Erosive Power Research Articles

Study on Rock Characteristics for Assessing the Hydraulic Erodibility of Sandstones in the Manahari River Section, Sub-Himalaya, Central Nepal

The long-term erosion of the bed rock is steered by the power of the stream of variable magnitude and frequency which would give us the idea about bed rock incision and its channel morphology. Large numbers of infrastructural development work such as roads, bridges are undergoing in the Manahari Area. Hence, hydraulic erosion of the rocks is always a topic of interest while carrying out these construction works. Therefore, the main aim of this study is to determine the hydraulic erodibility of the Siwalik rocks under the action of stream power. Erodibility of the rocks and the stream powers of the Manahari River were determined by extensive field survey and laboratory analysis of rock material properties. Rock mass strength, block particle size, discontinuity/inter-particle bond shear strength, the shape of materials units, and their orientation relative to the flow were assessed to determine erodibility of the rocks. The longitudinal and cross-sectional surveys were carried out to find out the hydraulic parameters to calculate the erosive power of the stream i.e., slope of the channel surface, hydraulic radius, and velocity. The erodibility index ranges from 22 to 198 on the basis of their rock mass properties whereas the stream power value ranges from 1 to 6 kW/m2. The value of the stream power obtained at the bankfull condition at different flow time intervals i.e., 10, 25, 50, and 100 years ranges from 5 to 25 kW/m2. With this range of stream power at different time interval flow, the Manahara River has the capacity to erode maximum of the sandstones present in the riverbed as all the values of the erodibility plot above the threshold line of erosion. However, the relation between the erodibility index and stream power at normal flow condition shows that the Siwalik sandstones of the study area are not erodible under the influence of the available stream power.

Hyperconcentrated flows shape bedrock channels

AbstractGeomorphological evidence of incised bedrock channels is widespread in all mountain landscapes worldwide. However, the processes controlling incision and gorge formation in bedrock have not directly been observed in an actualistic way. Here, we show a LiDAR change detection deciphering the erosive power of a 60,000 m3 hyperconcentrated flow (transition between flood and debris flow) in a deeply incised rock gorge in June, 2020. The flow laterally eroded up to 1 m of massive limestone and widened a 4 m narrow section of the gorge by up to 15%. Sinuosity, convergence, and gradient of the channel were proven to not influence erosivity indicating the hyperconcentrated nature of erosion. Furthermore, other than in prior studies no abrasion of thin rock veneer dominates erosion but mechanically excited breakout of rock fragments. Magnitude-frequency relations of eroded volumes mimic subaerial rock wall retreat. We show how single hyperconcentrated flows can erode bedrock channels far more efficient than decades of turbulent flows and hypothesise that repeated hyperconcentrated flows in phases of enhanced precipitation or by elevated material supply could control erosion boosts in gorge formation, e.g. in the Lateglacial or during climatic fluctuations.

Comparative study of different cavitation erosion assessment methods in cavitating flow around a Delft Twist hydrofoil

Cavitation erosion is a common phenomenon in hydraulic machines, which severely threatens their stable operation. Although several methods for erosion risk assessment have been proposed, few researchers work on the comparative study of different cavitation erosion assessment methods. Therefore, this study utilized Large Eddy Simulation (LES) combined with Zwart-Gerber-Belamri (ZGB) cavitation model to conduct the numerical simulation for the cavitating flow around a Delft Twist hydrofoil. The Erosive Power Method (EPM), Improved Gray Level Method (IGLM) and Energy Conservative Method (ECM) are employed separately to evaluate the cavitation erosion. Among the three results, the EPM results cannot accurately predict erosion in the middle region and trailing edge region, where the U-shaped vortex collapse. The results of IGLM and ECM can predict the erosion in the middle region and erosion caused by the U-shaped vortex at the trailing edge. IGLM still needs artificial thresholds, while ECM emphasizes areas with higher cavitation risk by amplifying parameter n. The ECM method is more objective from the simulation results.

Analysis on the relationship between runoff erosion power and sediment transport in the Fujiang River basin and its response to land use change

In recent years, the acceleration of urbanization in the Yangtze River Economic Belt (YREB) has brought about problems such as soil erosion, ecosystem degradation and decline in ecological service functions. Therefore, this paper selects the Fujiang River Basin (FRB) in Upper Yangtze River (UYR), and analyzes the relationship between runoff erosion power (REP) and sediment transport (ST) on the basis of analyzing the variation characteristics of hydrological elements. Based on SWAT model, a variety of scenarios are set up to quantitatively analyze the impact of different land use changes on runoff and ST and REP in the basin. The results indicated that: (1) The annual precipitation in FRB from 1960 to 2018 did not change significantly, while the annual runoff, annual ST and annual REP decreased significantly. Compared with runoff and runoff depth, the relationship between sediment transport modulus (STM) and REP is the best, especially the power function between them is better than the linear function. (2) The results of the evaluation indexes of the simulation results of the SWAT model based on the measured runoff and sediment data from 2008 to 2018 are pass and above, that is, the simulation results are considered reliable. (3) Under the five scenarios of conversion of sloping farmland to forest, conversion of dry land to paddy field and conversion of grassland to bushland and forest land, the runoff and ST in the basin decreased but the overall range was small. The simulation results of SWAT model show that the erosion of specific areas in the basin shows the greatest degree of weakening with the decrease of REP.

Drainage Morphometric analysis of Yagachi watershed area, Karnataka State, India

The Yagachi River watershed in Karnataka State has been chosen for a thorough analysis to recognize the drainage system, morphometric features, and vulnerability of the watershed area to erosion. As a prerequisite to the analysis of morphometric features utilizing ArcGIS software, the stream networks and sub-watersheds (viz., SW01, SW02, SW03 and SW04) were delineated by making use of topographic sheets and the Digital Elevation Model (DEM). Yagachi watershed covers an area of 551.45 sq. km and observed predominant drainage patterns are sub-parallel and dendritic with sixth-order drainage. Higher stream orders (U=6), implying greater surface runoff and sediment load, and low mean stream length values in the upper reaches, signifying youthful morphological development and strong erosion potential, are characteristics of streams in the watershed. Drainage density values (1.262 to 1.930 km/km2), particularly at upper reaches in the NW part of the watershed, fine to very fine drainage texture values (7.572 and 8.337), moderate to high values of length of overland flow (Lg) and constant of channel maintenance (CCM) indicate steep to moderate slopes, fairly significant surface runoff, and high erosive power of the streams and greater sediment load. The elongated form of the watershed is shown by the computed lower form factor (Ff) and elongation ratio (Re) values. Relief characteristics of the watershed area, although suggest that the study area is vulnerable to erosion and in youth stage, in reality, the area is characterised more by the features of the late mature stage of landform development. The observed anomaly is attributed to the mountain-plain environment as the steeply sloped hill ranges of Bababudan formations are located in the northwestern parts of the Yagachi watershed area. However, the sub-watershed SW03 with high stream length, drainage density and relief value with fine drainage texture is relatively more susceptible to erosion.

Response of erosion rate to hydrodynamic parameters in sheet and rill erosion process on saturated soil slopes

Sheet erosion and rill erosion are two important forms of slope erosion. The initiation and development of those forms are significantly affected by erosive power of water flow. Identifying main erosion forms and exploring the relationships between hydrodynamic parameters and erosion rates, especially in a saturated soil slope simultaneous the development of sheet-rill erosion, are important to reveal erosion intrinsic mechanism. The objectives of this study were to quantify erosion rates, hydrodynamic parameters, and determine the relationships between hydrodynamic parameters and the soil erosion rate at sheet and rill erosion stages of saturated soil slopes. A series of indoor soil flume simulated rainfall experiments were conducted on a saturated soil slope at three rainfall intensities (30, 60, and 90 mm h−1), four slope lengths (1, 2, 4, and 8 m), and five slope gradients (2°, 5°, 10°, 15°, and 20°). Results revealed that erosion rates at sheet and rill erosion stages on a saturated soil slope increased from 5.31 to 22.31 kg m−2 s−1 and 23.91 to 140.35 kg m−2 s−1, respectively. The values of flow shear stress, stream power, unit stream power at those two stages were within the scope of 0.064–0.151 m s−1 and 0.175–0.327 m s−1, 0.77–2.97 Pa and 1.59–6.70 Pa, 0.24–0.80 W m−2 and 0.53–1.80 W m−2, and 0.041–0.12 m s−1 and 0.07–0.36 m s−1. Hydrodynamic parameters of flow velocity, shear stress, stream power, and unit stream power at rill erosion stage were 2.01 to 2.77, 1.18 to 2.31, 1.31 to 2.51, and 1.20 to 2.57 times those at sheet erosion stage. Furthermore, erosion rates at sheet and rill erosion stages increased linearly with the increase of flow velocity, shear stress, stream power, and unit stream power under different experimental conditions. The erosion rates at those two erosion stages were accurately predicted by stream power and flow velocity (R2sw=0.86, R2rv=0.92). This study is helpful for unraveling the dynamic mechanism of sheet-rill erosion process and establishing reasonable process-based soil erosion models.

Polyphony, sonic texture and acoustic ecology in Cynan Jones’s Stillicide

Polyphony, sonic texture and acoustic ecology in Cynan Jones’s <i>Stillicide</i>

Analysis of Spatial and Temporal Characteristics of Runoff Erosion Power in Fujiang River Basin Based on the SWAT Model

As an erosion dynamic index considering the three elements of flood, runoff erosion power (REP) can better reflect the influence of precipitation, underlying surface, and other factors on the erosion and sediment transport (ST) of flood events. Therefore, it is of great significance to study the variation characteristics of the REP and its relationship with ST in the basin for soil erosion control. In this paper, the Fujiang River Basin (FRB) was selected to analyze the characteristics of runoff and ST at four hydrological stations in the basin from 2009 to 2018, including Santai, Jiangyou, Shehong, and Xiaoheba. Combined with the concept of the REP, six kinds of water–sediment relationship were compared and analyzed. Furthermore, by constructing the SWAT model, the spatial distribution characteristics of runoff, ST, and REP in the FRB were analyzed in depth, and the spatial scale effect of the REP in the basin was explored. The conclusions are as follows: (1) The power function relationship between REP and sediment transport modulus (STM) is better than the other five kinds of water–sediment relationship. (2) Based on the SWAT model, the evaluation indexes of the monthly runoff and ST of the four hydrological stations are credible, good, and excellent in the rating period (RP) and the validation period (VP). (3) The annual REP in the main stream from upstream to downstream is mostly a single change trend, while in each primary tributary, the overall value is larger than that of the main stream and the interannual difference is obvious. The average annual REP generally shows the distribution characteristics of ‘large at the junction of the upper and middle reaches and small in the rest of the area’. With the increase in the control area, the multi-year average REP has a decreasing trend, especially when the catchment area above the sub-watershed is &gt;7318 km2; the change of the multi-year average REP is single and obviously slows down, with an average value of 23.8 mm·m3·s−1·km−2.

The optimal explanatory power of soil erosion and water yield in karst mountainous areas

The optimal explanatory power of soil erosion and water yield in karst mountainous areas

The Mojave Section of the San Andreas Fault (California): 1. Shaping the Terrace Stratigraphy of Little Rock Creek Through the Competition Between Rapid Strike‐Slip Faulting and Lateral Stream Erosion Over the Last 40 k.y.

AbstractTo determine the post‐40 ka slip‐rate along the Mojave section of the San Andreas Fault (MSAF) we re‐analyze the sedimentary record preserved where Little Rock (LR) Creek flows across the fault. At this location, interaction between the northeast‐flowing stream and right‐lateral fault has resulted in the abandonment and preservation of 11 strath terraces and one paleo‐floodplain in the downstream trailing corner of the river, two of which are also preserved upstream to provide cross‐fault matches. A new model of fault‐induced river deflection, together with standard terrace riser restoration, yields strike‐slip displacements of 1,140 ± 160 m for the older terrace and 360 ± 70 m for the younger one. When combined with new 10Be dating and reinterpretation of prior measurements the displaced terraces yield right‐lateral slip‐rates of 27.7+6.9/−3.5 and 26.8+3.4/−3.0 mm/yr over the last 23 k.y. and last 40 k.y., where uncertainties are at 95% credible intervals. These new rate determinations are consistent with independent late Holocene estimates, indicating that the long‐term rate of strain accumulation along the MSAF is relatively fast and does not vary significantly when averaged over timescales of 15–20 k.y. Using our new model of stream deflection, we find that the fluvial sequence was emplaced in two distinct periods, each characterized by a temporally stable but markedly different deflected river geometry. Each period coincides with a distinct stage of erosive power along LR Creek determined from independent paleoclimate proxies. Importantly, application of the new river‐deflection model allows strike‐slip displacements to be determined in the absence of upstream piercing points.

Polycyclic aromatic hydrocarbons in estuarine sediments as a consequence of the mine tailings remobilization and transport in the Rio Doce basin.

The Fundão dam failure in 2015 severely impaired the economy, the lives of riverine communities, and the aquatic ecosystems of the Rio Doce basin in southeast Brazil. Several contaminants, including polycyclic aromatic hydrocarbons (PAHs), were transported downstream, deposited in the estuary, and released into the Atlantic Ocean. The high concentration of PAHs in estuarine sediments may pose ecological risks and deleterious effects to benthic organisms, so here we aimed at determining the source and fate of these compounds before and after the tailings' arrival. The mean concentration of the analyzed Σ16PAHs increased from 34.05 µg kg-1 in the prefailure period to 751.77 µg kg-1 one year after the arrival of the tailing. The classification of the sediment quality changed from low to moderate contamination. Our results suggest that there was PAHs remobilization by mine tailings along the Rio Doce basin. The target analytes exhibited mostly a pyrolytic profile from fossil fuel and biomass burning. In addition to other contaminants deposited in the estuary after the arrival of the tailings, this study revealed that the profile change of PAHs in the estuary region is a consequence of the mud's erosive power. Integr Environ Assess Manag 2024;20:169-178. © 2023 SETAC.

The Neogene to Quaternary evolution of the Neuquén Andes broken foreland forced by tectonic, climatic and surface processes (southern Central Andes)

The Andes offer a distinctive example of the intricate interplay among climate, tectonics, and surface processes. This is exemplified by the mountain range's north-south orientation, which contrasts with the prevailing east-west wind direction. This interplay controls the uplift evolution of the broken foreland and thus the sediment transfer and erosion from mountain ranges to their forelands. The Neuquén Andes is a peculiar segment of the southern Central Andes, registering dramatic North-South variabilities in elevation, climate, and tectonic intensities established during the Neogene and Quaternary. In this study, we aimed to identify the tectono-stratigraphic evidence of the Neogene to Quaternary evolution of paleo-environments and drainage networks in the intramountainous basin of Pampa de Agua Amarga in the broken foreland of the southern Neuquén Andes of Argentina.Starting with a non-depositional and/or erosional phase during the Paleogene, the Pampa de Agua Amarga Basin underwent several phases of syn-orogenic sedimentation in the late Oligocene to early Miocene. The basin gradually shifted from a lacustrine to an alluvial depositional environment, with alluvial deposits becoming dominant in the mid-Miocene and fluvial deposits dominating in the Pliocene. A significant event occurred during the late Pliocene to early Pleistocene when coarse fluvial deposits were deposited, marking the last aggradation phase. In the early Pleistocene, the onset of incision triggered the drainage system to cut through the downstream topographic barrier. The excavation of the basin was abrupt, as evidenced by a mid-Pleistocene stepped fluvial terrace and alluvial fan that filled a large canyon across the southern end of the downstream topographic barrier.The study confirms the regional trend that Miocene basin infill is related to dry climate and high tectonic uplift, which overwhelmed the erosive power of the drainage network. The lowering of tectonic uplift intensity in the southern Neuquén Basin during the Plio-Pleistocene, along with sudden fluctuations in the global colder and wetter climate, ultimately led to the excavation of the intramountainous basin. The Westerlies Wind Belts generate high precipitation rates in the southern Neuquén Andean Cordillera, feeding the Negro River catchment in the retroarc Andean broken foreland. Consequently, the erosive power of the Negro River catchment overcame the declining tectonic uplift, causing significant erosion of the entire broken foreland and Cordillera of the southern Neuquén Andes. Conversely, more intense tectonic uplifts in the northern Neuquén Andes built a more effective orographic barriers that limited precipitation rates of both the Westerlies Wind Belt and South America Summer Monsoon, and preserved the intramountainous basins and mountain interior from erosion.

Development of testing apparatus for investigating electromagnetic dynamics of contactors: A pilot study

It is easy to find electromagnetic contactors in modern electromechanical devices owing to their advantages, which encompass a simple structure, ease of use, and low cost. However, these devices also have inherent drawbacks, including heat dissipation, contact erosion, and inefficient power consumption during long-term operation. This has sparked interest in contact soft-landing, which aims to reduce issues like contact bounces, contact welding, and arcing. This paper presents the development of a testing apparatus for investigating the electromagnetic dynamics of contactors or mechanical relays, aimed at developing an open-loop model-based controller for contact soft-landing. Theoretical equations based on physical theorems are derived to describe the behavior of the electromagnetic coil under varying factors. Additionally, a pilot study was conducted using the proposed testing apparatus to explore the relationship between heat dissipation, flowing current, air gap, and the Lorentz force produced by exposing ferromagnetic material to the magnetic field surrounding the electromagnetic coil. The experimental and simulation results showed good fitting, with a normalized root mean squared error ranging from 2.5% to 4.5% for various scenarios. Notably, it was found that the flowing current passing through the electromagnetic coil can be controlled by changing the duty cycle of the pulse width modulation signal driving the conductivity of the MOSFET. However, the results suggest that a modulation frequency greater than 5 kHz is not suitable for driving the electromagnetic coil.

Accelerated Miocene incision along the Yangtze River driven by headward drainage basin expansion.

Along the southeastern margin of the Tibetan Plateau, the onset of rapid fluvial incision during the Miocene is commonly attributed to growth of high topography. Recent recognition of lacustrine strata preserved atop interfluves, however, suggest that headward expansion of river networks drove migration of the topographic divide. Here, we explore the impact of this process on fluvial incision along the Yangtze River. Landscape evolution simulations demonstrate that expansion of the Yangtze watershed since the Late Miocene could be responsible for 1 to 2 kilometers of fluvial incision. The distribution of modern knickpoints and river profiles is consistent with this hypothesis. We suggest that increased erosive power associated with capture and basin integration drove accelerated incision during the Late Miocene. Our results imply that eastern Tibet was elevated before middle Cenozoic time and that the tempo of fluvial incision may be out of phase with uplift of plateau topography.

Rainfall erosivity in the Republic of North Macedonia: Fournier index approach

Rainfall erosivity is a crucial factor influencing soil erosion, which results from the detachment, transportation, and deposition of soil particles caused by rainfall and runoff. Rainfall erosivity assessment is a fundamental process aimed at quantifying the erosive power of rainfall events in a given region. The paper provides an overview of rainfall erosivity assessment in several heterogeneous regions of the Republic of North Macedonia based on rainfall data from meteorological stations characterized by different climatic and geographical conditions. Having into consideration that rainfall erosivity can be quantified by using various indices, this study uses two common ones: Fournier Index (FI) and the Modified Fournier Index (MFI) based on monthly and annual precipitation totals for the period 1951-2020. The results imply that in general, the studied stations belong to a low class of erosivity. It is found that FI has greater sensitivity and provides more details, also showing years with high and even very high rainfall erosivity while MFI gives more information for moderate rainfall erosivity.

Drainage network rearrangement during the formation and segmentation of a Paleogene intraplate half-graben: Insights from fluvial captures records and longitudinal profiles

Rivers play an important role in modifying landscapes through denudation processes, which can be influenced by changes in tectonics, climate and eustasy, causing erosive pulses and river capture events that alter the geometry and topology of the drainage network. Therefore, drainage networks are not static features over time and are modified and rearranged by shifts in their boundary conditions until a state of dynamic equilibrium is reached in the landscape. The region of the Paraíba do Sul Middle Valley (PSMV), in Southeastern Brazil, has important records of captures and recent drainage rearrangements, which show a state of transition in the landscape and, consequently, the reorganization of drainage networks. This region is in the central segment of the Continental Rift of Southeastern Brazil (CRSB), a prominent tectonic feature that can be described as an intraplate half-graben. While fluvial profiles and fluvial gradient indices are valuable tools for studying the landscape evolution, their application to investigate the erosive power of rivers and how the topography of a half-graben affects the rearrangement of the drainage network over geological time is still limited. Specifically, there is a need to explore how the topography of the active border of a half-graben differs from that of the flexural border in terms of river network organization and fluvial erosion patterns. This study aims to characterize the different stages of rearrangements of the drainage network and their relation with the events of formation and segmentation of a half-graben. A total of 21 basins were analyzed in both Fault and Flexural Border sectors, extracting geomorphic parameters, such as slope, drainage area, concavity, χ and ksn. A more specific study was carried out in areas where river captures were recognized as been related to the half-graben formation and segmentation events. The ksn calculated for the main rivers demonstrates that the formation of the rift and its consequent configuration in half-graben granted a greater erosive power for the basins that drained the active fault of the rift, represented by the basins of the Fault Border Sector of the study area. The tectonic events registers in the fluvial system were analyzed using the χ method and the main migration tendency of the dividers was extracted from the difference in the values of this parameter in areas close to the interfluves. With this, it becomes evident that the geometric configuration imposed in the half-graben establishes, from the beginning of the rift phase, an important control on the erosion potential of the rivers located in the active and flexural borders. This control resulted in ancient river captures, currently exposed as inflections in the main river channels towards the local depocenters, thus demonstrating that this type of tectonic event can generate disturbances in the river system that can be observed even today, tens of millions of years after it happened.

Control of inherited structural fabric on the development and exhumation of passive margins – Insights from the Araçuaí Orogen (Brazil)

The Araçuaí Orogen, in eastern Brazil, was formed during the Neoproterozoic – Cambrian amalgamation of West Gondwana. During the Mesozoic – Cenozoic opening of the South Atlantic Ocean, and the associated divergent tectonics, the orogen developed as basement to the passive margin of South America and was progressively covered by thick offshore sedimentary basins, particularly the Espírito Santo, Mucuri, and Cumuruxatiba basins, in which hydrocarbon systems have been exploited. Our understanding of the Araçuaí Orogen's passive margin evolution, erosion, and sediment transfer to these basins ultimately depends on constraining the onshore exhumation in response to Mesozoic – Cenozoic events. Here, new and previously published data from apatite fission-track (AFT) analyses and inverse thermal history modelling of (Pre)Cambrian basement rocks from the Araçuaí Orogen resolve three discrete basement cooling and associated erosional exhumation episodes. In the Pre-Rift phase, Jurassic – Hauterivian erosion of the Araçuaí Orogen is most likely related to the adjoining intra-continental West Gondwana flexural subsidence, which increased hillslope and river erosion power. In the Rift and Transitional phases, Barremian – Albian accelerated phase of erosion is associated with the uplift of the Atlantic rift shoulders and the establishment of an oceanic base-level. In the Drift phase, reactivations in response to far-field stresses likely triggered a Late Cretaceous – Paleocene rapid erosion event. The rates at which these events unfolded vary spatially and are controlled by inherited structures. The Araçuaí Orogen experienced slower denudation rates in areas closer to the São Francisco Craton, which suggests that the tectonic reactivation and related surface uplift during the Mesozoic–Cenozoic is in first-order controlled by lithospheric rigidity. Furthermore, the structural framework of the Paramirim and Pirapora aulacogens and NE-oriented shear zones in the orogen’s southeast facilitated later reactivations. From the spatial pattern of denudation/exhumation of the Araçuaí Orogen during the Mesozoic – Cenozoic, we draw inferences on the tectonic development of the offshore basins regarding their hydrocarbon potentials.

Comparison of deterministic wind speed generation models for wind erosion modeling

The diurnal patterns of hourly wind speed data are fundamentally important in precise wind erosion modeling. Several deterministic wind speed simulation models, including the Guo (1/π), Guo (1/2), wind generator (WINDGEN), Ephrath, Debele, and Goudriaan models, have been developed to quantitatively generate hourly wind speed data. In this study, the performances of these popular deterministic wind speed generation models were investigated using observed hourly wind speed data obtained from 191 climate stations in arid and semi-arid areas of China. The performances of the Guo (1/π), Guo (1/2) and WINDGEN models were the best for hourly wind speed generation. Linear regression analysis revealed that all models tended to underestimate wind speeds. The patterns of diurnal variation and the amplitude of the measured hourly wind speed data generally governed the model performance. The performances of the Guo (1/π), WINDGEN, Guo (1/2), Goudriaan, Debele, and Ephrath models successively decreased for the daily average erosive wind power density (AWPD) estimation. To improve the Guo (1/π) and Guo (1/2) models for AWPD evaluation, the calibrated parameters (π and 2) of the second term in the Guo (1/π) and Guo (1/2) models showed different values for each station. The accuracy of the AWPD obtained by the Guo (1/π) and Guo (1/2) models with the calibrated parameters were significantly improved, which could further influence the accuracy of wind erosion modeling. More studies are required to investigate the relationship between the calibrated parameters in the Guo (1/π) and Guo (1/2) models and geographic conditions linked with wind erosion.

Extreme streamflow and sediment load changes in the Yellow River Basin: Impacts of climate change and human activities

In recent decades, the increasing frequency and magnitude of extreme hydrological events due to climate change and human activities have caused substantial economic losses and damages to human wellbeing. Here, we investigated the spatiotemporal variations of streamflow extremes (QE) and sediment load extremes (SE) in the Yellow River (YR) during 1956–2019. Furthermore, the effects of main human activities and climate change were identified by establishing quantitative relationships between these factors and changing hydrological extremes. Specifically, the QE and SE have decreased significantly (p < 0.05) since 1956 except the headwater (reach above Tangnaihai). However, the QE increased significantly (p < 0.05) during 2000–2019 due to increased extreme precipitation, while the SE tended to stabilize at most stations. Besides, the contribution of QE to annual streamflow declined distinctly in the upper-middle reaches (Lanzhou-Tongguan reach) but increased significantly in the lower reaches (reach below Huayuankou). Likewise, the contribution of SE to annual sediment load increased remarkably in the middle-lower reaches (Huayuankou-Lijin reach). Furthermore, the timing of QE and SE generally tended to disperse from the flood season to the four seasons. While extreme precipitation fundamentally caused the extreme water and sediment discharge, the magnitude and hazard of QE and SE can be strongly regulated by human activities. Particularly, mainstream dams can artificially regulate QE and SE magnitudes and relationships and reduce their synchronization probability, and intra-basin engineering construction and revegetation measures can substantially reduce their possible peaks in a power function form. In addition, changes in the extreme water–sediment relationships indicated that declining erosive power in the middle reaches and decreasing sediment availability in the lower reaches dominated SE reduction. This study provides a scientific basis for flood risk management and water resources development and utilization in large complex river basins.

Near‐continuous monitoring of a coastal salt marsh margin: Implications for predicting marsh edge erosion

AbstractMechanisms that control marsh edge erosion include wind‐generated waves, vegetation productivity, land use and land change, and geotechnical properties of sediments. However, existing models for predicting marsh edge evolution focus primarily on edge retreat rates as a function of wave energy while accounting for other controlling factors as empirical constants. This simplification arises from a lack of high‐frequency monitoring of marsh evolutions. In particular, marsh erosion is timescale dependent, and conducting field observations on short temporal and spatial scales could elucidate the progression of erosion, which may improve marsh erosion predictive models. This study developed and validated a near‐continuous camera and erosion pin monitoring system to document marsh edge erosion at a high frequency (i.e., daily) in Terrebonne Bay, Louisiana. This was supplemented with daily wave power to explore the relationships between daily erosion and wave power. Long‐term average erosion rates derived from satellite and aerial imagery from 1989 through 2019 compare similarly to rates derived from longer‐term site visits (i.e., monthly) at approximately 2.2 m/yr. High‐magnitude erosion events (&gt;20 cm/day) are driven by a buildup in wave energy over a 7‐day time period coupled with a strong 1‐day wave event, indicating a gradual reduction in marsh edge resistance with continued wave attack. Long‐term erosion monitoring methods, including monthly field visits, provide results that align well with previously reported relationships between wave power and erosion. High‐frequency measurements, however, illustrate that the previously published trends smooth over the large‐magnitude short‐term erosion events, potentially obscuring the physical processes of marsh edge erosion. For example, satellite and aerial imagery provide a long period of record, but they may underestimate the average annual erosion rate in the region, the effect of which may become exasperated over the varying temporal scales considered in coastal planning efforts across the USA and worldwide.