Similarity Analysis: Revealing the Regional Difference in Geomorphic Development in Areas with High and Coarse Sediment Yield of the Loess Plateau in China

The development of loess landforms is controlled by underlying, pre-existing paleotopography. Previous studies have focused on the inheritance of loess landform and the control of underlying paleotopography on modern terrain based on the digital elevation model (DEM), while the similarities and differences between modern terrain and underlying paleotophotography have not been directly spatialized. In this study, areas with high and coarse sediment yield (AHCSY) in the Loess Plateau of China were selected to form the study area, and the DEM of the study area’s underlying paleotophotography was reconstructed using detailed geological maps, loess thickness maps, and underlying paleotopographic information. The hypsometric integral (HI) and spatial similarity analysis methods were used to compare the spatialized difference between underlying and modern terrain of the Loess Plateau from the perspectives of the landform development stage and surface elevation, respectively. The results of the HI method demonstrate that essentially, there are similarities between the geomorphologic development stages of underlying and modern terrain, and only some local differences exist in some special areas. The results regarding the spatialized coefficient of relative difference and the Jensen–Shannon divergence demonstrate that the thicker the loess is, the weaker the similarity is, and vice versa. Meanwhile, according to the present loess landform division, the order of regional similarity from low to high is as follows: loess tableland, broken loess tableland, hilly regions, dunes, and the Yellow River Trunk. The use of the similarity analysis method to analyze similarities between underlying and modern terrain plays an important role in revealing the inheritance of loess landforms

An Integrated Algorithm for Extracting Terrain Feature-Point Clusters Based on DEM Data

Terrain feature points, such as the peaks and saddles, are the basic framework of surface topography and its undulations, which significantly affect the spatial distribution of surface topography. In the past, terrain feature points were extracted separately for each type, while the internal connections between the terrain feature points were ignored. Therefore, this work proposes an integrated algorithm for extracting terrain feature-point clusters, including the peaks, saddles and runoff nodes, based on the DEM data. This method includes two main processes: positive terrain-constrained ridgeline extraction and terrain feature-point cluster extraction. Firstly, a threshold determination method of flow accumulation in the hydrological analysis is proposed by combining morphological characteristics with runoff simulation, and the ridgelines are extracted based on this threshold. Subsequently, the peaks and their control areas are extracted by space segmentation. Meanwhile, the saddles and runoff nodes are obtained by spatial intersection. Finally, the integrated terrain feature-point clusters are obtained by merging the three extracted terrain feature points. This method was experimented with in the six typical sample areas in Shaanxi Province and verified its results by contour lines and optical images. It shows that the spatial positions of the extracted terrain feature clusters are accurate, and the coupling relationships are great. Finally, the experiments show that the statistical attributes of point clusters and their spatial distribution trends have an obvious correlation with geomorphic types and geomorphic zoning, which can provide an important reference for geomorphic zoning and mapping

An Integrated Algorithm for Extracting Terrain Feature-Point Clusters Based on DEM Data

Terrain feature points, such as the peaks and saddles, are the basic framework of surface topography and its undulations, which significantly affect the spatial distribution of surface topography. In the past, terrain feature points were extracted separately for each type, while the internal connections between the terrain feature points were ignored. Therefore, this work proposes an integrated algorithm for extracting terrain feature-point clusters, including the peaks, saddles and runoff nodes, based on the DEM data. This method includes two main processes: positive terrain-constrained ridgeline extraction and terrain feature-point cluster extraction. Firstly, a threshold determination method of flow accumulation in the hydrological analysis is proposed by combining morphological characteristics with runoff simulation, and the ridgelines are extracted based on this threshold. Subsequently, the peaks and their control areas are extracted by space segmentation. Meanwhile, the saddles and runoff nodes are obtained by spatial intersection. Finally, the integrated terrain feature-point clusters are obtained by merging the three extracted terrain feature points. This method was experimented with in the six typical sample areas in Shaanxi Province and verified its results by contour lines and optical images. It shows that the spatial positions of the extracted terrain feature clusters are accurate, and the coupling relationships are great. Finally, the experiments show that the statistical attributes of point clusters and their spatial distribution trends have an obvious correlation with geomorphic types and geomorphic zoning, which can provide an important reference for geomorphic zoning and mapping

<b>Supplemental Material - Factors controlling distribution of mountainous gullies at the regional scale: An example of the Yuanmou dry-hot valley (SW China)</b>

Supplemental Material for Factors controlling distribution of mountainous gullies at the regional scale: An example of the Yuanmou dry-hot valley (SW China) by Haiqing Yang, Leichao Bai, Wei Lv, Lei Wang, Yushu Zhou and Bin Zhang in Journal of Progress in Physical Geography: Earth and Environment.</p

Modeling the impacts of fully-filled check dams on flood processes using CAESAR-lisflood model in the Shejiagou catchment of the Loess Plateau, China

Study region: The Shejiagou catchment on the Loess Plateau, China Study focus: This study used CAESAR-lisflood to simulate the impacts on flood processes of fully-filled check dams with different numbers, silt land areas and connection modes. According to the model results, the protective measures of fully-filled check dams and recommendations for promoting the construction of check dams were proposed in the study. New hydrological insights for the region: CAESAR-lisflood model in the study obtained higher accuracy with both the Nash-Sutcliff coefficient of efficiency and the coefficient of determination greater than 0.8. Our results showed the presence of fully-filled check dams made the flood process tend to balance, and reduced the flood volume by 9.56–75.52%, peak discharge by 14.25–89.74%, runoff kinetic energy by 30.21–99.75% and runoff power by 20.17–95.23% under different layout scenarios. Meanwhile, the results indicated that the impacts of fully-filled check dams in main channel mainly manifested in the energy dissipation of silt land and energy increase at the outside slope of dam body, which was aggravated by downstream channel with steep slope. The combination of fully-filled check dams could amplify the flood control efficiency of individual dam. These results provide a scientific basis for reinforcement of fully-filled check dams and optimization of check dams layout in the future on the Chinese Loess Plateau