In the Ulan Buh Desert, which is located in a seasonally frozen region, a frozen soil layer can appear in the winter after the wind erosion of dry sand from the surface of a mobile sand dune, thus altering the wind-sand transport process. To clarify the wind-sand transport pattern after the emergence of a frozen soil layer, this study used wind tunnel experiments to study the variations in the wind erosion rate and sediment transport pattern of frozen and nonfrozen desert soil with different soil moisture contents (1-5%). The results revealed that the relationships of the wind speed, soil moisture content and wind erosion rate are in line with an exponential function, and the wind erosion rate decreases by 6-52% after the desert soil is frozen. When the soil moisture content of the nonfrozen desert and frozen desert soil is 4% and 3%, respectively, the wind erosion rate of the soil can be reduced by more than 65% compared with that of natural dry sand (soil moisture content of 0.28%), i.e., the wind erosion rate can be effectively reduced. The sediment transport rate of nonfrozen desert soil decreases with increasing height, with an average ratio of approximately 65% for saltation. The sediment transport rate of frozen desert soil first increases but then decreases with increasing height, with an average ratio of approximately 80% for saltation. When sand particles hit the source of frozen desert soil, the interaction between particles and bed surface is dominated by the process of impact and rebound, so that more particles move higher, and some sand particles move from creep to saltation. In summary, freezing has an inhibitory effect on the wind-sand activity of desert soil, and freezing makes it easier for sand to move upwards.

Flood hazards pose a significant threat to communities and ecosystems alike. Triggered by various factors such as heavy rainfall, storm surges, or rapid snowmelt, floods can wreak havoc by inundating low-lying areas and overwhelming infrastructure systems. Understanding the feedback between local geomorphology and sediment transport dynamics in terms of the extent and evolution of flood-related damage is necessary to build a system-level description of flood hazard. In this research, we present a multispectral imagery-based approach to broadly map sediment classes and how their spatial extent and relocation can be monitored. The methodology is developed and tested using data collected in the Ahr Valley in Germany during post-disaster reconnaissance of the July 2021 Western European flooding. Using uncrewed aerial vehicle-borne multispectral imagery calibrated with laboratory-based soil characterization, we illustrate how fine and coarse-grained sediments can be broadly identified and mapped to interpret their transport behavior during flood events and their role regarding flood impacts on infrastructure systems. The methodology is also applied to data from the 2022 flooding of the Yellowstone River, Gardiner, Montana, in the United States to illustrate the transferability of the developed approach across environments. Here, we show how the distribution of soil classes can be mapped remotely and rapidly, and how this facilitates understanding their influence on local flow patterns to induce bridge abutment scour. The limitations and potential expansions to the approach are also discussed.

Wave-induced liquefaction is a geological hazard under the action of cyclic wave load on seabed. Liquefaction influences the suspended sediment concentration (SSC), which is essential for sediment dynamics and marine water quality. Till now, the identification of liquefaction state and the effect of liquefaction on SSC have not been sufficiently accounted for in the sediment model. In this study, we introduced a method for simulating the liquefaction-induced resuspension flux into an ocean model. We then simulated a storm north of the Yellow River Delta, China, and validated the results using observational data, including significant wave heights, water levels, excess pore water pressures, and SSCs. The liquefaction areas were mainly distributed in coastal zones with water depths less than 12 m, and the simulated maximum potential soil liquefaction depth was 1.39 m. The liquefaction-induced SSC was separated from the total SSC of both liquefaction- and shear-induced SSCs by the model, yielding a maximum liquefaction-induced SSC of 1.07 kg center dot m(-3). The simulated maximum proportion of liquefaction-induced SSC was 26.2% in regions with water depths of 6-12 m, with a maximum significant wave height of 3.4 m along the 12 m depth contour. The erosion zone at water depths of 8-12 m was reproduced by the model. Within 52.5 h of the storm, the maximum erosion thickness along the 10 m depth contour was enhanced by 33.9%. The model is applicable in the prediction of liquefaction, and provides a new method to simulate the SSC and seabed erosion influenced by liquefaction. Model results show that liquefaction has significant effects on SSC and seabed erosion in the coastal area with depth of 6-12 m. The validity of this method is confined to certain conditions, including a fully saturated seabed exhibiting homogeneity and isotropic properties, small liquefaction depth, residual liquefaction dominating the development of pore pressures, no influence by structures, and the sediment composed of silt and mud that experiences frequent wave-induced liquefaction.

Flash floods induced by high-intensity and short-duration monsoon rainfall can cause severe damage in arid regions. To properly size in-stream infrastructures, such as levees, bridges, and culverts, it is crucial to accurately calculate the peak runoff and sediment load from these flash floods. This case study utilized the Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) model to simulate flash floods and sediment transport in the Lucky Hills watershed located in the Walnut Gulch Experimental Watershed in southern Arizona. The Lucky Hills watershed has two rain gauges and three flumes to measure runoff and sediment load. The HEC-HMS model was used to simulate the three largest precipitation events observed in 2007, 2009, and 2010 with precipitation volumes of 41.66, 46.36, and 37.85 mm, and durations of 126, 99, and 101 min, respectively. The study discussed various methods for simulating rainfall loss, surface and channel flow routing, and soil erosion. Watershed delineations were adopted to evaluate the accuracy of the simulated runoff and sediment concentration. Results showed that the HEC-HMS model can accurately predict surface runoff and sediment concentration, but the threshold value for subbasin size is critical for the model to converge to accurate results.