The Experts below are selected from a list of 1389 Experts worldwide ranked by ideXlab platform
Yanhe Huang - One of the best experts on this subject based on the ideXlab platform.
-
rill erosion processes on a steep Colluvial Deposit slope under heavy rainfall in flume experiments with artificial rain
Catena, 2018Co-Authors: Fangshi Jiang, Ming-kuang Wang, Jinshi Lin, Zhenzhi Zhan, Jialin Chen, Yanhe HuangAbstract:Abstract Understanding rill erosion processes is important in the prediction of soil erosion and the prevention of soil loss. However, limited information is available concerning the impacts of rainfall on rill erosion on steep slopes. Colluvial Deposits with steep slopes make up the packed material underlying the collapsing walls in benggang, which collapse due to hydraulic pressure and gravity. They contain loose materials and large amounts of coarse particles. The objectives of this study were to investigate the impacts of rainfall intensity and slope gradient on the rill erosion process, rill development and rill flow dynamic mechanisms on the steep slopes of Colluvial Deposits. The Colluvial soils were subjected to simulated rainfall in a 5-m2 (5-m by 1-m) flume at heavy rainfall intensities (100, 120, and 140 mm h−1) and on five steep slopes (20, 25, 30, 35, and 40°). Rill erosion contributed significantly to Colluvial slope erosion; on average, rills accounted for 61% of the soil loss, and the effects of slope gradient were greater than those of the rainfall intensity. After rill development, rill density, rill length, width, and depth all significantly increased. Correspondingly, the soil loss rate sharply raised and irregularly fluctuated. Moreover, the collapse of rill heads or sidewalls tended to increase the relative contribution to rill erosion and rill development. The rill flow was characterized by transitional and subcritical flow regimes. The rill flow velocity was the most sensitive hydraulic parameter, and the unit stream power provided the optimal hydrodynamic parameter to characterize the dynamic mechanisms of rill erosion on Colluvial Deposits. The collapse of rill heads or sidewalls could result in negative values for critical shear stress, critical stream power, and critical unit stream power of rill erosion, which were −19 Pa, −5.3 N m−1 s−1, and −0.09 m s−1, respectively. These results provide a better understanding of the mechanism of rill erosion on steep slopes.
-
Sediment selective behaviors of Colluvial Deposit materials on steep slopes and under heavy rainfall conditions in southeastern China
Journal of Soil and Water Conservation, 2018Co-Authors: Fangshi Jiang, Yanhe Huang, Ming-kuang Wang, Jinshi Lin, Gan ZhaoAbstract:Characterizing sediment selectivity during transport will improve understanding of soil erosion processes, but few studies have focused on steep slopes and soil with loose, coarse material. This study examined Colluvial Deposits, which contain loose materials with large amounts of coarse particles. These soils were subjected to simulated rainfall in a 5 m2 (5 m by 1 m) box at heavy rainfall intensities (1, 1.33, 1.67, 2, and 2.33 mm min−1) and on five steep slopes (20°, 25°, 30°, 35°, and 40°). During the experiments, the particle size of the eroded material gradually coarsened, then stabilized and often showed short-term fluctuations as the rainfall progressed. During interrill erosion processes, the sediment became enriched with finer particles because of the low runoff energy of interrill flow; the dominant transport mechanism was the suspension-saltation transport of sediment with a grain size finer than 0.537 mm. However, the sediment was coarser after rill development than before, and increased stream power meant that bed-load transport by rolling of the larger sediment grains (coarser than 0.957 mm) became an increasingly important mechanism; bed-load transport also increased with rainfall intensity, so the particle-size distribution for high-intensity rainfall resembled that of the original soil. Finally, during rill erosion processes, rill bank collapse occured and the original soil contained coarse, heavy particles that could more easily be rolled on steep slopes. These factors could increase the relative importance of bed-load transport. The results of this study have important implications for assessment and modeling of erosion processes in disturbed soils with large amounts of coarse particles.
-
Mulching effects on erosion from steep slopes and sediment particle size distributions of gully Colluvial Deposits
CATENA, 2018Co-Authors: Jinshi Lin, Fangshi Jiang, Ming-kuang Wang, Gaoli Zhu, Jia Wei, Yanhe HuangAbstract:Abstract Mulching is an effective soil conservation practice for permanent gullies in southern China. Knowledge of the sediment characteristics that occur in mulched soils of Colluvial Deposits could improve the utility of mulching for soil conservation. A rainfall simulation experiment was designed to evaluate the effects of mulch on the runoff, erosion, and particle size distribution of eroded sediments. Straw mulch coverage of 0, 25, 50, 75, and 95% was tested with simulated rainfall. The effective particle size distribution of the sediment was compared with the ultimate particle size distribution to investigate the detachment and transport mechanisms involved in sediment mobilization. Mulching delayed the runoff initiation time and reduced the average runoff rate. Compared with bare soil, the increased mulch coverage decreased the soil loss rate by 13.0 to 90.3%. Moreover, the peak sediment concentration decreased from 80 to 200 g L− 1 under the different mulch coverage conditions. The optimal straw application rate was 1.5 to 3.0 Mg ha− 1 in the permanent gully's Deposits. The relationship between instantaneous kinetic energy of rainfall and the proportion of effective clay- and sand-sized particles was well represented using an exponential equation. The effective clay-sized sediments under the different mulch coverage conditions were 2 to 4 times more common than those of the original soil, although there were only 13.9% sand-sized particles in the sediment when the mulch coverage was 95%. The silt-sized sediment was transported as primary particles under the different mulch coverage conditions. The effective to ultimate ratio of silt-sized particles fluctuated around 1. There were depletions of clay and silt in the Colluvial Deposit soil with mulch cover, and the enrichment ratios of clay and silt were larger than 1 while most of the enrichment ratios for sand were
-
Effects of Rainfall Intensity and Slope Gradient on Steep Colluvial Deposit Erosion in Southeast China
Soil Science Society of America Journal, 2014Co-Authors: Fangshi Jiang, Yanhe Huang, Ming-kuang Wang, Jinshi Lin, Gan ZhaoAbstract:Rainfall intensity and slope gradient are important factors that affect soil erosion; however, contradictory observations have been made due to different experimental conditions and materials. Colluvial Deposits with loose, coarse material and steep slopes are easily erodible, but the erosion mechanism of Colluvial Deposition remains obscure. This work investigated the effects of heavy and storm rainfall intensity and steep slope gradients on the infiltration, runoff, and soil loss of Colluvial soil. The rainfall intensity ranged from 1.00 to 2.33 mm min⁻¹, and the slope gradient ranged from 36 to 84%. The infiltration rates declined sharply in the initial stage, whereas an opposite trend was observed for runoff rates until a steady state was reached after 5 min. Single- and multiple-peak models illustrated the two types of changes for the sediment yield process. The infiltration volume and the coefficient increased with increasing rainfall intensity and decreased with increasing slope, whereas the runoff coefficient decreased with increasing rainfall intensity and increased with increasing slope. Runoff volume and sediment yield increased with increasing rainfall intensity but had a critical slope gradient of 58% and >47%. The sediment concentration increased with increasing rainfall intensity, and first increased and then decreased with increasing slope gradients at rainfall intensities of 1.00 and 1.33 mm min⁻¹ but increased at rainfall intensities of 1.67, 2.00, and 2.33 mm min⁻¹. The findings of this study can be used to clarify the erosion mechanisms in disturbed soils with high coarse particle content.
Fangshi Jiang - One of the best experts on this subject based on the ideXlab platform.
-
rill erosion processes on a steep Colluvial Deposit slope under heavy rainfall in flume experiments with artificial rain
Catena, 2018Co-Authors: Fangshi Jiang, Ming-kuang Wang, Jinshi Lin, Zhenzhi Zhan, Jialin Chen, Yanhe HuangAbstract:Abstract Understanding rill erosion processes is important in the prediction of soil erosion and the prevention of soil loss. However, limited information is available concerning the impacts of rainfall on rill erosion on steep slopes. Colluvial Deposits with steep slopes make up the packed material underlying the collapsing walls in benggang, which collapse due to hydraulic pressure and gravity. They contain loose materials and large amounts of coarse particles. The objectives of this study were to investigate the impacts of rainfall intensity and slope gradient on the rill erosion process, rill development and rill flow dynamic mechanisms on the steep slopes of Colluvial Deposits. The Colluvial soils were subjected to simulated rainfall in a 5-m2 (5-m by 1-m) flume at heavy rainfall intensities (100, 120, and 140 mm h−1) and on five steep slopes (20, 25, 30, 35, and 40°). Rill erosion contributed significantly to Colluvial slope erosion; on average, rills accounted for 61% of the soil loss, and the effects of slope gradient were greater than those of the rainfall intensity. After rill development, rill density, rill length, width, and depth all significantly increased. Correspondingly, the soil loss rate sharply raised and irregularly fluctuated. Moreover, the collapse of rill heads or sidewalls tended to increase the relative contribution to rill erosion and rill development. The rill flow was characterized by transitional and subcritical flow regimes. The rill flow velocity was the most sensitive hydraulic parameter, and the unit stream power provided the optimal hydrodynamic parameter to characterize the dynamic mechanisms of rill erosion on Colluvial Deposits. The collapse of rill heads or sidewalls could result in negative values for critical shear stress, critical stream power, and critical unit stream power of rill erosion, which were −19 Pa, −5.3 N m−1 s−1, and −0.09 m s−1, respectively. These results provide a better understanding of the mechanism of rill erosion on steep slopes.
-
Sediment selective behaviors of Colluvial Deposit materials on steep slopes and under heavy rainfall conditions in southeastern China
Journal of Soil and Water Conservation, 2018Co-Authors: Fangshi Jiang, Yanhe Huang, Ming-kuang Wang, Jinshi Lin, Gan ZhaoAbstract:Characterizing sediment selectivity during transport will improve understanding of soil erosion processes, but few studies have focused on steep slopes and soil with loose, coarse material. This study examined Colluvial Deposits, which contain loose materials with large amounts of coarse particles. These soils were subjected to simulated rainfall in a 5 m2 (5 m by 1 m) box at heavy rainfall intensities (1, 1.33, 1.67, 2, and 2.33 mm min−1) and on five steep slopes (20°, 25°, 30°, 35°, and 40°). During the experiments, the particle size of the eroded material gradually coarsened, then stabilized and often showed short-term fluctuations as the rainfall progressed. During interrill erosion processes, the sediment became enriched with finer particles because of the low runoff energy of interrill flow; the dominant transport mechanism was the suspension-saltation transport of sediment with a grain size finer than 0.537 mm. However, the sediment was coarser after rill development than before, and increased stream power meant that bed-load transport by rolling of the larger sediment grains (coarser than 0.957 mm) became an increasingly important mechanism; bed-load transport also increased with rainfall intensity, so the particle-size distribution for high-intensity rainfall resembled that of the original soil. Finally, during rill erosion processes, rill bank collapse occured and the original soil contained coarse, heavy particles that could more easily be rolled on steep slopes. These factors could increase the relative importance of bed-load transport. The results of this study have important implications for assessment and modeling of erosion processes in disturbed soils with large amounts of coarse particles.
-
Mulching effects on erosion from steep slopes and sediment particle size distributions of gully Colluvial Deposits
CATENA, 2018Co-Authors: Jinshi Lin, Fangshi Jiang, Ming-kuang Wang, Gaoli Zhu, Jia Wei, Yanhe HuangAbstract:Abstract Mulching is an effective soil conservation practice for permanent gullies in southern China. Knowledge of the sediment characteristics that occur in mulched soils of Colluvial Deposits could improve the utility of mulching for soil conservation. A rainfall simulation experiment was designed to evaluate the effects of mulch on the runoff, erosion, and particle size distribution of eroded sediments. Straw mulch coverage of 0, 25, 50, 75, and 95% was tested with simulated rainfall. The effective particle size distribution of the sediment was compared with the ultimate particle size distribution to investigate the detachment and transport mechanisms involved in sediment mobilization. Mulching delayed the runoff initiation time and reduced the average runoff rate. Compared with bare soil, the increased mulch coverage decreased the soil loss rate by 13.0 to 90.3%. Moreover, the peak sediment concentration decreased from 80 to 200 g L− 1 under the different mulch coverage conditions. The optimal straw application rate was 1.5 to 3.0 Mg ha− 1 in the permanent gully's Deposits. The relationship between instantaneous kinetic energy of rainfall and the proportion of effective clay- and sand-sized particles was well represented using an exponential equation. The effective clay-sized sediments under the different mulch coverage conditions were 2 to 4 times more common than those of the original soil, although there were only 13.9% sand-sized particles in the sediment when the mulch coverage was 95%. The silt-sized sediment was transported as primary particles under the different mulch coverage conditions. The effective to ultimate ratio of silt-sized particles fluctuated around 1. There were depletions of clay and silt in the Colluvial Deposit soil with mulch cover, and the enrichment ratios of clay and silt were larger than 1 while most of the enrichment ratios for sand were
-
Effects of Rainfall Intensity and Slope Gradient on Steep Colluvial Deposit Erosion in Southeast China
Soil Science Society of America Journal, 2014Co-Authors: Fangshi Jiang, Yanhe Huang, Ming-kuang Wang, Jinshi Lin, Gan ZhaoAbstract:Rainfall intensity and slope gradient are important factors that affect soil erosion; however, contradictory observations have been made due to different experimental conditions and materials. Colluvial Deposits with loose, coarse material and steep slopes are easily erodible, but the erosion mechanism of Colluvial Deposition remains obscure. This work investigated the effects of heavy and storm rainfall intensity and steep slope gradients on the infiltration, runoff, and soil loss of Colluvial soil. The rainfall intensity ranged from 1.00 to 2.33 mm min⁻¹, and the slope gradient ranged from 36 to 84%. The infiltration rates declined sharply in the initial stage, whereas an opposite trend was observed for runoff rates until a steady state was reached after 5 min. Single- and multiple-peak models illustrated the two types of changes for the sediment yield process. The infiltration volume and the coefficient increased with increasing rainfall intensity and decreased with increasing slope, whereas the runoff coefficient decreased with increasing rainfall intensity and increased with increasing slope. Runoff volume and sediment yield increased with increasing rainfall intensity but had a critical slope gradient of 58% and >47%. The sediment concentration increased with increasing rainfall intensity, and first increased and then decreased with increasing slope gradients at rainfall intensities of 1.00 and 1.33 mm min⁻¹ but increased at rainfall intensities of 1.67, 2.00, and 2.33 mm min⁻¹. The findings of this study can be used to clarify the erosion mechanisms in disturbed soils with high coarse particle content.
Jinshi Lin - One of the best experts on this subject based on the ideXlab platform.
-
rill erosion processes on a steep Colluvial Deposit slope under heavy rainfall in flume experiments with artificial rain
Catena, 2018Co-Authors: Fangshi Jiang, Ming-kuang Wang, Jinshi Lin, Zhenzhi Zhan, Jialin Chen, Yanhe HuangAbstract:Abstract Understanding rill erosion processes is important in the prediction of soil erosion and the prevention of soil loss. However, limited information is available concerning the impacts of rainfall on rill erosion on steep slopes. Colluvial Deposits with steep slopes make up the packed material underlying the collapsing walls in benggang, which collapse due to hydraulic pressure and gravity. They contain loose materials and large amounts of coarse particles. The objectives of this study were to investigate the impacts of rainfall intensity and slope gradient on the rill erosion process, rill development and rill flow dynamic mechanisms on the steep slopes of Colluvial Deposits. The Colluvial soils were subjected to simulated rainfall in a 5-m2 (5-m by 1-m) flume at heavy rainfall intensities (100, 120, and 140 mm h−1) and on five steep slopes (20, 25, 30, 35, and 40°). Rill erosion contributed significantly to Colluvial slope erosion; on average, rills accounted for 61% of the soil loss, and the effects of slope gradient were greater than those of the rainfall intensity. After rill development, rill density, rill length, width, and depth all significantly increased. Correspondingly, the soil loss rate sharply raised and irregularly fluctuated. Moreover, the collapse of rill heads or sidewalls tended to increase the relative contribution to rill erosion and rill development. The rill flow was characterized by transitional and subcritical flow regimes. The rill flow velocity was the most sensitive hydraulic parameter, and the unit stream power provided the optimal hydrodynamic parameter to characterize the dynamic mechanisms of rill erosion on Colluvial Deposits. The collapse of rill heads or sidewalls could result in negative values for critical shear stress, critical stream power, and critical unit stream power of rill erosion, which were −19 Pa, −5.3 N m−1 s−1, and −0.09 m s−1, respectively. These results provide a better understanding of the mechanism of rill erosion on steep slopes.
-
Sediment selective behaviors of Colluvial Deposit materials on steep slopes and under heavy rainfall conditions in southeastern China
Journal of Soil and Water Conservation, 2018Co-Authors: Fangshi Jiang, Yanhe Huang, Ming-kuang Wang, Jinshi Lin, Gan ZhaoAbstract:Characterizing sediment selectivity during transport will improve understanding of soil erosion processes, but few studies have focused on steep slopes and soil with loose, coarse material. This study examined Colluvial Deposits, which contain loose materials with large amounts of coarse particles. These soils were subjected to simulated rainfall in a 5 m2 (5 m by 1 m) box at heavy rainfall intensities (1, 1.33, 1.67, 2, and 2.33 mm min−1) and on five steep slopes (20°, 25°, 30°, 35°, and 40°). During the experiments, the particle size of the eroded material gradually coarsened, then stabilized and often showed short-term fluctuations as the rainfall progressed. During interrill erosion processes, the sediment became enriched with finer particles because of the low runoff energy of interrill flow; the dominant transport mechanism was the suspension-saltation transport of sediment with a grain size finer than 0.537 mm. However, the sediment was coarser after rill development than before, and increased stream power meant that bed-load transport by rolling of the larger sediment grains (coarser than 0.957 mm) became an increasingly important mechanism; bed-load transport also increased with rainfall intensity, so the particle-size distribution for high-intensity rainfall resembled that of the original soil. Finally, during rill erosion processes, rill bank collapse occured and the original soil contained coarse, heavy particles that could more easily be rolled on steep slopes. These factors could increase the relative importance of bed-load transport. The results of this study have important implications for assessment and modeling of erosion processes in disturbed soils with large amounts of coarse particles.
-
Mulching effects on erosion from steep slopes and sediment particle size distributions of gully Colluvial Deposits
CATENA, 2018Co-Authors: Jinshi Lin, Fangshi Jiang, Ming-kuang Wang, Gaoli Zhu, Jia Wei, Yanhe HuangAbstract:Abstract Mulching is an effective soil conservation practice for permanent gullies in southern China. Knowledge of the sediment characteristics that occur in mulched soils of Colluvial Deposits could improve the utility of mulching for soil conservation. A rainfall simulation experiment was designed to evaluate the effects of mulch on the runoff, erosion, and particle size distribution of eroded sediments. Straw mulch coverage of 0, 25, 50, 75, and 95% was tested with simulated rainfall. The effective particle size distribution of the sediment was compared with the ultimate particle size distribution to investigate the detachment and transport mechanisms involved in sediment mobilization. Mulching delayed the runoff initiation time and reduced the average runoff rate. Compared with bare soil, the increased mulch coverage decreased the soil loss rate by 13.0 to 90.3%. Moreover, the peak sediment concentration decreased from 80 to 200 g L− 1 under the different mulch coverage conditions. The optimal straw application rate was 1.5 to 3.0 Mg ha− 1 in the permanent gully's Deposits. The relationship between instantaneous kinetic energy of rainfall and the proportion of effective clay- and sand-sized particles was well represented using an exponential equation. The effective clay-sized sediments under the different mulch coverage conditions were 2 to 4 times more common than those of the original soil, although there were only 13.9% sand-sized particles in the sediment when the mulch coverage was 95%. The silt-sized sediment was transported as primary particles under the different mulch coverage conditions. The effective to ultimate ratio of silt-sized particles fluctuated around 1. There were depletions of clay and silt in the Colluvial Deposit soil with mulch cover, and the enrichment ratios of clay and silt were larger than 1 while most of the enrichment ratios for sand were
-
Effects of Rainfall Intensity and Slope Gradient on Steep Colluvial Deposit Erosion in Southeast China
Soil Science Society of America Journal, 2014Co-Authors: Fangshi Jiang, Yanhe Huang, Ming-kuang Wang, Jinshi Lin, Gan ZhaoAbstract:Rainfall intensity and slope gradient are important factors that affect soil erosion; however, contradictory observations have been made due to different experimental conditions and materials. Colluvial Deposits with loose, coarse material and steep slopes are easily erodible, but the erosion mechanism of Colluvial Deposition remains obscure. This work investigated the effects of heavy and storm rainfall intensity and steep slope gradients on the infiltration, runoff, and soil loss of Colluvial soil. The rainfall intensity ranged from 1.00 to 2.33 mm min⁻¹, and the slope gradient ranged from 36 to 84%. The infiltration rates declined sharply in the initial stage, whereas an opposite trend was observed for runoff rates until a steady state was reached after 5 min. Single- and multiple-peak models illustrated the two types of changes for the sediment yield process. The infiltration volume and the coefficient increased with increasing rainfall intensity and decreased with increasing slope, whereas the runoff coefficient decreased with increasing rainfall intensity and increased with increasing slope. Runoff volume and sediment yield increased with increasing rainfall intensity but had a critical slope gradient of 58% and >47%. The sediment concentration increased with increasing rainfall intensity, and first increased and then decreased with increasing slope gradients at rainfall intensities of 1.00 and 1.33 mm min⁻¹ but increased at rainfall intensities of 1.67, 2.00, and 2.33 mm min⁻¹. The findings of this study can be used to clarify the erosion mechanisms in disturbed soils with high coarse particle content.
Alessio Nicosia - One of the best experts on this subject based on the ideXlab platform.
-
comment on rill erosion processes on steep Colluvial Deposit slope under heavy rainfall in flume experiments with artificial rain by f jiang et al
Catena, 2020Co-Authors: Vito Ferro, Alessio NicosiaAbstract:Abstract Since rill flows are characterized by small water depths and steeply sloping channels, the corresponding hydraulic conditions are very different to those which are typically found in channels of streams and rivers. Furthermore, limited information is currently available on the effect of rainfall on flow resistance. The objective of this comment was to investigate the applicability of a recently theoretically deduced rill flow resistance equation, based on a power-velocity profile, using measurements carried out by Jiang et al. for both different slope steepness conditions and rainfall intensity. The relationship between the velocity profile parameter Γ, the channel slope and the flow Froude number was calibrated using the data by Jiang et al. The theoretical approach and the measurements carried out in the investigated conditions allowed to state that a) the Darcy-Weisbach friction factor can be accurately estimated using the proposed theoretical approach, b) the data were supportive of the slope independence hypothesis of rill velocity stated by Govers and c) the Darcy-Weisbach friction factor varies with rainfall intensity.
Ming-kuang Wang - One of the best experts on this subject based on the ideXlab platform.
-
rill erosion processes on a steep Colluvial Deposit slope under heavy rainfall in flume experiments with artificial rain
Catena, 2018Co-Authors: Fangshi Jiang, Ming-kuang Wang, Jinshi Lin, Zhenzhi Zhan, Jialin Chen, Yanhe HuangAbstract:Abstract Understanding rill erosion processes is important in the prediction of soil erosion and the prevention of soil loss. However, limited information is available concerning the impacts of rainfall on rill erosion on steep slopes. Colluvial Deposits with steep slopes make up the packed material underlying the collapsing walls in benggang, which collapse due to hydraulic pressure and gravity. They contain loose materials and large amounts of coarse particles. The objectives of this study were to investigate the impacts of rainfall intensity and slope gradient on the rill erosion process, rill development and rill flow dynamic mechanisms on the steep slopes of Colluvial Deposits. The Colluvial soils were subjected to simulated rainfall in a 5-m2 (5-m by 1-m) flume at heavy rainfall intensities (100, 120, and 140 mm h−1) and on five steep slopes (20, 25, 30, 35, and 40°). Rill erosion contributed significantly to Colluvial slope erosion; on average, rills accounted for 61% of the soil loss, and the effects of slope gradient were greater than those of the rainfall intensity. After rill development, rill density, rill length, width, and depth all significantly increased. Correspondingly, the soil loss rate sharply raised and irregularly fluctuated. Moreover, the collapse of rill heads or sidewalls tended to increase the relative contribution to rill erosion and rill development. The rill flow was characterized by transitional and subcritical flow regimes. The rill flow velocity was the most sensitive hydraulic parameter, and the unit stream power provided the optimal hydrodynamic parameter to characterize the dynamic mechanisms of rill erosion on Colluvial Deposits. The collapse of rill heads or sidewalls could result in negative values for critical shear stress, critical stream power, and critical unit stream power of rill erosion, which were −19 Pa, −5.3 N m−1 s−1, and −0.09 m s−1, respectively. These results provide a better understanding of the mechanism of rill erosion on steep slopes.
-
Sediment selective behaviors of Colluvial Deposit materials on steep slopes and under heavy rainfall conditions in southeastern China
Journal of Soil and Water Conservation, 2018Co-Authors: Fangshi Jiang, Yanhe Huang, Ming-kuang Wang, Jinshi Lin, Gan ZhaoAbstract:Characterizing sediment selectivity during transport will improve understanding of soil erosion processes, but few studies have focused on steep slopes and soil with loose, coarse material. This study examined Colluvial Deposits, which contain loose materials with large amounts of coarse particles. These soils were subjected to simulated rainfall in a 5 m2 (5 m by 1 m) box at heavy rainfall intensities (1, 1.33, 1.67, 2, and 2.33 mm min−1) and on five steep slopes (20°, 25°, 30°, 35°, and 40°). During the experiments, the particle size of the eroded material gradually coarsened, then stabilized and often showed short-term fluctuations as the rainfall progressed. During interrill erosion processes, the sediment became enriched with finer particles because of the low runoff energy of interrill flow; the dominant transport mechanism was the suspension-saltation transport of sediment with a grain size finer than 0.537 mm. However, the sediment was coarser after rill development than before, and increased stream power meant that bed-load transport by rolling of the larger sediment grains (coarser than 0.957 mm) became an increasingly important mechanism; bed-load transport also increased with rainfall intensity, so the particle-size distribution for high-intensity rainfall resembled that of the original soil. Finally, during rill erosion processes, rill bank collapse occured and the original soil contained coarse, heavy particles that could more easily be rolled on steep slopes. These factors could increase the relative importance of bed-load transport. The results of this study have important implications for assessment and modeling of erosion processes in disturbed soils with large amounts of coarse particles.
-
Mulching effects on erosion from steep slopes and sediment particle size distributions of gully Colluvial Deposits
CATENA, 2018Co-Authors: Jinshi Lin, Fangshi Jiang, Ming-kuang Wang, Gaoli Zhu, Jia Wei, Yanhe HuangAbstract:Abstract Mulching is an effective soil conservation practice for permanent gullies in southern China. Knowledge of the sediment characteristics that occur in mulched soils of Colluvial Deposits could improve the utility of mulching for soil conservation. A rainfall simulation experiment was designed to evaluate the effects of mulch on the runoff, erosion, and particle size distribution of eroded sediments. Straw mulch coverage of 0, 25, 50, 75, and 95% was tested with simulated rainfall. The effective particle size distribution of the sediment was compared with the ultimate particle size distribution to investigate the detachment and transport mechanisms involved in sediment mobilization. Mulching delayed the runoff initiation time and reduced the average runoff rate. Compared with bare soil, the increased mulch coverage decreased the soil loss rate by 13.0 to 90.3%. Moreover, the peak sediment concentration decreased from 80 to 200 g L− 1 under the different mulch coverage conditions. The optimal straw application rate was 1.5 to 3.0 Mg ha− 1 in the permanent gully's Deposits. The relationship between instantaneous kinetic energy of rainfall and the proportion of effective clay- and sand-sized particles was well represented using an exponential equation. The effective clay-sized sediments under the different mulch coverage conditions were 2 to 4 times more common than those of the original soil, although there were only 13.9% sand-sized particles in the sediment when the mulch coverage was 95%. The silt-sized sediment was transported as primary particles under the different mulch coverage conditions. The effective to ultimate ratio of silt-sized particles fluctuated around 1. There were depletions of clay and silt in the Colluvial Deposit soil with mulch cover, and the enrichment ratios of clay and silt were larger than 1 while most of the enrichment ratios for sand were
-
Effects of Rainfall Intensity and Slope Gradient on Steep Colluvial Deposit Erosion in Southeast China
Soil Science Society of America Journal, 2014Co-Authors: Fangshi Jiang, Yanhe Huang, Ming-kuang Wang, Jinshi Lin, Gan ZhaoAbstract:Rainfall intensity and slope gradient are important factors that affect soil erosion; however, contradictory observations have been made due to different experimental conditions and materials. Colluvial Deposits with loose, coarse material and steep slopes are easily erodible, but the erosion mechanism of Colluvial Deposition remains obscure. This work investigated the effects of heavy and storm rainfall intensity and steep slope gradients on the infiltration, runoff, and soil loss of Colluvial soil. The rainfall intensity ranged from 1.00 to 2.33 mm min⁻¹, and the slope gradient ranged from 36 to 84%. The infiltration rates declined sharply in the initial stage, whereas an opposite trend was observed for runoff rates until a steady state was reached after 5 min. Single- and multiple-peak models illustrated the two types of changes for the sediment yield process. The infiltration volume and the coefficient increased with increasing rainfall intensity and decreased with increasing slope, whereas the runoff coefficient decreased with increasing rainfall intensity and increased with increasing slope. Runoff volume and sediment yield increased with increasing rainfall intensity but had a critical slope gradient of 58% and >47%. The sediment concentration increased with increasing rainfall intensity, and first increased and then decreased with increasing slope gradients at rainfall intensities of 1.00 and 1.33 mm min⁻¹ but increased at rainfall intensities of 1.67, 2.00, and 2.33 mm min⁻¹. The findings of this study can be used to clarify the erosion mechanisms in disturbed soils with high coarse particle content.