Understanding Of Erosion Processes Research Articles

Assessing decadal soil redistribution rates using 239+240Pu across diverse lithologies in Southeast Alaska

AbstractQuantifying soil redistribution rates, including both erosion and deposition, is critical for understanding erosion processes, landscape evolution, land management strategies, and the carbon cycle. In the Northeast Pacific coastal temperate rainforest, the interaction of perhumid climate and dense coniferous forest tends to form Spodosols which are soils characterized by a subsurface accumulation of organic matter and iron and aluminum oxides, across a range of contrasting lithologies. Deep Spodosols are frequently found on steep backslopes (up to 60%) of colluvial deposits, where shallower soils would typically be expected. We hypothesized that deep Spodosols in Southeast Alaska indicate slope stability, exhibiting negligible soil redistribution rates and stable surfaces regardless of the lithology. Our objective was to quantify soil redistribution rates for Spodosols formed on steep slopes across a range of lithologies in hilly and mountainous areas of Juneau, AK. We used 239+240Pu isotopes to quantify soil erosion and deposition rates in Spodosols formed on colluvial deposits from tonalite, slate, metavolcanic rock, and phyllite. 239+240Pu measurements revealed negligible soil redistribution rates for all studied pedons, ranging from erosion rates of 0.51 t/ha/year to deposition rates up to 0.43 t/ha/year. No difference was detected between the hill and mountain landforms, further supporting the idea that Spodosols could indicate slope stability over decadal timescales across the region. Understanding the resilience of Spodosols to erosion processes in varied lithologies and landforms on steep slopes is paramount for making informed decisions regarding sustainable land use, landslide risk mitigation, and effective carbon sequestration strategies.

Global patterns in sandy beach erosion: unraveling the roles of anthropogenic, climatic and morphodynamic factors

Beach erosion is a complex process influenced by multiple factors operating at different spatial scales. Local (e.g., waves, tides, grain size, beach width and coastal development) and regional (e.g., sea level rise and mean sea level pressure) factors both shape erosion processes. A comprehensive understanding of how these drivers collectively impact sandy beach erosion is needed. To address this on a global-scale we assembled a database with in-situ information on key physical variables from 315 sandy beaches covering a wide morphodynamic range and complemented by satellite data on regional variables. Our results revealed the combined influence of local and regional factors on beach erosion rates. Primary drivers were regional anomalies in mean sea level pressure and variations in mean sea level, and local factors such as tide range, beach slope and width, and Dean’s parameter. By analyzing morphodynamic characteristics, we identified five distinct clusters of sandy beaches ranging from wave-dominated microtidal reflective beaches to tide-modified ultradissipative beaches. This energy dissipation gradient emerged as a critical factor, with erosion rates increasing with beach width and dissipativeness. Our study also highlighted the tangible impact of climate change on beach erosion patterns. Hotspots were identified, where intensification of regional anomalies in mean sea level pressure, increasing onshore winds and warming rates, and rising sea levels synergistically accelerated erosion rates. However, local variables were found to either amplify the effects of regional factors on erosion or enhance a beach’s resistance, mitigating erosive trends initiated by regional drivers. Our analysis showed that more than one-fifth of the analyzed beaches are experiencing intense, extreme, or severe erosion rates, and highlighted the significant role of human activities in explaining erosion trends, particularly in microtidal reflective and intermediate beaches. This underscores the long-term threat of coastal squeeze faced by sandy beaches worldwide and emphasizes the need to consider both local and regional drivers in order to understand erosion processes. Integrating localized measurements with broader satellite observations is required for a comprehensive understanding of the main drivers behind coastal evolution, which in turn is needed to manage and preserve these fragile ecosystems that are at risk.

Determination of the potential soil losses and prioritization of sub-watersheds: Insight from North African highland system

Soil erosion has negative effects on people and property, hinders the sustainable development of natural resources, and poses a threat to the economic growth of territories worldwide, and is particularly acute for African countries. Consequently, identifying and prioritizing areas susceptible to this phenomenon is crucial for the implementation of efficient preventative measures. In this study, the empirical Erosion Potential Method (EPM) was used to quantify soil losses, and two Game Theory (GT) algorithms (Borda and Condorcet) were employed to identify locations prone to soil erosion and prioritize sub-watershed (SW) based on hydromorphometric characteristics in a hydrological system from High Atlas in Morocco. For this purpose, 26 factors were calculated, subsequently, a linear correlation analysis was conducted to assess the relationship between potential soil erosion and various influencing factors. The EPM model findings indicated average loss rates of roughly 3356 m3/km2/year, which are corroborated by 217 inventory points gathered in the most productive sediment locations, with an AUC value of 80 %. The results of prioritization using GT algorithms show that the SW6 and SW8 are classified as areas with high vulnerability to soil erosion, and the sub-watersheds located upstream of the Lakhdar river watershed are the units that deserve prioritization in terms of planning intervention. The validation of results indicates that the Borda algorithm performed better (AUC= 92 %) than the Condorcet algorithm (AUC= 72 %). This innovative approach enhances our understanding of erosive processes within specific spatial units, enabling informed decision-making and making a substantial contribution to the sustainable and efficient management of water resources. This represents a significant advancement compared to previous studies in the region.

THE STUDY OF SOIL EROSION UNDER A SYSTEMIC CONCEPTION

This article aimed to understand how erosion processes can be analyzed from a systemic point of view. Soil erosion is considered here a naturally occurring phenomenon, which can be (and usually is) influenced by human activities, constituting one of the main environmental problems of the planet, in addition to being the main modeling agent of the terrestrial surface. The consequences of the accelerated action of erosion processes are numerous, such as: reduction of natural fertility and productive capacity of soils; silting and pollution of water bodies; impoverishment of rural communities; rural exodus; among many others. Understanding the dynamics of this phenomenon becomes fundamental because a comprehension of a spatio-temporal scope, coupled with the knowledge of the possible problems that may occur with its accelerated performance, provides support for the development of sustainable management. Given that soils are the 'foundation' of the fauna, flora, and mainly of human subsistence, it is a valuable resource. The analytical procedures of this manuscript followed the construction of a system based on a case study, exemplifying how the systemic approach can be developed in the studies of erosive processes. By analyzing soil erosion from a systemic approach, it was possible to observe how the different flows of matter and energy occurred between the variables, explain the importance of understanding erosion processes in an integrated way, and avoid fragmented and reductionist interpretations.

Patterns of runoff and erosion on bare slopes in different climate zones

Soil erosion by rainfall and runoff is a land surface process strongly controlled by climate and is one of the most threatening environmental problems in the world. Understanding erosion processes in different climates is exceptionally important but remains unclear. A wide range of climatic gradients in China provides an ideal opportunity to investigate the effects of climate on water erosion. In this study, we selected 8 bare plots orthogonally distributed in eastern China and obtained 40 plot-years of data from 424 natural rainstorms. Then, quality-controlled data were standardized to achieve effective comparisons among different climate types. We analyzed the rainfall erosivity (R), surface runoff (r), and soil loss (A) in different climate zones with a thermal gradient of Cold-Warm-Hot and a precipitation gradient of Continental-Oceanic. Our results indicate that climatic factors have complex leverage over water erosion in multiple pathways. (1) Basic rainfall characteristics increase with increasing climatic gradients of temperature and precipitation, as does the frequency of extreme events. The yields of resultants r and A are accordingly higher in the Oceanic than in the Continental zone, yet they discordantly increase in the order of Warm-Hot-Cold. Annual maximum storms in the Continental and Warm zones have more control over the annual values of R, r, and A. The R-r-A relationships are more sensitive in the Continental or Cold zones than in other zones. (2) The potential risks of surface movements differ significantly across climatic gradients. The potentialities of r and A generally increase along increasing precipitation gradients from Continental to Oceanic and increase in the temperature order of Warm-Hot-Cold. (3) The interactions between rainfall and soil exhibit different Continental and Oceanic patterns due to climate-induced differences in rainfall patterns and soil conditions. In the case of an extreme rainstorm, rill erosion is expected to occur more readily in the Cold and Continental areas. (4) Different climatic elements play various roles in the generation of runoff and erosion. Precipitation controls the magnitude of annual yield, while temperature dominates the potential risk. These results provide robust evidence that patterns of rainfall, runoff, erosion, and their relationships are not consistent among different climate zones. This study offers systematic insight into how climate drives surface processes on hillslopes. This work can serve as a reference for the improvement of land surface models for global applicability and climate change, as well as for the standardization approach to plot data in comparative analyses.

Hillslope soil erosion and mobility in pine plantations and native deciduous forest in the coastal range of south‐Central Chile

Significant areas of Latin America, and especially of Chile, have been forested with forest plantations to provide timber and fiber and to decrease soil erosion after deforestation. Despite their potential contribution to reducing erosion processes, the magnitude of this decline has not been adequately assessed. In this study, we estimated soil loss and mobility for one year on steep hillslopes using the traditional erosion-pin approach at five micro-catchments planted with Pinus radiata with different stand ages and compared them to an adjacent secondary broadleaf Nothofagus sp. native forest. Annual net soil loss (ASL) positively correlated with cumulative rainfall (R2 = .49, p < .001). ASL averaged 65.03 ± 9.8 mg ha−1 yr−1, with the lowest ASL in the natural forest with 21.4 ± 3.1 mg ha−1 yr−1 and the highest in one of the 1-year-old plantation micro-catchments (88.9 ± 9.3 mg ha−1 yr−1). ASL under plantation stands of different ages displayed no significant differences. All areas showed similar net soil loss index values, averaging 83.0 ± 1%, suggesting that most of the sediment left the hillslope. The RUSLE model predicted ASL moderately well across all sites and conditions (0.41, p = .018), but it tends to underestimate ASL, particularly for native forests. On average, soils on hilly terrain under plantation forest may suffer losses up to four times greater than natural forests. The latter stresses the need to improve our understanding of erosive processes that may be still active under planted forest, and to better assess the effect of management practices on soil erosion, particularly on previously highly degraded and erodible soils.

In situ field measurement of wind erosion and threshold velocity in relation to soil properties in arid and semiarid environments

Field measurement of wind erosion linked to soil properties improves our understanding of erosion processes in arid and semiarid regions to combat this environmental threat. The aim of this study was to investigate wind erosion and threshold velocity (Vt) in relation to soil properties using a portable wind tunnel in 60 sites of Kerman, the largest province of Iran. The result indicated that wind erosion rates ranged from 0.03 g m−2 min−1 to 3.41 g m−2 min−1, indicating a wide variability in the erodibility of soils. Wind erosion was inversely attributed to Vt following a power function. In all cases, the influence of soil properties on wind erosion was supported by their opposite effect on threshold velocity. Clay and silt fractions, mean weight diameter (MWD) of aggregates, dry stable aggregates (DSA), shear strength, surface gravel, the concentrations of K+, Ca2+, and Mg2+, soil organic carbon (SOC) and calcium carbonate equivalent (CCE) were inversely proportional to wind erosion rates following nonlinear functions. Wind erosion was significantly increased as electrical conductivity (EC) and sodium adsorption ratio (SAR) increased. Critical values of 5.7–8.9 m s−1 at 10-m height for Vt, 7% for clay content, .3 mm for MWD, 25% for DSA, and 5% for surface gravel were recognized, approximately. Multiple regression analysis indicated that SAR and MWD were the best predictors of wind erosion rate. Meanwhile, MWD, surface gravel, clay content, and SOC had the best estimation for threshold velocity.

Potential of phosphorus fractions to trace sediment sources in a rural catchment of Southern Brazil: Comparison with the conventional approach based on elemental geochemistry

In areas with extensive soil erosion, there is a need to identify the sources supplying sediment to rivers in order to improve our understanding of erosion processes and to guide the implementation of effective soil management measures. Geochemical elements are often used as tracers in sediment fingerprinting studies. Among them, P has often been used as it may specifically trace sediment originating from cropland. Although P-fractions can provide more detailed information than the total P content, their potential to distinguish between different potential sources of sediments has rarely been tested. The objective of the current research was to evaluate the contribution of sediment sources in a rural catchment (Arvorezinha, 1.23 km2) of Southern Brazil, using different sets of tracers (i.e. P-fractions only, geochemical tracers only, and a combination of both tracers). Three potential sediment source types were identified in the catchment: (i) cropland, (ii) unpaved roads and (iii) stream channel banks. Thirty-one suspended sediment samples were collected in the river draining this catchment during 9 significant floods between 2009 and 2011. Estimates of P-fractions were obtained by Hedley fractionation using anion exchange resin membrane (Presin); 0.5 mol L−1 NaHCO3 (pH 8.5) (Pbic); 0.1 mol L−1 NaOH (PNaOH0.1); 1.0 mol L−1 HCl (PHCl); 0.5 mol L−1 NaOH (PNaOH0.5); and residual P (Presidual). Total organic (Porg) and inorganic P (Pinorg) were obtained by the ignition method. The concentrations of PHCl, PNaOH0.5 and Pinorg in suspended sediments were higher than those found in the sources. Accordingly, these fractions were considered not to be conservative and were excluded from further analysis. With the exception of Presidual, all P-fractions passed the Kruskal-Wallis H-test and were considered as potential tracers of sediment sources. When the P-fractions were combined with geochemical tracers, the discrimination power was much higher than when using geochemical tracers only. The Mahalanobis distance was 9% higher than that observed in the geochemical approach. The calculated contribution of sediment sources using the three approaches was very similar, and cropland was the dominant source of sediment, with calculated contributions of 56 ± 19, 46 ± 16 and 48 ± 16% for those approaches based on geochemical elements, P-fractions, and geochemical + P-fractions, respectively. These results demonstrate the effectiveness of some P-fractions to trace potential sediment sources in rural catchments, as they have a high discriminant power while remaining conservative during sediment transport in the catchment.

Understanding erosion processes using rare earth element tracers in a preformed interrill-rill system

Tracking sediment source and movement is essential to fully understanding soil erosion processes. The objectives of this study were to identify dominant erosion process and to characterize the effects of upslope interrill erosion on downslope interrill and rill erosion in a preformed interrill-rill system. A coarse textured soil with 2% clay and 20% silt was packed into a physical model of a scaled small watershed, which was divided into eight topographic units and was tagged with eight rare earth element (REE) oxides. Three 30-min rains were made at the sequential intensities of 60, 90, and 120mmh−1, and runoff and sediment were collected every 2min at the outlet. REE concentration in sediment was measured and used to estimate source contributions after fine-enrichment correction. Results showed that interrill erosion rate and sediment concentration increased with downslope distance, indicating that sediment transport might have controlled interrill erosion rates. In contrast, rill erosion rate was limited by rill detachment and development process. Rill erosion contributed most soil loss; however, the proportion decreased from 78 to 61% as rainfall intensity increased and rill network matured over three rains. Interrill erosion was more sensitive than rill erosion to rainfall intensity increases. The former was mostly affected by rainfall intensity in this experimental setup, while the latter was controlled by flow discharge, gradient, and rill evolution stage. The greatest sediment concentration and delivery rate occurred in the stage of the fastest rill development. The increased sediment delivery from interrill areas appeared to suppress rill detachment by concentrated flow. This study enhanced our understanding of interrill and rill erosion processes and provided the scientific insights for improving soil erosion models.

The potential for gamma-emitting radionuclides to contribute to an understanding of erosion processes in South Africa

Abstract. Several research projects undertaken by the authors and others over the last 14 years have used fallout and geogenic radionuclides for understanding erosion processes and sediment yield dynamics in South Africa over the last 100–200 years as European settlers colonised the interior plains and plateaux of the country and imported new livestock and farming techniques to the region. These projects have used two fallout radionuclides (210Pb and 137Cs) to date sediments accumulating in reservoirs, farm dams, wetlands, alluvial fans and floodouts and have used other fallout nuclides (7Be) and long-lived geogenic radionuclides (e.g. 40K, 235U) as part of a composite fingerprint exploring contemporary sediment sources and changes to sources through time. While successful in many parts of the world, applying these techniques in Southern Africa has posed a number of challenges often not encountered elsewhere. Here we explore some of the benefits and challenges in using gamma-emitting radionuclides, especially 137Cs, in these landscapes. Benefits include the potential for discriminating gully sidewall from topsoil sources, which has helped to identify contemporary gully systems as sediment conduits, rather than sources, and for providing a time-synchronous marker horizon in a range of sedimentary environments that has helped to develop robust chronologies. Challenges include the spatial variability in soil cover on steep rocky hillslopes, which is likely to challenge assumptions about the uniformity of initial fallout nuclide distribution, the paucity of stable (non-eroding) sites in order to estimate atmospheric fallout inventories, and the limited success of 210Pb dating in some rapidly accumulating high altitude catchments where sediments often comprise significant amounts of sand and gravel. Despite these challenges we present evidence suggesting that the use of gamma-emitting radionuclides can make a significant contribution to our understanding of erosion processes and sediment yield dynamics. Future research highlighted in the conclusion will try to address current challenges and outline new projects established to address them more fully.

Diseño de un sistema de adquisición de datos para fotogrametría con vehículos aéreos no tripulados (UAV)

&lt;p class="p1"&gt;Este trabajo detalla el diseño e implementación de un sistema de adquisición de datos para un Sistema Aéreo no Tripulado (UAV), capaz de registrar en forma sistemática la información proveniente de sensores y dispositivos de imagen, manteniendo una referencia espacial y temporal precisa. El objetivo es emplear este sistema para recopilar información que posteriormente se procesa con técnicas fotogramétricas para crear modelos de elevación digital de alta resolución que permitan evaluar la cantidad de suelo erosionado en un cierto intervalo temporal. Dicha solución busca mejorar a futuro la cuantificación y el entendimiento de los procesos de erosión con respecto a las metodologías tradicionales que se usan en Costa Rica.&lt;/p&gt;

Monitoring and assessment of soil erosion at micro-scale and macro-scale in forests affected by fire damage in northern Iran.

Understanding the occurrence of erosion processes at large scales is very difficult without studying them at small scales. In this study, soil erosion parameters were investigated at micro-scale and macro-scale in forests in northern Iran. Surface erosion and some vegetation attributes were measured at the watershed scale in 30 parcels of land which were separated into 15 fire-affected (burned) forests and 15 original (unburned) forests adjacent to the burned sites. The soil erodibility factor and splash erosion were also determined at the micro-plot scale within each burned and unburned site. Furthermore, soil sampling and infiltration studies were carried out at 80 other sites, as well as the 30 burned and unburned sites, (a total of 110 points) to create a map of the soil erodibility factor at the regional scale. Maps of topography, rainfall, and cover-management were also determined for the study area. The maps of erosion risk and erosion risk potential were finally prepared for the study area using the Revised Universal Soil Loss Equation (RUSLE) procedure. Results indicated that destruction of the protective cover of forested areas by fire had significant effects on splash erosion and the soil erodibility factor at the micro-plot scale and also on surface erosion, erosion risk, and erosion risk potential at the watershed scale. Moreover, the results showed that correlation coefficients between different variables at the micro-plot and watershed scales were positive and significant. Finally, assessment and monitoring of the erosion maps at the regional scale showed that the central and western parts of the study area were more susceptible to erosion compared with the western regions due to more intense crop-management, greater soil erodibility, and more rainfall. The relationships between erosion parameters and the most important vegetation attributes were also used to provide models with equations that were specific to the study region. The results of this paper can be useful for better understanding erosion processes at the micro-scale and macro-scale in any region having similar vegetation attributes to the forests of northern Iran.

Accelerated erosion in a watershed in the southeastern region of Brazil

An understanding of erosive processes and the washing away of sediments to watersheds is an essential tool for decision makers planning water resource use. This study assessed the potential for surface runoff due to natural attributes together with land use/land cover to highlight the potential for accelerated erosion in the Araras River Watershed (352.77 km2) at a 1:50,000 scale. The analytic hierarchy process was used with the data provided to combine geoenvironmental attributes (soil, rock, water, relief and land use/land cover) that trigger erosive processes. Just over 51 % of the basin area presented an average potential for surface runoff, while 76.5 % presented a low to average potential for accelerated erosion. Despite this, upstream areas used for water collection for Araras city show a medium to high potential for surface runoff and accelerated erosion, reducing water infiltration and recharge, and resulting in the silting of reservoirs and water quality damage.

Upper washita river experimental watersheds: sediment database.

One main objective for studying sediment in the Upper Washita River Experimental Watersheds was to improve the scientific understanding of the effectiveness of watershed conservation practices and floodwater-retardation structures in controlling floods and soil erosion in southwest Oklahoma. This paper summarizes the sediment data collection program in the watersheds during the 1961 to 2012 time period. Gaging sites, record lengths, sampling procedures, data processing, and instrumentation are described. Examples of data use and analyses are presented to illustrate the potential use and relevance of the sediment data and to highlight past research findings. The sediment data, especially the breakpoint data from the unit source watersheds, are of great importance in understanding erosion processes, assessing the effectiveness of conservation practices, and evaluating and validating process-based soil erosion models. Data formats and availability are discussed, and the download URLs for accessing the data are specified.

Soil Erosion Prediction Using Morgan-Morgan-Finney Model in a GIS Environment in Northern Ethiopia Catchment

Even though scientific information on spatial distribution of hydrophysical parameters is critical for understanding erosion processes and designing suitable technologies, little is known in Geographical Information System (GIS) application in developing spatial hydrophysical data inputs and their application in Morgan-Morgan-Finney (MMF) erosion model. This study was aimed to derive spatial distribution of hydrophysical parameters and apply them in the Morgan-Morgan-Finney (MMF) model for estimating soil erosion in the Mai-Negus catchment, northern Ethiopia. Major data input for the model include climate, topography, land use, and soil data. This study demonstrated using MMF model that the rate of soil detachment varied from &lt;20 t ha−1y−1to &gt;170 t ha−1y−1, whereas the soil transport capacity of overland flow (TC) ranged from 5 t ha−1y−1to &gt;42 t ha−1y−1. The average soil loss estimated by TC using MMF model at catchment level was 26 t ha−1y−1. In most parts of the catchment (&gt;80%), the model predicted soil loss rates higher than the maximum tolerable rate (18 t ha−1y−1) estimated for Ethiopia. Hence, introducing appropriate interventions based on the erosion severity predicted by MMF model in the catchment is crucial for sustainable natural resources management.

Advances in Soil Erosion Research: Processes, Measurement, and Modeling

Abstract. Soil erosion by the environmental agents of water and wind is a continuing global menace that threatens the agricultural base that sustains our civilization. For over 70 years, ASABE members have been at the forefront of research to understand erosion processes, measure erosion and related processes, and model very complex sediment detachment, transport, and deposition. The ASABE Erosion Control Group (SW-22) and Erosion Control Research (SW-223) committees periodically sponsor international symposia to provide an avenue for exchange of ideas and information by engineers, scientists, and students from around the world. The two most recent symposia were the Soil Erosion Research for the 21st Century Symposium held in January 2001 in Honolulu, Hawaii, and the International Symposium on Erosion and Landscape Evolution (ISELE) held in September 2011 in Anchorage, Alaska. This article describes these two events, provides a description of major outcomes, and introduces a collection of papers that were presented as part of the 2011 ISELE in Alaska. The ISELE sessions focused on seven themes: water erosion process research; aeolian erosion and fugitive dust emission; highly disturbed, urban, and arid lands; erosion measurement and assessment; prevention and control of upland and in-stream erosion; soil erosion modeling; and impacts of global change on erosion and landscape evolution. More than 120 people from 16 countries attended the ISELE and gave 112 oral and poster presentations. From those presentations, 24 papers were accepted for publication in Transactions of the ASABE (22 papers, this issue) and Applied Engineering in Agriculture (two papers, next issue). The results from these symposia and in these papers show active and vibrant research to address soil erosion problems, particularly in the face of global environmental changes.

Tracing Soil Erosion from Watershed Using Rare Earth Elements

Soil erosion continues to be one of the world's biggest environmental problems. Understanding erosion processes is the key to develop soil erosion prediction models that can provide a scientific basis for soil and water conservation planning. REE tracer method has been considered as an ideal monitoring technique. This paper introduced REE tracing method briefly, and reviewed the application of REE trace method in spatial and temporal distribution of soil erosion from watershed. The causes of error of REE tracing method were also analyzed to enhance its accuracy and precision. Finally, the shortcomings in current studies and the important direction of future researches were pointed out that could provide scientific references for improving the REE tracing method and extending its application in wider research areas.

Comparison of two stream gauging systems for measuring runoff and sediment yield for a semi‐arid watershed

ABSTRACTOur ability to understand erosion processes in semi‐arid ecosystems depends on establishing relationships between rainfall and runoff. This requires collection of extensive and accurate hydrologic and sediment data sets. A supercritical flume with a total load traversing slot sediment sampler used on several sites at the Walnut Gulch Experimental Watershed (WGEW) near Tombstone, AZ has proven to be a reliable way to measure flow and sediment discharge from small watersheds. However, it requires installation of a costly structure that is only suitable for relatively small flows. A more commonly used method based on ease of installation and expense is the pump sampler. One example of this is a set of instrumentation developed by the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO), in which the pump sediment sampler is part of an in‐channel, fully automated system for measuring water velocity, depth, turbidity and collecting runoff samples. A 3.7 ha arid watershed at WGEW was instrumented with both systems and hydrologic and sediment data were collected and compared during a 2 year period. Total sediment yield for the entire period measured by the CSIRO pump sampler (11.6 t ha‐1) was similar to that by traversing slot sampler (11.5 t ha‐1). The pump sampler accurately estimated the amount of fine (&lt; 0.5 mm) sediment fractions exported, but consistently underestimated the coarse (&gt;0.5 mm) sediment fractions. Median sediment diameter of samples collected by traversing slot and pump sampler were 0.32 and 0.22 mm, respectively. This study outlines the benefits and limitations of the pump sampler based system for monitoring sediment concentration and yield in high‐energy headwater catchments, and makes recommendations for improvement of its performance. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Geochemistry of Erosion Processes on Badland Slopes

Understanding erosion processes is important to prevent natural disasters such as slope failure and bedrock erosion in immature sedimentary rocks. Pliocene–Pleistocene illite-rich, non-smectite mudstone of the Gutingkeng Formation is distributed over 250 km2 in southern Taiwan, forming badlands (locally called moon-world) with mud volcanoes nearby. These volcanoes erupt saline water and natural gas, and producing a Na+, Ca2+, Cl-, and SO42- rich unsaturated Popcorn crust, which covers the mudstone slope surfaces in the moon-world area. In the crust porewater, ion strength reaches about 10 mol/L; zeta potential on particle surfaces shows a highly positive voltage. Repulsion occurs between particles under this high voltage in the crust, which is rapidly slaked to form mud by heavy precipitation. The zone that is rapidly slaked by precipitation reaches 10-20 cm beneath the crust surface. Ion strength of porewater of fresh mudstone is 0.5 mol/L approaches 0 mV (range 0.2-0.5 mol/L, pH 4-6). The surface charge of particles decreases with the infiltration of precipitation into the crust and fresh rock, with a minus surface charge occurring with increased rain infiltration. This leads to many cracks forming on the surface of mudstone, which is different from the mechanism of rapid slaking. Evaporation from the 10-20 cm-thick zone between the crust and the underlying fresh mudstone would stop if water was not supplied from depth, which is supported by in-situ measurements of water evaporation in the field. These mudstones erode readily under high precipitation because of the repulsion caused by the high ion strength of porewater. High-salinity porewater including mudstone is distributed near the active mud volcanoes where saline water rises and there is a rapid uplift rate. Rapid slaking occurred with some elements in the concentrated crust and near the surface drying zone.

Análise morfométrica como subsídio ao zoneamento territorial: o caso das bacias do Córrego Carioca, Córrego do Bação e Ribeirão Carioca na região do Alto Rio das Velhas-MG

A região do Alto Rio das Velhas está inserida no contexto da província geológica do Quadrilátero Ferrífero, na região Central de Minas, sendo caracterizada pelo uso conflituoso dos terrenos, com intenso desenvolvimento da mineração, crescente ocupação urbana e forte expansão imobiliária. Os diversos processos erosivos, os mananciais assoreados e as áreas degradadas são outros problemas ambientais observados. Esse estudo analisou as características morfométricas da rede de drenagem e do relevo das bacias do Córrego Carioca, Córrego do Bação e Ribeirão Carioca, afluentes do rio Itabirito, tributário do rio das Velhas, visando a auxiliar na compreensão da vulnerabilidade natural dos terrenos às intervenções antrópicas, na compreensão dos processos erosivos e a na definição do zoneamento territorial, além de complementar análises realizadas em outros estudos, objetivando a compreensão da dinâmica superficial na área. As bacias do Córrego do Bação e Ribeirão Carioca mostraram índices morfométricos que as caracterizam como as mais vulneráveis às intervenções antrópicas e aos processos erosivos. devido à morfologia suave, a bacia do ribeirão Carioca é a que apresenta condições menos restritivas à ocupação para fins imobiliários, principalmente para utilização para chacreamento. Conclui-se que parâmetros morfométricos contribuem para a compreensão da vulnerabilidade de terrenos à erosão, permitindo um melhor ordenamento territorial de bacias hidrográficas.