Impact-entrainment relationship in a saltating cloud
The problem of impact-entrainment relationship is one of the central issues in understanding saltation, a primary aeolian mode. The AA. present the detailed results of the impact and entrainment parameters measured by a particle dynamic analyser
(PDA) that employs phase Doppler technique in a wind tunnel. The primary objectives are to define the probability distribution of the speed and angle of impacting and entrained particles, and establish the relationship between impact and entrainment
Aerodynamic entrainment thresholds and dislodgement rates on impervious and permeable beds
Using a range of grain sizes and flow conditions, the series of laboratory experiments reported here compares directly the aerodynamic entrainment of loose grains overlying fixed permeable sediment beds with that occurring over fixed impervious beds.
Thresholds of particle entrainment in a poorly sorted sandy gravel-bed river
This paper presents an analysis of a new data set on threshold conditions for bed material entrainment in the poorly sorted sandy gravel-bed of the Arbúcies River (NE Spain), an interesting example of a perennial to ephemeral transitional
hydrological environment. This paper assesses the relationship between the particle size of bedload samples and the shear stress conditions needed for their entrainment. The largest-grain method and the reference or fractional transport rate method have been
Initiation of motion of gravels in concentrated overland flow : cohesive forces and probability of entrainment
Threshold conditions for entrainment of gravel by concentrated overland flow are here discussed. The measured data indicate that cohesive forces may arise and must be taken into account by the models describing grain entrainment. Some models
Spatial variations in surface sediment structure in riffle–pool sequences : a preliminary test of the Differential Sediment Entrainment Hypothesis (DSEH)
Riffle-pool sequences are maintained through the preferential entrainment of sediment grains from pools rather than riffles. This preferential entrainment has been attributed to a reversal in the magnitude of velocity and shear stress under high
flows; however the Differential Sediment Entrainment Hypothesis (DSEH) postulates that differential entrainment can instead result from spatial sedimentological contrasts. Here the AA. use a novel suite of in situ grain-scale field measurements from
a riffle-pool sequence to parameterize a physically-based model of grain entrainment. Field measurements include pivoting angles, lift forces and high resolution digital elevation models (DEMs) acquired using terrestrial laser scanning, from which particle
exposure, protrusion and surface roughness were derived. The entrainment model results show that grains in pools have a lower critical entrainment shear stress than grains in either pool exits or riffles. Field data were collected from Bury Green Brook
This review deals with the entrainment of gravel bedload : theory, laboratory studies, field studies, the relevance of studies in nonfluvial environments and the significance of studies of bedload entrainment.
Critical discharge for entrainment of poorly sorted gravel
Entrainment criteria for gravel-sized particles on river beds are usually defined in terms of shear stress, but some workers have proposed that critical-discharge relationships are more reliable and more convenient. Comparisons with published data
Entrainment, displacement and transport of tracer gravels
estimates from tracer gravels. The expected variation with grain size of tracer displacement length is developed and illustrated using displacement lengths calculated from measurements of entrainment, surface size distribution and transport rate
Etude sur le sens des phénomènes rythmiques et périodiques en géographie humaine. La notion-clé est celle de l'entraînement (synchronisation), qui est, par hypothèse, créatrice de territoires et de lieux. Ainsi l'adoption des temps de Londres (GMT
Debris flows initiated by runoff, erosion, and sediment entrainment in western North America. Special issue
The papers in this special issue represent recent advances in understanding debris flows that initiate by surface runoff and increase in volume through entrainment of sediment : 5 papers focus on debris flows in areas burned by wildfire, and 3
papers focus on debris flows in unburned areas. They are organized into 4 groups and are presented in the following order : 1) initiation studies, 2) entrainment and volumetric studies, 3) predictive methods, and 4) mitigation issues.
Evaluation de l'entraînement du carbone organique et du phosphore total dans le bassin du lac Ladoga et de la baie de la Neva
Caractéristiques de l'entraînement de ces composés sur les bassins versants du lac Ladoga et des territoires contigüs. Régionalisation des modules d'entraînement du carbone organique et du phosphore total dans les secteurs du bouclier cristallin de
Processus de lessivage latéral dans une chaîne de sol sur ligne de pente douce et ligne de pente plus forte. L'entraînement des particules argileuses a été mesuré par méthode hydrométrique et un bilan géochimique a été dressé par spectrophotométrie
pour les différents horizons des deux pentes. L'entraînement latéral a été déterminant pour la pédogenèse dans les deux cas mais la quantité de matériel entraîné est plus importante sur pente forte (ruissellement). L'entraînement vertical reste fonction
Magnitude and frequency relations of bankfull flows and bed-material entrainment in the Llano River watershed, Central Texas, USA
Bankfull channel geometry and bed-material entrainment are examined in the Llano River watershed in central Texas, which is characterized by mixed alluvial-bedrock boundaries and a highly variable flow regime. Field data, including cross-section
surveys and sediment samples from 17 sites, are coupled with one-dimensional hydraulic models and flood-frequency analyses to compute recurrence intervals of bankfull and entrainment conditions. Recurrence intervals of flows that entrain median-sized bed
material are consistently less than 1 year, whereas flows that define bankfull morphology range from 1 to 4 years (median of 1.75 years). Recurrence intervals of flows responsible for incipient entrainment of relatively coarse bed material are typically
Bedload transport in the instrumented catchment of the Rio Cordon. Part I : Analysis of bedload records, conditions and threshold of bedload entrainment
entrainment through flow and sediment transport data collected by a specially designed gauging station. The main purpose of this paper is to show quantitatively what modern findings on critical stress imply for the critical discharge approach.
Sediment entrainment by a soft-bedded glacier : a model based on regelation into the bed
Experimental results indicate that wet-based, soft-bedded glaciers may penetrate their substrates by regelation (melting and refreezing) and thereby entrain sediment. In principle, there should be a steady depth of penetration at which the downward
Sediment entrainment potential in modified alluvial streams : implications for re-mobilization of stored in-channel sediment
This study examines spatial patterns of sediment entrainment potential in 3 alluvial streams in the Lower Hatchie River Basin of western Tennessee with a history of channelization and significant land use change (historic deforestation). The purpose
Emerging infections and nested martingales : the entrainment of affluent populations into the disease ecology of marginalization
approche de l'endémicité. La ségrégation croissante et la marginalisation de sous-populations crée, en termes de maladies infectieuses incurables, le paradoxe d'un système d'apartheid hautement intégré, entraînant les riches dans les maladies des pauvres
Entraînement du strontium 90 de la couverture du sol avec l'écoulement des cours d'eau dans l'Océan Glacial Arctique
Evaluation de cet entraînement sur 30 ans (1961-1990) pour des cours d'eau situés dans les parties européenne et asiatique du Nord russe. Mise en évidence de la différence entre les régions suivant la quantité de strontium transporté pour les
Les AA. étudient les divers aspects du partenariat stratégique. Ils montrent que la fédéralisation de la Belgique a entraîné une plus grande responsabilité des autorités publiques en matière économique et sociale, ce qui a entraîné la stimulation du