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The paleotopography of loess landform represents the initial surface before the evolution of the Aeolian depositional process. This paleotopography served as an indicator of the paleo-geography and erosion base that restrained the evolution of the current landform. In this case study, a landform-derived placement method involving electrical resistivity prospecting is proposed for paleotopography reconstruction. The method consists of extracting terrain feature knowledge and terrain feature-based paleotopography prospecting and reconstruction. The field experiment is validated and used in three typical loess landform areas in the Chinese Loess Plateau. These typical loess landforms include loess hill, loess ridge, and loess tableland. Terrain features considered include peaks, saddles, ridges, and gullies. The results show significant electrical resistivity difference between the paleotopography and loess strata. The electrical resistivity method could effectively detect the paleotopography and different loess layers. The reconstructed paleotopography using the feature-based method could effectively represent the morphology of the paleosurface compared to the result of the interpolation method. The reconstructed paleotopography also appears as a coincident terrain relief compared to modern topography; such a relief demonstrates significant landform inheritance between modern terrain and paleotopography. In the loess hill and ridge landform areas, the relative elevation difference of paleotopography is approximately 50 m whereas that of the modern terrain is roughly 150 m, indicating that the loess deposition process increased the topographic relief from paleotopography to modern terrain by approximately 100 m. Similar altitude of the paleotopographic peaks (roughly 10 m height difference) appears in the two nearby loess ridge and hill areas. The results indicate that paleo-geography of this area should be a landform of peneplain and almost a planation surface. [ABSTRACT FROM AUTHOR]

The underlying pre-existing paleotopography directly influences the loess deposition process and shapes the morphology of current loess landforms. An understanding of the controlling effects of the underlying paleotopography on loess deposition is critical to revealing the mechanism of loess-landform formation. However, these controlling effects exhibit spatial variation as well as uncertainty, depending on a study's data sources, methodologies and particular research scope. In this study, the geological history of a study area in the Loess Plateau of China that is subject to severe soil erosion is investigated using detailed geological information and digital elevation models (DEMs), and an underlying paleotopographic model of the area is constructed. Based on the models of modern terrain and paleotopography, we introduce a watershed hierarchy method to investigate the spatial variation of the loesslandform inheritance relationship and reveal the loess deposition process over different scales of drainage. The landform inheritance relationships were characterized using a terrain-relief change index (TRCI) and a bedrock terrain controllability index (BTCI). The results show that the TRCI appears to have an inverse relationship with increasing research scope, indicating that, compared with the paleotopography of the region, modern terrain has lower topographic relief over the entire area, while it has higher topographic relief in the smaller, local areas. The BTCI strengthens with increasing drainage area, which demonstrates a strong controlling effect over the entire study area, but a weak effect in the smaller, local areas because of the effect of paleotopography on modern terrain. The results provide for an understanding of the spatial variation of loess deposition in relation to paleotopography and contribute to the development of a process-based loess-landform evolution model. [ABSTRACT FROM AUTHOR]

Although many studies have investigated slope gradient uncertainty derived from Digital Elevation Models (DEMs), the research concerning slope length uncertainty is far from mature. This discrepancy affects the availability and accuracy of soil erosion as well as hydrological modeling. This study investigates the formation and distribution of existing errors and uncertainties in slope length derivation based on 5-m resolution DEMs of the Loess Plateau in the middle of China. The slope length accuracy in three different landform areas is examined to analyse algorithm effects. The experiments indicate that the accuracy of the flat test area is lower than that of the rougher areas. The value from the specific contributing area (SCA) method is greater than the cumulative slope length (CSL), and the differences between these two methods arise from the shape of the upslope area. The variation of mean slope length derived from various DEM resolutions and landforms. The slope length accuracy decreases with increasing grid size and terrain complexity at the six test sites. A regression model is built to express the relationship of mean slope length with DEM resolution less than 85 m and terrain complexity represented by gully density. The results support the understanding of the slope length accuracy, thereby aiding in the effective evaluation of the modeling effect of surface process. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of loess-covered landforms is largely controlled by the pre-Quaternary underlying bedrock terrain, which is one of the most important factors in understanding the formation mechanism of the landforms. This study used multiple data sources to detect 1729 outcropping points of underlying terrain, in order to construct a digital elevation model (DEM) of the paleotopography of an area of the Loess Plateau subject to severe soil erosion. Four terrain characteristics, including terrain texture, slope gradient, the hypsometric curve, and slope aspect, were used to quantify topographic differences and reveal the loess-deposition process during the Quaternary. A loess thickness map was then created to show the spatial distribution of loess deposits in the test area. Finally, the geomorphological inheritance characteristics of the loess-covered landforms were evaluated in different landform divisions. The results showed the significant inheritance of modern topography from the underlying topography with a similar general relief trends. The average thickness of loess deposits was computed to be 104.6m, with the thickest part located in the Xifeng loess tableland area. In addition, the slope aspects of the North and Northwest seem to have favored Quaternary loess deposition, which supported the hypothesis of an eolian origin for loess in China. The modern surface has lower topographic relief compared to the underlying terrain due to loess deposition. [Copyright &y& Elsevier]