Erosion Rates in Dam Catchments in Jordan—Effects of Topography, Geology, and Urbanizations

Erosion as a natural process produces soils, which are very important natural resources for the fest land plant- and animal kingdoms. Loss of the soil cover reduces agricultural production, biodiversity, and the role of soil as a filter for infiltrating water to replenish the groundwater. It also threatens the food supplies. The knowledge of erosion rates of rocks and terrains is important for developing proactive measures to protect soils from erosion and loss. In this study, erosion rates of catchment areas were calculated based on dams’ catchment extensions and the sediment loads transported by flood flows into dams’ lakes. The study results show that the chemically, via floodwater, transported quantities of materials are negligible compared to the solid materials transported by the water. It calculates erosion rates ranging from 0.013 to 0.212 mm/yr (13 - 212 m/106 yr) for the different catchment areas. Erosion rates in Jordan are, generally, higher than those calculated for the different parts of the world ranging from 2.5 to 60 m/106 yr. This fact can be explained by the very steep topography, calcareous rock cover of the catchment areas and the barren rock exposures.

Quantitative Model for Estimating Soil Erosion Rates Using 137 Cs *1

A quantitative model was developed to relate the amount of 137 Cs loss from the soil profile to the rate of soil erosion. According to mass balance model, the depth distribution pattern of 137 Cs in the soil profile, the radioactive decay of 137 Cs, sampling year and the difference of 137 Cs fallout amount among years were taken into consideration. By introducing typical depth distribution functions of 137 Cs into the model, detailed equations for the model were got for different soils. The model shows that the rate of soil erosion is mainly controlled by the depth distribution pattern of 137 Cs, the year of sampling, and the percentage reduction in total 137 Cs. The relationship between the rate of soil loss and 137 Cs depletion is neither linear nor logarithmic. The depth distribution pattern of 137 Cs is a major factor for estimating the rate of soil loss. Soil erosion rate is directly related with the fraction of 137 Cs content near the soil surface. The influences of the radioactive decay of 137 Cs, sampling year and 137 Cs input fraction are not large compared with others.

Solid Particle Erosion of AISI 304 SS Caused by Alumina Particles

This research work was carried out with the aim of continuing to expand knowledge on the behaviour of AISI 304 stainless steel against solid particle erosion. In this particular case, the steel was subjected to the impact of alumina particles, which are hard abrasives with irregular and angular shapes. Different characterization techniques were applied to gain a better understanding of alumina. For instance, particle size distribution was obtained using the Analysette 28 Image Sizer and the particle size was between 300 - 400 µm. SEM and EDS analysis were used to know the morphology and chemical composition of both the abrasive particles and AISI 304 stainless steel. Additionally, mechanical properties values such as the hardness and Young’s modulus of AISI 304 steel were attained using a Berkovich indenter (model TTX-NHT, CSM Instruments). On the other hand, two tests were carried out for each impact angle used, 30˚, 45˚, 60˚ and 90˚, with a particle velocity of 24 ± 2 m/s and an abrasive flow rate of 63 ± 0.5 g/min, employing a test rig based on ASTM G76-95 standard. SEM images using two detectors, Backscattered Electron Detector (BED) and Low Electron Detector (LED), were employed to identify the wear mechanisms on the AISI 304 eroded surfaces at 30˚ and 90˚. Finally, the erosion rates of AISI 304 compared to those results reached by AISI 1018 steel and AISI 420 stainless steel tested under identical conditions in previous works.

A STUDY ON ^(10)Be IN QUARTZ FROM LOESS OF CHINA (Ⅰ)——In situ COSMOGENIC ^(10)Be AND EROSION RATES OF SOURCE REGIONS OF LOESS

In situ cosmogenic ^(10)Be in quartz from loess deposited in the last 2,000,000 a is considered to have been derived mainly from initial ^(10)Be in source regions and it bears abundant information about changes in erosion rates of source regions. As [have been estimated, the concentrations of 'in situ cosmogenic ^(10)Be' in quartz from samples GL47(L1) andGL83 (L2) collected from the Luochuan loess section are 5×10~5 atom/g and 2.2×10~6 atom/g, respectively. As calculated on the basis of the above estimates, the erosion rates of the source regions are: εBeL1=1.5×10^(-3) cm/a for the L1 period (10,000—90,000 a) and εBeL2=3.8×10^(-4) cm/a for the L2 period (130,000—190,000 a). Studies of 'in situ cosmogeuic ^(10)Be' in quartz from loess at deeper levels are expected to be applied to ^(10)Be dating of loess strata.

Soil Erosion Spatial Distribution Character of Sloping Field in the Sichuan Hilly Basin:Taking a Cultivated Slope in Neijiang as Example

^137Cs nuclear tracing technique was used to estimate rates of soil redistribution on a sloping field with traditional erosion control measures located near Shangqiao Village, Neijiang City, in the Sichuan Hilly Basin of China. The downslope changes of ^137 Cs inventory and its corresponding soil erosion rates in the sloping field show a rolling trend and have two peak values in two inflexions of the sloping field, these result reflects that the changes of microphysiognomy play a key role on the spatial soil redistribution of the sloping field.

Soil Erodibility Rates through a Hydraulic Flume Erosometer: Test Assembly and Results in Sandy and Clayey Soils

This paper presents a proposal for erodibility quantitative evaluation through a hydraulic flume based on the Inderbitzen erosion test. The equipment scheme and procedures for result calculation are described, following a review of literature. Through the proposed procedure, 24 tests are conducted, in order to study the erodibility of a sandy soil and a clayey soil, in undeformed and reconstituted conditions. These are conducted using grass roots in controlled quantities, to quantify root effects on erodibility. The results of soil loss by elapsed time and the definition of the erodibility K factor shows that clayey soil is 90% less erodible compared with sandy soil. Also, roots show no significant relationship with K factor and the undeformed sample is less erodible, compared with reconstituted sample. The test methodology and the results allowed soil classification, analytical data and comparative results between different cases.

Influence of Metal Oxides on the Arc Erosion Behaviour of Silver Metal Oxides Electrical Contact Materials

In the present work investigations have been made to see the role of metal oxides on the performance of the silver metal oxides electrical contact materials. Silver metal oxide materials of three different compositions Ag-10CdO, Ag-7.6SnO2-2.3ln2O3 and Ag-10ZnO were prepared by internal oxidation process under identical processing conditions. These materials were tested for electrical conductivity, hardness, and erosion loss. Performing an accelerated test on the actual contactor assessed the electrical performance, involving erosion loss and temperature rise of the processed materials. The arc-eroded surface was characterized under scanning electron microscope. The study of the eroded surfaces of contacts indicates that the thermal stability of metal oxides depends on nature of silver-metal oxide interface and their mode of erosion. An attempt is made to correlate the surface features of the eroded contacts with the thermal stability of metal oxides.

Using ^(137)Cs Tracing Methods to Estimate Soil Redistribution Rates and to Construct a Sediment Budget for a Small Agricultural Catchment in the Three Gorges Reservoir Region,China

Soil erosion and associated off-site sedimentation are threatening the sustainable use of the Three Gorges Dam. To initiate management intervention to reduce sediment yields, there is an increasing need for reliable information on soil erosion in the Three Gorges Reservoir Region （TGRR）. The purpose of this study is to use 137Cs tracing methods to construct a sediment budget for a small agricultural catchment in the TGRR. Cores were taken from a pond and from paddy fields, for laTCs measurements. The results show that the average sedimentation rate in the pond since 1963 is 1.50 g cm-2 yr-1 and the corresponding amount of sediment deposited is 1,553 t. The surface erosion rate for the sloping cultivated lands and the sedimentation rate in the paddy fields were estimated to be 3,770 t km-2 yr-1 and 2,600 t km-2 yr^1 respectively. Based on the estimated erosion and deposition rates, and the area of each unit, the post 197o sediment budget for the catchment has been constructed. A sediment delivery ratio of 0.5 has been estimated for the past 42 years. The data indicate that the sloping cultivated lands are the primary sediment source areas, and that the paddy fields are deposition zones. The typical land use pattern （with the upper parts characterized by sloping cultivated land and the lower parts by paddy fields） plays an important role in reducing sediment yield from agricultural catchments in the TGRR. A 137Cs profile for the sediment deposited in a pond is shownto provide an effective means of estimating the land surface erosion rate in the upstream catchment.

Numerical simulation of predicting and reducing solid particle erosion of solid-liquid two-phase flow in a choke

Chokes are one of the most important components of downhole flow-control equipment. The particle erosion mathematical model, which considers particle-particle interaction, was established and used to simulate solid particle movement as well as particle erosion characteristics of the solid-liquid two-phase flow in a choke. The corresponding erosion reduction approach by setting ribs on the inner wall of the choke was advanced. This mathematical model includes three parts： the flow field simulation of the continuous carrier fluid by an Eulerian approach, the particle interaction simulation using the discrete particle hard sphere model by a Lagrangian approach and calculation of erosion rate using semiempirical correlations. The results show that particles accumulated in a narrow region from inlet to outlet of the choke and the dominating factor affecting particle motion is the fluid drag force. As a result, the optimization of rib geometrical parameters indicates that good anti-erosion performance can be achieved by four ribs, each of them with a height （H） of 3 mm and a width （B） of 5 mm equaling the interval between ribs （L）.

Gravity erosion and lithology in Pisha sandstone in southern Inner Mongolia

Pisha sandstone is a soft rock found in the southern zone of the Inner Mongolia Autonomous Region of Inner Mongolia. The presence of soft Pisha sandstone in the middle reaches of the Yellow River coincides with large areas of bedrock erosion in the river’s basin, with the average total erosion modulus as high as 44 570 t/(km^2·a). Such high levels of erosion are one of the main sources of coarse mud and sands in the Yellow River. Erosion by gravitational forces such as snow glide and landslip are the main erosion types in Pisha sandstone region. The gravity erosion modulus can be as high as 25 615 t/(km^2·a), accounting for 30.6% of the total average erosion. Our paper investigates the characteristics of Pisha sandstone in relation to the development of gravity erosion mechanisms. We conducted field investigations in Pisha sandstone region for original state rock sampling. Test results from analyses of the rock properties indicate that the mineral composition, structure and microstructure characteristics of Pisha sandstone determine its varying capacity to resist weathering. Degrees of weathering in slightly different lithological layers of Pisha sandstone lead to different erosion rates. In this way, erosion forces combined with the varying lithological strata in the rock aggravate gravitational erosion in Pisha sandstone.

Uranium comminution age responds to erosion rate semiquantitatively

Here we present(^(234)U/^(238)U)data from river sediments collected on the Tibetan Plateau.The(^(234)U/^(238)U)ratios of a specific grain size fraction show good correlation with erosion rates,which were determined by in-situ–produced cosmogenic nuclides.This correlation has previously been observed in a wide range of geomorphic settings,suggesting that(^(234)U/^(238)U)ratios of fluvial sediments have great potential to quantify erosion rates.

Two-flow model for piping erosion based on liquid-solid coupling

Previous studies have indicated that piping erosion greatly threatens the safe operation of various hydraulic structures. However, few mathematical models are available to perfectly describe the erosion process due to the complexity of piping. The focus of the present work is to propose a new fluid solid coupling model to eliminate the shortcomings of existing work. A 'pseudo-liquid' assumption is suggested to simulate the particle movement in the erosion process. Then, based on the mass and momentum conservations of the moving particles and flowing water, a new two-flow model is established by using the continuity equations and motion equations. In the model, the erosion rate of soil is determined with a particle erosion law derived from tests results of STERPI. And ERGUN's empirical equation is used to determine the interaction forces between the liquid and the solid. A numerical approach is proposed to solve the model with the finite volume method and SIMPLE algorithm. The new model is validated with the tests results of STERPI. And the soil erosion principles in piping are also explored.

A field investigation of wind erosion in the farming–pastoral ecotone of northern China using a portable wind tunnel: a case study in Yanchi County

The farming-pastoral ecotone in northern China is an extremely fr@e ecological zone where wind erosion of cropland and rangeland is easy to occur. In this study, using a portable wind tunnel as a wind simulator, we conducted field simulated wind erosion experiments combined with laboratory analysis to investigate wind erosion of soils in trampled rangeland, non-tilled cropland and tilled cropland in Yanchi County, China. The results showed that compared with rangeland, the cropland had a higher soil water holding capacity and lower soil bulk density. The wind erosion rate of trampled rangeland was much higher than those of non-tilled cropland and tilled cropland. For cropland, the wind erosion rate of the soil after tilling was surprisingly less than that of the soil before tilling. With increasing of wind speed, the volume mean diameter of the eroded sediment collected by the trough in the wind tunnel generally increased while the clay and silt content decreased for all soils. The temporal variation in wind erosion of the trampled rangeland indicated that particle entrainment and dust emission decreased exponentially with erosion time through the successive wind erosion events due to the exhaustion of erodible particles.

Experimental studies on the erosion rate of different heat treated carbon steel economiser tubes of power boilers by fly ash particles

The experimental investigations on the effect of the fly ash particle size, velocity, impingement angle, and feed rate were done with an emphasis on the effect of erosion on annealed SA 210 GrA1 （A） and normalized SA 210 GrA1 （N） carbon steel economizer-tube materials. Erosion rates were evaluated with different impingement angles ranging from 15° to 90°, at four different velocities of 32.5, 35, 37.5, and 40 m/s, and at four different feed rates of fly ash particles of 2, 4, 6 and 8 g/min. The erodent used was fly ash particles, sizes ranging from 50-250 μm of irregular shapes. Erosion rate is found to be the maximum at the impingement angle of 30°. Erosion rates of the carbon steel tube in different heat treatment conditions, annealed and normalized, at a constant velocity of 32.5 m/s with different angles were studied. In all cases of feed rates, impingement angles, particle sizes, and velocities of fly ash particles, it has been found that the erosion rate of the annealed tube is less than that of the normalized tube. Empirical correlations for erosion rate relating the velocity, size, feed rate, and impingement angle of the particles and elongation property of the target materials were arrived. Morphologies of the eroded surface were examined by scanning electron microscope （SEM）.

Microstructure and Erosion Resistance of in-situ SiAlON Reinforced BN-SiO2 Composite Ceramics

BN-SiO-SiAlON composite ceramics were successfully prepared by the means of hot pressed sintering.Xe plasma flow generated by HallThruster was used for sputtering the surface of the samples in order to evaluate the plasma erosion resistance.XRD,TEM,SEM,and LSCM were used to characterize the phase composition and morphologies of as-made composite ceramics before and after Xe plasma erosion.The ceramics were composed of h-BN,fused silica,and SiAlON,which maintained structuralstability during the process of Xe plasma sputtering.In conclusion,comparing with BN-SiOcomposite ceramics,the plasma erosion rate of BN-SiO-SiAlON composite ceramics decreases significantly at first then rises with the increase of AlN addition.Erosion pits can be observed by using SEM on the surface after plasma sputtering,which demonstrates that the BN grains have dropped off the surface.In addition,mechanicaldenudation by high-speed Xe ions is recognized as the injury mechanism for the BN-matrix composite materials.

Influence of Vegetation on Runoff and Sediment in Wind-water Erosion Crisscross Region in the Upper Yellow River of China

All characteristics of vegetation,runoff and sediment from 1960 to 2010 in the Xiliu Gully Watershed,which is a representative watershed in wind-water erosion crisscross region in the upper reaches of the Yellow River of China,have been analyzed in this study.Based on the remote sensing image data,and used multi-spectral interpretation method,the characteristics of vegetation variation in the Xiliu Gully Watershed have been analyzed.And the rules of precipitation,runoff and sediment's changes have been illuminated by using mathematical statistics method.What′s more,the influence mechanism of vegetation on runoff and sediment has been discussed by using the data obtained from artificial rainfall simulation test.The results showed that the main vegetation type was given priority to low coverage,and the area of the low vegetation coverage type was reducing year by year.On the country,the area of the high vegetation coverage type was gradually increasing.In a word,vegetation conditions had got better improved since 2000 when the watershed management project started.The average annual precipitation of the river basin also got slightly increase in 2000–2010.The average annual runoff reduced by 37.5%,and the average annual sediment reduced by 73.9% in the same period.The results of artificial rainfall simulation tests showed that the improvement of vegetation coverage could increase not only soil infiltration but also vegetation evapotranspiration,and then made the rainfall-induced runoff production decrease.Vegetation root system could increases the resistance ability of soil to erosion,and vegetation aboveground part could reduce raindrop kinetic energy and splash soil erosion.Therefore,with the increase of vegetation coverage,the rainfall-induced sediment could decrease.

Transport Rate of Surface Erosion by the Hydrodynamics

The coherence and exposure degree are used in analyzing initiation of slope sediment.The initial ve- locity is built by using a critical roiling model.A transport rate formula of slope erosion is established using the Meyer-Peter model.The formula is tested by experiment and agrees well but the errors are big when the flow discharge and rain intensity are smaller.

Soil loss and sedimentation rates in a subcatchment of the Yellow river Basin in China

Soil loss by water erosion is one of the main threats to soil health and food production in intensively used agricultural areas.To assess its significance to overall sediment production,we applied the Water and Tillage Erosion Model/Sediment Delivery model(WaTEM/SEDEM)to the Luoyugou catchment,a sub-catchment of the Yellow River Basin within the Chinese Loess Plateau.WaTEM/SEDEM considers rill and interrill erosion and deposition rates to calculate the sediment yield rates leaving the catchment.Ter-races were established in the 1990s to reduce soil loss in this area,but no soil erosion modeling has been published regarding the effect of this mitigation measure.Therefore,we applied 1000 Monte Carlo simulations of the WaTEM/SEDEM,and the modeled average soil loss by rill and interrill erosion for 2020 was 12.2±0.5 t ha^(-1)yr^(-1),with a sediment yield at the outlet of 53,207.8±11,244.1 t yr^(-1).The results indicated that the terracing reduced gross soil loss rates(from 51.8t ha^(-1)yr^(-1)in 1986 to 12.2±0.5 t ha^(-1)yr^(-1)in 2020),while land cover changes,mainly the conversion of forests and grassland,partly coun-teracted the mitigation(combined effect:76%reduction).Modeled sediment loads by rill and interrill erosion accounted for 22.8%of the total long-term sediment production recorded by flow discharge measurements.Other processes not considered by the model,such as landslides,gully erosion,riverbank erosion,and sediment production by construction,seem to predominantly influence the overall sedi-ment yield.Considering years with baseline sediment production only,the measured and modeled sediment yields compared favorably,indicating that the latter processes primarily contribute during extreme events.

Minimum Bedrock Exposure Ages and Their Implications:Larsemann Hills and Neighboring Bolingen Islands,East Antarctica

Considerable controversy exists over whether or not extensive glaciation occurred during the global Last Glacial Maximum（LGM） in the Larsemann Hills.In this study we use the in situ produced cosmogenic nuclide ^（10）Be（half life 1.51 Ma） to provide minimum exposure ages for six bedrock samples and one erratic boulder in order to determine the last period of deglaciation in the Larsemann Hills and on the neighboring Bolingen Islands.Three bedrock samples taken from Friendship Mountain（the highest peak on the Mirror Peninsula,Larsemann Hills;～2 km from the ice sheet） have minimum exposure ages ranging from 40.0 to 44.7 ka.The erratic boulder from Peak 106（just at the edge of the ice sheet） has a younger minimum exposure age of only 8.8 ka.The minimum exposure ages for two bedrock samples from Blundell Peak（the highest peak on Stornes Peninsula,Larsemann Hills;～2 km from the ice sheet） are about 17 and 18 ka.On the Bolingen Islands（southwest to the Larsemann Hills;～10 km from the ice sheet）,the minimum exposure age for one bedrock sample is similar to that at Friendship Mountain（i.e.,44 ka）.Our results indicate that the bedrock exposure in the Larsemann Hills and on the neighboring Bolingen Islands commenced obviously before the global LGM（i.e.,20-22 ka）,and the bedrock erosion rates at the Antarctic coast areas may be obviously higher than in the interior land.

Tectonic-thermal history and hydrocarbon potential of the Pearl River Mouth Basin,northern South China Sea:Insights from borehole apatite fission-track thermochronology

The Pearl River Mouth Basin(PRMB)is one of the most petroliferous basins on the northern margin of the South China Sea.Knowledge of the thermal history of the PRMB is significant for understanding its tectonic evolution and for unraveling its poorly studied source-rock maturation history.Our investigations in this study are based on apatite fission-track(AFT)thermochronology analysis of 12 cutting samples from 4 boreholes.Both AFT ages and length data suggested that the PRMB has experienced quite complicated thermal evolution.Thermal history modeling results unraveled four successive events of heating separated by three stages of cooling since the early Middle Eocene.The cooling events occurred approximately in the Late Eocene,early Oligocene,and the Late Miocene,possibly attributed to the Zhuqiong II Event,Nanhai Event,and Dongsha Event,respectively.The erosion amount during the first cooling stage is roughly estimated to be about 455-712 m,with an erosion rate of 0.08-0.12 mm/a.The second erosion-driven cooling is stronger than the first one,with an erosion amount of about 747-814 m and an erosion rate between about 0.13-0.21 mm/a.The erosion amount calculated related to the third cooling event varies from 800 m to 3419 m,which is speculative due to the possible influence of the magmatic activity.