The Lancang–Mekong River basin, as an important transboundary river in Southeast Asia, is challenged by rapid socio-economic development, especially the construction of hydropower dams. Furthermore, substantial factors, such as terrain, rainfall, soil properties and agricultural activity, affect and are highly susceptible to soil erosion and sediment yield. This study aimed to estimate average annual soil erosion in terms of spatial distribution and sediment deposition by using the revised universal soil loss equation (RUSLE) and GIS techniques. This study also applied remote sensing and available data sources for soil erosion analysis. Annual soil erosion in most parts of the study area range from 700 to 10,000 t/km²/y with a mean value of 5350 t/km²/y. Approximately 45% of the total area undergoes moderate erosion. Moreover, the assessments of sediment deposition and erosion using the modified RUSLE and the GIS techniques indicate high sediment erosion along the flow direction of the mainstream, from the upper Mekong River to the Mekong Delta. The northern part of the upper Mekong River and the central and southern parts of the lower Mekong River are the most vulnerable to the increase in soil erosion rates, indicating sediment deposition.

Glacier recessions caused by climate change may uncover pro‐glacial lakes that form important sedimentation basins regulating the downstream sediment delivery. The impact of modern pro‐glacial lakes on fluvial sediment transport from three different Norwegian glaciers: Nigardsbreen, Engabreen and Tunsbergdalsbreen, and their long‐term development has been studied. All of these lakes developed in modern times in overdeepened bedrock basins.The recession of Nigardsbreen uncovered a 1.8 km long and on average 15 m deep pro‐glacial lake basin during 1937 to 1968. Since then the glacier front has been situated entirely on land, and the sediment input and output of the lake has been measured. The suspended sediment transport into and out of the lake averaged 11 730 t yr⁻¹ and 2340 t yr⁻¹ respectively. Thus, 20% remained in suspension at the outlet. The measured mean annual bedload supplied to the lake was 11 800 t yr⁻¹, giving a total transport of 23 530 t yr⁻¹ which corresponds to a specific sediment yield of 561 t km⁻² yr⁻¹.A 1.9 km long and up to 90 m deep pro‐glacial lake basin downstream from Engabreen glacier was uncovered during 1890 to 1944. The average suspended sediment load delivered from the glacier during the years 1970–1981 amounted to 12 375 t yr⁻¹and the transport out of the lake was 2021 t yr⁻¹, giving an average of 16% remaining in suspension. The mean annual bedload was 8000 t yr⁻¹, thus the total transport was 20 375 t yr⁻¹, giving a specific sediment yield of 566 t km⁻² yr⁻¹.For Tunsbergdalsbreen glacier, measurements in the early 1970s indicated that the suspended sediment transport was on average 44 000 t yr⁻¹. From 1987 to 1993 the recession of the glacier uncovered a small pro‐glacial lake, 0.3 km long and around 9 m deep. Downstream from this, the suspended sediment load measured in 2009 was 28 000 t yr⁻¹, indicating that as much as 64% remained in suspension. Flow velocity, grain size of sediment, and morphology of the lake are important factors controlling the sedimentation rate in the pro‐glacial lakes. A survey of the sub‐glacial morphology of Tunsbergdalsbreen revealed that there are several overdeepened basins beneath the glacier. The largest is 4 km long and 100 m deep. When the glacier melts back they will become lakes and act as sedimentation basins. Despite an expected increase in sediment yield from the glacier, little sediment will pass these lakes and downstream sediment delivery will be reduced markedly. Beneath Nigardsbreen there was only a small depression that may form a lake and the sediment delivery will not be significantly affected. © 2014 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

The rich and complex phenomena of the transport of active particles like microorganisms in shear flows are of great significance to various biological and environmental applications. Recent studies have shown that the motility and gyrotaxis of algae could greatly influence their transport in waters. However, little attention has been paid to the initial and transient transport regime when the classical Taylor dispersion model is not applicable. To tackle this problem, we resort to Gill's generalized dispersion model for passive particles like solute, which has the potential for accurately describing the entire transport process. For the first time, we extend Gill's model to the active particles, and the effects of swimming, gyrotaxis, and flow shear on the microorganism dispersion in an open‐channel flow have been thoroughly investigated. We first theoretically solve the transient drift and dispersion coefficients, based on which we obtain analytical solutions for concentration distributions of microorganisms, and further validate these results by numerically solving the governing equation. We find that when there is no flow, the longitudinal dispersion of microorganisms can be weakened by the gravitactic accumulation in the vicinity of water surface, while enhanced by a stronger swimming ability of the microorganisms. The effect of the flow shear does not affect the form of the asymptotic concentration distribution, but can greatly enhance the transient drift velocity and the dispersivity. We further analyze the effect of turbulence on microorganisms' dispersion by combing the direct numerical simulation and the random walk simulation. The increase of turbulence is shown to decrease the vertical non‐uniformity of the concentration distribution, as well as the relative contribution of active behavior to both the drift and Taylor dispersivity during transport.