The technique makes use of a microseismic timer to determine the compressional wave velocity (clast-sound velocity) in each clast of a group chosen from a single deposit. From these data a groupe mean velocity is determined that is proportional
to the age of the deposit : the youngest deposits having the highest velocities. The clast-sound velocity method can be applied to many unconsolidated bouldery deposits up to approximately one million years old.
The sizing of particles in terms of terminal velocity : a note on the interpretation of data of GERETY and SLINGERLAND with particles sized in terms of terminal velocity
Discussion of some data obtained by GERETY and SLINGERLAND (1983) which is based on the hypothesis that classification of samples of aerosols above eroding surfaces should be based on terminal velocities rather than on measures of size
The purpose of this paper is to re-evaluate the riffle-pool sequence in Dry Creek near Winters, California, and to test the velocity-reversal hypothesis by hydraulic modelling using detailed channel topography surveyed at Dry Creek. The AA. also use
measured flow-depth data to assist in model calibration and calculation of cross-sectional area and mean (section average) flow velocity. It is implicit in the discussion that there is a direct relation between near-bed velocities measured and mean (section
Decadal and millennial velocities of rock glaciers, Selwyn Mountains, Canada
The intent of this work is to : 1) present surface velocities on 15 rock glaciers averaged over 12 years (1983-1995) in the Selwyn Mountains; 2) calculate long-term velocities using rock glacier length and lichen age; 3) compare the velocities
determined using these 2 methods; 4) identify controls on surface velocities.
Experimental investigation of the velocity of a sand cloud blowing over a sandy surface
The AA. report the detailed results of the velocity of a sand blowing over a sandy surface measured by PDA (particle dynamic analyser) which employs a phase Doppler technique in a wind tunnel. The primary objectives are to define the velocity
distribution of particles in a blowing sand cloud and variation of the mean velocity of the blowing sand cloud with height. An attempt is made to discuss the particle turbulence, the velocity fluctuation of particles passing a fixed point, in a blowing sand
Bagnold's kink : a physical feature of a wind velocity profile modified by blown sand?
This paper shows that a kink is indeed a physical feature of the modified wind velocity profile and that it is caused, as Bagnold (1941) suggested, by a maximum, occurring at some height above the surface, in the momentum extracted by the grains
from the wind. Comments are made on both the form of the modified wind velocity profile and the fluid shear stress profile in the grain layer.
There is a recognized need to enhance research of hydraulic, geomorphic and sediment-transport processes in rivers. This research often includes studies of the velocity distribution in rivers. This paper describes the use of the top-setting wading
rod and a table and an analytical expression to more easily obtain vertical velocity profiles in rivers.
Velocity-discharge relationships in three lowland rivers
The use of different functional forms to describe the variation of velocity with discharge is explored for four cross-sections, nine short reaches (100-250 m), and three long reaches (2-7 km) in three lowland rivers in Lincolnshire.
Tidal variation in field settling velocities of suspended sediment in a tidal channel
In this study, field settling velocities of the suspended sediment have been measured during two tidal periods, in Ho Bugt, on October 17, 1989 and July 24, 1990. During both periods, the current velocity, salinity, water temperature and suspended
sediment concentration were measured together with the field settling velocities of the fine-grained suspended sediment. Discussion of the results and study of the flocculation process.
Discussion on estimating depth-averaged velocities in rough channels
In this short communication the 4 estimate criteria of the depth-averaged local velocity proposed by Byrd et al. (Earth surface processes and landforms, 2000, vol. 25, pp. 167-173) are compared both with the three-point method of Bathurst
and with the average velocity obtained by integrating the velocity profile suggested by Ferro and Pecoraro (Water Resources Research, 2000, vol. 36, pp. 2761-2770).
An automated salt-tracing gauge for flow-velocity measurement
This article introduces the SVG (salt-velocity gauge), a novel automated technique for measuring flow velocity by means of salt tracing. Two implementations of the SVG technique are described : an outdoors simulated rainfall experiment in Senegal
; a laboratory-based flume experiment. This article demonstrates that a fixed value of the correction factor α is inappropriate, since the correction factor varies with velocity, diffusion and the length of the control section.
A new statistical model for threshold friction velocity of sand particle motion
Aeolian features ; Aeolian transport ; Forecast ; Friction velocity ; Model ; Random process ; Sand ; Threshold ; Wind erosion
A theoretical formulation of threshold friction velocity of sand particles is established by considering the equilibrium of moment forces acting on an irregular particle following Bagnold's scheme. Owing to the statistical nature
of the microstructure of soil surface, of the particle shape and of positions in the bed, the threshold friction velocity is random. Based on the probability theory of multi-dimension random variable, the probability of the threshold friction velocity, its mean value
and standard deviation are calculated. The mean value and standard deviation are fitted as functions of sand particle's diameter. A formula of wet threshold friction velocity is also given.
A three-dimensional analysis on lift-off velocities of sand grains in wind-blown sand flux
This paper focuses on a key problem in wind-blown sand transport research, the lift-off velocities of sand grains. A three-dimensional grain-bed collision model comprising an impact sand grain, a creeping sand grain and a sustaining grain
is presented. Based on this model, the analytical formulae of sand grains'linear and angular velocities are derived. Comparisons of the results with the results gained by a two-dimensional grain-bed collision model show that all components of both rebound
and ejected velocities gained by the three-dimensional model are lower than the corresponding ones done by two-dimensional model apart from the horizontal rebound velocity. It also shows the lateral velocity and the lateral angular velocity, as well
as the upward angular velocity, cannot be obtained by a two-dimensional model, and cannot be ignored when the impact velocity is high.
The AA. investigate the feasibility of applying 5 standard methods [the logarithmic mean velocity profile, the Reynolds stress profile, the turbulent kinetic energy (TKE) profile, the wall similarity and spectral methods] that were initially
developed to estimate shear velocity in smooth bed flow to turbulent flow over a loose bed of coarse gravel under sub-threshold conditions. The analysis is based on quasi-instantaneous three-dimensional (3D) full depth velocity profiles with high spatial
and temporal resolution that were measured with an Acoustic Doppler Velocity Profiler (ADVP) in an open channel. The results confirm the importance of detailed velocity profile measurements for the determination of shear velocity in rough-bed flows. Results
from all methods fall into a range of 20% variability and no systematic trend between methods was observed. The wall similarity method appears to be a promising tool for estimating shear velocity under rough-bed flow conditions and in field studies
Velocity characteristics along a small step-pool channel
This paper summarizes measurements of velocity along 3 reaches of a small mountain channel with step-pool bedforms. Data analyses focused on characteristics of velocity profiles, and on correlations between velocity characteristics and the potential
control variables bedform type, reach gradient and flow depth. To test the hypothesis that velocity characteristics are related to channel bedform types, ANOVA and ANCOVA tests were performed. The bed-generated turbulence and skin friction of runs appear
Predicting wind velocities from sand dune and draa spacings determined by Fourier analysis in Interpretation of windflow characteristics from Eolian landforms.
The spacing of sand dunes and draas (dune groups) is one parameter that can be used to estimate wind velocity and available wind power. Measurements of spacings can be made directly from LANDSAT imagery or aerial photography. Fourier analysis
of these measurements reveals the predominant spacings. Assuming that shear velocity is the dominant factor determining the wave leugth of bedforms, the spacing can be used to compute the threshold shear velocity using mathematical relationships derived by Wilson (1972
). These values may then be used to estimate wind velocity at any other height above the surface or to estimate available wind power.
Measurement of the spatial distribution of fluvial bedload transport velocity in both sand and gravel
Maps are presented of the spatial distribution of two-dimensional bedload transport velocity vectors. Bedload velocity data were collected using the bottom tracking feature of an acoustic Doppler current profiler (aDcp) in both a gravel-bed reach
and a sand-bed reach of Fraser River, British Columbia. This new technique yields noisy data; thus data smoothing is required, and the AA. present their methods for doing so. Finally, maps of bedload velocity are produced and compared to measured
distributions of bedload transport rate, shear stress, and water velocity.
Modelling the hysteresis in the velocity pattern of slow-moving earth flows : the role of excess pore pressure
This paper describes the velocity pattern of a slow-moving earth flow containing a viscous shear band and a more or less rigid landslide body on top. To explain the hysteresis loop in the velocity pattern, the A. considers the role of excess pore
pressure in the rheological behaviour of earth flow by means of a mechanistic model. He describes changes in lateral internal stresses due to a change in the velocity of the earth flow, which generates excess pore pressure followed by pore pressure
dissipation. Model results are compared with a hysteresis in the velocity pattern, which was measured on the Valette landslide complex (French Alps).
Settling velocity characteristics of sediment detached from a soil surface by raindrop impact
The aim of the study was to ascertain whether the detachment of sediment from a soil surface by raindrop impact is a selective or aselective process. Relationships between particle size and settling velocity were established.