Estimating rill erosion and sediment transport processes along a saturated purple soil slope

2021 ◽  
Author(s):  
Han Zhen ◽  
Xiaoyan Chen ◽  
Yanhai Li ◽  
Shiqi Chen ◽  
Xiaojie Gu ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Sediment Concentration ◽  
Transport Processes ◽  
Purple Soil ◽  
Rill Erosion ◽  
Soil Slope ◽  
Sediment Transportation ◽  
Erosion Models ◽  
Increasing Trend ◽  
Soil Slopes

A plough pan with reduced permeability always accumulates infiltrated water along slopes then saturates the cultivated layer under continuous rain. Topsoil saturation is a frequent phenomenon and an important process of the special soil slopes. A methodology and device system was used in this study to keep cultivated purple soil saturated. Strands of scouring tests were developed to quantify the rill erosion and sediment transport processes along a saturated purple soil slope at four experiment slopes (5°, 10°, 15°, and 20°) and three flow discharges (2, 4 and 8 L min−1). The experimental results indicated that the sediment transport capacity on a saturated purple soil slope ranged from 0.03 to 1.56 kg s−1 m−1 with the increasing trend along the slope gradient and flow discharge, and the increasing trend could be well matched by a nonlinear multivariable equation. The sediment concentration of the saturated purple soil slope exponentially increased with rill length and decreased with the increment rate and the maximum sediment concentrations observed in this study in different hydraulic events ranged from 108.13 to 1174.20 kg m-3. Saturated and non-saturated purple soil slopes erode differently with the maximum sediment concentration of saturated purple soil slope recorded at approximately 1.42-2.10 times the values for non-saturated purple soil slope. The findings of this research help illustrate the sediment transportation and erosion behaviors of a saturated purple soil slope, and serve as the basis for determining the parameters in the erosion models of the purple soil slope.

scholarly journals Effects of Biochar on Sediment Transport and Rill Erosion after Two Consecutive Years of Seasonal Freezing and Thawing

2021 ◽  
Vol 13 (13) ◽  
pp. 6984
Author(s):  
Tianxiao Li ◽  
Pengfei Yu ◽  
Dong Liu ◽  
Qiang Fu ◽  
Renjie Hou ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Sowing Date ◽  
Sediment Concentration ◽  
Transport Processes ◽  
Rill Erosion ◽  
Freezing And Thawing ◽  
Seasonal Freezing ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Slope Runoff

This research explored the effects of biochar on slope runoff and sediment transport processes and the hydrodynamic mechanism of rill erosion under the seasonal freeze–thaw climate in the black soil area of Northeast China. The four slopes of 1.8, 3.6, 5.4 and 7.2° were set, corn straw biochar was used, and three biochar contents of 0 kg m−2 (B0 treatment), 6 kg m−2 (B6 treatment) and 12 kg m−2 (B12 treatment) were applied. The experimental plot was placed outdoors to simulate the freeze–thaw cycle of sloping farmland under natural conditions. Three artificial simulated rainfall tests were carried out before the end of seasonal freeze–thaw cycles and spring sowing date (May) in 2018 and 2019. The sediment transport process of runoff and the variation of hydrodynamic parameters in rills were analyzed under one and two seasons of freezing and thawing in natural outdoor conditions. The results show that biochar has a positive effect on reducing rainfall runoff and soil loss after one year and two years of seasonal freezing and thawing. The effect of biochar on the sediment concentration of slope runoff increased with increasing application time; in the second year, the B6 and B12 treatments reduced the sediment concentration by 5.5–14.8% and 3.3–13.6%, respectively, compared with the values of the first year. The Reynolds number (Re) in the rill flow after the B6 and B12 treatments decreased with increasing duration, which effectively reduced the turbulence degree of the flow on the rill of the slope. With the increase in duration, the rill critical erosion power increased; in 2018 and 2019, the critical shear force, critical runoff power and critical unit runoff power were 0.403 Pa, 0.098 m s−1, and 0.002 N m−1 and 0.497 Pa, 0.124 m s−1, and 0.003 N m−1, respectively. This result indicates that increasing the duration and number of seasonal freeze–thaws can promote the development of biochar control of the runoff and sediment processes on slope and rill development.

Runooff ratio as a factor in the empirical modelling of soil erosion by individual rainstorms

Soil Research ◽  
1997 ◽  
Vol 35 (1) ◽  
pp. 1 ◽  
Author(s):  
P. I. A. Kinnell
Keyword(s):  
Soil Loss ◽  
Sediment Concentration ◽  
Rill Erosion ◽  
Local Conditions ◽  
Empirical Modelling ◽  
Control Practice ◽  
Number Of Factors ◽  
Erosion Models ◽  
Erosivity Index ◽  
Bare Fallow

A number of factors that influence erosion have separate and differing effects on flow discharge and sediment concentration, depending on local conditions. Empirical erosion models that do not have mechanisms to help account for these separate and differing effects often lack the capacity to predict event erosion adequately in many locations. In this paper, the product of the EI30 index, the erosivity index used in the Universal Soil Loss Equation (USLE) and the revised version (RUSLE), and the runoff ratio (QR) is discussed in relation to its capacity to act as an event erosivity index where sheet and rill erosion occur either separately or together in a rainstorm. An analysis of runoff and soil loss data shows the index to be superior to the EI30 index as an event erosivity index for storms on bare fallow plots at Holly Springs, Mississippi. The inclusion of runoff as an independent term in the USLE/RUSLE results in a need to determine new values for the soil erodibility factor, K. Existing USLE/RUSLE equations for determining L and S (topographic factors), C (a crop and crop management factor), and P (an erosion control practice factor) may be used as first approximations provided that the values of the new index are determined for the unit plot condition. Since many of the factors that determine L, S, C, and P influence runoff, new methods to determine these parameters need to be developed in the future if the new index is to be used most effectively.

scholarly journals Inferring Sediment Transport Capacity from Soil Microtopography Changes on a Laboratory Hillslope

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 929
Author(s):  
Sayjro Nouwakpo ◽  
Chi-hua Huang ◽  
Laura Bowling ◽  
Phillip Owens ◽  
Mark Weltz
Keyword(s):  
Experimental Data ◽  
Sediment Transport ◽  
Transport Processes ◽  
Transport Capacity ◽  
Erosion Modeling ◽  
Subsurface Hydrology ◽  
Concentrated Flow ◽  
Erosion Models ◽  
Flow Hydraulics ◽  
The Impact

In hillslope erosion modeling, the Transport Capacity (Tc) concept describes an upper limit to the flux of sediment transportable by a flow of given hydraulic characteristics. This widely used concept in process-based erosion modeling faces challenges due to scarcity of experimental data to strengthen its validity. In this paper, we test a methodology that infers the exceedance of transport capacity by concentrated flow from changes to soil surface microtopography sustained during rainfall-runoff events. Digital Elevation Models (DEMs) corresponding to pre- and post-rainfall events were used to compute elevation change maps and estimate spatially-varying flow hydraulics ω taken as the product of flow accumulation and local slope. These spatial data were used to calculate a probability of erosion PE at regular flow hydraulics intervals. The exceedance of Tc was inferred from the crossing of the PE = 0.5 line. The proposed methodology was applied to experimental data collected to study the impact of soil subsurface hydrology on soil erosion and sediment transport processes. Sustained net deposition occurred under drainage condition while PE for seepage conditions mostly stayed in the net erosion regime. Results from this study suggest pulsating erosion patterns along concentrated flow networks with intermittent increases in PE to local maxima followed by declines to local minima. These short-range erosion patterns could not be explained by current Tc-based erosion models. Nevertheless, Tc-based erosion models adequately capture observed decline in local PE maxima as ω increased. Applying the proposed approach suggests a dependence of Tc on subsurface hydrology with net deposition more likely under drainage conditions compared to seepage conditions.

scholarly journals Hydrodynamics and suspended sediment transport in the Camboriú estuary - Brazil: pre jetty conditions

2009 ◽  
Vol 57 (2) ◽  
pp. 123-135 ◽  
Author(s):  
Eduardo Siegle ◽  
Carlos A. F. Schettini ◽  
Antonio H. F. Klein ◽  
Elírio E. Toldo Jr.
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Spring Tide ◽  
Sediment Concentration ◽  
Transport Processes ◽  
Stokes Drift ◽  
Tidal Range ◽  
Background Information ◽  
Suspended Sediment Transport ◽  
Estuarine Hydrodynamics

Estuarine hydrodynamics is a key factor in the definition of the filtering capacity of an estuary and results from the interaction of the processes that control the inlet morphodynamics and those that are acting in the mixing of the water in the estuary. The hydrodynamics and suspended sediment transport in the Camboriú estuary were assessed by two field campaigns conducted in 1998 that covered both neap and spring tide conditions. The period measured represents the estuarine hydrodynamics and sediment transport prior to the construction of the jetty in 2003 and provides important background information for the Camboriú estuary. Each field campaign covered two complete tidal cycles with hourly measurements of currents, salinity, suspended sediment concentration and water level. Results show that the Camboriú estuary is partially mixed with the vertical structure varying as a function of the tidal range and tidal phase. The dynamic estuarine structure can be balanced between the stabilizing effects generated by the vertical density gradient, which produces buoyancy and stratification flows, and the turbulent effects generated by the vertical velocity gradient that generates vertical mixing. The main sediment source for the water column are the bottom sediments, periodically resuspended by the tidal currents. The advective salt and suspended sediment transport was different between neap and spring tides, being more complex at spring tide. The river discharge term was important under both tidal conditions. The tidal correlation term was also important, being dominant in the suspended sediment transport during the spring tide. The gravitational circulation and Stokes drift played a secondary role in the estuarine transport processes.

scholarly journals Experimental validation of some basic assumptions used in physically based soil erosion models

2011 ◽  
Vol 8 (1) ◽  
pp. 1247-1286 ◽  
Author(s):  
S. Wirtz ◽  
M. Seeger ◽  
J.-F. Wagner ◽  
J. B. Ries
Keyword(s):  
Soil Erosion ◽  
Experimental Validation ◽  
Sediment Concentration ◽  
External Factors ◽  
Fallow Land ◽  
Rill Erosion ◽  
Basic Assumptions ◽  
Erosion Models ◽  
Physically Based ◽  
Process Based Models

Abstract. In spring 2009, four rill experiments were accomplished on a fallow land. Most external factors as well as discharge quantity (9 L min-1) were held constant or at least in the same range. Following most process based soil erosion models, detachment or runoff values should therefore be similar, but the experimental results show clear differences in sediment concentration, runoff and other measured and calculated values. This fact underlines the problems of process based models: concerning rill erosion, different processes take part and the process described by the models is only responsible for a part of the eroded material.

Three-Dimensional Flow Structures and Suspended-Sediment Transport in the Dam Area of Large Reservoir

2014 ◽  
Vol 501-504 ◽  
pp. 1981-1985
Author(s):  
Dong Dong Jia ◽  
Jian Yin Zhou ◽  
Xue Jun Shao ◽  
Xi Bao Zhang
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Transport Processes ◽  
Flow Structures ◽  
Suspended Sediment Transport ◽  
Large Reservoir ◽  
Secondary Currents ◽  
Load Sediment

The three-dimensional (3-D) flow structures and suspended-load sediment transport processes in the dam area of the Three Gorges Project (TGP) with large water depth were simulated by a 3-D mathematical model. The characteristics of flow structures and suspended-load concentration distribution were analyzed based on the simulated results. Strong 3-D features of flow structures can be found in the dam area, the secondary currents are significant. The suspended-load sediment concentration reduced much faster in wider valley areas, where deposits accumulated. Due to impact of secondary currents, the maximum concentration of suspended-load occurs at the convex side while the minimum at the concave side. It demonstrates that the 3-D numerical modeling is a useful prediction technique and research tool to enhance our understanding of flow structures and mass transport processes in natural rivers with complex boundary.

scholarly journals On sediment transport under dam-break flow

2002 ◽  
Vol 473 ◽  
pp. 265-274 ◽  
Author(s):  
DAVID PRITCHARD ◽  
ANDREW J. HOGG
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Numerical Models ◽  
Sediment Concentration ◽  
Transport Processes ◽  
Dam Break ◽  
Suspended Sediment Transport ◽  
Test Bed ◽  
Small Depth ◽  
Dam Break Flow

We present exact solutions for suspended sediment transport under one-dimensional dam-break flow, both over a dry bed and into a small depth of tail water. We explicitly calculate the suspended sediment concentration, including erosion and deposition, and investigate the effect of varying the erosional and depositional models employed. These solutions order insight into sediment transport processes under floods or sheet flow events, and we also discuss their application as test-bed solutions for the validation of numerical models.

New Instrumentation for Sediment Dynamics Studies

2002 ◽  
Vol 36 (1) ◽  
pp. 55-58 ◽  
Author(s):  
Severine Thomas ◽  
Peter V. Ridd ◽  
Peter J. Smith
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Technical Note ◽  
Sediment Dynamics ◽  
Transport Processes ◽  
Erosion And Deposition ◽  
Deposition Rates ◽  
New Instrumentation

The study of sediment transport processes is hampered by a lack of instrumentation for measuring important parameters such as erosion and deposition rates. This technical note describes three novel pieces of equipment that have been designed to provide information about erosion, deposition, suspended sediment concentration and light.

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