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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.
Sequential aerial photographs of a small headwater catchment in the Waiapu basin, East Coast Region, North Island, New Zealand, were interpreted to measure and analyse temporal changes in active area of gullies and gully complexes for a longer time span (1939–2003) and with higher temporal resolution compared to previous studies. We focus on the conditions leading to the development of gullies and gully complexes under pasture and forest by using topographic thresholds (slope–area relationships) of catchments for the initiation of gullies and gully complexes. In addition, the influence of two different lithologies as well as the occurrence of major rainfall events was related to gully activity. Twenty gullies and four gully complexes (occupying 62·5 ha or 12·5 per cent of the catchment area) occurred in the study catchment between 1939 and 2003. However, the majority of these were not active at all of the dates studied. Gullies developed in the sandstone‐dominated Tapuwaeroa Formation tended to attain their maximum size by 1957 with a mean catchment area of 2·1 ha. Gullies developed in mudstone of the Whangai Formation attained their maximum size in 1939 with a mean catchment area of 4·31 ha. Exceptions are gullies which developed into mass movement deposits or into an earth flow deposit as well as gullies developed under indigenous forest. Topographic threshold values for gullies under pasture and indigenous forest show that values for gullies under forest plot far above the threshold line of gullies under pasture, indicating that the topographical threshold for gully development under forest is higher compared to under pasture. A threshold value of 9·4 ha in catchment area is needed for the development of gully complexes under pasture, all located in the Whangai Formation and with the same orientation as the strike of the mudstones. Gully‐complex area and dominance of mass‐movement erosion increased with larger catchment area. A decreasing distance to the threshold line for gullies under pasture indicates a later development for gully complexes. No gully complexes developed under indigenous forest, indicating that the threshold value for gully‐complex development is higher than for gully complexes under pasture and was not reached in the study area. A model of shifting topographical threshold for gully development for a given catchment is developed which depends on land use. When a catchment has an indigenous forest cover the topographical threshold is very high. After conversion to pasture, threshold values decrease drastically. With the invasion of scrub, the threshold slowly increases and returns to a similar level to that under indigenous forest after reforestation. Development of gullies and gully complexes is a highly dynamic phenomenon, and phases of expansion and inactivity indicate that models describing only unidirectional advancing stages without periods of inactivity are not suitable. Therefore, this study adds more phases to models of gully and gully‐complex development in the East Coast Region. The threshold line for gully initiation under pasture and a value of 9·4 ha in catchment area for gully‐complex initiation permits one to predict which catchments, under similar environmental settings, develop gullies and gully complexes on a physical basis. This enables land managers to implement sustainable land‐use strategies to reduce erosion rates of gullies and gully complexes. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

4.
Previous studies on erosional relations between inter-gullied and gullied lands have mainly concentrated on exploration of water and sediment relations, with few quantitative studies of evolution relations between inter-gullied land and gullied landform erosion in small catchments. This paper, using information from a 1:5000 digital orthophotomap (DOM), digital elevation model(DEM), and topographic map of the same period and of the same scale, quantitatively analyzes the impact and interactions of inter-gullied and gullied land geomorphologic characteristics on the dissected extent of a catchment using orthogonal polynomial regression analysis. Results indicate that gullies play a leading role in the catchment morphologic evolution and extent of cracked ground surface. When inter-gullied land areas are the same, a 0. 1 km2 gullied land area has the maximum effect on the erosive evolution intensity of the catchment cracked degree. The smaller the catchment area is, the greater the extent of cracked ground surface and gully intensity would be. The geomorphologic evolution mechanism of gullied catchments can be explained as a function of geomorphologic indicators of inter-gullied and gullied land characteristics.  相似文献   

5.
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6.
1 INTRODUCTION In the past years, because of a lack of modern techniques, the research on gullied/inter-gullied land erosion mainly depended on field monitoring, such as utilizing marking posts and/or topographic maps to investigate gullied/inter-gullied …  相似文献   

7.
Large (>0.1 km2) gully–mass movement complexes (badass gullies) are significant contributors to the sediment cascade in New Zealand's steepland East Coast Region catchments. The scale of change taking place in these gully systems allows significant evolution in morphology and sediment dynamics to be tracked at annual to decadal timescales. Here we document changes in two adjacent badass gullies in Waipaoa catchment (Tarndale and Mangatu) to infer sediment generation processes and connectivity using a morphological budgeting approach. A baseline dataset for this study is provided by a LiDAR-derived digital elevation model (DEM) in 2005. We produced new DEMs and orthophoto mosaics using photogrammetry in 2017, 2018, and 2019 to quantify gully morphodynamics and associated volumes of sediment erosion and deposition in both systems as they co-evolved. Results indicate ongoing rapid development of both gully complexes. Severe erosion took place at the gully heads with lowering and migration (up to 25 m vertically and laterally) of the topographic divide separating the two gullies between 2005 and 2019. Over the same period, net lowering of each gully system was ~250 mm year−1. Key sediment-generating processes included surface erosion, deep-seated landslides, and debris flows. Longer term, the overall contribution of sediment from both badass gullies to the Waipaoa catchment has been declining. In the mid-20th century, both gullies yielded in excess of 300 kt year−1. From 2005 to 2019, 80 kt year−1 was yielded from Tarndale and 110 kt year−1 from Mangatu. Our most recent surveys demonstrated considerable variability in sediment yield, ranging from 76 kt year−1 (2017–2018) to 291 kt year−1 (2018–2019). The annual variability observed reflects the complex morphodynamics of discrete hillslopes and tributary fans in these badass gully systems and underlines the importance of integrating decadal and annual surveys when assessing system trajectory. © 2020 John Wiley & Sons, Ltd.  相似文献   

8.
The relationship between climate, landscape connectivity and sediment export from mountain ranges is key to understanding the propagation of erosion signals downstream into sedimentary basins. We explore the role of connectivity in modulating the composition of sediment exported from the Frontal Cordillera of the south-central Argentine Andes by comparing three adjacent and apparently similar semi-glaciated catchment-fan systems within the context of an along-strike precipitation gradient. We first identify that the bedrock exposed in the upper, previously glaciated reaches of the cordillera is under-represented in the lithological composition of gravels on each of three alluvial fans. There is little evidence for abrasion or preferential weathering of sediment sourced from the upper cordillera, suggesting that the observed bias can only be explained by sediment storage in these glacially widened and flattened valleys of the upper cordillera (as revealed by channel steepness mapping). A detailed analysis of the morphology of sedimentary deposits within the catchments reveals catchment-wide trends in either main valley incision or aggradation, linked to differences in hillslope–channel connectivity and precipitation. We observe that drier catchments have poor hillslope–channel connectivity and that gravels exported from dry catchments have a lithological composition depleted in clasts sourced from the upper cordillera. Conversely, the catchment with the highest maximum precipitation rate exhibits a high degree of connectivity between its sediment sources and the main river network, leading to the export of a greater proportion of upper cordillera gravel as well as a greater volume of sand. Finally, given a clear spatial correlation between the resistance of bedrock to erosion, mountain range elevation and its covariant, precipitation, we highlight how connectivity in these semi-glaciated landscapes can be preconditioned by the spatial distribution of bedrock lithology. These findings give insight into the extent to which sedimentary archives record source erosion patterns through time.  相似文献   

9.
This paper analyses the factors that control rates and extent of soil erosion processes in the 199 ha May Zegzeg catchment near Hagere Selam in the Tigray Highlands (Northern Ethiopia). This catchment, characterized by high elevations (2100–2650 m a.s.l.) and a subhorizontal structural relief, is typical for the Northern Ethiopian Highlands. Soil loss rates due to various erosion processes, as well as sediment yield rates and rates of sediment deposition within the catchment (essentially induced by recent soil conservation activities), were measured using a range of geomorphological methods. The area‐weighted average rate of soil erosion by water in the catchment, measured over four years (1998–2001), is 14·8 t ha?1 y?1, which accounts for 98% of the change in potential energy of the landscape. Considering these soil loss rates by water, 28% is due to gully erosion. Other geomorphic processes, such as tillage erosion and rock fragment displacement by gravity and livestock trampling, are also important, either within certain land units, or for their impact on agricultural productivity. Estimated mean sediment deposition rate within the catchment equals 9·2 t ha?1 y?1. Calculated sediment yield (5·6 t ha?1 y?1) is similar to sediment yield measured in nearby catchments. Seventy‐four percent of total soil loss by sheet and rill erosion is trapped in exclosures and behind stone bunds. The anthropogenic factor is dominant in controlling present‐day erosion processes in the Northern Ethiopian Highlands. Human activities have led to an overall increase in erosion process intensities, but, through targeted interventions, rural society is now well on the way to control and reverse the degradation processes, as can be demonstrated through the sediment budget. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

10.
Rock resistance to erosion is an often described factor in geomorphic studies, and is generally considered to strongly influence the shape of erosional landforms. However, the property of the rock mass that enables it to resist erosion is rarely considered, and its measurement is rarely justified and assessed adequately. Allison (1988, 1990) examined the intact strength properties of several types of carbonate rocks and considered that dynamic Young's modulus is a good indicator of rock material strength for geomorphic purposes, and cast doubts on the reliability of Schmidt hammer tests for this purpose. Alternative approaches to rock characterization from the view point of evaluating rock intact strength are considered.  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.
We examined the contributions of bedrock groundwater to the upscaling of storm‐runoff generation processes in weathered granitic headwater catchments by conducting detailed hydrochemical observations in five catchments that ranged from zero to second order. End‐member mixing analysis (EMMA) was performed to identify the geographical sources of stream water. Throughfall, hillslope groundwater, shallow bedrock groundwater, and deep bedrock groundwater were identified as end members. The contribution of each end member to storm runoff differed among the catchments because of the differing quantities of riparian groundwater, which was recharged by the bedrock groundwater prior to rainfall events. Among the five catchments, the contribution of throughfall was highest during both baseflow and storm flow in a zero‐order catchment with little contribution from the bedrock groundwater to the riparian reservoir. In zero‐order catchments with some contribution from bedrock groundwater, stream water was dominated by shallow bedrock groundwater during baseflow, but it was significantly influenced by hillslope groundwater during storms. In the first‐order catchment, stream water was dominated by shallow bedrock groundwater during storms as well as baseflow periods. In the second‐order catchment, deeper bedrock groundwater than that found in the zero‐order and first‐order catchments contributed to stream water in all periods, except during large storm events. These results suggest that bedrock groundwater influences the upscaling of storm‐runoff generation processes by affecting the linkages of geomorphic units such as hillslopes, riparian zones, and stream channels. Our results highlight the need for a three‐dimensional approach that considers bedrock groundwater flow when studying the upscaling of storm‐runoff generation processes. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

13.
The SIBERIA landscape evolution model was used to simulate the geomorphic development of the Tin Camp Creek natural catchment over geological time. Measured hydrology, erosion and geomorphic data were used to calibrate the SIBERIA model, which was then used to make independent predictions of the landform geomorphology of the study site. The catchment, located in the Northern Territory, Australia is relatively untouched by Europeans so the hydrological and erosion processes that shaped the area can be assumed to be the same today as they have been in the past, subject to the caveats regarding long‐term climate fluctuation. A qualitative, or visual comparison between the natural and simulated catchments indicates that SIBERIA can match hillslope length and hillslope profile of the natural catchments. A comparison of geomorphic and hydrological statistics such as the hypsometric curve, width function, cumulative area distribution and area–slope relationship indicates that SIBERIA can model the geomorphology of the selected Tin Camp Creek catchments. Copyright 2002 © Environmental Research Institute of the Supervising Scientist, Commonwealth of Australia.  相似文献   

14.
This study investigates how medium‐term gully‐development data differ from short‐term data, and which factors influence their spatial and temporal variability at nine selected actively retreating bank gullies situated in four Spanish basin landscapes. Small‐format aerial photographs using unmanned, remote‐controlled platforms were taken at the gully sites in short‐term intervals of one to two years over medium‐term periods of seven to 13 years and gully change during each period was determined using stereophotogrammetry and a geographic information system. Results show a high variability of annual gully retreat rates both between gullies and between observation periods. The mean linear headcut retreat rates range between 0·02 and 0·26 m a–1. Gully area loss was between 0·8 and 22 m² a–1 and gully volume loss between 0·5 to 100 m³ a–1, of which sidewall erosion may play a considerable part. A non‐linear relationship between catchment area and medium‐term gully headcut volume change was found for these gullies. The short‐term changes observed at the individual gullies show very high variability: on average, the maximum headcut volume change observed in 7–13 years was 14·3 times larger than the minimum change. Dependency on precipitation varies but is clearly higher for headcuts than sidewalls, especially in smaller and less disturbed catchments. The varying influences of land use and human activities with their positive or negative effects on runoff production and connectivity play a dominant role in these study areas, both for short‐term variability and medium‐term difference in gully development. The study proves the value of capturing spatially continuous, high‐resolution three‐dimensional data using small‐format aerial photography for detailed gully monitoring. Results confirm that short‐term data are not representative of longer‐term gully development and demonstrate the necessity for medium‐ to long‐term monitoring. However, short‐term data are still required to understand the processes – particularly human activity at varying time scales – causing fluctuations in gully erosion rates. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

15.
The development and evolution of gullies on soil-mantled hillslopes can devastate agricultural regions and cause widespread soil and landscape degradation. Since 2000, international symposia have been organized to address gully erosion processes, and this paper and special issue provide additional context for the 7th International Symposium on Gully Erosion held at Purdue University in 2016. Several important themes of gully erosion emerged during this symposium that warranted additional discussion here. These topics include the importance and impact of technology transfer, disciplinary fragmentation as an impediment for research advancement, the difficulty in defining the erodibility of sediment within gullies, and the opportunities afforded by remote sensing technology. It is envisioned that such symposia will continue to enhance the capabilities of researchers and practitioners to monitor, model, and manage these important geomorphic processes and to mitigate landscape degradation. © 2018 John Wiley & Sons, Ltd.  相似文献   

16.
This study explores the frequency of bedrock exposure in a soil‐mantled low‐relief (i.e. non‐mountainous) landscape. In the High Plains of eastern Colorado, gully headcuts are among the few erosional features that will incise through the soil mantle to expose bedrock. We measured the last time of bedrock exposure using optically stimulated luminescence dating of alluvial sediment overlying bedrock in gully headcuts. Our dating suggests that headcuts in adjacent gullies expose bedrock asynchronously, and therefore, the headcuts are unlikely to have been triggered by a base‐level drop in the trunk stream. This finding supports the hypothesis that headcuts can develop locally in gullies as a result of focused scour in locations where hydraulic stress during a flash flood is sufficiently high, and/or ground cover is sufficiently weak, to generate a scour hole that undermines vegetation. Alluvium dating also reveals that gullies have been a persistent part of this landscape since the early Holocene. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

17.
Fractures are discontinuities in rock that can be exploited by erosion. Fractures regulate cohesion, profoundly affecting the rate, style, and location of Earth surface processes. By modulating the spatial distribution of erodibility, fractures can focus erosion and set the shape of features from scales of fluvial bedforms to entire landscapes. Although early investigation focused on fractures as features that influence the orientation and location of landforms, recent work has started to discern the mechanisms by which fractures influence the erodibility of bedrock. As numerical modeling and field measurement techniques improve, it is rapidly becoming feasible to determine how fractures influence geomorphic processes, as opposed to when or where. However, progress is hampered by a lack of research coordination across scales and process domains. We review studies from hillslope, glacial, fluvial, and coastal domains from the scale of reaches and outcrops to entire landscapes. We then synthesize this work to highlight similarities across domains and scales and suggest knowledge gaps, opportunities, and methodological challenges that need to be solved. By integrating knowledge across domains and scales, we present a more holistic conceptualization of fracture influences on geomorphic processes. This conceptualization enables a more unified framework for future investigation into fracture influences on Earth surface dynamics. © 2018 John Wiley & Sons, Ltd.  相似文献   

18.
Incision as a result of fluvial erosion is an important process to model when simulating landform evolution. For gullies, it is apparent that coupled with the processes that cause incision there must be a range of processes that stop incision. Once started, rills and gullies will grow infinitely without a reduction in support area and/or being arrested by deposition and armouring. Some of these processes have been well studied under the heading of inter-rill erosion. Other limiting processes are related to the shape of the landform and how downstream deposition areas are linked geomorphically to the upstream gullies. Armouring is also an important process that reduces gully incision and extension, where the gully erodes to bedrock and the resistant base limits further development. Post-mining landscapes are new surfaces with new materials and provide the opportunity to examine gully initiation, extension and stabilization. The work presented here has largely been driven by the mining industry, where there has been a need to assess erosion over hazardous wastes like mine tailings and low-level nuclear waste. We demonstrate the usefulness of computer-based landscape evolution models and the more recent soilscape models (that include both surface and subsurface processes) to understand both fluvial and diffusive processes as well as armouring in a digital elevation model framework (as well as landscape evolution). Landscape evolution models provide insights into complex non-linear systems such as gullies. A key need is that of field data to parameterize and validate the models. It is argued that current models have more capability than field data available for parameterization and importantly the validation of model outputs.  相似文献   

19.
The sediment delivery ratio was estimated for two periods (28 years and eight years) following reforestation of seven tributary catchments (0·33 to 0·49 km2) in the headwaters of the Waipaoa River basin, North Island, New Zealand. In these catchments, gully erosion, which largely resulted from clearance of the natural forest between 1880 and 1920, is the main source of sediment to streams. Reforestation commenced in the early 1960s in an attempt to stabilize hillslopes and reduce sediment supply. Efforts have been partially successful and channels are now degrading, though gully erosion continues to supply sediment at accelerated rates in parts of the catchment. Data from the area indicate that the sediment delivery ratio (SDR) can be estimated as a function of two variables, ψ (the product of catchment area and channel slope) and A g (the temporally averaged gully area for the period). Sediment input from gullies was determined from a well defined relationship between sediment yield and gully area. Sediment scoured from channels was estimated from dated terrace remnants and the current channel bed. Terrace remnants represent aggradation during major floods. This technique provides estimates of SDR averaged over periods between large magnitude terrace‐forming events and with the present channel bed. The technique averages out short‐term variability in sediment flux. Comparison of gully area and sediment transport between two periods (1960–1988 and 1988–1996) indicates that the annual rate of sediment yield from gullies for the later period has decreased by 77 per cent, sediment scouring in channels has increased by 124 per cent, and sediment delivered from catchments has decreased by 78 per cent. However, average SDR for the tributaries was found to be not significantly different between these periods. This may reflect the small number of catchments examined. It is also due to the fact that the volume of sediment scoured from channels was very small relative to that produced by gullies. According to the equation for SDR determined for the Waipaoa headwaters, SDR increases with increasing catchment area in the case where A g and channel slope are fixed. This is because the amount of sediment produced from a channel by scouring increases with increasing catchment area. However, this relationship does not hold for the main stem of the study catchments, because sediment delivered from its tributaries still continues to accumulate in the channel. Higher order channels are, in effect, at a different stage in the aggradation/degradation cycle and it will take some time until a main channel reflects the effects of reforestation and its bed adjusts to net degradation. Results demonstrate significant differences among even low order catchments, and such differences will need to be taken into consideration when using SDR to estimate sediment yields. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

20.
Gully erosion is a major environmental threat on the Moldavian Plateau (MP) of eastern Romania. The permanent gully systems consist of two main gully types. These are: (1) discontinuous gullies, which are mostly located on hillslopes and (2) large continuous gullies in valley bottoms. Very few studies have investigated the evolution of continuous gullies over the medium to longer term. The main objective of this study was to quantitatively analyse the development of continuous gullies over six decades (1961–2020). The article aimed at predicting temporal patterns of gully head erosion based on field data from multiple gullies. Fourteen representative continuous gullies were selected near the town of Barlad, most of them having catchment areas < 500 ha. Linear gully head retreat (LGHR) and areal gully growth (AGG) rates were quantified for six decades. Two main periods were distinguished and compared (i.e., the wet 1961–1980 period and the drier 1981–2020 period). Results indicate that gully erosion rates have significantly decreased since 1981. The mean LGHR of 7.7 m yr−1 over 60 years was accompanied by a mean AGG of 213 m2 yr−1. However, erosion rates between 1961 and 1980 were 4.0 times larger for LGHR and 5.9 times more for AGG compared to those for 1981–2020. Two regression models indicate that annual precipitation depth (P) is the primary controlling factor, explaining 57% of LGHR and 53% of AGG rate. The contributing area (CA) follows, with ~33%. Only 43% of total change in LGHR and 46% of total change in AGG results from rainfall-induced runoff during the warm season. Accordingly, the cold season (with associated freeze–thaw processes and snowmelt runoff) has more impact on gully development. The runoff pattern, when flow enters the trunk gully head, is largely controlled by the upper approaching discontinuous gully.  相似文献   

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