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1.
For sake of improving our current understanding on soil erosion processes in the hilly–gully loess regions of the middle Yellow River basin in China, a digital elevation model (DEM)-based runoff and sediment processes simulating model was developed. Infiltration excess runoff theory was used to describe the runoff generation process while a kinematic wave equation was solved using the finite-difference technique to simulate concentration processes on hillslopes. The soil erosion processes were modelled using the particular characteristics of loess slope, gully slope, and groove to characterize the unique features of steep hillslopes and a large variety of gullies based on a number of experiments. The constructed model was calibrated and verified in the Chabagou catchment, located in the middle Yellow River of China and dominated by an extreme soil-erosion rate. Moreover, spatio-temporal characterization of the soil erosion processes in small catchments and in-depth analysis between discharge and sediment concentration for the hyper-concentrated flows were addressed in detail. Thereafter, the calibrated model was applied to the Xingzihe catchment, which is dominated by similar soil erosion processes in the Yellow River basin. Results indicate that the model is capable of simulating runoff and soil erosion processes in such hilly–gully loess regions. The developed model are expected to contribute to further understanding of runoff generation and soil erosion processes in small catchments characterized by steep hillslopes, a large variety of gullies, and hyper-concentrated flow, and will be beneficial to water and soil conservation planning and management for catchments dealing with serious water and soil loss in the Loess Plateau.  相似文献   

2.
Drainage network extension in semi‐arid rangelands has contributed to a large increase in the amount of fine sediment delivered to the coastal lagoon of the Great Barrier Reef, but gully erosion rates and dynamics are poorly understood. This study monitored annual erosion, deposition and vegetation cover in six gullies for 13 years, in granite‐derived soils of the tropical Burdekin River basin. We also monitored a further 11 gullies in three nearby catchments for 4 years to investigate the effects of grazing intensity. Under livestock grazing, the long‐term fine sediment yield from the planform area of gullies was 6.1 t ha‐1 yr‐1. This was 7.3 times the catchment sediment yield, indicating that gullies were erosion hotspots within the catchment. It was estimated that gully erosion supplied between 29 and 44% of catchment sediment yield from 4.5% of catchment area, of which 85% was derived from gully wall erosion. Under long‐term livestock exclusion gully sediment yields were 77% lower than those of grazed gullies due to smaller gully extent, and lower erosion rates especially on gully walls. Gully wall erosion will continue to be a major landscape sediment source that is sensitive to grazing pressure, long after gully length and depth have stabilised. Wall erosion was generally lower at higher levels of wall vegetation cover, suggesting that yield could be reduced by increasing cover. Annual variations in gully head erosion and net sediment yield were strongly dependent on annual rainfall and runoff, suggesting that sediment yield would also be reduced if surface runoff could be reduced. Deposition occurred in the downstream valley segments of most gullies. This study concludes that reducing livestock grazing pressure within and around gullies in hillslope drainage lines is a primary method of gully erosion control, which could deliver substantial reductions in sediment yield. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

3.
Growth of a permanent, valley‐bottom gully from 1964 to 2000 was determined annually from survey and sediment‐discharge data and compared with runoff and base?ow discharges. Data were analysed to test the hypothesis that rates of gully growth decay exponentially with time in response to shrinking catchment area caused by gully enlargement. Also, monthly values of growth rates and runoff, averaged over the 36‐year record, were analysed with mass‐wasting data to determine the extent to which colluvium availability affected growth rates seasonally. From 1964 to 2000, the gully volume increased by 9200 m3, accounting for 34 per cent of sediment yield from the watershed. There were tight power‐law relationships between annual growth rates and annual runoff, with runoff exponents of 1·57 and 1·30 for headward and volumetric growth, respectively. Increases in gully length, area, and volume were ?tted successfully assuming an exponential decay in growth rate with time. Rather than being due to a decrease in catchment area, however, the decline in growth rate was caused by a 77 per cent decrease in the ratio of runoff to base?ow, which also widened the gully and reduced the mean slope of its banks. Order‐of‐magnitude seasonal changes in erosion ef?ciency, de?ned as the fraction of stream power used to evacuate sediment from the gully, were roughly correlated with colluvium availability, as indicated by seasonal changes in the number of bank mass‐wasting events. No more than 2·2 per cent of stream power was used to evacuate sediment during any month. This study demonstrates the danger of attributing declining rates of gully growth to a shrinking catchment area if corroborative runoff and base?ow data are not available. Moreover, it illustrates that stream power alone provides only a rough and physically indirect measure of erosion potential. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

4.
Distributed erosion models, which simulate the physical processes of water flow and soil erosion, are effective for predicting soil erosion in forested catchments. Although subsurface flow through multiple pathways is dominant for runoff generation in forested headwater catchments, the process-based erosion model, Geo-spatial interface for Water Erosion Prediction Project(Geo WEPP), does not have an adequate subsurface component for the simulation of hillslope water flow. In the current study, t...  相似文献   

5.
Gully rehabilitation can contribute to catchment management by stabilizing erosion and reducing downstream sediment yields, yet the globally observed responses are variable. Developing the technical basis for gully rehabilitation and establishing guidelines for application requires studies that evaluate individual rehabilitation measures in specific environments. An eight-year field experiment was undertaken to evaluate sediment yield and vegetation responses to several gully rehabilitation measures. The rehabilitation measures aimed to reduce surface runoff into gully head cuts, trap sediment on gully floors and increase vegetation cover on gully walls and floors. The study occurred in a savanna rangeland in northeast Australia. Two gullies were subject to treatments while four gullies were monitored as untreated controls. A runoff diversion structure reduced headcut erosion from 4.3 to 1.2 m2 yr−1. Small porous check dams and cattle exclusion reduced gully total sediment yields by more than 80%, equivalent to a reduction of 0.3 to 2.4 t ha−1 yr−1, but only at catchment areas less than 10 ha. Fine sediment yields (silt and clay) were reduced by 7 and 19% from the two treated gullies, respectively. The porous check dam deposits contained a lower percentage of the fine fraction than the parent soil. Significant regeneration of gully floor vegetation occurred, associated with trapping of organic litter and fine sediment. Increases in vegetation cover and biomass were comprised of native perennial grasses, trees and shrubs. In variable climates, long-term gully rehabilitation will progress during wetter periods, and regress during droughts. Understanding linkages between rehabilitation measures, their hydrologic, hydraulic and vegetation effects and gully sediment yields is important to defining the conditions for their success.  相似文献   

6.
Based on observations of runoff plots and field investigations of gully cross-sections, impacts of various soil and water conservation measures on runoff and sediment yield are analyzed for different rainfall conditions. The results show that antecedent rainfall and rainfall intensity are the main factors affecting the runoff and soil erosion processes. Rainfall events with antecedent rainfall can produce high runoff and sediment yield. Large differences in the characteristics of two rainfall events will result in greater variations of total runoff and sediment yield from the same runoff plot. Under the same soil control measure and rainfall condition, soil and water conservation measures can reduce the impacts of antecedent rainfall and rainfall intensity on runoff and soil erosion. Among various measures, level terrace seems to be the greatest for soil conservation purposes. Combining with engineering measures,Vegetation measures is also effective in controlling runoff and soil erosion. In the initial stage of vegetation enclosure measures, engineering measure is necessary to improve the environment for ecological recovery. Gully head protection can control gully erosion effectively, but the effectiveness of gully head protection would be reduced when rainfall intensity increases. Therefore, the design of a gully head protection structure must be based on local hydrological conditions.  相似文献   

7.
Sediment production, transport and yield were quantified over various timescales in response to rainfall and runoff within an alluvial gully (7 · 8 ha), which erodes into dispersible sodic soils of a small floodplain catchment (33 ha) along the Mitchell River, northern Australia. Historical air photographs and recent global positioning system (GPS) surveys and LiDAR data documented linear increases in gully area and volume, indicating that sediment supply has been relatively consistent over the historic period. Daily time lapse photography of scarp retreat rates and internal erosion processes also demonstrated that erosion from rainfall and runoff consistently supplied fine washload (< 63 µm) sediment in addition to coarse lags of sand bed material. Empirical measurements of suspended sediment concentrations (10 000 to >100 000 mg/L) and sediment yields (89 to 363 t/ha/yr) were high for both Australian and world data. Total sediment yield estimated from empirical washload and theoretical bed material load was dominated by fine washload (< 63 µm). A lack of hysteresis in suspended sediment rating curves, scarp retreat and sediment yield correlated to rainfall input, and an equilibrium channel outlet slope supported the hypothesis that partially or fully transport‐limited conditions predominated along the alluvial gully outlet channel. This is in contrast to sediment supply‐limited conditions on uneroded floodplains above gully head scarps. While empirical data presented here can support future modelling efforts to predict suspended sediment concentration and yield under the transport limiting situations, additional field data will also be needed to better quantify sediment erosion and transport rates and processes in alluvial gullies at a variety of spatial and temporal scales. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

8.
Model predictions concerning the endangerment of on‐site and off‐site damages due to runoff, soil erosion and sedimentation under alternative design and operation policies are of particular importance in recent catchment planning and management. By using the raster‐based model approach, linear landscape elements, such as streets and roads, and their impacts on flow paths are often neglected. Therefore, the aim of this study was to analyse the effects of linear landscape elements on patterns of soil erosion, sediment transport and sedimentation. To accomplish this, roads are considered while determining flow paths. Simulations in the well‐investigated catchment of the Wahnbach River (54 km²) in a low mountain range in Germany were carried out using a combination of different models for hydrology and soil erosion. Although the study focuses on the catchment scale of the Wahnbach River, detailed investigations concerning the sub‐catchment scale (21 ha) were also conducted. The simulation results show that these spatial structures mainly affect the pattern of soil erosion and sedimentation. On the sub‐catchment scale, improved identification of active zones for sediment dynamic becomes possible. On the catchment scale, the predicted runoff is about 20% higher, and sediment outputs were four times larger than predicted when roads were considered. Soil erosion increases by 37% whereas sedimentation is reduced by 29%. The model improvement could not be evaluated on the catchment scale because of the high variability and heterogeneity of land use and soils, but road impacts could be explained by simulations on the sub‐catchment scale. It can be concluded that runoff concentration due to rerouted flow paths leads to lower non‐concentrated and higher concentric‐linear surface runoff. Thus, infiltration losses decline and surface runoff and soil erosion increase because sedimentation is reduced. Further, runoff concentration can cause soil erosion hot spots. In the model concept used in this study, buffering of runoff and sediments on the upslope side of roads and in local depressions adjacent to roads cannot be simulated. Flow paths will only be rerouted because of road impacts, but the temporal ponding of water is not simulated. Therefore, the drastic increase of predicted sediment output due to road impact does not seem to be reliable. However, results indicate that the consideration of roads when determining flow paths enabled more detailed simulations of surface runoff, soil erosion and sedimentation. Thus, progress in model‐based decision‐making support for river catchment planning and management can be achieved. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

9.
SomepeOPlehaverecognizedtheSPatialvariationoflandionnsandgeomorphicPeainthehillyloessregion,NOIthClam(Chenetal.1988).SuchvariationshaVe~linkedtotheverticalzonationofsoilerosionandsedimentproduedoninthisarea(Catetat.1994).HoWeVer,noneOftheStlldiesaPProachtheProbleminaqUantitativemanner.NorweretherelationsbetweensoilerosionPr~sontheoneban4andhydrologicandghgogicalcharacteristicsofthevariouSslopezonesontheother,dearlyestatiIisned.Inaaamon,~stubbesintheareahaveprtridtahotoshowthe~rtanceo…  相似文献   

10.
A three year monitoring programme of gully‐head retreat was established to assess the significance of sediment production in a drainage network that expanded rapidly by gully‐head erosion on the low‐angled alluvio‐lacustrine Njemps Flats in semi‐arid Baringo District, Kenya. This paper discusses the factors controlling the large observed spatial and temporal variation in gully‐head retreat rates, ranging from 0 to 15 m a?1. The selected gullies differed in planform and in runoff‐contributing catchment area but soil material and land use were similar. The data were analysed at event and annual timescales. The results show that at annual timescale rainfall amount appears to be a good indicator of gully‐head retreat, while at storm‐event timescale rainfall distribution has to be taken into account. A model is proposed, including only rainfall (P) and the number of dry days (DD) between storms: which explains 56 per cent of the variation in retreat rate of the single‐headed gully of Lam1. A detailed sediment budget has been established for Lam1 and its runoff‐contributing area (RCA). By measuring sediment input from the RCA, the sediment output by channelized flow and linear retreat of the gully head for nine storms, it can be seen that erosion shifts between different components of the budget depending on the duration of the dry period (DD) between storms. Sediment input from the RCA was usually the largest component for the smaller storms. The erosion of the gully head occurred as a direct effect of runoff falling over the edge (GHwaterfall) and of the indirect destabilization of the adjacent walls by the waterfall erosion and by saturation (GHmass/storage). The latter component (GHmass/storage) was usually much larger that the former (GHwaterfall). The sediment output from the gully was strongly related to the runoff volume while the linear retreat, because of its complex behaviour, was not. Overall, the results show that the annual retreat is the optimal timescale to predict retreat patterns. More detailed knowledge about relevant processes and interactions is necessary if gully‐head erosion is to be included in event‐based soil erosion models. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

11.
Gully erosion is a major environmental problem, posing significant threats to sustainable development. However, insights on techniques to prevent and control gullying are scattered and incomplete, especially regarding failure rates and effectiveness. This review aims to address these issues and contribute to more successful gully prevention and control strategies by synthesizing the data from earlier studies. Preventing gully formation can be done through land use change, applying soil and water conservation techniques or by targeted measures in concentrated flow zones. The latter include measures that increase topsoil resistance and vegetation barriers. Vegetation barriers made of plant residues have the advantage of being immediately effective in protecting against erosion, but have a short life expectancy as compared to barriers made of living vegetation. Once deeply incised, the development of gullies may be controlled by diverting runoff away from the channel, but this comes at the risk of relocating the problem. Additional measures such as headcut filling, channel reshaping and headcut armouring can also be applied. To control gully channels, multiple studies report on the use of check dams and/or vegetation. Reasons for failures of these techniques depend on runoff and sediment characteristics and cross-sectional stability and micro-environment of the gully. In turn, these are controlled by external forcing factors that can be grouped into (i) geomorphology and topography, (ii) climate and (iii) the bio-physical environment. The impact of gully prevention and control techniques is addressed, especially regarding their effect on headcut retreat and network development, the trapping of sediment by check dams and reduction of catchment sediment yield. Overall, vegetation establishment in gully channels and catchments plays a key role in gully prevention and control. Once stabilized, gullies may turn into rehabilitated sites of lush vegetation or cropland, making the return on investment to prevent and control gullies high. © 2020 John Wiley & Sons, Ltd.  相似文献   

12.
ＰＨＹＳＩＣＡＬＰＲＯＣＥＳＳＢＡＳＥＤＳＯＩＬＥＲＯＳＩＯＮＭＯＤＥＬＩＮＡＳＭＡＬＬＷＡＴＥＲＳＨＥＤＩＮＴＨＥＨＩＬＬＹＬＯＥＳＳＲＥＧＩＯＮ１ＣＡＩＱｉａｎｇｇｕｏ２ＡＢＳＴＲＡＣＴＡｐｈｙｓｉｃａｌｐｒｏｃｅｓｂａｓｅｄｐｅｒｓｔｏｒｍ...  相似文献   

13.
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14.
MODELING EPHEMERAL GULLY EROSION FOR CONSERVATION PLANNING   总被引：9，自引：0，他引：9  
1INTRODUCTIONEphemeral gully erosion,which is caused by concentrated flow within cultivated farm fields,is distinct from rill erosion.Ephemeral gully erosion is also distinct from gully erosion in permanent,deep,incised channels,formed by headcuts moving upstream.Ephemeral gully erosion is often overlooked.It is not estimated with rill-interrill erosion prediction technology such as the Revised Universal Soil Loss Equation(Renard et al.,1997),and it is often not measured in field survey…  相似文献   

15.
Climate change is expected to effect storm runoff and erosion processes in Mediterranean watersheds at multiple spatial scales. Models are typically applied to estimate these impacts; however, the scarcity of spatially distributed data for parameterization, calibration and validation often prevents application of these models, particularly for larger catchments. This report, the first part of a two‐part article, presents an application and evaluation of the MEFIDIS model for two Mediterranean meso‐scale watersheds (115 and 290 km2) in a data‐scarce environment. A multi‐scale assessment method was used that combines quantitative validation and qualitative evaluation, consisting of three steps: (1) calibration at the small (field) scale using results from rainfall simulation experiments; (2) calibration and validation for catchment‐scale results while changing catchment‐scale parameters only (channel roughness and a parameter controlling the distribution of saturated areas); and (3) qualitative evaluation of within‐watershed erosion processes using empirical estimates of sediment delivery ratio and gully location. The results indicate that calibrating MEFIDIS at the field scale can provide reasonable results for catchment runoff and sediment export and for within‐watershed erosion processes. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

16.
A typical gully sub-basin with a complex geomorphological form is used to do a model test of gravity erosion of loess by considering the sequence of slopes in a prototype gully creating a sequence of underlying surface forms in the upper reaches. The results show that the runoff from heavy rainfall is the main external force for the erosion of loess, and also is an important influencing factor to stimulate and intensify the development of gravity erosion. The soil structure and the height of the...  相似文献   

17.
In Mediterranean mountain agroecosystems, soil erosion associated with the development of ephemeral gullies is a common environmental problem that contributes to a loss of nutrient-rich topsoil. Little is known about the influence of ephemeral gully erosion on particle size distribution and its effect on soil organic (SOC) and inorganic (SIC) carbon among different sized soil particles in agricultural soils. In this study, laboratory tests were conducted using velocity settling tube experiments to examine the effects of erosion on sediment particle size distributions from an incised ephemeral gully, associated with an extreme event (235 mm). We also consider subsequent deposition on an alluvial fan in order to assess the distribution of SOC and SIC concentrations and dissolved carbon before and after the extreme event. Soil fractionation was carried out on topsoil samples (5 cm) collected along an ephemeral gully in a cultivated field, located in the lower part of a Mediterranean mountain catchment. The results of this study showed that the sediment transported downstream by runoff plays a key role in the particle size distribution and transportability of soil particles and associated carbon distribution in carbonate rich soils. The eroding sediment is enriched in clay and silt-sized particles at upslope positions with higher SOC contents and gradually becomes coarser and enriched in SIC at the end of the ephemeral gully because the finest particles are washed-out of the study field. The extreme event was associated with an accumulation of dissolved organic carbon at the distal part of the depositional fan. Assessment of soil particle distribution using settling velocity experiments provides basic information for a better understanding of soil carbon dynamics in carbonate rich soils. Processes of soil and carbon transport and relationships between soil properties, erodibility and aggregate stability can be helpful in the development of more accurate soil erosion models. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.  相似文献   

18.
A simple field‐based monitoring programme was established in a small catchment (area 4·6 km2) to find the rates of gully erosion in the Siwalik Hills, Nepal. The rates are used to estimate the amount of sediment produced by gully erosion in the catchment. Three large and active gullies were selected with areas ranging from 0·44 to 0·78 ha. Aerial photographs taken in 1964, 1978 and 1992 were ortho‐rectified and used to study the dynamics of gully heads. The same gullies were also monitored manually using an orthogonal reference system fixed by erosion pins around the gully heads. Results from the aerial photos indicated that the gullies expanded remarkably over the period from 1964 to 1992, by 34 to 58 per cent. Head‐retreat rates during that period were 0·48, 0·55 and 0·73 m a?1 and average annual sediment evacuation was estimated as 2534 ± 171, 959 ± 60 and 2783 ± 118 m3 a?1 for the three gullies respectively. From the field measurement, estimated volumes were found to vary from 731 ± 57 to 2793 ± 201 m3 a?1 over the monitoring period of two years. It was also found that the gullies produce sediment which accounts for up to 59 per cent of the sediment produced from surface erosion in the headwater catchment. The findings are useful for planning and executing appropriate control measures and constructing a sediment hazard map at the catchment scale. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

19.
Shrink–swell soils, such as those in a Mediterranean climate regime, can cause changes in terms of hydrological and erosive responses because of the changing soil water storage conditions. Only a limited number of long‐term studies have focused on the impacts on both hydrological and erosive responses and their interactions in an agricultural environment. In this context, this study aims to document the dynamics of cracks, runoff and soil erosion within a small Mediterranean cultivated catchment and to quantify the influence of crack processes on the water and sediment supplied to a reservoir located at the catchment outlet using water and sediment measurements at a cultivated field outlet as baseline. Detailed monitoring of the presence of topsoil cracks was conducted within the Kamech catchment (ORE OMERE, Tunisia), and runoff and suspended sediment loads were continuously measured over a long period of time (2005–2012) at the outlets of a field (1.32 ha) and a catchment (263 ha). Analysis of the data showed that topsoil cracks were open approximately half of the year and that the rainfall regime and water table level conditions locally control the seasonal cracking dynamics. Topsoil cracks appeared to seriously affect the generation of runoff and sediment concentrations and, consequently, sediment yields, with similar dynamics observed at the field and catchment outlets. A similar time lag in the seasonality between water and sediment delivery was observed at these two scales: although the runoff rates were globally low during the presence of topsoil cracks, most sediment transport occurred during this period associated with very high sediment concentrations. This study underlines the importance of a good prediction of runoff during the presence of cracks for reservoir siltation considerations. In this context, the prediction of cracking effects on runoff and soil erosion is a key factor for the development of effective soil and water management strategies and downstream reservoir preservation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

20.
In the region of the basaltic plateau in Southern Brazil, problems of runoff and erosion on the deep ferrallitic soils are becoming increasingly recognized. Land use change from conventional tillage using disk plough to no‐tillage on residues without terracing occurred at the beginning of the 1990s and it spread very quickly. Measurements of runoff and sediment concentrations on 1 m2 plots receiving natural rainfall and simulated rainfall under different crops with different stages of growth and different tillage systems, field surveys and measurements of rills and gullies in nested experimental catchments indicate a relative decrease of runoff on slopes but an increase of subsurface flow, and a marked decrease of sheet and rill erosion and soil loss from plot to catchment scales. Nevertheless, the extension of parts of the gully system is still continuing, strongly influenced by extreme rainfall. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

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