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Terraced slopes are widely used in the Loess Plateau to control gully erosion, yet their potential to induce new erosion patterns remains overlooked. Here we used unmanned aerial vehicle (UAV) photogrammetry to obtain centimeter‐resolution digital surface models (DSMs) and derived hydrological networks, slopes, aspects, and curvatures of the terraced slopes. Our analysis reveals terraces disrupted natural water pathways, spurring new rill formations during each rainy season—a process neglected by models. Intriguingly, despite gentler gradients, terraced slopes exhibited higher erosion rates than steeper gullies, with widespread rills on terrace ridges. Vegetation‐induced deposition surpassed erosion by 1.52 times, but moisture evaporation on sunny slopes limited plant growth and enhanced erosion. We propose targeted strategies tailored to these erosion mechanisms, including terrace redesign, runoff diversion, slope strengthening, and suitable vegetation, advancing sustainable land management. However, this study faces limitations due to the reliance on drone photogrammetry, which may be influenced by environmental factors like varying solar angles and vegetation growth, and the lack of extensive field validation to support the UAV‐derived data. Our study spotlights drone photogrammetry's potential for elucidating complex erosion dynamics on terraced slopes. [ABSTRACT FROM AUTHOR]

Proton nuclear magnetic resonance (NMR) is widely applied to characterize the microscopic properties of hydrogen‐containing porous media. The transverse relaxation time cutoff (T2c) value is the crucial parameter for the quantitative analysis of NMR data. Currently, there is no universal method for the determination of the T2c in clayey soils. This study aimed to develop a laboratory method for determining the T2c of remoulded loess by the freezing point of loosely bound water. Malan loess, a kind of typical clayey silt, was used as test material. Based on the soil freezing characteristic, NMR measurements were performed on remoulded loess with different macro‐parameter controls during the cooling process to obtain the T2 spectrum at each target temperature. By analysing the variation of unfrozen water content with temperature reduction, the freezing point of loosely bound water and the T2c value within the freezing‐point range was determined. The freezing point of loosely bound water in remoulded loess is about −3 to −5°C and that of firmly bound water is less than −5°C. Accordingly, the T2c value of remoulded loess is determined to be 1.5–1.8 ms. The assessment of heating and cooling process and different methods for determining the T2c shows that the laboratory method by the freezing point is effective and reliable, and the T2c determined by statistical methods is worthy of further study and improvement. The saturated permeability of remoulded loess is evaluated according to the determined T2c, and two NMR‐based permeability equations can well reflect pore water distribution in remoulded loess, but to a certain extent, both equations ignore soil microstructure, pore connectivity and chemical effects of pore solution. The laboratory method by the freezing point and the determined T2c value of remoulded loess fill the gap of NMR measurement in loess analysis and are of great significance for low‐plastic clays and clay types. [ABSTRACT FROM AUTHOR]

Rill erosion on unpaved roads is widespread and highly destructive on the Loess Plateau of China, but the exploration of its evolution mechanism is scarce. In this study, a multiphase runoff scour experiment was performed on an abandoned field road in the Loess Plateau, China. Using a terrestrial laser scanner (TLS), scour experiments are used to evaluate the dynamic evolution of rill erosion and fill. The results show that soil erosion decreases significantly after the initial surge. During the first scouring, the depths of erosion and fill reached their maximum, which were 5.49 ± 7.62 mm and 5.72 ± 16.37 mm, respectively, and the fourth erosion and fill rates are only 24% and 35% of the first. Unlike the upstream and midstream, which are dominated by erosion, the downstream is mainly characterized by fill, and the downstream fill depth is 1.46 times the erosion depth; however, this ratio is 0.52 and 0.74 in the upstream and midstream, respectively. A comparison of the erosion raster with slope change revealed that rapid slope change due to erosion was mainly concentrated at 10–15°. In addition, a comparison of the fill raster with the slope found that slopes greater than 30° during the second scouring tended to flatten out most by filling, as the hydrodynamic forces of steep slopes were easily dissipated. The relationship between slope, erosion, and fill is complex and variable for each scouring. Orthophotos revealed that the U‐shaped bottom topography was conducive to concentrated overland flow, which significantly worsens the rill erosion on the road surface. This indicates that even if the slope is very gentle, the terrain easy to collect water will cause considerable erosion damage. Prevention of rill erosion on the unpaved loess road surface, therefore, requires focused drainage development. This study provides important further scientific insights into the evolution of loess road rill erosion and road erosion damage to inform erosion hazard management in the context of fragile loess landscapes. [ABSTRACT FROM AUTHOR]

From 2011 to 2013, a mega project, known as the Gully Land Consolidation Project (GLCP), was implemented in the hilly gully region atop China's Loess Plateau. However, the GLCP involved large-scale slope excavation and gully backfilling that changed the local geological environment, which led to serious geohazards, such as erosion, soil salinization, and dam failure. In this study, various geohazards caused by the GLCP in the Gutun watershed (GTW) were investigated by combined remote sensing analysis, geophysical exploration, and field surveys, and the relationships between the hazards were also explored. According to the achieved results, increased soil erosion with an average doubling from 2018 to 2020 is widely distributed in the GTW. Furthermore, 195 areas containing clear evidence of salt precipitates were observed in some of the newly created arable lands, especially downstream of the dam. This was mainly attributed to the high water table, evaporation, and soluble salt concentration of the loess. Fifty-nine newly built silt dams, primarily located in the branch channels and at the gully mouth of the Gutun channel, broke in 2020. The osmotic damage and softening caused by the combined effect of the incomplete compaction of the dam body and concentrated heavy rainfall were the main reasons of the dam breaks. The different types of disasters in the GTW after the implementation of the GLCP show a strong spatial relationship that follows the surface water flow path and forms a disaster chain consisting of slope erosion, silt dam breaks, and the soil salinization of near-dam farmlands downstream. This disaster chain amplifies disaster risks and losses. These findings can guide the improvement of the GLCP and inform geohazard mitigation strategies in areas impacted by the GLCP. [ABSTRACT FROM AUTHOR]

A mega project, Mountain Excavation and City Construction (MECC), was launched in the hilly and gully region of the Chinese Loess Plateau in 2012, in order to address the shortage of available land and create new flat land for urban construction. However, large-scale land creation and urban expansion significantly alters the local geological environment, leading to severe ground deformation. This study investigated the topographic changes, ground deformation, and their interactions due to the MECC project in the Yan'an New District (YND). First, new surface elevations were generated using ZiYuan-3 (ZY-3) stereo images acquired after the construction in order to map the local topographic changes and the fill thickness associated with the MECC project. Then, the interferometric synthetic aperture radar (InSAR) time series and 32 Sentinel-1A images were used to assess the spatial patterns of the ground deformation in the YND during the postconstruction period (2017–2018). By combining the InSAR-derived results and topographic change features, the relationship between the ground deformation and large-scale land creation was further analyzed. The results indicated that the MECC project in the YND has created over 22 km2 of flat land, including 10.8 km2 of filled area, with a maximum fill thickness of ~110 m. Significant uneven ground deformation was detected in the land-creation area, with a maximum subsidence rate of approximately 121 mm/year, which was consistent with the field survey. The strong correlation between the observed subsidence patterns and the land creation project suggested that this recorded uneven subsidence was primarily related to the spatial distribution of the filling works, along with the changes in the thickness and geotechnical properties of the filled loess; moreover, rapid urbanization, such as road construction, can accelerate the subsidence process. These findings can guide improvements in urban planning and the mitigation of geohazards in regions experiencing large-scale land construction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mathematical morphology was effective to distinguish the loess evolutionary stages. • A clearer evolutionary pattern showed the process from loess tablelands to hills. • Residual tablelands were the most vulnerable areas where tablelands disappear. The geomorphic evolution of loess tablelands (LTs), loess ridges (LRs) and loess hills (LHs) affects the availability of local farmland. The present study distinguished the evolutionary stages of different loess geomorphic units using mathematical morphology and analyzed the evolutionary process from LT to LR to LH from geomorphic characteristics and the physical meaning of the geomorphic parameters. Remote sensing images were used to interpret the LT-LR-LH landforms in the Heshui County watershed. The interpreted results indicated a gradual decrease in LT and increase in LR and LH in the Heshui County watershed from southwest to northeast. Geomorphic parameters were used to assess the evolutionary stage and establish the classification criteria. The results showed that geomorphic parameters were useful to distinguish the evolutionary stages of different loess geomorphic units, and circularity (C) played a key role in the setting of classification criteria. An evolutionary pattern of LT-LR-LH landforms was quantified and visualized. Generally, the evolution of loess tablelands followed a trend from LT to LR to LH with the further subdivision of LT-LR-LH into 9 stages of loess geomorphic units. This study provides new insight into the evolution of LT-LR-LH loess landforms and revealed the location where LTs disappeared. These classification criteria and evolutionary patterns may be extended to other loess areas to assess the extent of landform evolution. [ABSTRACT FROM AUTHOR]