In China′s Loess Plateau area, gully head is the most active zone of a drainage system in gully areas. The differentiation of loess gully head follows geospatial patterns and reflects the process of the loess landfor...In China′s Loess Plateau area, gully head is the most active zone of a drainage system in gully areas. The differentiation of loess gully head follows geospatial patterns and reflects the process of the loess landform development and evolution of its drainage system to some extent. In this study, the geomorphic meaning, basic characteristics, morphological structure and the basic types of loess gully heads were systematically analysed. Then, the loess gully head′s conceptual model was established, and an extraction method based on Digital Elevation Model(DEM) for loess gully head features and elements was proposed. Through analysing the achieved statistics of loess gully head features, loess gully heads have apparently similar and different characteristics depending on the different loess landforms where they are found. The loess head characteristics reflect their growth period and evolution tendency to a certain degree, and they indirectly represent evolutionary mechanisms. In addition, the loess gully developmental stages and the evolutionary processes can be deduced by using loess gully head characteristics. This study is of great significance for development and improvement of the theoretical system for describing loess gully landforms.展开更多
The inhomogeneous and non-flat paleotopography in a depositional landform area profoundly controls the process of modem gully evolution and shapes the structure of a gully network. However, this controlling effect of ...The inhomogeneous and non-flat paleotopography in a depositional landform area profoundly controls the process of modem gully evolution and shapes the structure of a gully network. However, this controlling effect of paleotopography on modem gully evolution is mostly ignored because of the difficulties in paleotopography reconstruction. In this study, loess area in China is selected as case area for its typical depositional landform area and inhomogeneous and non-flat paleotopography during the Quaternary. The paleotopography underlying loess is considered while evaluating its controlling effects on the gully evolutionary process. On the basis of the geophysical prospecting, detailed geological information, and high-resolution digital elevation model, we reconstruct the pre-Quaternary paleotopographic surface in the case area. Comparative analysis is conducted to reveal the modern gully evolution in relation to the paleotopography. Results show that the concave area of the paleotopography acts as the basement of the high-order modern gully evolution in the hilly-gully area, although this concave area can be covered and buried by the loess depositional process during the Quaternary. A significant controlling effect of paleotopography on high-order modern gully evolution can be observed in a depositional landform with a hilly-gully underlying topography, whereas a relatively weak controlling effect exists in a flat underlying topograpnlcal area oecause of the strong horizontal shift effect of gully formation process. Several low-order modern gullies also exist and limit the controlling effect of paleotopography. These results reveal a controlled high-order modern gully evolutionary process and a rather dynamic low-order modem gully evolutionary process in the hilly-gully area. These results also help us understand the variations in different modern gully evolution in relation to paleotopography and the different management schemes for soil conservation and ecological restoration during the gully evolutionary proce展开更多
The expression of gully landforms can be regarded as an indicator of the evolutionary process of gullies. Most existing studies on the expression of gully landforms focus on plane characteristics. However, the vertica...The expression of gully landforms can be regarded as an indicator of the evolutionary process of gullies. Most existing studies on the expression of gully landforms focus on plane characteristics. However, the vertical characteristics of a gully should be given considerable attention because gullies have mainly eroded the surface in the vertical direction. Current studies on vertical characteristics of gullies mainly focused on a single gully or rarely a few gullies, thereby failing to express the entire gully landform in a certain area. In this study, gully profile combination (GPC) was proposed to investigate the morphology and reveal the evolution of gully landforms. It was defined as the combination of vertical projection of all gully profiles in the entire drainage basin. Then, a gully evolution index and its statistic values were used to reveal the evolution of gully landforms based on GPC. The proposed method was applied and validated in three typical loess gully landform areas (i.e., loess tableland, ridge, and hill) in the Loess Plateau of China. Results show that GPC can effectively express gully landforms. The specific geomorphological feature (monoclinic loess tableland) can also be identified using GPC. The gully evolution index results also demonstrate different magnitudes of gully evolutionary stages in a certain area, which reflect the diversity of gullies. The average and median values of the gully evolution index increase in the three typical loess gully landforms. From loess tableland, loess ridge, and loess hill, the average values are 0.653, 0.703, and 0.763, and the median values are 0.661, 0.719, and 0.783, respectively. This method is also found to be stable with gully extraction thresholds for distinguishing different loess gully land-forms. Accordingly, the evolution magnitudes of loess gully are obtained.展开更多
The gully is the most dynamic and changeable landform unit on the Loess Plateau,and the characteristics of gully landforms are key indicators of gully evolution.Different gully profiles are connected and combined thro...The gully is the most dynamic and changeable landform unit on the Loess Plateau,and the characteristics of gully landforms are key indicators of gully evolution.Different gully profiles are connected and combined through runoff nodes.Thus,it is necessary to cluster gully profiles into a gully profile combination(GPC)to reveal the spatial variation in gully landforms throughout the Loess Plateau.First,the gradient and gully evolution index(GEI)of two sample areas in Changwu and Suide in Shaanxi Province,China are calculated and analysed based on GPC.Then,the gradient and GEI are calculated by using 90-m-resolution digital elevation model(DEM)data for the severe soil erosion area with the basin as the research unit.On this basis,the spatial variation in the development degree is analysed with Getis-Ord Gi*.The results show that the degree of gully undercutting decreases from southeast to northwest under the influence of rainfall.Due to the soil properties,the loess in the northwest is more prone to collapse,resulting in the decrease of GEI from northwest to southeast.The development degree of gullies is closely related to rivers.The strong erosive capacity of rivers leads to greater differences in gullies within the basin.At the same time,the skewness and kurtosis of the gully index in the basin are correlated;when the distribution of the gully index in the basin is less normal,the distribution of the gully index is more concentrated.These results reveal the spatial variation characteristics of the Loess Plateau based on GPC.展开更多
基金Under the auspices of National Youth Science Foundation of China(No.41001294)Key Project of National Natural Science Foundation of China(No.40930531)Research Fund of State Key Laboratory Resources and Environment Information System(No.2010KF0002SA)
文摘In China′s Loess Plateau area, gully head is the most active zone of a drainage system in gully areas. The differentiation of loess gully head follows geospatial patterns and reflects the process of the loess landform development and evolution of its drainage system to some extent. In this study, the geomorphic meaning, basic characteristics, morphological structure and the basic types of loess gully heads were systematically analysed. Then, the loess gully head′s conceptual model was established, and an extraction method based on Digital Elevation Model(DEM) for loess gully head features and elements was proposed. Through analysing the achieved statistics of loess gully head features, loess gully heads have apparently similar and different characteristics depending on the different loess landforms where they are found. The loess head characteristics reflect their growth period and evolution tendency to a certain degree, and they indirectly represent evolutionary mechanisms. In addition, the loess gully developmental stages and the evolutionary processes can be deduced by using loess gully head characteristics. This study is of great significance for development and improvement of the theoretical system for describing loess gully landforms.
基金supported by the National Natural Science Foundation of China(Grant Nos.41601411,41671389,41571383&41271438)AProject Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions-PAPD(Grant No.164320H101)
文摘The inhomogeneous and non-flat paleotopography in a depositional landform area profoundly controls the process of modem gully evolution and shapes the structure of a gully network. However, this controlling effect of paleotopography on modem gully evolution is mostly ignored because of the difficulties in paleotopography reconstruction. In this study, loess area in China is selected as case area for its typical depositional landform area and inhomogeneous and non-flat paleotopography during the Quaternary. The paleotopography underlying loess is considered while evaluating its controlling effects on the gully evolutionary process. On the basis of the geophysical prospecting, detailed geological information, and high-resolution digital elevation model, we reconstruct the pre-Quaternary paleotopographic surface in the case area. Comparative analysis is conducted to reveal the modern gully evolution in relation to the paleotopography. Results show that the concave area of the paleotopography acts as the basement of the high-order modern gully evolution in the hilly-gully area, although this concave area can be covered and buried by the loess depositional process during the Quaternary. A significant controlling effect of paleotopography on high-order modern gully evolution can be observed in a depositional landform with a hilly-gully underlying topography, whereas a relatively weak controlling effect exists in a flat underlying topograpnlcal area oecause of the strong horizontal shift effect of gully formation process. Several low-order modern gullies also exist and limit the controlling effect of paleotopography. These results reveal a controlled high-order modern gully evolutionary process and a rather dynamic low-order modem gully evolutionary process in the hilly-gully area. These results also help us understand the variations in different modern gully evolution in relation to paleotopography and the different management schemes for soil conservation and ecological restoration during the gully evolutionary proce
基金the National Natural Science Foundation of China (Nos. 41971333, 41930102, 41601411 , 41671389)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions-PAPD (Grant No. 164320H101).
文摘The expression of gully landforms can be regarded as an indicator of the evolutionary process of gullies. Most existing studies on the expression of gully landforms focus on plane characteristics. However, the vertical characteristics of a gully should be given considerable attention because gullies have mainly eroded the surface in the vertical direction. Current studies on vertical characteristics of gullies mainly focused on a single gully or rarely a few gullies, thereby failing to express the entire gully landform in a certain area. In this study, gully profile combination (GPC) was proposed to investigate the morphology and reveal the evolution of gully landforms. It was defined as the combination of vertical projection of all gully profiles in the entire drainage basin. Then, a gully evolution index and its statistic values were used to reveal the evolution of gully landforms based on GPC. The proposed method was applied and validated in three typical loess gully landform areas (i.e., loess tableland, ridge, and hill) in the Loess Plateau of China. Results show that GPC can effectively express gully landforms. The specific geomorphological feature (monoclinic loess tableland) can also be identified using GPC. The gully evolution index results also demonstrate different magnitudes of gully evolutionary stages in a certain area, which reflect the diversity of gullies. The average and median values of the gully evolution index increase in the three typical loess gully landforms. From loess tableland, loess ridge, and loess hill, the average values are 0.653, 0.703, and 0.763, and the median values are 0.661, 0.719, and 0.783, respectively. This method is also found to be stable with gully extraction thresholds for distinguishing different loess gully land-forms. Accordingly, the evolution magnitudes of loess gully are obtained.
基金supported by the National Natural Science Foundation of China(No.41971333 and 41930102)the Priority Academic Programme Development of Jiangsu Higher Education Institutions-PAPD(Grant No.164320H101)。
文摘The gully is the most dynamic and changeable landform unit on the Loess Plateau,and the characteristics of gully landforms are key indicators of gully evolution.Different gully profiles are connected and combined through runoff nodes.Thus,it is necessary to cluster gully profiles into a gully profile combination(GPC)to reveal the spatial variation in gully landforms throughout the Loess Plateau.First,the gradient and gully evolution index(GEI)of two sample areas in Changwu and Suide in Shaanxi Province,China are calculated and analysed based on GPC.Then,the gradient and GEI are calculated by using 90-m-resolution digital elevation model(DEM)data for the severe soil erosion area with the basin as the research unit.On this basis,the spatial variation in the development degree is analysed with Getis-Ord Gi*.The results show that the degree of gully undercutting decreases from southeast to northwest under the influence of rainfall.Due to the soil properties,the loess in the northwest is more prone to collapse,resulting in the decrease of GEI from northwest to southeast.The development degree of gullies is closely related to rivers.The strong erosive capacity of rivers leads to greater differences in gullies within the basin.At the same time,the skewness and kurtosis of the gully index in the basin are correlated;when the distribution of the gully index in the basin is less normal,the distribution of the gully index is more concentrated.These results reveal the spatial variation characteristics of the Loess Plateau based on GPC.
