scholarly journals Slope- watershed coupling simulation under different vegetation coverage based on GAST model

2021 ◽  
Author(s):  
Kang Yongde ◽  
Hou Jingming ◽  
Tong Yu ◽  
Shi Baoshan ◽  
Pan Zhanpeng
Keyword(s):  
Sediment Transport ◽  
Soil Erosion ◽  
Reconstruction Algorithm ◽  
Vegetation Coverage ◽  
Hydrodynamic Process ◽  
Depth Reconstruction ◽  
Split Point ◽  
Edge Based ◽  
Control Equation ◽  
Volume Method

A non-equilibrium sediment transport soil erosion model based on finite volume method (FVM) coupled with two-dimensional hydrodynamic process is proposed, application of the GPU techniques in the numerical model, making it possible to simulate the sediment transport and bed evolution in a high resolution but efficient way. The first-order Gudonov format FVM is used to discreting the control equation. The variables on both sides of the unit interface are obtained by limiting slope interpolation. An efficient and robust non-negative depth reconstruction algorithm is used to solve the dry-wet boundary problem. This algorithm makes the model have second-order accuracy in space, and also effectively suppresses the numerical oscillation. Harten, Lax van Leer Contact (HLLC) approximate Riemann solver is used to calculate mass and momentum flux, and the friction source term is calculated by the proposed split point implicit method. These values are evaluated by a novel 2D edge-based MUSCL scheme. The code is programmed using C++ and CUDA, which can be run on GPU to greatly accelerate the calculation speed. In this paper, two numerical experiments show that the model performs well in accuracy and robustness of the algorithm in the process of slope erosion and watershed erosion. The constructed model can simulate the soil erosion of slope and watershed gully under different vegetation coverage, and characterize the erosion process of interaction between slope and gully.

scholarly journals Effect of Forest Management Operations on Aggregate-Associated SOC Dynamics Using a 137Cs Tracing Method

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 859
Author(s):  
Geng Guo ◽  
Xiao Li ◽  
Xi Zhu ◽  
Yanyin Xu ◽  
Qiao Dai ◽  
...  
Keyword(s):  
Forest Management ◽  
Soil Erosion ◽  
Management Practices ◽  
Negative Impact ◽  
Dynamic Change ◽  
Aggregate Size ◽  
Nutrient Loss ◽  
Vegetation Coverage ◽  
Forest Conversion ◽  
Mountain Areas

Although forest conversions have long been a focus in carbon (C) research, the relationship between soil erosion and the dynamic change of soil organic carbon (SOC) has not been well-quantified. The objective of this study was to investigate the effects of converting CBF (coniferous and broad-leaved mixed forests) to economic forests, including CF (chestnut forest), HF (hawthorn forest), and AF (apple forest), on the soil structure and nutrient loss in the Huaibei Rocky Mountain Areas, China. A 137Cs tracer method was used to provide soil erosion data in order to quantify the loss of aggregate-associated SOC. The results showed that forest management operations caused macro-aggregates to decrease by 1.69% in CF, 4.52% in AF, and 3.87% in HF. Therefore, the stability of aggregates was reduced. The SOC contents in each aggregate size decreased significantly after forest conversion, with the largest decreases occurring in AF. We quantified the loss of 0.15, 0.38, and 0.31 Mg hm−2 of aggregate-associated SOC after conversion from CBF to CF, AF, and HF, respectively. These results suggest that forest management operations have a negative impact on soil quality and fertility. CF has better vegetation coverage and less human interference, making it more prominent among the three economic forests species. Therefore, when developing forest management operations, judicious selection of tree varieties and appropriate management practices are extremely critical. In addition, measures should be taken to increase surface cover to reduce soil erosion and achieve sustainable development of economic forests.

Element Edge Based Discretization for TCAD Device Simulation

2021 ◽  
Author(s):  
Juan Sanchez ◽  
Qiusong Chen
Keyword(s):  
Computer Aided Design ◽  
Field Effect Transistor ◽  
Semiconductor Device ◽  
Device Simulation ◽  
Polarization Effects ◽  
Effect Transistor ◽  
Edge Based ◽  
Volume Method ◽  
Aided Design ◽  
Novel Devices

<div><div><div><p>Technology computer-aided design (TCAD) semiconductor device simulators solve partial differential equations (PDE) using the finite volume method (FVM), or related methods. While this approach has been in use over several decades, its methods continue to be extended, and are still applicable for investigating novel devices. In this paper, we present an element edge based (EEB) FVM discretization approach suitable for capturing vector-field effects. Drawing from a 2D approach in the literature, we have extended this method to 3D. We implemented this method in a TCAD semiconductor device simulator, which uses a generalized PDE (GPDE) approach to simulate de- vices with the FVM. We describe how our EEB method is compatible with the GPDE approach, allowing the modeling of vector effects using scripting. This method is applied to solve polarization effects in a 3D ferro capacitor, and a 2D ferroelectric field-effect transistor. An example for field- dependent mobility in a 3D MOSFET is also presented.</p></div></div></div>

Regulation and Critical Threshold of Grass Cover on Slope Runoff in LoessHilly Gully Region under Artificial

2021 ◽  
Author(s):  
Qiufen Zhang ◽  
Xizhi Lv ◽  
Rongxin Chen ◽  
Yongxin Ni ◽  
Li Ma
Keyword(s):  
Soil Erosion ◽  
Rainfall Intensity ◽  
Climatic Conditions ◽  
Vegetation Coverage ◽  
Critical Threshold ◽  
Runoff Generation ◽  
Grassland Vegetation ◽  
Slope Flow ◽  
The Impact ◽  
Slope Runoff

&lt;p&gt;The slope runoff caused by rainstorm is the main cause of serious soil and water loss in the loess hilly area, the grassland vegetation has a good inhibitory effect on the slope runoff, it is of great significance to reveal the role of grassland vegetation in the process of runoff generation and control mechanism for controlling soil erosion in this area. In this study, typical grassland slopes in hilly and gully regions of the loess plateau were taken as research objects. Through artificial rainfall in the field, the response rules of slope rainfall-runoff process to different grass coverage were explored. The results show that: (1) The time for the slope flow to stabilize is prolonged with the increase of vegetation coverage, and shortened with the increase of rainfall intensity; (2) At 60 mm&amp;#183;h &lt;sup&gt;&amp;#8722;1&lt;/sup&gt; rainfall intensity, the threshold of grassland vegetation coverage is 75.38%; at 90 mm&amp;#183;h&lt;sup&gt; &amp;#8722;1&lt;/sup&gt; rainfall intensity, the threshold of grassland vegetation coverage is 90.54%; at 120 mm&amp;#183;h &lt;sup&gt;&amp;#8722;1&lt;/sup&gt; rainfall intensity, the impact of grassland vegetation coverage on runoff is not significant; (3) the Reynolds number and Froude number of slope flow are 40.07&amp;#8210;695.22 and 0.33&amp;#8210;1.56 respectively, the drag coefficient is 1.42&amp;#8210;43.53. Under conditions of heavy rainfall, the ability of grassland to regulate slope runoff is limited. If only turf protection is considered, about 90% of grassland coverage can effectively cope with soil erosion caused by climatic conditions in loess hilly and gully regions. Therefore, in loess hilly areas where heavy rains frequently occur, grassland's protective effect on soil erosion is obviously insufficient, and investment in vegetation measures for trees and shrubs should be strengthened.&lt;/p&gt;

scholarly journals Modeling the dynamics of soil erosion and size-selective sediment transport over nonuniform topography in flume-scale experiments

2011 ◽  
Vol 47 (2) ◽  
Author(s):  
B. C. P. Heng ◽  
G. C. Sander ◽  
A. Armstrong ◽  
J. N. Quinton ◽  
J. H. Chandler ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Soil Erosion

Soil Erosion and Sediment Transport in the Morogoro River Catchment, Tanzania

1972 ◽  
Vol 54 (3-4) ◽  
pp. 125-155 ◽  
Author(s):  
Anders Rapp ◽  
Valter Axelsson ◽  
Len Berry ◽  
D. Hammond Murray-Rust
Keyword(s):  
Sediment Transport ◽  
Soil Erosion ◽  
River Catchment

How spatial vegetation distribution affects soil erosion and sediment transport

2021 ◽  
Author(s):  
Malte Kuegler ◽  
Thomas Hoffmann ◽  
Jana Eichel ◽  
Lothar Schrott ◽  
Juergen Schmidt
Keyword(s):  
Soil Erosion ◽  
Vegetation Cover ◽  
Vegetation Pattern ◽  
Vegetation Coverage ◽  
Future Research ◽  
Initial Increase ◽  
Vegetation Patterns ◽  
Erosion Rates ◽  
Catchment Areas ◽  
The Impact

&lt;p&gt;There are a multitude of factors that affect soil erosion and the process of sediment movement. One particular factor known to have a considerable impact is vegetation coverage within catchment areas.&amp;#160; Previous studies have examined the impact of vegetation cover on erosion.&amp;#160;However, there is a lack of research on how the spatial distribution of vegetation influences erosion rates.&lt;/p&gt;&lt;p&gt;A greater understanding of hillslope erosion is fundamental in modelling previous and future topographic changes under various climate conditions. Here, the physical based erosion model EROSION 3D &amp;#169; is used to evaluate the impact of a variety of vegetation patterns and degrees of vegetation cover on sediment erosion and transport. The model was applied on a natural catchment in La Campana (Central Chile). For this purpose, three different vegetation patterns were created: (i) random distribution, (ii) water-dependent distribution (TWIR) and (iii) banded vegetation pattern distribution. Additional to this, the areas covered by vegetation generated in the first step were expanded by steps of 10% [0...100%]. The Erosion3D &amp;#169; model then was applied on all vegetation patterns and degrees of cover.&lt;/p&gt;&lt;p&gt;Our results show an initial increase of soil erosion with increasing plant coverage within the catchment up to a certain cover threshold ranging between 10 and 40%. At larger vegetation cover soil erosion rates decline. The strength of increase and decline, as well as the cover-threshold is strongly conditioned by the spatial vegetation pattern. In the light of this, future research should pay particular attention to the properties of the plants and their distribution, not solely on the amount of biomass within catchment areas.&lt;/p&gt;

Study on Dynamic Changes of Soil Erosion in the North and South Mountains of Lanzhou

2021 ◽  
Author(s):  
Hua Zhang ◽  
Jinping Lei ◽  
Cungang Xu ◽  
Yuxin Yin
Keyword(s):  
Soil Erosion ◽  
Environmental Factors ◽  
Water Area ◽  
Vegetation Coverage ◽  
Dynamic Changes ◽  
The North ◽  
Joint Influence ◽  
Bare Land ◽  
Temporal And Spatial ◽  
North And South

Abstract This study takes the north and south mountains of Lanzhou as the study area, calculates the soil erosion modulus of the north and south mountains of Lanzhou based on the five major soil erosion factors in the RUSLE model and analyzes the temporal and spatial dynamic changes of soil erosion and the characteristics of soil erosion under different environmental factors. The results show that the soil erosion intensity of the north and south mountains of Lanzhou is mainly micro erosion in 1995, 2000, 2005, 2010, 2015 and 2018. They are distributed in the northwest and southeast of the north and south mountains. Under different environmental factors, the soil erosion modulus first increased and then decreased with the increase of altitude; the soil erosion modulus increased with the increase of slope; the average soil erosion modulus of grassland and woodland was larger, and the average soil erosion modulus of water area was the smallest; except for bare land, the average soil erosion modulus decreased with the increase of vegetation coverage. The soil erosion modulus in the greening range is lower than that outside the greening scope, mainly the result of the joint influence of precipitation, soil and vegetation.

Coastal Hydrodynamic and Sediment-Salinity Transport Simulations for Southwest Louisiana Using Measured Vegetation Data

2015 ◽  
Author(s):  
Xiao Han ◽  
Ning Zhang
Keyword(s):  
Sediment Transport ◽  
Storm Surge ◽  
Water System ◽  
Water Systems ◽  
Vegetation Coverage ◽  
Target Area ◽  
Sediment Distribution ◽  
Entire Area ◽  
Lake Charles ◽  
The City

Storm-surge flood is a major thread to the inhabitants and the health of the marshes in Southwest Louisiana. The floods caused direct damages to the area, but also indirectly caused excessive sedimentations in the water system, especially in Calcasieu Ship Channel which is a vital industrial water way connecting the City of Lake Charles to the Gulf. It is well known that coastal wetlands and marshes have significant impacts on the prevention and reduction of coastal floods. The wetland vegetation creates larger frictions to the flooding water and acts as the first line of defense against any storm surge floods. In this study, we center Calcasieu Ship Channel, and hydrodynamic and sediment transport simulations were conducted for Calcasieu Ship Channel and surrounding areas. The target area ranges from the city of Lake Charles as the north end and the Gulf of Mexico as the south end, and includes three connected water systems, Calcaiseu Lake, Prien Lake and Lake Charles. The entire Calcasieu Ship Channel running from north to south is included in the domain along with the Gulf Intracoastal Waterway (GIWW) in east and west directions. In authors’ previous study, only the area of south portion of the ship channel, Calcasieu Lake and its surrounding wetlands was simulated and studied. This study is a major upgrade to the model, which provides more complete understanding of the flow and sediment transport in the entire area, as well as the interactions among all water systems surrounding the ship channel. There are wetlands (two National Wild Life Refuges, one in the west and one in the east) surrounding Calcaiseu Lake, while there are various of vegetated and non-vegetated areas surrounding Prien Lake and Lake Charles. The standard 2-D depth averaged shallow water solver was utilized for the simulation of the flow phase and a standard Eulerian scalar transport equation was solved for the sediment and salinity phases. In the sediment phase, the sediment deposition and re-suspension effects are included, while in the salinity phase, the precipitation and evaporation are included. A realistic vegetation model was implemented to represent various types of vegetation coverage in the target area, and appropriate friction values were assigned to different non-vegetated areas. Measured and observed vegetation data were utilized. A coastal storm surge flood was simulated, and effects of vegetation on flood reduction and sediment distribution were investigated. The total flooded area, the flood speed, and the distribution of the flooding water and sediments were compared between vegetated and non-vegetated areas to show the differences between different types of surfaces.

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