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1.
Erosion caused by concentrated flows in agricultural areas is responsible for important soil losses, and rapid sediment transfer through the channel network. The main factors controlling concentrated flow erosion rates include the erodibility of soil materials, soil use and management, climate and watershed topography. In this paper, two topographic indices, closely related to mathematical expressions suggested by different authors, are used to characterize the influence of watershed topography on gully erosion. The AS1 index is defined as the product of the watershed area and the partial area‐weighted average slope. The AS2 index is similar to the AS1 but uses the swale slope as the weighting factor. Formally, AS2 is the product of the watershed area and the length‐weighted average swale slope. From studies made using different ephemeral gully erosion databases, it is shown that a high correlation consistently exists between the topographic indices and the volume of eroded soil. The resulting relationships are therefore useful to assess soil losses from gully erosion, to identify the most susceptible watersheds within large areas, and to compare the susceptibility to gully erosion among different catchments. This information is also important in studying the response of natural drainage network systems to different rainfall inputs. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

2.
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   

3.
ROCESSES OF EPHEMERAL GULLY EROSION   总被引：2，自引：0，他引：2  
IINTRoDUCTIONEphemeralgulliesaresmallerosionalchannelsonagriculturalIandscapescausedbytheconcentrationofoverlandflowtypicallybetweentwoopposingslopes(ahollow),oftenformedduringasingIerainfaIlevent.Sincethescouredsoilvolumeisnotverylargewithinthesegullies,farmerscaneasilyrefillthem.Ingeneral,ephemeralgulliescanreappearatornearthesamelocationonayearlybasisbecausethesurfacetopograPhyofthefielddoesnotchangeappreciably.Mostephemeralgulliesoccuroncultivatedfieldswithhighlyerodiblesoils,withlit…  相似文献   

4.
Although there is much evidence of intense soil erosion in cultivated areas of Navarre (Spain), information on it is currently scarce. Rill and ephemeral gully volumes can be used as a guide to minimum erosion rates. With the main purpose of determining the annual soil loss rates in cultivated areas of central Navarre, a detailed assessment of rainfall and of rill and gully erosion was made in 19 small catchments from October 1999 to September 2001. Seventeen of them were randomly selected, and were cultivated with winter cereals, vineyards or sunflowers. The other two catchments were selected to represent partially uncultivated lands abandoned for ten years. Channel cross‐sections were measured by using a 1‐m‐wide micro‐topographic profile meter, describing 632 cross‐sections and processing information from 31 600 pins. Erosive events happened every year in the three study areas. For cereal catchments, soil losses occurred in only one or two rainfall events each year, usually at the end of autumn and in some summers, with high erosion rates (0·20–11·50 kg m?2 a?1). In vineyards, soil losses occurred several times per year, and in any season. This is attributed to the small percentage of surface covered by the crop throughout the year. Again, high erosion rates were found (0·33–16·19 kg m?2 a?1), with ephemeral gully erosion causing more loss than rill erosion. No‐till is proposed as an effective conservation measure. From this large data set, it can be stated that rill erosion and ephemeral gully erosion are widespread in Mediterranean regions, and that much more attention should be paid to the problem. Abandoned fields showed very high erosion rates (16·19 kg m?2 a?1 on average), suggesting that the abandonment of marginal lands without implementing any erosion control can lead to severe erosion rates. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

5.
Few models can predict ephemeral gully erosion rates (e.g. CREAMS, EGEM). The Ephemeral Gully Erosion Model (EGEM) was specifically developed to predict soil loss by ephemeral gully erosion. Although EGEM claims to have a great potential in predicting soil losses by ephemeral gully erosion, it has never been thoroughly tested. The objective of this study was to evaluate the suitability of EGEM for predicting ephemeral gully erosion rates in Mediterranean environments. An EGEM‐input data set for 86 ephemeral gullies was collected: detailed measurements of 46 ephemeral gullies were made in intensively cultivated land in southeast Spain (Guadalentin study area) and another 40 ephemeral gullies were measured in both intensively cultivated land and abandoned land in southeast Portugal (Alentejo study area). Together with the assessment of all EGEM‐input parameters, the actual eroded volume for each ephemeral gully was also determined in the field. A very good relationship between predicted and measured ephemeral gully volumes was found (R2 = 0·88). But as ephemeral gully length is an EGEM input parameter, both predicted and measured ephemeral gully volumes have to be divided by this ephemeral gully length in order to test the predictive capability of EGEM. The resulting relationship between predicted and measured ephemeral gully cross‐sections is rather weak (R2 = 0·27). Therefore it can be concluded that EGEM is not capable of predicting ephemeral gully erosion for the given Mediterranean areas. A second conclusion is that ephemeral gully length is a key parameter in determining the ephemeral gully volume. Regression analysis shows that a very significant relation between ephemeral gully length and ephemeral gully volume exists (R2 = 0·91). Accurate prediction of ephemeral gully length is therefore crucial for assessing ephemeral gully erosion rates. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

6.
Concentrated flow erosion is the dominant form of winter erosion in northern France. This study correlates the ephemeral rill and gully volumes measured in 20 cultivated catchments (4–95 ha) for three consecutive winters with the size of the potential runoff-contributing areas. These areas were identified by characterizing soil surface state through crust development stage, importance of surface wheel tracks and roughness grade. A single and significant relationship was found between the size of runoff-contributing areas, estimated by this criterion, and the rill and gully volumes. This identified the proportion of the catchment area occupied by fields with a degraded surface structure as the main factor controlling the variability of erosion in a context of concentrated flow erosion on cultivated land. The extension of degraded areas was shown to be controlled by dynamic interactions between weather, land occupation and soil physical properties. This criterion accounts for the uneven distribution of rainfall in space and time. Morphological factors, such as talweg length and slope, are believed to determine part of the residual variability.  相似文献   

7.
Although there is much evidence of intense soil erosion in cultivated areas of Navarre （Spain）, scarce information currently is available regarding soil loss rates, the spatial and temporal distribution of erosion, and the factors controlling these processes. Rills and ephemeral gullies are frequently responsible for a high percentage of total soil erosion, and these features can be considered a good approximation for the minimum erosion rates. With the main purpose of determining the annual soil loss rates in cultivated areas of Central Navarre, a detailed assessment of rainfall and rill and gully erosion was made in 19 small watersheds cultivated with winter grains or vineyards. The study period spanned from 1995 to 2001. For cereal watersheds, soil losses were caused by only one or two rainfall events each year. High erosion rates were observed （0.20-11.50 kg/m^2 per year）. In vineyards, soil losses were caused by several rainfall events each year, occurring year round. High erosion rates were observed in these vineyards （0.33 y 16.19 kg/m^2 per year）. No erosion was observed in those cultivated watersheds with no-till practices. It can be concluded that rill and ephemeral gully erosion can be very significant in Mediterranean regions, and much more attention should be paid to the problem.  相似文献   

8.
Knowledge of soil loss rates by water erosion under given climate, soil, topography, and management conditions is important for establishing soil conservation schemes. In Galicia, a region with Atlantic climatic conditions in Spain, field observations over the last decade indicate that interrill, rill and ephemeral gully erosion may be an important sediment source. The aim of this work was to assess concentrated erosion rates, describe types of rills and ephemeral gullies and determine their origin, evolution and importance as sediment sources. Soil surface state and concentrated flow erosion were surveyed on medium textured soils, developed over basic schists of the Ordenes Complex series (Coruña province, Spain) from 1997 to 2006. Soil surface state was characterized by crust development, tillage features and roughness degree. Soil erosion rate was directly measured in the field. Concentrated flow erosion took place mainly on seedbeds and recently tilled surfaces in late spring and by autumn or early winter. During the study period, erosion rates were highly variable and the following situations could be distinguished: (a) no incision or limited rill incision, i.e. below 2 Mg ha?1 year?1; (b) generalized rill and ephemeral gully incision in the class of mean values between 2·5 and 6·25 Mg ha?1 year?1, this was the most common erosion pattern; and (c) heavy erosion as observed during an extremely wet winter period, between October 2000 and February 2001, with erosion figures that may be about ten orders of magnitude higher, up to 55–60 Mg ha?1 year?1. Therefore, low values of soil losses are dominant, but also large values of rill and ephemeral gully erosion occurred during the study period. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

9.
ＰＨＹＳＩＣＡＬＰＲＯＣＥＳＳＢＡＳＥＤＳＯＩＬＥＲＯＳＩＯＮＭＯＤＥＬＩＮＡＳＭＡＬＬＷＡＴＥＲＳＨＥＤＩＮＴＨＥＨＩＬＬＹＬＯＥＳＳＲＥＧＩＯＮ１ＣＡＩＱｉａｎｇｇｕｏ２ＡＢＳＴＲＡＣＴＡｐｈｙｓｉｃａｌｐｒｏｃｅｓｂａｓｅｄｐｅｒｓｔｏｒｍ...  相似文献   

10.
Abstract

The investigation of basins for planning soil conservation requires a selective approach to identify smaller hydrological units, which would be suitable for more efficient and targeted conservation management programmes. One criterion, generally used to determine the vulnerability of catchments to erosion, is the sediment yield of a basin. In India, sediment yield data are generally not collected for smaller sub-catchments and it becomes difficult to identify the most vulnerable areas for erosion that can be treated on a priority basis. An index-based approach, based on the surface factors mainly responsible for soil erosion, is suggested in this study. These factors include soil type, vegetation, slope and various catchment properties such as drainage density, form factor, etc. The method is illustrated with a case study of sub-catchments immediately upstream of the Ukai Reservoir located on the River Tapi in Gujarat State, India. The area is divided into 16 watersheds and different soil, vegetation, topography and morphology-related parameters are estimated separately for each watershed. Satellite data are used to evaluate the soil and vegetation indices, while a GIS system is used to evaluate the topography and morphology-related indices. The integrated effect of all the parameters is evaluated to find different areas vulnerable to soil erosion. Two watersheds were identified as being most susceptible to soil erosion. Based on the integrated index, a priority rating of the watersheds for soil conservation planning is recommended.  相似文献   

11.
G. V. Wilson 《水文研究》2013,27(14):2032-2040
The internal erosion of soil pipes can induce pipe collapses that affect soil erosion processes and landform evolution. The objective of this study was to determine the spatial distribution of pipe collapses in agricultural fields of Goodwin Creek watershed. Ground survey was carried out to detect pipe collapses, and the location, size and surface elevation was measured with differential GPS. A total of 143 of the 145 pipe collapses were found in cropland, and the density was approximately 0.58 collapses per hectare. The spatial distribution of pipe collapses was not uniform as pipe collapses were concentrated in the flat alluvial plains where the land use was dominated by cropland. One of the four parcels had 90% of the pipe collapses with a density of 7.7 collapses per hectare. The mean depth, area and volume of these pipe collapses were 0.12 m, 0.34 m2 and 0.02 m3, respectively, and all these properties exhibited a skewed distribution. The drainage area–slope gradient equation, which has been widely used for erosion phenomenon prediction, did not represent pipe collapses in this study as the coefficient of determination was <0.01. This is clear evidence that subsurface flow is not represented by surface topographic characteristics. The pipe collapses were found to intercept runoff, thereby reducing the slope length factor by 6% and the drainage area by 7%. Both of these factors can reduce the sheet and rill erosion; however, the increased subsurface flow could enhance ephemeral gully erosion. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.  相似文献   

12.
The soil factor is crucial in controlling and properly modeling the initiation and development of ephemeral gullies (EGs). Usually, EG initiation has been related to various soil properties (i.e. sealing, critical shear stress, moisture, texture, etc.); meanwhile, the total growth of each EG (erosion rate) has been linked with proper soil erodibility. But, despite the studies to determine the influence of soil erodibility on (ephemeral) gully erosion, a universal approach is still lacking. This is due to the complex relationship and interactions between soil properties and the erosive process. A feasible soil characterization of EG erosion prediction on a large scale should be based on simple, quick and inexpensive tests to perform. The objective of this study was to identify and assess the soil properties – easily and quickly to determine – which best reflect soil erodibility on EG erosion. Forty‐nine different physical–chemical soil properties that may participate in establishing soil erodibility were determined on agricultural soils affected by the formation of EGs in Spain and Italy. Experiments were conducted in the laboratory and in the field (in the vicinity of the erosion paths). Because of its importance in controlling EG erosion, five variables related to antecedent moisture prior to the event that generated the gullies and two properties related to landscape topography were obtained for each situation. The most relevant variables were detected using multivariate analysis. The results defined 13 key variables: water content before the initiation of EGs, organic matter content, cation exchange capacity, relative sealing index, two granulometric and organic matter indices, seal permeability, aggregates stability (three index), crust penetration resistance, shear strength and an erodibility index obtained from the Jet Test erosion apparatus. The latter is proposed as a useful technique to evaluate and predict soil loss caused by EG erosion. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

13.
Sediment yield is a complex function of many environmental factors including climate,hydrology,vegetation,basin topography,soil types,and land cover.We present a new semi-physical watershed sediment yield model for the estimation of suspended sediment in loess region.This model is composed by three modules in slope,gully,and stream phases.For slope sediment yield,a balance equation is established based on the concept of hydraulic erosion capacity and soil erosion resistance capacity.According to the statistical analysis of watershed characteristics,we use an exponential curve to approximately describe the spatial variability of watershed soil erosion resistance capacity.In gully phase,the relationship between gully sediment concentration and flow velocity is established based on the Bagnold'stream power function.In the stream phase,we assume a linear dependence of the sediment volume in the reach on the weighted sediment input and output.The proposed sediment yield model is operated in conjunction with a conceptual hydrologic model,and is tested over 16 regions including testing grounds,and small,medium and large watersheds in the loess plateau region in the mid-reach of Yellow River.Our results indicate that the model is reasonable in structure and is able to provide a good simulation of sediment generation and transportation processes at both flood event scale and inter-annual time scale.The proposed model is generally applicable to the watersheds with soil texture similar to that of the loess plateau region in the Yellow River basin in China.  相似文献   

14.
This paper predicts the geographic distribution and size of gullies across central Lebanon using a geographic information system (GIS) and terrain analysis. Eleven primary (elevation; upslope contributing area; aspect; slope; plan, profile and tangential curvature; flow direction; flow width; flow path length; rate of change of specific catchment area along the direction of flow) and three secondary (steady‐state; quasi‐dynamic topographic wetness; sediment transport capacity) topographic variables were generated and used along with digital data collected from other sources (soil, geology) to statistically explain gully erosion field measurements. Three tree‐based regression models were developed using (1) all variables, (2) primary topographic variables only and (3) different pairs of variables. The best regression tree model combined the steady‐state topographic wetness and sediment transport capacity indices and explained 80% of the variability in field gully measurements. This model proved to be simple, quick, realistic and practical, and it can be applied to other areas of the Mediterranean region with similar environmental conditions, thereby providing a tool to help with the implementation of plans for soil conservation and sustainable management. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

15.
The objective of this study is to explore in a critical way the potential of high-altitude (stereo) aerial photographs for the assessment of ephemeral gully erosion rates. On 28 May 1995, an intensive rainfall event (30 mm h−1 during 30 min, return period = 3 years) occurred in central Belgium. Ephemeral gullies formed within an area of 218 ha (study area 1) were mapped and measured both in the field and by high-altitude aerial photos taken at the same time. Comparison of these two methods shows that if only one of the two surveying techniques had been used, only 75 per cent of the total ephemeral gully length would have been detected, so that the combination of aerial and field data leads, in fact, to the best possible determination of total gully length within the selected area. A correction factor (C) is proposed, so that the results of an ephemeral gully erosion survey based on high-altitude (stereo) aerial photos can be adjusted for the undetected gullies. Next, a sequential series of high-altitude stereo aerial photographs, taken in six different years, was analysed in order to determine ephemeral gully erosion rates in three selected study areas (study areas 2, 3 and 4). Selection criteria were chosen so that these three areas were similar to study area 1 and representative for the cultivated areas in central Belgium where intense soil erosion regularly occurs. Ephemeral gullies were mapped and their total length was measured from the aerial photos. Using a mean gully cross-section of 0·2635 m2 (determined in study area 1), the average eroded volume is 1·89 m3 ha−1 in six months for study area 1, 0·86 m3 ha−1 in six months for area 2, 1·44 m3 ha−1 in six months for area 3, and 2·37 m3 ha−1 in six months for area 4. According to the correction factor (C), these mean ephemeral gully erosion volumes have to be increased by 44 per cent. The ephemeral gully erosion rates based on high-altitude stereo aerial photos, correspond well with the results of other surveys carried out in the Belgian loess belt. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

16.
Although obvious in the field, the impact of road building on hydrology and gullying in Ethiopia has rarely been analysed. This study investigates how road building in the Ethiopian Highlands affects the gully erosion risk. The road between Makalle and Adwa in the highlands of Tigray (northern Ethiopia), built in 1993–1994, caused gullying at most of the culverts and other road drains. While damage by runoff to the road itself remains limited, off‐site effects are very important. Since the building of the road, nine new gullies were created immediately downslope of the studied road segment (6·5 km long) and seven other gullies at a distance between 100 and 500 m more downslope. The road induces a concentration of surface runoff, a diversion of concentrated runoff to other catchments, and an increase in catchment size, which are the main causes for gully development after road building. Topographic thresholds for gully formation are determined in terms of slope gradient of the soil surface at the gully head and catchment area. The influence of road building on both the variation of these thresholds and the modification of the drainage pattern is analysed. The slope gradient of the soil surface at the gully heads which were induced by the road varies between 0·06 and 0·42 m m?1 (average 0·15 m m?1), whereas gully heads without influence of the road have slope gradients between 0·09 and 0·52 m m?1 (average 0·25 m m?1). Road building disturbed the equilibrium in the study area but the lowering of topographic threshold values for gullying is not statistically significant. Increased gully erosion after road building has caused the loss of fertile soil and crop yield, a decrease of land holding size, and the creation of obstacles for tillage operations. Hence roads should be designed in a way that keeps runoff interception, concentration and deviation minimal. Techniques must be used to spread concentrated runoff in space and time and to increase its infiltration instead of directing it straight onto unprotected slopes. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

17.
Quantifying the extent of soil erosion at a fine spatial resolution can be time consuming and costly; however, proximal remote sensing approaches to collect topographic data present an emerging alternative for quantifying soil volumes lost via erosion. Herein we compare terrestrial laser scanning (TLS), and both unmanned aerial vehicle (UAV) and ground photography (GP) structure‐from‐motion (SfM) derived topography. We compare the cost‐effectiveness and accuracy of both SfM techniques to TLS for erosion gully surveying in upland landscapes, treating TLS as a benchmark. Further, we quantify volumetric soil loss estimates from upland gullies using digital surface models derived by each technique and subtracted from an interpolated pre‐erosion surface. Soil loss estimates from UAV and GP SfM reconstructions were comparable to those from TLS, whereby the slopes of the relationship between all three techniques were not significantly different from 1:1 line. Only for the TLS to GP comparison was the intercept significantly different from zero, showing that GP is more capable of measuring the volumes of very small erosion features. In terms of cost‐effectiveness in data collection and processing time, both UAV and GP were comparable with the TLS on a per‐site basis (13.4 and 8.2 person‐hours versus 13.4 for TLS); however, GP was less suitable for surveying larger areas (127 person‐hours per ha?1 versus 4.5 for UAV and 3.9 for TLS). Annual repeat surveys using GP were capable of detecting mean vertical erosion change on peaty soils. These first published estimates of whole gully erosion rates (0.077 m a?1) suggest that combined erosion rates on gully floors and walls are around three times the value of previous estimates, which largely characterize wind and rainsplash erosion of gully walls. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

18.
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   

19.
This paper reports the results of a field investigation aimed to establish morphological similarity between rills and ephemeral gullies. Rill measurements were made on 14 plots having a surface area of 22–352 m2 located on a 14·9% slope and on a plot 6·0 m wide and 22·0 m long having a uniform 22·0% slope. The plots are located on the experimental station for soil erosion measurements, ‘Sparacia’, of the Agricultural Faculty of Palermo University, in Sicily, Italy. All plots are subjected to natural rainfall. The measurements were made immediately following five events between November 2004 and December 2005. The ephemeral gully measurements were made on a cultivated area of about 120 ha, located in Central Sicily, which is representative of many soil‐crop conditions in the Mediterranean basin. The morphological similarity between rill and ephemeral gully was first tested. Then a power relationship between rill or gully volume and length, theoretically deduced by dimensional analysis and self‐similarity theory, was applied. This power relationship needs a different scale factor for rill and gully measurements. Finally, using two dimensionless groups representative of the channel morphology variables, the analysis showed that a single relationship can be applied to rill and gully measurements. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

20.
Glenn Wilson 《水文研究》2011,25(15):2354-2364
The role of soil pipeflow in ephemeral gully erosion is not well understood. Experiments were conducted on continuous soil pipes to better understand the role of internal erosion of soil pipes and its relation to ephemeral gully development. Soil beds of 140 cm length, 100 cm width and 20 cm depth had a single soil pipe of different initial sizes (2, 4, 6, 8, and 10 mm diameter) extend from a water reservoir to the outlet. Experiments were run on Providence silt loam and Smithdale loam soils under a constant head of 15 cm established for 30 min. Either the tunnel collapsed or the head could not be maintained. Soil pipes that were initially 2 and 4 mm clogged instantaneously at their mouth and did not exhibit flow, whereas, pipes initially ≥ 6 mm enlarged by 268, 397, and 699% on average for the 6, 8, and 10 mm diameters, respectively. Critical shear stress values were found to be essentially zero, and erodibility values gave erosion indexes that were extremely high. The rapid internal erosion resulted in erratic flow and sediment concentrations with periods of no flow as pipes were temporarily clogged followed by surges of high flow and high sediment concentrations. Tensiometers within 6 cm of the soil pipes did not exhibit pressure increases typically associated with pipe clogging. Flow through 10 mm diameter soil pipes exhibited tunnel collapse for both soils tested. Tunnel collapse typically occurred within minutes of flow establishment suggesting that ephemeral gullies could be misinterpreted as being caused by convergent surface flow if observations were made after the runoff event instead of when flow is first established through soil pipes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

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