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1.
SomepeOPlehaverecognizedtheSPatialvariationoflandionnsandgeomorphicPeainthehillyloessregion,NOIthClam(Chenetal.1988).SuchvariationshaVe~linkedtotheverticalzonationofsoilerosionandsedimentproduedoninthisarea(Catetat.1994).HoWeVer,noneOftheStlldiesaPProachtheProbleminaqUantitativemanner.NorweretherelationsbetweensoilerosionPr~sontheoneban4andhydrologicandghgogicalcharacteristicsofthevariouSslopezonesontheother,dearlyestatiIisned.Inaaamon,~stubbesintheareahaveprtridtahotoshowthe~rtanceo…  相似文献   

2.
A one‐dimensional uncoupled model governed by this research is a physics‐based modelling of the rainfall‐runoff induced erosion process. The presented model is composed of three parts of a three‐dimensional (3D) hillslope geometry, a nonlinear storage (kinematic wave) model for hillslope hydrological response, and an unsteady physically based surface erosion model. The 3D hillslope geometry model allows describing of the hillslope morphology by defining their plan shape and profile curvature. By changing these two topographic parameters, nine basic hillslope types are derived. The modelling of hillslope hydrological response is based on a flow continuity equation as the relation of discharge and flow depth is passed on kinematic wave approximation. The erosion model is based on a mass conservation equation for unsteady flow. The model assumes that suspended sediment does not affect flow dynamics. The model also accounts for the effect of flow depth plus loose soil depth on soil detachment. The presented model was run for two different precipitations, slope content, and length, and results were plotted for sediment detachment/deposition rate. Based on the obtained results, in hillslopes with convex and straight profile curvatures, sediment detachment only occurred in the whole length of the hillslope. However, in concave ones, sediment detachment and deposition only occurred together in hillslope. The hillslopes with straight profiles and convergent plans have the highest rate of detachment. Also, results show that most detachment rates occur in convex profile curvatures, which are about 15 times more than in straight profiles. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

3.
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   

4.
The Southern U.S. Piedmont ranging from Virginia to Georgia underwent severe gully erosion over a century of farming mainly for cotton (1800s–1930s). Although tree succession blanketed much of this region by the middle 20th century, gully erosion still occurs, especially during wet seasons. While many studies on gully erosion have focused on soil loss, soil carbon exchange, and stormwater response, the impacts on soil moisture, groundwater, and transpiration remain under-studied. Using a newly developed 2D hydrologic model, this study analyzes the impacts of gully erosion on hillslope hydrologic states and fluxes. Results indicate that increases in gully incision lead to reduction in groundwater table, root zone soil moisture, and transpiration. These reductions show seasonal variations, but the season when the reduction is maximum differs among the hydrologic variables. Spatially, the impacts are generally the greatest near the toe of the hillslope and reduce further away from it, although the reductions are sometimes non-monotonic. Overall, the impacts are larger for shallow gully depths and diminish as the incision goes deeper. Lastly, the extent of impacts on a heterogeneous hillslope is found to be very different with respect to a homogeneous surrogate made of dominant soil properties. These results show that through gully erosion, the landscape not only loses soil but also a large amount of water from the subsurface. The magnitude of water loss is, however, dependent on hydrogeologic and topographic configuration of the hillslope. The results will facilitate (a) mapping of relative susceptibility of landscapes to gullying, (b) understanding of the impacts of stream manipulations such as due to dredging on hillslope eco-hydrology, (c) prioritization of mitigation measures to prevent gullying, and (d) design of observation campaigns to assess the impacts of gullying on hydrologic response.  相似文献   

5.
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   

6.
FORMATION AND EROSION PROCESSES OF THE LOESS PLATEAU   总被引：2，自引：0，他引：2  
IPROCESSANDZONINGOFLOESSACCUMULATIONLoessisatypicalkindofaeoliansediment,theprocessesofitsgeomorphicformationcanbesummarizedasfollows.l.lWell-distributedDustFalloutfromHighAltitudeThedustisdefinedasthefineparticles(<0.1mm)whichcanbeliftedandcarriedupasdustcloudsintheaiLIftheoriginallandsurfaceofaregionisanevenhighlandsurroundedbyriversandgullies,thefallingdustremainedonthesurfaceofthisevenhighland,butthedustfallingonslopesoftheriverandgullieswastransportedoutoftheregion.Onthet…  相似文献   

7.
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   

8.
It has been long hypothesized that topography, as well as climate and rock strength, exert first order controls on erosion rates. Here we use detrital cosmogenic 10Be from 50 basins, ranging in size from 1 to 150 km2, to measure millennial erosion rates across the San Gabriel Mountains in southern California, where a strong E–W gradient in relief compared to weak variation in precipitation and lithology allow us to isolate the relationship between topographic form and erosion rate. Our erosion rates range from 35 to 1100 m/Ma, and generally agree with both decadal sediment fluxes and long term exhumation rates inferred from low temperature thermochronometry. Catchment-mean hillslope angle increases with erosion rate until ～ 300 m/Ma, at which point slopes become invariant with erosion rate. Although this sort of relation has been offered as support for non-linear models of soil transport, we use 1-D analytical hillslope profiles derived from existing soil transport laws to show that a model with soil flux linear in slope, but including a slope stability threshold, is indistinguishable from a non-linear law within the scatter of our data. Catchment-mean normalized channel steepness index increases monotonically, though non-linearly, with erosion rate throughout the San Gabriel Mountains, even where catchment-mean hillslope angles have reached a threshold. This non-linearity can be mostly accounted for by a stochastic threshold incision model, though additional factors likely contribute to the observed relationship between channel steepness and erosion rate. These findings substantiate the claim that the normalized channel steepness index is an important topographic metric in active ranges.  相似文献   

9.
The aim of this study was to investigate how the spatial distribution of grass influenced run-off and erosion from a hillslope with loess and cinnamon soils in the rocky area of Northern China. We set up a trial to test the two soils with different treatments, including bare soil (BS), grass strips on the upper (UGS) and lower (DGS) parts of the slope, grass cover over the entire slope (GS), and a grass carpet on the lower part of the slope (GC), under simulated rainfall conditions. The results showed that the run-off coefficients for the loess and cinnamon soils decreased by between 4% and 20% and by between 2% and 37%, respectively, when covered with grass. Grass spatial distribution had little effect on the run-off, but more effect on erosion than vegetation coverage degree. The most effective location of grass cover for decreasing hillslope erosion was at the foot, and the high efficiency was mainly due to controlling of rill formation and sediment deposition. The soil loss from GS, DGS, and GC on the loess and cinnamon soils was between 77% and 93% less and 55% and 80% less, respectively, compared with the loss from BS. However, the soil characteristics had little effect on soil erosion for well-vegetated slopes. The results highlight the importance of vegetation re-establishment at the foot of hillslope in controlling soil erosion.  相似文献   

10.
Hillslopes are thought to poorly record tectonic signals in threshold landscapes. Numerous previous studies of steep landscapes suggest that large changes in long‐term erosion rate lead to little change in mean hillslope angle, measured at coarse resolution. New LiDAR‐derived topography data enables a finer examination of threshold hillslopes. Here we quantify hillslope response to tectonic forcing in a threshold landscape. To do so, we use an extensive cosmogenic beryllium‐10 (10Be)‐based dataset of catchment‐averaged erosion rates combined with a 500 km2 LiDAR‐derived 1 m digital elevation model to exploit a gradient of tectonic forcing and topographic relief in the San Gabriel Mountains, California. We also calibrate a new method of quantifying rock exposure from LiDAR‐derived slope measurements using high‐resolution panoramic photographs. Two distinct trends in hillslope behavior emerge: below catchment‐mean slopes of 30°, modal slopes increase with mean slopes, slope distribution skewness decreases with increasing mean slope, and bedrock exposure is limited; above mean slopes of 30°, our rock exposure index increases strongly with mean slope, and the prevalence of angle‐of‐repose debris wedges keeps modal slopes near 37°, resulting in a positive relationship between slope distribution skewness and mean slope. We find that both mean slopes and rock exposure increase with erosion rate up to 1 mm/a, in contrast to previous work based on coarser topographic data. We also find that as erosion rates increase, the extent of the fluvial network decreases, while colluvial channels extend downstream, keeping the total drainage density similar across the range. Our results reveal important textural details lost in 10 or 30 m resolution digital elevation models of steep landscapes, and highlight the need for process‐based studies of threshold hillslopes and colluvial channels. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

11.
G. R. Hancock  K. G. Evans 《水文研究》2006,20(14):2935-2951
Gullying is a significant process in the long‐term dynamics and evolution of both natural and rehabilitated (i.e. post‐mining) landscapes. From a landscape management perspective it is important that we understand gully initiation and development, as it is well recognized that catchment disturbance can result in the development of gullies that can be very difficult to rehabilitate. This study examines gully position using geomorphic statistics relating to features such as depth, width and length in a catchment undisturbed by European activity in the Northern Territory, Australia. The results demonstrate that gullying occurs throughout the catchment and that a slope–area threshold does not exist and that gully position broadly follows the catchment area–slope relationship. Simple relationships relating catchment area and slope to gully depth, width and length provide poor results, despite these relationships having been found to apply for ephemeral gullies in cropland. The results suggest that gully initiation thresholds are low as a result of an enhanced fire regime. A threshold model for gully position that uses catchment area and slope to switch between gully and hillslope was evaluated and found broadly to capture gully position. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

12.
李伊菲  石耀霖  张怀 《地球物理学报》1954,63(10):3740-3750
量化分析构造、侵蚀与气候之间的相互作用关系是现代地球动力学的前沿.断层陡崖是伸展构造环境中的一种常见地貌特征,是构造与地表过程密切耦合作用下演化的结果.断层崖面形态各异,如断层陡坎、断层三角面和断层梯形面等.本文基于数值模拟方法,对断层滑动速率、断层滑动周期、河流下切系数、山坡蠕移系数等关键性控制因素对断层崖形态和几何特征的影响进行了系统分析,主要结论为：依据参数空间的动力学对比模拟结果,可以将断层陡崖分为三个主要类型,即沟壑型、断层三角面型和尖锥型;断层陡崖的最终形态主要受地表演化过程（即河流下切、山坡蠕移）的控制;三角面型陡崖的高度和宽度随时间增大,但坡度角在演化过程中基本不变,其几何特征主要受控于断层滑动速率,且在相同的气候和岩性条件下,与断层滑动速率呈正相关;在十万年时间尺度下,断层滑动周期与三角面的形态和几何特征基本无关.断层滑动速率与三角面坡度角间的正相关关系可用于解释观测数据的统计结果,如希腊和保加利亚的观测数据.  相似文献   

13.
STUDY ON THE DYNAMIC PROCESS OF RILL EROSION OF LOESS SLOPE SURFACE   总被引：3，自引：0，他引：3  
1 mTRODUCTIONAs a woridwide concem, excessive water erosion induces land degradation, causes losses of plantnutrients, and Ieads to off site enVironmental problems such as sedimentahon streams and reservoirs. mllerosion, which results from concentraed flow in a lindted and confined space, plays imPortant roles inthe erosion systCm on uPland areas. Data listed in Table l show its contribution and imPoftance to thetOtal slope soil losses. In the last decades, stodies on the physical mecha…  相似文献   

14.
I. INTRODUCTIONSumming up recent research achievements, Huang (1993) pointed out that the capaciucs ordetachment and transport by rill now were much greater than tboso by rain drop impact and sheet now. soil erosion by water on upper slope area is frcquenhy discussed interms of interrill and rill erosional sub--processes. Compared with rill erosion, interrlll erosion contributes a very small proportion to the sediment transported downwards (Foster,1982). Field experiments conducted by Ca…  相似文献   

15.
1 INTRODUCTION An important goal of geomorphology is to understand the dynamics of landform evolution, and within geomorphology, the development of slopes has long been of great interest to modern and classical scholars (Gilbert, 1877; Davis, 1898; Penck, 1972; Bryan, 1940; Carson and Kirkby, 1972; Chorley et al., 1984; Abrahams et al., 1985; Selby, 1993). Accompanied with slope evolution, soil, water, and nutrients run off at the same time. All these earth surface processes have great…  相似文献   

16.
Excessive soil erosion and deposition is recognised as a significant land degradation issue. Quantifying soil erosion and deposition is a non-trivial task. One of these methods has been the mathematical modelling of soil erosion and deposition patterns and the processes that drive them. Here we examine the capability of a landscape evolution model to predict both soil erosion rate and pattern of erosion and deposition. This numerical model (SIBERIA) uses a Digital Elevation Model (DEM) to represent the landscape and calculates erosion and deposition at each grid point in the DEM. To assess field soil redistribution rates (SRR) and patterns the distribution of the environmental tracer 137Cs has been analysed. Net hill slope SRR predicted by SIBERIA (a soil loss rate of 1.7 to 4.3 t ha-1 yr-1) were found to be in good agreement with 137Cs based estimates (2.1 – 3.4 t ha-1 yr-1) providing confidence in the predictive ability of the model at the hillslope scale. However some differences in predicted erosion/deposition patterns were noted due to historical changes in landscape form (i.e. the addition of a contour bank) and possible causes discussed, as is the finding that soil erosion rates are an order of magnitude higher than likely soil production rates. The finding that SIBERIA can approximate independently quantified erosion and deposition patterns and rates is encouraging, providing confidence in the employment of DEM based models to quantify hillslope erosion rates and demonstrating the potential to upscale for the prediction of whole catchment erosion and deposition. The findings of this study suggest that LEMs can be a reliable alternative to complex and time consuming methods such as that using environmental tracers for the determination of erosion rates. The model and approach demonstrates a new approach to assessing soil erosion that can be employed elsewhere. © 2018 John Wiley & Sons, Ltd.  相似文献   

17.
1 INTRODUCTION Erosion caused by ephemeral flows is a frequent phenomenon in nature and contributes to the shape of the landscape. This type of erosion may cause great soil losses in agricultural areas, which are quickly transferred to the watershed outlets through the rill and gully network (Bennett et al., 2000; Poesen et al., 2003). Concentrated flow erosion is controlled by the erodibility of surface materials, climate, soil use and management, and watershed topography. Several metho…  相似文献   

18.
V. Hrissanthou 《水文研究》2006,20(18):3939-3952
The Yermasoyia Reservoir is located northeast of the town of Limassol, Cyprus. The storage capacity of the reservoir is 13·6 × 106 m3. The basin area of the Yermasoyia River, which feeds the reservoir, totals 122·5 km2. This study aims to estimate the mean annual deposition amount in the reservoir, which originates from the corresponding basin. For the estimate of the mean annual sediment inflow into the reservoir, two mathematical models are used alternatively. Each model consists of three submodels: a rainfall‐runoff submodel, a soil erosion submodel and a sediment transport submodel for streams. In the first model, the potential evapotranspiration is estimated for the rainfall‐runoff submodel, and the soil erosion submodel of Schmidt and the sediment transport submodel of Yang are used. In the second model, the actual evapotranspiration is estimated for the rainfall‐runoff submodel, and the soil erosion submodel of Poesen and the sediment transport submodel of Van Rijn are used. The deposition amount in the reservoir is estimated by means of the diagram of Brune, which delivers the trap efficiency of the reservoir. Daily rainfall data from three rainfall stations, and daily values of air temperature, relative air humidity and sunlight hours from a meteorological station for four years (1986–89) were available. The computed annual runoff volumes and mean annual soil erosion rate are compared with the respective measurement data. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

19.
Predicting the location of gully heads in various environments is an important step towards predicting gully erosion rates. So far, field data collection and modelling of topographic thresholds for gully head development has mainly focused on gullies that formed in forested areas, rangelands, pastures and cropland. Such information for gullies in badlands however is very scarce. Therefore, this paper aims to extend the database on gully head topographical thresholds through data collection in a badland area and to improve the prediction of gully heads forming at sites with a very low erosion resistance value. For this, we chose a badland site located in central Italy that is characterized by biancana forms and both active and dormant gullies. The definition of the conditions under which present‐day gully heads developed allowed a better modelling of the gully head threshold equation, with modification of a previous model and the exemplification of how to use the updated model. The model shows that the resistance to gully head retreat depends on slope gradient and drainage area at gully heads, land use at the moment of gully development (as numerically expressed using parameters derived from the Runoff Curve Number method), surface rock fragment cover, presence of joints, pipes, and factors/processes affecting detachment rate. This study attempted to better understand environmental conditions that control the development of gully heads in badlands through a combination of field data collection of gully heads, an analysis of land use changes over 10 centuries, focusing on the period 1820–2005, and land use management through repeat photography and a critical examination of historical documents. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

20.
Pikes Peak Highway is a partially paved road between Cascade, Colorado and the summit of Pikes Peak. Significant gully erosion is occurring on the hillslopes due to the concentration of surface runoff, the rearrangement of drainage pathways along the road surface and adjacent drainage ditches, and the high erodibility of weathered Pikes Peak granite that underlies the area. As a result, large quantities of sediment are transported to surrounding valley networks causing significant damage to water quality and aquatic, wetland, and riparian ecosystems. This study establishes the slope/drainage area threshold for gullying along Pikes Peak Highway and a cesium‐137 based sediment budget highlighting rates of gully erosion and subsequent valley deposition for a small headwater basin. The threshold for gullying along the road is Scr = 0 · 21A–0·45 and the road surface reduces the critical slope requirement for gullying compared to natural drainages in the area. Total gully volume for the 20 gullies along the road is estimated at 5974 m3, with an erosion rate of 64 m3 yr–1 to 101 m3 yr–1. Net valley deposition is estimated at 162 m3 yr–1 with 120 m3 yr–1 unaccounted for by gullying. The hillslope–channel interface is decoupled with minimal downstream sediment transport which results in significant local gully‐derived sedimentation. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

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