Showing papers on "Stream power published in 2019"

Water erosion processes and dynamic changes of sediment size distribution under the combined effects of rainfall and overland flow.

Abstract: Water erosion is a time-varying processes controlled by both rainfall and overland flow. A better understanding of dynamic changes in the sediment load and size distribution with various erosive forces can help to develop and verify erosion models. Here, a total of 11 laboratory simulation experiments were conducted in a 1 m by 3 m flume with 3 storm rainfall intensities (60, 90, 120 mm h−1) and 2 inflow rates (5, 7.5 L min−1) on a silty clay red soil. Time-series measurements of the quantity and size distribution of eroded materials were made during 50 min rainfall/inflow time. The mean weight diameter of the effective sediment, sediment enrichment ratio, average stream power and rainfall power were measured and calculated. Fine sediment particles were associated with the short-lived initial stage, which was combined with sheet flow erosion and splash erosion, whereas coarse particles were associated with the rill development and rill stable stages, which were dominated by rill erosion and interrill erosion, respectively. The

Modelling terrain erosion susceptibility of logged and regenerated forested region in northern Borneo through the Analytical Hierarchy Process (AHP) and GIS techniques

Abstract: This research examines the susceptibility of logged and regenerated forest region to erosion through the application of the analytical hierarchy process (AHP) and geographical information systems (GIS). In order to estimate terrain erosion susceptibility, ten geo-environmental variables were taken into account as possible factors relevant to terrain erosion. They are slope, aspect, relative relief, slope length and steepness (LS) factor, curvature, landforms, topographic wetness index (TWI), stream power index (SPI), stream head density, and land use/land cover. Pairwise comparison matrixes were generated to derive the weightages and ratings of each variable and their classes. These were integrated to generate the terrain erosion susceptibility index (TESI) map. Among the variables used in the analysis the land use/land cover, slope, SPI, stream head density, and LS factor were shown to have high contribution towards terrain erosion susceptibility. The areas with a concave slopes > 25° and high relative relief, LS factor, TWI, and stream head densities were found to be more susceptible to erosion such as gullying or landslides. The conversion of TESI into terrain erosion susceptibility zonation (TESZ) map shown that 25% of the total area is highly susceptible to erosion. Among this, 10% of the area possesses a very high vulnerability to landslides and gullying or soil slips and these areas coincide with logging roads and skidder trails. Linear regression analysis between TESI and TESZ with spatial distribution of mean annual rainfall in the region does not show any significant relationships (p > 0.10). However, high rainfall triggers rapid downstream movement of unsupported slopes in the region. The terrain erosion susceptibility zonation map expresses the realistic condition of logged terrain matching with field observations in the area in terms of erosion. The results can serve as basic data for future development programs in the region, in any projects where the terrain susceptibility is critical by planning infrastructure to avoid high risk zones.

Long-profile evolution of transport-limited gravel-bed rivers

Abstract: . Alluvial and transport-limited bedrock rivers constitute the majority of fluvial systems on Earth. Their long profiles hold clues to their present state and past evolution. We currently possess first-principles-based governing equations for flow, sediment transport, and channel morphodynamics in these systems, which we lack for detachment-limited bedrock rivers. Here we formally couple these equations for transport-limited gravel-bed river long-profile evolution. The result is a new predictive relationship whose functional form and parameters are grounded in theory and defined through experimental data. From this, we produce a power-law analytical solution and a finite-difference numerical solution to long-profile evolution. Steady-state channel concavity and steepness are diagnostic of external drivers: concavity decreases with increasing uplift rate, and steepness increases with an increasing sediment-to-water supply ratio. Constraining free parameters explains common observations of river form: to match observed channel concavities, gravel-sized sediments must weather and fine – typically rapidly – and valleys typically should widen gradually. To match the empirical square-root width–discharge scaling in equilibrium-width gravel-bed rivers, downstream fining must occur. The ability to assign a cause to such observations is the direct result of a deductive approach to developing equations for landscape evolution.

Fluvial landscape evolution controlled by the sediment deposition coefficient: Estimation from experimental and natural landscapes

Abstract: The evolution of a fluvial landscape is a balance between tectonic uplift, fluvial erosion, and sediment deposition. The erosion term can be expressed according to the stream power model, stating that fluvial incision is proportional to powers of river slope and discharge. The deposition term can be expressed as proportional to the sediment flux divided by a transport length. This length can be defined as the water flux times a scaling factor ζ. This factor exerts a major control on the river dynamics, on the spacing between sedimentary bedforms, or on the overall landscape erosional behavior. Yet, this factor is difficult to measure either in the lab or in the field. Here, we propose a new formulation for the deposition term based on a dimensionless coefficient, G, which can be estimated at the scale of a landscape from the slopes of rivers at the transition between a catchment and its fan. We estimate this deposition coefficient from 29 experimental catchment–alluvial fan systems and 68 natural examples. Based on our data set, we support the idea of Davy and Lague (2009) that G is a relevant parameter to characterize the erosional and transport mode of a fluvial landscape, which can be field calibrated, with a continuum from detachment-limited (G = 0) to transport-limited behavior (G >0.4 from the studied examples).

Channel adjustment after artificial neck cutoffs in a meandering river of the Zoige basin within the Qinghai-Tibet Plateau, China

Abstract: Neck cutoff is an essential process that significantly changes the morphodynamic characteristics of a meandering bend In reality, however, observing natural processes of a neck cutoff is very difficult In this study, we artificially triggered neck cutoffs by excavating a 04 m (width) × 05 m (depth) ditch to connect the beginning and ending of two highly convoluted bends along a meandering tributary of the upper Black River, a major tributary of the Upper Yellow River situated in the northeastern side of the Qinghai-Tibet Plateau in China Our morphologic and hydraulic measurements in summers of 2013, 2014, 2016, and 2017, the subsequent hydraulic-geometry analysis, and three-dimensional simulation showed that both artificial ditches expanded fast to the size comparable to the former channel in a three-year period and the oxbow channel was disconnected from the former channel quickly, though sediment supply may be limited in this area The morphological adjustment was featured by (1) distinct temporal trends of the development of the width/depth ratio between the two cutoff channels, (2) different diversion factors of the total discharge to the cutoff channel, and (3) diverse interaction patterns between cutoff and former channels These discrepancies were supported by simulated different three-dimensional velocity distributions in the two cutoff channels, suggesting the importance of the clustered local velocities Comparing these results with those reported in earlier studies showed that besides channel slope, unit stream power, and bank strength, the diversion angle between the cutoff and former channel played an important role in controlling channel adjustment The discrepancy of the adjustment processes between the cutoff channel in this study and those in two previous ones revealed that channel adjustment after neck cutoff behaved differently under different physical settings and require more field-based studies

Application of 1D and 2D hydrodynamic modeling to study glacial lake outburst flood (GLOF) and its impact on a hydropower station in Central Himalaya

Abstract: The existence of numerous lakes in the higher reaches of the Himalaya makes it a potential natural hazard as it imposes a risk of glacial lake outburst flood (GLOF), which can cause great loss of life and infrastructure in the downstream regions. Hydrodynamic modeling of a natural earth-dam failure and hydraulic routing of the breach hydrograph allow us to characterize the flow behavior of a potential flood along a given flow channel. In the present study, the flow hydraulics of a potential GLOF generated due to the moraine failure of the Satopanth lake located in the Alaknanda basin is analyzed using one-dimensional and two-dimensional hydrodynamic computations. Field measurements and mapping were carried out at the lake site and along the valley using high-resolution DGPS points. The parameters of Manning’s roughness coefficient and terrain elevation were derived using satellite-based raster, the accuracy of which is verified using field data. The volume of the lake is calculated using area-based scaling method. Unsteady flood routing of the dam-break outflow hydrograph is performed along the flow channel to compute hydraulic parameters of peak discharge, water depth, flow velocity, inundation and stream power at a hydropower dam site located 28 km downstream of the lake. Assuming the potential GLOF event occurs contemporaneously with a 100-year return period flood, unsteady hydraulic routing of the combined flood discharge is performed to evaluate its impact on the hydropower dam. The potential GLOF resulted in a peak discharge of ~ 2600 m3s−1 at the dam site which arrived 38 min after the initiation of the moraine-failure event. The temporal characteristics of the flood wave analyzed using 2D unsteady simulations revealed maximum inundation depth and flow velocity of 7.12 m and 7.6 ms−1, respectively, at the dam site. Assuming that the control gates of the dam remain closed, water depth increases at a rate of 4.5 m per minute and overflows the dam approximately 4 min after the flood wave arrival.

Response of soil detachment rate by raindrop-affected sediment-laden sheet flow to sediment load and hydraulic parameters within a detachment-limited sheet erosion system on steep slopes on Loess Plateau, China

Abstract: The response of soil detachment rate by raindrop-affected sediment-laden sheet flow to sediment load and hydraulic parameters was investigated within a detachment-limited sheet erosion system on steep slopes to understand sheet erosion processes fully and derive an accurate experimental model. An experiment was conducted at slopes of 12.23%, 17.63%, 26.8%, 36.4%, 40.4% and 46.63% under rainfall intensities of 48, 60, 90, 120, 138 and 150 mm h−1, respectively, by using simulated rainfall. Results showed that the soil detachment rate by raindrop-affected sediment-laden sheet flow decreased as the sediment load by sheet flow increased, and the decrease was a power function of sediment load by sheet flow with NSE = 0.58, MSE = 0.0099 and R2 = 0.58. In addition, the soil detachment rate by raindrop-affected sediment-laden sheet flow increased as a linear function of shear stress, stream power and unit stream power. Shear stress and stream power could be used to predict the soil detachment rate by raindrop-affected sediment-laden sheet flow accurately through a linear equation. Stream power (R2 = 0.87, MSE = 0.003 and NSE = 0.87) was a better predictor of soil detachment rate by raindrop-affected sediment-laden sheet flow than shear stress (NSE = 0.83, MSE = 0.004 and R2 = 0.83). However, prediction based on unit stream power (NSE = 0.43, MSE = 0.01 and R2 = 0.43) was poor. These findings can improve our understanding and modelling of sheet erosion processes on steep slopes in the loess region of China.

Stream power determination in GIS. An index to evaluate the most ’sensitive’ points of a river

Abstract: This paper focuses on the problem of measuring stream power in a hydrographic network using the original definition provided by Bagnold in 1996. Recent digital elevation models have enabled the calculation of channel gradients and, consequently, stream power with a finer spatial resolution, and this has created promising and novel opportunities to investigate river geomorphological processes and forms. The work carried out in this study includes defining and implementing a methodological approach that could be automated within a geographic information system and that meets two requirements: (1) it uses a DEM as input data at a suitable resolution; (2) it estimates the stream power Ω , as well as its variability along the considered stream, in the best possible way using available data. In particular, the methodological approach was implemented in a GIS environment (GRASS GIS) and applied to a sample basin to highlight the variability in Ω along the main stream and its most important tributaries. The sudden and more substantial variations in stream power were then related to the processes acting in the fluvial system. This approach made it possible to highlight how erosion, solid transport, and sedimentation phenomena occurring along the fluvial reaches are related to abrupt variations (increase/decrease) in the “power” available. The results of this study support the idea that the automated and standardized screening of stream power variability along a stream can be used as a preliminary diagnostic element to identify the most “sensitive” points of the stream on which to concentrate subsequent investigations (field checks to verify the causes), with the aim of mitigating risks due to the dynamics of the riverbed.

The Generation and Scaling of Longitudinal River Profiles

Abstract: 9 The apparent success of inverse modeling of continent-wide drainage inventories is per10 plexing. An ability to obtain reasonable fits between observed and calculated longitudi11 nal river profiles implies that drainage networks behave simply and predictably at length 12 scales of O(102–103) km and timescales of O(100–102) Ma. This behavior suggests that 13 rivers respond in a predictable way to large-scale tectonic forcing. On the other hand, it 14 is acknowledged that stream power laws are empirical approximations since fluvial pro15 cesses are complex, non-linear, and probably susceptible to disparate temporal and spatial 16 shocks. To bridge the gap between these different perceptions of landscape evolution, we 17 present and interpret a suite of power spectra for African river profiles that traverse differ18 ent climatic zones, lithologic boundaries, and biotic distributions. At wavelengths & 102 19 km, power spectra have slopes of −2, consistent with red noise, demonstrating that pro20 files are self-similar at these length scales. At wavelengths . 102 km, there is a cross-over 21 transition to slopes of −1, consistent with pink noise, for which power scales according to 22 the inverse of wavenumber. Onset of this transition suggests that spatially correlated noise, 23 perhaps generated by instabilities in water flow and by lithologic heterogeneities, becomes 24 more prevalent at wavelengths shorter than ∼ 100 km. At longer wavelengths, this noise 25 gradually diminishes and self-similar scaling emerges. Our analysis is consistent with the 26 concept that complexities of river profile development are characterized by an adaptation 27 of the Langevin equation, by which simple advective models of erosion are driven by a 28 combination of external forcing and noise. 29

Modelling soil detachment by overland flow for the soil in the Tibet Plateau of China.

Abstract: The overland flow erosion is common and became more serious because of the climate warming inducing more runoff in the Tibet Plateau. The purposes of this study were to evaluate the effects of flow rate, slope gradient, shear stress, stream power, unit stream power and unit energy of water-carrying section on the soil detachment capacity for the soil in the Tibet Plateau of China due to the information is limited. To achieve this aim, laboratory experiments were performed under six flow rates (5, 10, 15, 20, 25 and 30 L min−1) and six slope gradients (8.74%, 17.63%, 26.79%, 36.40%, 46.63 and 57.73%) by using a slope-adjustable steel hydraulic flume (4 m length, 0.4 m width, 0.2 m depth). The results indicated that soil detachment capacity ranged from 0.173 to 6.325 kg m−2 s−1 with 1.972 kg m−2 s−1 on average. The soil detachment capacity increased with power function as the flow rate and the slope gradient augmented (R2 = 0.965, NRMSE = 0.177 and NSE = 0.954). The soil detachment capacity was more influenced by flow rate than by slope gradient in this study. The relation between soil detachment capacity and shear stress, stream power, unit stream power and unit energy of water-carrying section can be described by using the linear function and power function, the power function relationship performed better than the linear function in generally. The stream power exhibits the best performance in describing the soil detachment capacity among shear stress, stream power, unit stream power and unit energy of water-carrying section in this study. The erodibility value in this study was larger than and the critical shear stress was less than those for soil in the eastern China. There has a huge potential for the soil in the Tibet Plateau eroded by the water erosion when enough runoff exiting. More attention should be payed to the water erosion process and mechanism in the Tibet Plateau area in the future.

Assessing the contribution of the sediment content and hydraulics parameters to the soil detachment rate using a flume scouring experiment

Abstract: Rill erosion is one of the most important processes affecting soil detachment. Therefore, the quantification of the soil detachment process is important to establish a basic process-based erosion prediction model. The objective of this study was to assess the contributions of the hydraulics parameters and sediment content to the soil detachment rate of purple soil. Purple soil was collected from a typical hilly region in Sichuan, China. Six scouring experiments were conducted in two 1 m × 2 m boxes at six different flow discharge rates (2, 4, 6, 8, 10, and 12 L min−1) in an upslope drainage area (0.30 m2) with a 15° slope. The results show that the soil detachment rate greatly changes during the rill development stage and the soil detachment rate varies at a sediment content of 0.15 g L−1. Furthermore, the soil detachment rate is negatively related to the sediment content. The relationships between the sediment content and hydraulics parameters can be described with a negative power function. The soil detachment rate is positively related to the stream power; the relationship can be described with a linear function. The comprehensive relationship between the soil detachment rate and sediment content and stream power can be described with a binary linear equation. The proportional contribution of the sediment content to the soil detachment rate is 80.65% and that of the stream power is 19.35%. The sediment content has a negative effect on the soil detachment rate in rills. The stream power has a positive effect; it induces soil detachment. The negative effect of the sediment content on the soil detachment rate is influenced by the stream power. This study provides new insights into the effects of the sediment content and hydraulics on the rill erosion process.

Modelling of drainage dynamics influence on sediment routing system in a fold-and-thrust belt

Abstract: Drainage networks link erosional landscapes and sedimentary basins in a source‐to‐sink system, controlling the spatial and temporal distribution of sediment flux at the outlets. Variations of accumulation rates in a sedimentary basin have been classically interpreted as changes in erosion rates driven by tectonics and/or climate. We studied the interactions between deformation, rainfall rate and the intrinsic dynamics of drainage basins in an experimental fold‐and‐thrust belt subjected to erosion and sedimentation under constant rainfall and shortening rates. The emergence of thrust sheets at the front of a prism may divert antecedent transverse channels (perpendicular to the structural grain) leading to the formation of longitudinal reaches, later uplifted and incorporated in the prism by the ongoing deformation. In the experiments, transverse incisions appear in the external slopes of the emerging thrust sheets. Headward erosion in these transverse channels results in divide migration and capture of the uplifted longitudinal channels located in the inner parts of the prism, leading to drainage network reorganization and modification of the sediment routing system. We show that the rate of drainage reorganization increases with the rainfall rate. It also increases in a nonlinear way with the rate of uplift. We explain this behaviour by an exponent > 1 on the slope variable in the framework of the stream power erosion model. Our results confirm the view that early longitudinal‐dominated networks are progressively replaced by transverse‐dominated rivers during mountain building. We show that drainage network dynamics modulate the distribution of sedimentary fluxes at the outlets of experimental wedges. We propose that under constant shortening and rainfall rates the drainage network reorganization can also modulate the composition and the spatial distribution of clastic fluxes in foreland basins.

The System Approach

Abstract: Alluvial fans do not create steady and permanent landforms but are a transient feature with alternating phases of aggradation and entrenchment. The fans may reach a dynamic equilibrium when the supply of material from the source catchment is balanced by erosion, and when the subsidence rate, the fan elevation, and the shape remain constant. This is, however, a rare situation. Alluvial fans compose, more commonly, a non-equilibrium system and are hardly expected to reach stability. The evolution of alluvial fans involves both negative and positive self-enhancing feedbacks. Aggradation is a self-arresting feedback mechanism. Oversteepening following aggradation induces trenching and gullying as a negative feedback which leads to a reduction of the channel slope and to a more equilibrated grade, moving the stream power/resisting power ratio closer to the value of 1.0 and to improved coupling. Through-fan-trenching marks the ultimate stage of coupling, allowing continuity of the sediment movement through the fan into the axial basin. The alluvial fans are controlled by both autogenic and allogenic forcing, the latter not always necessary to explain significant changes.

Impact of river interventions on alluvial channel morphology

Abstract: Rivers play a significant role for sustainment and development of human race. The number of river interventions is increasing to meet water and energy demand. The present paper discusses impacts of...

Sediment transport capacity in erodible beds with reconstituted soils of different textures

Abstract: Precise estimation of sediment transport capacity and wide applicability of a prediction equation could provide a positive response to increasing challenges of soil erosion. Currently, the models developed by many researchers are focused on a few or single soils. In this study, a prediction equation of sediment transport capacity was attempted to establish from the flume experiments performed on erodible beds under the experimental settings of two slopes (5.6%, 16.7%), four unit width discharges (6.67 × 10−5, 1.33 × 10−4, 2.00 × 10−4 and 2.67 × 10−4 m2 s−1) and five reconstituted soils (sand contents of 0%, 30%, 50%, 70%, 100%). Here, the sediment transport capacity under clay-sand mixture of different soil texture were analyzed, and a prediction equation for sediment transport based on soil cohesion and hydraulic variables was established. The experiments confirmed that the sediment concentration and transport capacity increased with the unit width discharge and slope gradient as a power function, and was more dependent on slope gradient. Besides, the hydrological and erosive processes on the beds with reconstituted soils varied with soil texture, the beds with a high clay content had a stable channel of sediment transport. Comparatively, unit stream power was the most suitable hydraulic variable to describe the sediment transport capacity (r = 0.951, P

Erosion vulnerability of sandy clay loam soil in Southwest China: Modeling soil detachment capacity by flume simulation

Abstract: Soil detachment capacity (Dc) is a key parameter in many soil erosion models and is typically estimated using hydraulic parameters. However, the accuracy of predicting Dc and its relationship to hydraulic characteristics remains poorly understood for many soil types. This study investigates the predictability of Dc with hydraulics by simulated scour rill flow and quantifies erosion vulnerability to rill erosion as reflected by rill erodibility and critical hydraulic values for an Entisol from Southwestern China. Small samples (10 cm in diameter, 6 cm in depth) of sandy clay loam of Entisol were subjected to scouring by simulated rill flow under the combinations of flow discharges (18.8, 26.3, 46.6, 54.4, 64.6 l min−1) and slope gradients (3.5%, 8.7%, 17.6%, 26.8% and 36.4%). The results showed that Dc increased as a power function with flow discharge irrespective of slope gradients, and at low discharge gradients Dc increased as a power function with slope and with transitions to a linear function at higher discharge gradients. The association of flow discharges and slope gradients was a better predictor of Dc than flow depths and slope gradients. Shear stress and stream power were similar and better predictors of Dc than flow velocity, unit stream power and unit energy. Rill erodibility related to all hydraulic parameters were significantly different from zero under combination of flow discharges and slope gradients, and this was true for critical hydraulic values related to comprehensive data. Relatively higher rill erodibility and lower critical hydraulic values compared with other soils demonstrated that sandy clay loam of Entisol is susceptible to detachment. These results highlight the erosion vulnerability of Entisols and provide deeper insights on the reliability of hydraulic parameters which strongly affect soil detachment modeling.

Hydraulic Parameters for Sediment Transport and Prediction of Suspended Sediment for Kali Gandaki River Basin, Himalaya, Nepal

Abstract: Sediment yield is a complex phenomenon of weathering, land sliding, and glacial and fluvial erosion. It is highly dependent on the catchment area, topography, slope of the catchment terrain, rainfall, temperature, and soil characteristics. This study was designed to evaluate the key hydraulic parameters of sediment transport for Kali Gandaki River at Setibeni, Syangja, located about 5 km upstream from a hydropower dam. Key parameters, including the bed shear stress (τb), specific stream power (ω), and flow velocity (v) associated with the maximum boulder size transport, were determined throughout the years, 2003 to 2011, by using a derived lower boundary equation. Clockwise hysteresis loops of the average hysteresis index of +1.59 were developed and an average of 40.904 ± 12.453 Megatons (Mt) suspended sediment have been transported annually from the higher Himalayas to the hydropower reservoir. Artificial neural networks (ANNs) were used to predict the daily suspended sediment rate and annual sediment load as 35.190 ± 7.018 Mt, which was satisfactory compared to the multiple linear regression, nonlinear multiple regression, general power model, and log transform models, including the sediment rating curve. Performance indicators were used to compare these models and satisfactory fittings were observed in ANNs. The root mean square error (RMSE) of 1982 kg s−1, percent bias (PBIAS) of +14.26, RMSE-observations standard deviation ratio (RSR) of 0.55, coefficient of determination (R2) of 0.71, and Nash–Sutcliffe efficiency (NSE) of +0.70 revealed that the ANNs’ model performed satisfactorily among all the proposed models.

MCA on mechanism of river bed potholes growth: a study of middle Subarnarekha River basin, South East Asia

Abstract: Pothole is an exceptional dynamic micro-fluvial erosional landform of the river bed. Subarnarekha River is a rejuvenated antecedent river and occupies a significant part of the Chotanagpur Plateau. The river bed of the Subarnarekha River and the confluence zones of Subarnarekha-Lokjoriya and Subarnarekha-Kharsoti have favourable conditions for the development of potholes. Geological (joint and fracture on river bed) and hydrological (stream power, water discharge, flow velocity) parameters are taken into consideration to understand the mechanism of pothole growth. Multi-criteria analysis (MCA) has been done to understand the governing factor influencing the mechanism of pothole development. The results are analysed in a quantitative way, and the micro-scale field observations have been represented using ArcGIS10.2.2 and IBM SPSS 22. Using the MCA it has been inferred that ‘joint length’ is the prime contributing factor responsible for pothole formation in the middle Subarnarekha River basin, Ghatsila. The main significance of this research work is the study of micro-geomorphic landforms mechanism near confluence and other places of the river bed.

Local Factors Determining Spatially Heterogeneous Channel Migration in a Low-Energy Stream

Abstract: Since the 1990s, nature and water management policies have attempted to re-create natural rivers systems by mimicking curvy meandering planforms, based on the assumption that meandering is the natural channel-forming process. However, in low-energy river systems, the extent to which meandering plays a natural role is often minimal. This study aims to quantify contemporary lateral migration in the low-energy irregular sinuous lowland river system of the Drentsche Aa, The Netherlands, and to determine the factors influencing lateral channel migration in a heterogeneous valley fill. Although the river is classified as laterally immobile based on an empirical stability diagram, field observations prove that erosion and deposition are currently occurring. By analyzing historical and present-day maps, it was shown that lateral migration was highly spatially variable for the period 1924–2005. Sinuosity and valley gradient are not correlated to lateral migration rates, suggesting they are not a measure of lateral migration in the case study area, which is in line with the literature. Based on geomorphological and soil map analyses, it was shown that lateral migration rates are significantly higher in valley fills of aeolian sands than in clastic alluvial deposits, which on their turn are significantly higher than in peaty environments. Therefore, local conditions appear to be dominant over other factors such as stream power and bed grain size. These findings are important for river rehabilitation of low-energy rivers, because it shows that local valley fill conditions can greatly influence active lateral migration in the river.

Research on soil detachment rate and hydrodynamic parameters of dip/anti-dip slope in simulated karst trough valley

Abstract: Bedding dip has an important influence on soil detachment and flow hydrodynamics in a karst trough valley. The laboratory rainfall simulation was conducted with three bedding dips (bare slope, dip slope and anti-dip slope) under three rainfall intensities (30, 60, 90 mm h−1). The characteristics of soil detachment and hydrodynamic parameters were assessed, including water flow shear stress, stream power, unit stream power and unit flow energy. The significant effects of bedding dips and rainfall intensities and their interactions on soil detachment and hydrodynamic parameters were examined. The results showed that (1) the soil detachment rate decreased with increasing rainfall duration, and the soil detachment rate in 30° bedding dip of dip slope was much larger than those in bare slope and anti-dip slope in most rainfall intensities; (2) the 60° bedding dip of dip slope was the threshold that controlled the stream power, unit stream power and unit flow energy increased or decreased under different rainfall intensities; and (3) the soil detachment rate had extremely significant positive power relationships with water flow shear stress, stream power, unit stream power and unit flow energy. Meanwhile, the stream power was the most suitable parameter for predicting soil detachment in a karst trough valley slope. Therefore, these results could provide useful information for soil erosion prediction in a karst trough valley.

Validation of the Unit Stream Power Erosion and Deposition (USPED) Model at Yakima Training Center, Washington

Abstract: During the last seventy years, numerous models have been developed to predict soil erosion; some models also predict concomitant sediment deposition. All have been proven inadequate and/or inaccurate in one respect or another. This paper discusses the application of the new-generation Unit Stream Power Erosion and Deposition (USPED) model at the US Army's Yakima Training Center (YTC), Washington. We incorporated a novel approach that compares model results with observed soil erosion and sediment deposition across the landscape in a spatially distributed fashion. The model results matched visually estimated values 90% of the time, providing an encouraging validation of the model. Historically, erosion models have been compared with sediment outflow from watersheds, providing no information regarding sources and sinks of erosion and deposition within watersheds. The USPED model is relatively simple to apply and the validation approach provides information in terms of the intensity and spatial distribution of soil erosion and sediment deposition that can be used to optimize the placement and size of soil erosion and sediment control efforts.