Differences In Erosion Rates Research Articles

Evolution of Hvar island pocket beaches during the last 200 years (eastern Adriatic coast, Croatia)

This study examines the evolution of 30 pocket beaches on the island of Hvar in Croatia over the last ~200 years. The oldest available data was extracted from the Franciscan cadastre and dates back to 1834. The following period was analysed using State Geodetic Administration orthophotos from 1952 and 1958, while the recent period was studied using UAV, GNSS measurements, and photogrammetric techniques, aiming to create high-resolution models. All analyses were carried out using GIS and semi-automatic statistical tools. Our results show that the beaches on Hvar eroded on average 50 % of their total area during the studied period, while the shorelines retreated by 6.5 m. Significant changes in beach areas and shoreline retreat were observed in both periods, without differences in erosion rates (~2.3 m2/yr). Here we showed that rates of shoreline retreat of gravel/pebble beaches revealed to be slower compared to sand beaches (0.04 m/yr and 0.07–0.38 m/yr respectively). Most beaches are formed in alluvial fans and represent therefore part of geomorphic systems which relate beaches to their catchments. Therefore, land cover changes in the catchments, was found to be an important factor affecting beach morphology. Obtained results reveal that 85 % of the analysed catchments exhibited decline in arable land coinciding with obtained trends of beach erosion. We find out that changes in beach size correlates to the changes in shoreline retreat (r2 = 0.7) for 70 % of beaches. However, 30 % of the beaches could be also influenced by other effects, particularly socio-economic activities in the catchment, which could importantly impact on natural variability but could also be associated with errors in Cadastral mapping. This study has shown that there is a trend of beach erosion on Hvar island which is expected to continue in the future. The acquired knowledge can thus contribute to future beach vulnerability assessment.

SOIL EROSION BY HAND TOOLS FOR SMALL-SCALE TILLAGE ON HILLSLOPES ASSESSED THROUGH THE UNIVERSAL SOIL LOSS EQUATION

The objective of this study was to evaluate and compare the erosion rates generated by two types of hand tools for small-scale tillage on a hillslope, using experimental tests and the Universal Soil Loss Equation (USLE). The hand tools evaluated were a conventional hoe and a redesigned furrowing hoe. The experimental work was conducted in a 145 m2 plot with an average slope of 45% in Colombia. Three treatments were evaluated: a) Zero tillage and no herbicide (control); b) tillage with a conventional hoe plus herbicide; c) tillage with a furrowing hoe plus herbicide. Each treatment was represented by a sedimentation plot, using three repetitions in blocks (lower, middle, and upper parts of each plot), according to the maximum slope gradient. Both hand tillage tools generated high to extremely high erosion rates with differences of up to 8.1 times between them. Both types of tools accelerated soil erosion rates, being higher in furrowing hoe tillage. The USLE method showed no differences in erosion rates between the tillage methods, while differences were found in the experimental tests. This is explained by the lower sensitivity of the USLE to detect small-scale changes in factors such as soil type, cover, and slope.

Old orogen – young topography: Evidence for relief rejuvenation in the Bohemian Massif

Abstract The Bohemian Massif is the relic of a major Paleozoic mountain range that is known to have exhumed and its surface levelled in the Permian, but its Neogene landscape evolution is largely unconstrained. The landscape is characterized by rolling hills and extended planation surfaces above an elevation of about 500 m. However, at lower elevations deeply incised gorges confined by steep hillslopes are abundant and contrast impressively with the low relief landscapes above. Rivers with a bimodal morphology (i.e. steep at lower elevations and gentle at higher elevations) drain either to the north into the Vltava (Moldau) River or to the south into the Danube River. Hence, a continental drainage divide runs through the Bohemian Massif. Here, we quantify spatial characteristics of the Bohemian Massif landforms by computing landscape metrics like steepness index or geophysical relief derived from digital elevation models. From this we infer temporal change of the landscape in the past and predict them for the future evolution of the region. We show that the landscape is characterized by out-of-equilibrium river profiles with knickpoints abundantly at elevations between 450 m and 550 m separating steep channel segments at lower elevations from less steep channels at higher elevations. Hypsometric maxima at or close above knickpoint elevations, along with high and low values in geophysical relief as indicator for the degree of fluvial landscape dissection downstream and upstream of major knickpoints, support the idea of landscape bimodality. Furthermore, we find a distinct drainage divide asymmetry, which causes the reorganization of the drainage network of the region. Across-divide gradients in channel steepness predict the northward migration of the Danube-Vltava drainage divide including growth and shrinkage of tributary catchments, thus controlling changes in the Central European drainage pattern. All aspects suggest that the region experienced relief rejuvenation during the last few million years. We suggest that this relief rejuvenation is related to the inversion of the Molasse basin with a long wavelength rock uplift pattern and low uplift rates. Vertical motion of crustal blocks at discrete faults may locally affect the uplift pattern. However, the contrasting bedrock properties between the sedimentary cover (Molasse sediments) and the crystalline basement (Bohemian Massif) cause substantial differences in erosion rate and are thus the superior control on the topographic variations of the entire region.

Best Management Practices, Erosion, Residual Woody Biomass, and Soil Disturbances Within Biomass and Conventional Clearcut Harvests in Virginia’s Coastal Plain

Abstract Forest residue utilization for energy has increased in the southeastern United States and additional increases are anticipated. However, such removals generate concerns regarding potential accelerated erosion and nutrient drains, which could affect site productivity and stream water quality. To address erosion and water quality concerns, postharvest erosion rates, operational feature areas, best management practice (BMP) implementation, residual ground cover, soil disturbance, and forest residue concentrations were evaluated on ten biomass and ten conventional clearcut harvests in Virginia’s Coastal Plain. No significant differences in erosion rates (P = 0.4727) were observed between biomass (0.71 tons ac-1 yr-1) and conventional (0.61 tons ac-1 yr-1) harvests. BMP compliance percentages were similar (P = 0.6776) for both biomass (88.54%) and conventional (90.99%) harvests. BMP implementation scores were determined to be a significant predictor of erosion rates (P < 0.0001). A significant reduction (28%) in postharvest residue concentrations was observed for biomass (10.22 tons ac-1) versus conventional harvests (14.24 tons ac-1) (P = 0.0173). Scores for BMP implementation and erosion rates were not significantly different between treatments, indicating that sufficient residual biomass exists for appropriate implementation of BMPs. BMPs provided similar erosion protection on both biomass and conventional clearcut harvests. Study Implications: Forest residues are widely used to cover and stabilize bare soil as best management practices (BMPs) for erosion control. The expanding bioenergy market has raised concerns that overutilization of forest residues may occur. Comparisons of biomass and conventional harvests in the Coastal Plain of Virginia revealed few significant postharvest differences. Implementation of existing water quality BMPs is important for minimizing erosion on biomass harvests; however, the development of biomass harvesting guidelines in addition to current state BMPs appears unnecessary under current harvesting practices. Harvest residue management should be conducted to ensure adequate supplies of woody debris remain for site protection.

Concentration-runoff relationships of contrasting small mountainous rivers in the Pacific Northwest, USA: Insights into the weathering of rhenium relative to other weathering products

This study examines dissolved rhenium (Re) concentrations as a function of water runoff using river samples from two contrasting mountainous watersheds, the Eel and Umpqua Rivers in the Pacific Northwest, USA. These watersheds share many key characteristics in terms of size, discharge, climate, and vegetation, but they have a 15-fold difference in sediment yield due to differences in their tectonic setting and uplift and erosion rates. We evaluate concentration-runoff (C-R) relationships and ratios of coefficients of variation (CVC/CVR) for major cations, anions, dissolved inorganic carbon, selected trace elements including Re, and 87Sr/86Sr ratios. Recent research outlines the potential of Re to serve as a tracer for the oxidation of ancient/fossil organic matter because of its close association with petrogenic carbon (OCpetro) in rocks. In both the Eel and Umpqua Rivers, our measurements show that Re behaves similarly to major weathering derived-solutes corrected for atmospheric input, such as Ca2+*, Mg2+*, and Na+* with modest dilution across all tributaries with increasing runoff. Rhenium behaves dissimilarly from other trace elements, such as Mo and U, and is also dissimilar to biologically-cycled nutrients, such as NO3–, PO43−, and K+*, suggesting differences in sources, solute generation mechanisms, and flowpaths. Rhenium behavior is also distinct from that of colloids, which have increasing concentrations with increasing runoff. We find that Re and sulfate corrected for atmospheric input (SO42−*) have distinct C-R relationships, in which SO42−* undergoes greater dilution with increasing runoff. This implies that Re is not dominantly sourced from sulfide weathering, which leaves primary bedrock minerals and OCpetro hosted in bedrock of these watersheds as the likely dominant sources of dissolved Re release. At mean discharge, Re concentration in the Eel river (3.5 pmol L-1) is more than two times greater than Re concentrations in the Umpqua River (1.5 pmol L-1). Furthermore, comparison of two tributary watersheds with similar bedrock but marked differences in erosion rates show higher Re concentrations in Bull Creek (erosion rate of 0.5 mm yr−1) relative to Elder Creek (erosion rate of 0.2 mm yr−1). The results of this study suggest that dissolved Re in the Eel and Umpqua River basins is likely derived from primary mineral dissolution or OCpetro oxidation, and Re fluxes are higher in areas with higher erosion rates, suggesting that tectonic setting is one factor that controls Re release and therefore OCpetro oxidation.

Spatial analysis of eroding surface micro-topographies

Analysis of the spatial variability in erosion rates at the micro-scale has the potential to improve our understanding of how shore platforms erode. Comparing the erosion rate of a single measurement reading with the erosion rate of other increasingly distant readings would indicate whether average variation in erosion rate is homogeneous and at what spatial scale. Little variation in erosion rate from one measurement reading as distance increased would indicate that an area is eroding homogeneously and that the surface measured is responding as a single spatial unit. An increase or decrease in the variation in erosion rate difference with increasing distance from one reading would suggest that the area was not acting as a single spatial unit and that surface responses differ with scale. This study used a two-year dataset of traversing micro-erosion meter (TMEM) readings, collected from two limestone shore platforms on the north of Malta, at Ponta tal-Qammieħ and Blata l-Bajda, in order to explore the relationship between difference in erosion rate and distance from TMEM readings. A Microsoft Excel macro was developed and applied to calculate and analyse the average variation in erosion rate difference between all possible pairs of measurement readings over a set of fixed distances. The resultant analysis suggests that there are some consistent patterns between measurement periods and locations on a platform in terms of how erosion rate difference varies with distance between readings. These are not simple relationships to either characterise or explain but nevertheless, they suggest variations in how the same surface responds to erosional forces. These findings are significant for erosion research as they imply that spatial scales to erosion within even small areas may impact upon the representativeness of an average erosional loss for the platform site. It raises issues about how representative rates really are and contributes to the discussion about the wider understanding of erosion rates across spatial scale.

Optimizing the Dryland Sheet Erosion equation in South China

Optimisation of models applied in sheet erosion equations could facilitate effective management of sheet erosion in the field, and sustainable agricultural production. To optimise the characterisation of sheet erosion on slope farmland in South China, the present study conducted field simulation rainfall experiments with vegetated and fallow soils. According to the results, sheet erosion rate first increased with an increase in rainfall duration and then stabilised. Exclusive P. vulgaris planting and P. vulgaris in combination with earthworms could reduce sheet erosion by 10–60%, and the combined method could better control sheet erosion. There were significant differences in erosion rate between mild and steep slopes, and light and heavy rain conditions. The influence of rain intensity on sheet erosion was greater than that of slope. Soil organic matter (SOM), rain intensity, and slope can be used to optimise sheet erosion equations of exposed slopes, and SOM and hydraulic parameters can be used to optimise sheet erosion equations in vegetated slopes. The results of the present study could facilitate the reduction of the time and space variability errors in the establishment of sheet erosion models for vegetated slopes.

Embankment Breach Research: Observed Internal Erosion Processes

HighlightsThis study provides data from internal erosion tests on four intermediate-scale homogeneous embankment dams.Soil properties influence the breach formation process and breach timing.Results showed that observed erosion rates of the internal flow path varied by several orders of magnitude.Quality control of embankment construction can greatly influence breach development.Abstract. Internal erosion and embankment overtopping are the two most common causes of embankment dam and levee failures and incidents. Internal erosion is the removal of soil material by the flow of water through a continuous defect, cavity, or crack within a compacted fill and/or its foundation. Internal erosion initiates from vulnerabilities within the embankment. The embankment soil material plays a key role in both the erosion process and rate of failure, but characterizing soil properties and how they relate to the rate of failure can be challenging. Soil properties such as texture, density, strength, moisture content, and erodibility can vary greatly; thus, it is important to study the effects of these properties on the breach formation process and breach timing. The USDA Agricultural Research Service performed internal erosion breach experiments on four intermediate-scale homogeneous earthen embankments constructed of soils ranging from a silty sand to a lean clay material. The embankments were constructed to a height of 1.3 m, a top width of 1.8 m, and upstream and downstream slopes of 3(H):1(V). The embankment materials were characterized by water content, density, texture, strength, and erodibility. Erodibility was measured using a jet erosion test (JET) apparatus. A 40 mm diameter, continuous steel pipe was placed through each embankment during construction and removed to form an open-ended void through the embankment connected to the upstream reservoir. The removal of the pipe initiated internal erosion. The objectives of the experiments were to observe the development of the internal erosion process over time and to examine the influence of soil properties on the erosion rate, breach timing, geometry of the breach opening, and breach outflow. The rate of erosion and failure observed in these tests varied by several orders of magnitude, with the silty sand embankment eroding most rapidly and the lean clay embankment with a mean moisture content of 18% dry basis at standard compaction eroding the slowest. These observations were indicative of the soil textures. Although the two lean clay embankments were constructed of similar soils, the difference in erosion rates speak to the importance of quality control (e.g., compaction moisture content) during construction. Soil properties including soil texture, erodibility, and compaction moisture content are key predictors of erosion rate and observed failure. Keywords: Breach, Dam failure, Dams, Embankments, Erodibility, Internal erosion, Levees, Overtopping.

Comparison of synthetic mesh erosion and chronic pain rates after surgery for pelvic organ prolapse and stress urinary incontinence: a systematic review.

The aim of this study is to systematically compare rates of erosion and chronic pain after mesh insertion for pelvic organ prolapse (POP) and stress urinary incontinence (SUI) surgery. A systematic electronic search was performed on studies that evaluated the incidence of erosion and chronic pain after mesh insertion for POP or SUI. The primary outcome measurement was to compare mesh erosion rates for POP and SUI surgery. Secondary outcome measurements were incidence of de novo pain and a comparison of patient demographics for both surgeries. Twenty-six studies on 292,606 patients (n= 9077 for POP surgery and n= 283,529 for SUI surgery) met the inclusion criteria. Median follow-up was 26.38 ± 22.17months for POP surgery and 39.33 ± 27.68months for SUI surgery. Overall, the POP group were older (p< 0.0001) and had a lower BMI (p < 0.0001). Mesh erosion rates were significantly greater in the POP group compared to the SUI group (4% versus 1.9%) (OR 2.13; 95% CI 1.91-2.37; p< 0.0001). The duration from surgery to onset of mesh erosion was 306.84 ± 183.98days. There was no difference in erosion rates between abdominal and transvaginal mesh for POP. There was no difference in erosion rates between the transobturator and retropubic approach for SUI. The incidence of chronic pain was significantly greater in the POP group compared to the SUI group (6.7% versus 0.6%) (OR 11.02; 95% CI 8.15-14.9; p< 0.0001). The duration from surgery to onset of chronic pain was 325.88 ± 226.31days. The risk of mesh erosion and chronic pain is significantly higher after surgery for POP compared to SUI. These significant complications occur within the first year after surgery.

Bank erosion in a macrotidal tropical river: Exploring the relative impact of boat wash on riverbank erosion

AbstractMacrotidal tropical rivers are dynamic systems where wet‐season floods and tidal flows cause significant riverbank erosion and sediment transport. This study aimed to explore patterns of riverbank erosion and deposition in a large, tropical, macrotidal river in Northern Australia; the Daly River. In particular, we aimed to determine if recreational boat use was impacting bank erosion in this dynamic river. Erosion pins were installed at multiple levels on both banks at 10 sites along a 34 km reach of the river. Measurements were made every four to six weeks during the low water dry season, and opportunistically during the wet season (flooding period) and seasonal transition periods. A bank geotechnical assessment, riverbed cross‐sections and site bathymetry were undertaken. Whilst the wet season was a period of substantial erosion (mean rate of 0.64 mm day−1), the highest mean erosion rate (3.6 mm day−1) was observed in the early dry season (April to May), a period of stabilizing water levels but greatest boat traffic. Bank erosion at this time was measured on both sides of the river and the inside of meander bends, which is atypical of normal riverine bank erosion patterns, and indicative of erosion due to boat wash. As the dry season progressed, significant spatial differences in erosion rates were evident, where erosion was observed at sites upstream of a large shallow sand bar, while sites downstream from the sand bar gained material through the deposition of tidally transported sediment. This study highlights the importance of understanding the significance and interaction of various erosive factors in tropical tidal rivers and has demonstrated that boat wash may be an important contributor to dry season bank erosion in these systems. We encourage management agencies to consider the role of boats in any future river management program in these systems.

Modeling the Evolution of Aquatic Organisms in Dynamic River Basins

AbstractRivers are conduits for aquatic organisms and host an exceptional number of species. Over geologic time, rivers and the aquatic organisms that live in them are subject to changes in topography that can alter where rivers flow. Differences in erosion rates across drainage divides cause some river basins to grow and others to shrink. Occasionally, rivers are abruptly rerouted by river captures that create both new dispersal corridors and barriers for aquatic organisms. These changes in habitat connectivity can lead to the evolution of new species, which has prompted suggestions that river captures may be a mechanism to produce high freshwater biodiversity. We test this hypothesis by building a model, Bio‐SLANT (Biodiversity on Simulated LAndscapes using Neutral Theory). Bio‐SLANT couples a computational landscape model that simulates river basin reorganization to a macroevolutionary model that simulates the dispersal, speciation, and extinction of organisms. We first show that modeled basin area exerts a primary control on within‐basin species richness due to the species‐area relationship. We then describe the effects of drainage area exchange between river basins. River capture increases species richness, but only temporarily, whereas elevated rates of speciation and extinction provide a persistent biological record of river network reorganization. When river captures are frequent, speciation rates increase more than extinction rates, resulting in a positive diversification rate under most of the biological parameters tested. We explore the implications of our results for species richness in landscapes with basins of different relative sizes and for diversification in tectonically active and inactive settings.

Chemical reactions, porosity, and microfracturing in shale during weathering: The effect of erosion rate

The rate of chemical weathering has been observed to increase with the rate of physical erosion in published comparisons of many catchments, but the mechanisms that couple these processes are not well understood. We investigated this question by examining the chemical weathering and porosity profiles from catchments developed on marine shale located in Pennsylvania, USA (Susquehanna Shale Hills Critical Zone Observatory, SSHCZO); California, USA (Eel River Critical Zone Observatory, ERCZO); and Taiwan (Fushan Experimental Forest). The protolith compositions, protolith porosities, and the depths of regolith at these sites are roughly similar while the catchments are characterized by large differences in erosion rate (1–3 mm yr−1 in Fushan ≫ 0.2–0.4 mm yr−1 in ERCZO ≫ 0.01–0.025 mm yr−1 in SSHCZO). The natural experiment did not totally isolate erosion as a variable: mean annual precipitation varied along the erosion gradient (4.2 m yr−1 in Fushan > 1.9 m yr−1 in ERCZO > 1.1 m yr−1 in SSHCZO), so the fastest eroding site experiences nearly twice the mean annual temperature of the other two.Even though erosion rates varied by about 100×, the depth of pyrite and carbonate depletion (defined here as regolith thickness) is roughly the same, consistent with chemical weathering of those minerals keeping up with erosion at the three sites. These minerals were always observed to be the deepest to react, and they reacted until 100% depletion. In two of three of the catchments where borehole observations were available for ridges, these minerals weathered across narrow reaction fronts. On the other hand, for the rock-forming clay mineral chlorite, the depth interval of weathering was wide and the extent of depletion observed at the land surface decreased with increasing erosion/precipitation. Thus, chemical weathering of the clay did not keep pace with erosion rate. But perhaps the biggest difference among the shales is that in the fast-eroding sites, microfractures account for 30–60% of the total porosity while in the slow-eroding shale, dissolution could be directly related to secondary porosity. We argue that the microfractures increase the influx of oxygen at depth and decrease the size of diffusion-limited internal domains of matrix, accelerating weathering of pyrite and carbonate under high erosion-rate conditions. Thus, microfracturing is a process that can couple physical erosion and chemical weathering in shales.

Quantitative Assessment of Soil Erosion Based on CSLE and the 2010 National Soil Erosion Survey at Regional Scale in Yunnan Province of China

Regional soil loss assessment is the critical method of incorporating soil erosion into decision-making associated with land resources management and soil conservation planning. However, data availability has limited its application for mountainous areas. To obtain a clear understanding of soil erosion in Yunnan, a pixel-based estimation was employed to quantify soil erosion rate and the benefits of soil conservation measures based on Chinese Soil Loss Equation (CSLE) and data collected in the national soil erosion survey. Results showed that 38.77% of the land was being eroded at an erosion rate higher than the soil loss tolerance, the average soil erosion rate was found to be 12.46 t∙ha−1∙yr−1, resulting in a total soil loss of 0.47 Gt annually. Higher erosion rates mostly occurred in the downstream areas of the major rivers as compared to upstream areas, especially for the southwest agricultural regions. Rain-fed cropland suffered the most severe soil erosion, with a mean erosion rate of 47.69 t∙ha−1∙yr−1 and an erosion ratio of 64.24%. Lands with a permanent cover (forest, shrub, and grassland) were mostly characterized by erosion rates an order of magnitude lower than those from rain-fed cropland, except for erosion from sparse woods, which was noticeable and should not be underestimated. Soil loss from arable land, woodland and grassland accounted for 52.24%, 35.65% and 11.71% of the total soil loss, respectively. We also found significant regional differences in erosion rates and a close relationship between erosion and soil conservation measures adopted. The CSLE estimates did not compare well with qualitative estimates from the National Soil Erosion Database of China (NSED-C) and only 47.77% of the territory fell within the same erosion intensity for the two approaches. However, the CSLE estimates were consistent with the results from a national survey and local assessments under experimental plots. By advocating of soil conservation measures and converting slope cropland into grass/forest and terraced field, policy interventions during 2006–2010 have reduced soil erosion on rain-fed cropland by 20% in soil erosion rate and 32% in total soil loss compared to the local assessments. The quantitative CSLE method provides a reliable estimation, due to the consideration of erosion control measures and is potentially transferable to other mountainous areas as a robust approach for rapid assessment of sheet and rill erosion.

Erosion problem in tool steel using cold box core-making process

This paper presents the erosion results of the AISI H13 steel impinged by resin-bonded silica sand, using a testing rig that closely simulates the real blowing conditions during industrial core-making. Steel specimens were heat treated to obtain hardness of 294, 445 and 595 HV200 (29, 45 and 55 HRC). Erosion tests were carried out at impingement angles from 20° to 90° and air drag pressures of 1.38, 2.07 and 2.76 bar (20, 30 and 40 psi). The main results are summarized as follows: (i) The harder material, the lower erosion; (ii) the maximum erosion rate is at 30°; (iii) Little difference in erosion rate at impact angle of 60° and 90° for a constant pressure tested regardless of the hardness level; (iv) As the pressure increases, so does the erosion rate, being more sensitive for low impact angles. Finally, a differential form of the general erosion equation is applied on a practical core-making case to evaluate the erosion rate of the H13 steel at 30° and 90° impingement angles.

Microstructural evaluation and high-temperature erosion characteristics of high chromium cast irons

This present study investigated effect of chromium content on high temperature erosive wear characteristics of high chromium cast irons (Cr contain: 12%, 17%, 22% and 27% mass) for as cast specimens (AC) and heat treated specimens (QT), respectively. High temperature erosion test machine was used to investigate the erosive wear property of specimens at 1173 K. Alumina ball were used as particles at impact angles 30°, 60° and 90° and velocity is 100 m/s.As result, the addition of Cr is effective to increase the hardness of AC specimen, therefore, the erosion rate is also gradually reduced. On the other hand, for QT specimens, the erosion rate of 17Cr is almost same with 22–27Cr due to tempering process occurs that made M7C3 as dominant carbides in the matrix. The maximum difference hardness between AC with QT specimens is only 40 HV that difficult to consider its influence on the erosion rate. Therefore, the carbides of AC and QT were focused. From Cr/C ratio, it can be seen that there precipitated M3C and M7C3 into 12Cr and 17Cr, M7C3 into 22Cr and 27Cr. From the phase diagram, the microstructure is γ + M7C3 for each sample at 1173 K. Type and hardness of carbides are not changed at 1173 K for 22–27Cr AC and 22–27CrQT that resulted there is no significant difference in erosion rate after quenching compare to as cast. Therefore, the type of carbides is one of the main factors that can enhance the erosion resistance at 1173 K.

AUTHOR REPLY

Thank you for the insightful feedback on our study evaluating exchange of the artificial urinary sphincter (AUS) pressure regulating balloon. We agree it would be beneficial to know more of the details regarding the nature of incontinence (recurrent vs persistent) and the etiologies of the prior AUS explants, which was not obtained in 64% of the cohort. Of note, however, there was no significant difference in erosion rates, perhaps the most morbid outcome, between those with a prior AUS implant/explant and those who underwent pressure regulating balloon exchange with a virgin AUS. Further, it is important to emphasize that this procedure is beneficial in a very select cohort, ideally the nonirradiated patient with pure stress incontinence lacking urethral atrophy. Despite the efficacy demonstrated by our study, there is certainly a need for multi-institutional, prospective studies evaluating this management option for post AUS incontinence.

The near steady state landscape of western Namibia

Quantitative geomorphic field studies and modeling efforts have focused on the margins of southwestern Africa as an example for landscape evolution in prolonged aridity conditions and tectonic quiescence of passive margins. These efforts concluded that this region is a prime example of a steady state landscape, in which relief changes extremely slowly. Using cosmogenic isotopes, these studies suggested overall landscape exhumation rates of 5–10 m Ma−1 over the past 105–106 yrs. Slightly slower rates on flat-lying exposed bedrock surfaces and faster exhumation rates along the Namibian Great Escarpment as well as on steep slopes of granitic inselbergs, such as the Gross Spitzkoppe are also documented. Here we explore the state of “steady state” in central Namibia. Concentrations of 10Be were measured in bedrock and sediment samples collected throughout the watershed of the Ugab River (~29,000 km2), which drains the highlands of central Namibia and flows to the Atlantic Ocean. Samples were collected from the main stem of the ephemeral Ugab River, from the slopes and streams draining the Brandberg, which is the largest inselberg in the Namib, and from smaller inselbergs around it. We also sampled several other formerly large, but currently subdued, inselbergs such as the Messum Crater. 10Be concentrations in sediment transported along the axial Ugab River indicate that its drainage basin erodes uniformly at 5–6 m Ma−1 and sediment transport from its headwaters source to the ocean is rapid. 10Be concentrations measured in sediment transported in ephemeral streams draining the Brandberg indicate its erosion at ~4 m Ma−1. However, slower rates of 1–3 m Ma−1 were measured for bedrock samples collected from (a) flat lying bedrock surfaces within the Brandberg, (b) top of small tors that rise only a few meters above their surroundings, and (c) exhumed and denuded large magmatic complexes such as the Messum Crater. Furthermore, we found that bedrock buried under grus in the hyperarid zone of Namib (<100 mm yr−1) erodes at similar rates as the exposed bedrock. This difference between the rate of bedrock erosion and the overall average erosion rate of drainage basins has been previously attributed to the contribution of sediment weathered from underneath transported sediment and soil on the pediments. Our results do not fully support this explanation. Results from this and earlier studies point to two possible sources of relatively low dosed (i.e. more rapidly eroding) sediment: (a) the steep slopes and cliffs of the large inselbergs and the Great Escarpment, and (b) rock buried under soil in the upper, semi-arid, parts of the drainage systems, where soil and vegetation can promote weathering of plagioclase and biotite and the disintegration of granitic bedrock.We therefore suggest that the “steady state” landscape along the Namibian passive margin be viewed as follows: The entire landscape erodes slowly, generally at ~5 m Ma−1 and this maintains the view of steady state. Small differences in erosion rates between the landscape elements result in very slow and only small changes in relief over time scales ≥106 yrs. We find that the large inselbergs and the Great Escarpment erode primarily by retreat of steep slopes and cliffs within the drainage basins while preserving relief over considerable timescales. In the wetter upper reaches of the Namibian drainage systems, erosion of buried rock is most likely increased by the vegetation-covered soil.

Multiple episodes of fast exhumation since Cretaceous in southeast Tibet, revealed by low-temperature thermochronology

The southeast margin of the Tibetan plateau is characterized by deeply incised river valleys separated by a perched low relief landscape that gently descends from the high Tibetan plateau towards the southeast. When and how this unique landscape formed is debated. The onset of increased river incision is often interpreted as a proxy for the timing of surface uplift. Here, apatite and zircon (U–Th)/He and apatite fission track thermochronometries are employed to map the spatial and temporal pattern of exhumation in the region. Vertical profiles of granitic rocks were collected near Deqin (∼28.5°N) and Weixi (∼27.5°N). The two transects share a similar exhumation history, with two episodes of relatively fast exhumation (∼100–300 m/Myr) in the Cenozoic: during the Paleocene to Eocene (60–40 Ma) and Miocene to present (20–0 Ma), separated by an intervening period of slow exhumation. A pulse of moderate to high exhumation (70–300 m/Myr) during the mid- to late-Cretaceous (120–80 Ma) is also present in the data. However, the rate and total amount of exhumation near Deqin is larger than at Weixi and is especially pronounced in the interval between 20 Ma to present. We interpret this difference as possibly related to differences in erosion rates between the Lancang (Deqin) and the Jinsha (Weixi) rivers. The Paleocene to Eocene episode of fast exhumation is likely in response to early Cenozoic deformation along tectonic boundary structures, related to the transpressional collision of the Indian plate with this region. Pre-Miocene episodes of fast exhumation corroborate recent paleoaltimetric studies, which show that the southeast margin of the Tibetan plateau was elevated prior to the Oligocene.

Fundamental burnishing characteristics of Ni-based alloy using coated carbide tool

The fundamental characteristics of a developed burnishing process targeting an Ni-based alloy were investigated. A spherical burnishing tool, which was coated using diamond-like-carbon material, was rotated at a high speed and inclined from the normal direction of the target surface to obtain a sliding effect during the developed burnishing process. The Ni-based alloy, which was conducted the solution treatment and surface finishing with a file, was used as a workpiece. The burnished surface was evaluated by its roughness, profile, subsurface microstructure, and mechanical properties such as hardness and solid particle impact strength. The surface roughness was considerably improved because of the burnishing process, and the influence of thrust force on the roughness of the burnished surface was observed. In addition, the burnished surface appeared as a clear mirror. The difference in the subsurface microstructure between the preliminary and burnished surfaces was observed within a 20 μm depth from the surface, and the surface hardness was increased by the burnishing process. The difference in erosion rate between the preliminary and burnished surfaces was also observed within a 20 μm eroded depth, and the superiority of the developed burnishing process for an Ni-based alloy was experimentally verified.

Detrital thermochronology of Rhine, Elbe and Meuse river sediment (Central Europe): implications for provenance, erosion and mineral fertility

Here we present detrital apatite fission track (AFT), zircon fission track (ZFT) and a few apatite (U–Th)/He (AHe) data of Middle Pleistocene to modern Rhine, Meuse and Elbe river sediments in order to resolve processes that control detrital age distributions (provenance, erosion and mineral fertility). We used a modelling approach to compare observed with theoretically predicted age distributions from an interpolated in situ AFT and ZFT age map. In situ cooling ages do show large differences in the Rhine drainage basin, facilitating the differentiation between different source regions. Inconsistencies between observed and theoretical age distributions of the Meuse and Elbe samples can be explained by mixing and reworking of sediments with different provenances (Meuse Middle Pleistocene terrace sediment) and a yet unexplored source region with old AFT ages (Elbe samples). Overall, the results show that detrital thermochronology is capable of identifying the provenance of Middle Pleistocene to modern sediments. The AFT age distributions of Rhine sediments are dominated (~70%) by AFT ages representing the Alps. A possible explanation is higher erosion rates in the Alps as compared to areas outside the Alps. A Late Pleistocene sample from the Upper Rhine Graben contains apatite grains from the Molasse and Hegau volcanics, which we explain with a shift of the headwaters of the Rhine to the north as a result of intense Middle Pleistocene Riss glaciation. Contrary to the observed dominance of Alpine-derived AFT ages in Rhine sediments, the relative contribution of zircon ages with sources in the Alps is lower and significantly decreases downstream, suggesting a major source of zircons outside the Alps. This can be explained by increased zircon fertility of sediments derived from the Rhenish massif. Therefore, we conclude that erosion and mineral fertility are the main processes controlling detrital AFT and ZFT age distributions of the sampled river sediment. In case of the Rhine samples, AFT age distributions are mainly controlled by differences in erosion rates, whereas this impact is completely balanced by differences in mineral fertility for the ZFT data.