CiTG

This article presents a suite of numerical methods contained within a Matlab toolbox for constructing complete particle-size distributions from diverse particle-size data. These centre around the application of a constrained cubic-spline interpolation to logit-transformed cumulative percentage frequency data. This approach allows for the robust prediction of frequency values for a set of common particle-size categories. The scheme also calculates realistic, smoothly tapering tails for open-ended distributions using a non-linear extrapolation algorithm. An inversion of established graphic measures to calculate graphic cumulative percentiles is also presented. The robustness of the interpolation-extrapolation model is assessed using particle-size data from 4885 sediment samples from The Netherlands. The influence of the number, size and position of particle-size categories on the accuracy of modeled particle-size distributions was investigated by running a series of simulations using the empirical data set. Goodness-of-fit statistics between modeled distributions and input data are calculated by measuring the Euclidean distance between log-ratio transformed particle-size distributions. Technique accuracy, estimated as the mean goodness-of-fit between repeat sample measurements, was used to identify optimum model parameters. Simulations demonstrate that the data can be accurately characterized by 22 equal-width particle-size categories and 63 equiprobable particle-size categories. Optimal interpolation parameters are highly dependent on the density and position of particle-size categories in the original data set and on the overall level of technique accuracy.

A method for 3D interpolation of complete particle-size distributions is presented and applied to the Dutch province of Zeeland. Particle-size data are integrated into a common format using a cubic-spline interpolation scheme to create distributions with twenty-three particle-size categories ranging from 64 mm to 0.2 µm. Interpolation uses linear regression of log-ratio transformed particle-size distributions to estimate percentage frequency values for each of the twenty-three particle-size categories for each grid cell. The voxel model, has a spatial resolution (x,y,z) of 100 by 100 by 0.5 m and consists of ~1.7 billion voxel cells. This contains percentage frequency estimates for twenty-three particle-size categories. A full range standard particle-size statistics, e.g. mean, sorting, skewness and cumulative percentiles, can be calculated from these data.

Glacial sediment discharge was calculated by a combining empirical data with modelled ice flow velocities. The distribution of ice facies at the glacier terminus margin was logged and ice samples were taken to calculate representative sediment concentrations per unit volume of ice.

Abstract Glacier structure provides information about ice flow dynamics, sediment transport and past climatic conditions. We use an optical borehole televiewer for the first time in hot-water boreholes to map the internal structure and sediment distribution of a polythermal valley glacier: Midre Lovénbreen, Svalbard. Surface structure and sediment mapping complement data acquired from boreholes.

This study investigates sediment transport processes and sediment-landformdevelopment at two small valley glaciers of contrasting basal thermal-regime. A range of innovative techniques are applied to characterize and quantifyglacier structure, glacially transported sediment facies and sediment-landformassemblages at Glacier de Tsaneuron, Switzerland, and Midre Lov? nbreen, Svalbard.

Digital optical televiewing, recently developed to log and map terrestrial boreholes, provides a complete orientated image of borehole walls at a resolution of 1 mm along hole and typically <1 mm around hole. Here we provide an overview of optical televiewer (OPTV) technology and operation, and outline the potential contributions of the technique to ice-mass research with reference to an OPTV log of a borehole $ $21 m deep drilled in the lower accumulation area of Glacier de Tsanfleuron, Switzerland. The OPTV image of this borehole successfully reveals a variety of visibly contrasting ice types. These ice types have been characterized and their orientation mapped and, on the basis of this information, interpreted as: (1) primary foliation; (2) summer/autumn erosion surfaces; and (3) incipient foliation. Importantly, unrolled OPTV images can be inverted to recreate a virtual image of the borehole core, potentially, for the first time, allowing ice cores to be orientated.

This paper presents a methodological framework for inter-instrument comparison of different particle-size analysers. The framework consists of: (i) quantifying the difference between complete particle-size distributions, (ii) identifying the best regression model for homogenising data sets of particle-size distributions measured by different instruments, (iii) quantifying the precision of a range of particle-size analysers, and (iv) identifying the most appropriate instrument for analysing a given set of samples. The log-ratio transform is applied to particle-size distributions throughout this study to avoid the pitfalls of analysing percentage-frequency data in `closed-space'.  A Normalized Distance statistic is used to quantify the difference between particle-size distributions and assess the performance of log-ratio regression models. Forty-six different regression models are applied to sediment samples measured by both sieve-pipette and laser analysis. Interactive quadratic regression models offer the best means of homogenising data sets of particle-size distributions measured by different instruments into a comparable format. However, quadratic interactive logratio regression models require a large number of training samples (n>80) to achieve optimal performance compared to linear regression models (n=50). The precision of ten particle-size analysis instruments was assessed using a data set of ten replicate measurements made of four  previously published silty sediment samples. Instrument precision is quantified as the median \textit{Normalised Difference} measured between the ten replicate measurements made for each sediment sample. The Differentiation Power statistic is introduced to assess the ability of each instrument to detect differences between the four sediment samples. Differentiation Power scores show that instruments based on laser diffraction principles are able to differentiate most effectively between the samples of silty sediment at a 95% confidence level. Instruments applying the principles of sedimentation offer the next most precise approach.

In this paper the impact process and mechanism of overtopping flow on a vertical wall on a dike crest are investigated by means of a series of physical model tests. A double-peaked force was recognized in a time series of an overtoping flow. Four stages were summarized for the whole overtopping flow impact process. An empirical relationship between the maximum impact pressure and impact rising time was found. By using the pressure impulse concept, the empirically established constant product of maximum impact pressure and rising time can be used to develop new design formula in the future.