for studies that rely on this scaling for valley width estimation.

Riverbeds are often composed of different scales of dunes, whose sizes and shapes are highly variable over time and space. Characterization of these dunes is important in many research studies focused on fluvial processes. A tool is presented here that aims to identify different scales of dunes from riverbed elevation maps. A first step is to separate two scales of bedforms without smoothing steep slopes of the larger dunes. In a second step, dunes are identified and properties are computed.

Erosion is a threat for soils with rainfall as the driving force. The annual rainfall erosivity factor quantifies rainfall impact by analysing high-resolution rainfall time series (~ 5 min). Due to a lack of measuring stations, alternatives for its estimation are analysed in this study. The best results are obtained for regionalisation of the erosivity factor itself. However, the identified minimum of 60-year time series length suggests using rainfall generators as in this study as well.

Abrupt changes in tectonic uplift rates induce sharp changes in river profile, called knickpoints. When river erosion depends non-linearly on slope, we develop an analytic model for knickpoint velocity and find the condition of knickpoint merging. Then we develop analytic models that represent the two-directional link between tectonic changes and river profile evolution. The derivation provides new understanding on the links between tectonic changes and river profile evolution.

We describe the flow of sediment in river channels by replacing the complicated details of the turbulent water with probability arguments. Our major conclusions are that (1) sediment transport can be phrased in terms of the movements of individual sediment grains, (2) transport rates in river channels are inherently uncertain, and (3) sediment transport in rivers is directly analogous to a number of phenomena which we understand relatively well, such as molecules moving in air.

This paper presents a novel methodology to identify and quantitatively analyze deposition and erosion patterns in ephemeral ponds or in perennial lakes with strong water level fluctuations. We apply this method to unravel the water and sediment balance of Lac Wégnia, a designated Ramsar site in Mali. The study can be a showcase for monitoring Sahelian lakes using remote sensing data, as it sheds light on the actual drivers of change in Sahelian lakes.

To assess the effects of differences in grain-size distribution within debris flows on the morphology of debris-flow fans, fan morphologies were modeled experimentally. Even if debris flows exhibited similar flow properties, their runout distance differed in response to differences in their grain-size distribution. Differences in runout distance were responsible for variations in the direction of the descending flow that resulted in different debris-flow fan morphology.

We mapped and dated 187 earthflows to determine controls on earthflow formation and resulting topographic changes in the Teanaway basin, central Washington State, USA. Using a new relative dating technique and absolute dating, we find that 25 % of earthflows were active in the last ~500 years. Earthflows are lithologically controlled, actively narrow valleys, and increase sediment loads.

A levee-building model is presented to investigate the effects of flood on levee slope and river behaviors. Coarser grains that cause steep levee slopes lead to frequent switchings of river paths, but higher overflow velocity has an opposite effect. High levee slopes lead to more reoccupations of abandoned old river paths than low levee slopes when rivers switch their locations. The study helps us to assess flood hazards with river-path switching.

Himalayan rivers are full of giant boulders that rarely move except during glacial lake outburst floods (GLOFs), which therefore must be important drivers of erosion in the Himalayas. GLOFs are rare, so little is known about their long-term erosional impact. We found that rivers in Nepal have channel geometry that, compared with markers of upstream glaciation, confirm GLOFs as a major control on erosion. This previously unrecognized control should be accounted for in landscape evolution studies.

Climate change is rapidly altering high-alpine landscapes. The formation of new lakes in areas becoming ice free due to glacier retreat is one of the many consequences of this process. Here, we provide an estimate for the number, size, time of emergence, and sediment infill of future glacier lakes that will emerge in the Swiss Alps. We estimate that up to ~ 680 potential lakes could form over the course of the 21st century, with the potential to hold a total water volume of up to ~ 1.16 km³.