An integrated geoscience modelling approach to ground water and coastal flood risk

Understanding flood risk in Morayshire has required the adoption of a holistic work programme that brought together a multidisciplinary scientific team who used a variety of modelling techniques to investigate groundwater and coastal flood risk within the Lower Findhorn Catchment in Morayshire, N. E. Scotland. This work, which has been largely funded by Moray Council, delimits potential zones of ground water flooding and has informed the design and construction of flood defences, in parts of the catchment where both commercial and residential properties were at risk. It also assessed the potential for coastal flooding of the low-lying coastal zone. Determining the nature of the complex shallow Quaternary strata and the degree of continuity, heterogeneity and relative permeability of packages of sediment in 3D was critical to establishing the areas at risk of ground water flooding. A ‘source to sink approach’ was adopted covering not only the floodplain of the River Findhorn, but also the interfluves and the surrounding coastal zone. This was achieved by construction of a GSI 3D model of the shallow geology, based on extensive and detailed field investigation of the catchment geology, but also informed by conceptual models of the glacial and postglacial evolution of North East Scotland. The model was calibrated by borehole drilling and trial pitting, and subsequently reattributed with permeability values based on pumping test results and geotechnical analyses. The resulting 3D distribution of shallow subsurface permeability provided a major set of parameters for ZOOM groundwater modelling. This was used, together with outputs from third party hydrological models, to model groundwater flow directions, changes in the water table relative to base level (sea level), and to establish the potential groundwater component of river flooding in the catchment. Regional modelling of changes in Relative Sea Level is also and important component in determining the probable future trends in flood risk in the Lower Findhorn. Unusually for the UK, conceptual models and proxies indicate that little rise in sea level has occurred during the last 100 years and that the coastline is prograding. Consequently, modelling indicates that the risk of inundation of this low-lying portion of Morayshire by coastal flooding is slight, when compared to that from river flooding events

Relating in situ hydraulic conductivity, particle size and relative density of superficial deposits in a heterogeneous catchment

Estimating the permeability of superficial deposits is fundamental to many aspects of catchment science, but can be problematic where insufficient in situ measurements are available from pumping tests in piezometers. Consequently, common practice is to estimate permeability from the material description or, where available, particlesize distribution using a formula such as Hazen. In this study, we examine the relationships between particlesize, relativedensity and hydraulicconductivity in superficial deposits in Morayshire, Northern Scotland: a heterogeneous environment typical of many catchments subject to previous glaciations. The superficial deposits comprise glaciofluvial sands and gravels, glacial tills and moraines, raised marine sediments, and blown sands. Thirty-eight sites were investigated: hydraulicconductivity measurements were made using repeated Guelph permeameter measurements, cone resistance was measured in situ with a Panda dynamic cone penetrometer; material descriptions were made in accordance with BS5930:1999; and disturbed samples were taken for particlesize analysis. Overall hydraulicconductivity (K) varied from 0.001 m/d to >40 m/d; glacial till had the lowest K (median 0.027 m/d) and glacial moraine the highest K (median 30 m/d). However, within each geological unit there was great variability in measured hydraulicconductivity values. Multiple linear regression of the data indicated that log d10 and relativedensity (indicated by cone resistance or BS5930:1999 soil state description) were independent predictors of log K and together gave a relationship with an R2 of 0.80. Material description using the largest fraction (e.g. sand or gravel) had little predictive power. Therefore, in heterogeneous catchments, the permeability of superficial deposits is most strongly related to the finest fraction (d10) and relativedensity of the material. In situ Guelph permeameter measurements at outcrops with good geological characterisation provide an easy and reliable method of determining the permeability of particular units of superficial deposits

Model metadata report for the GSI3D model of the superficial geology of the ground seaward of the Drigg Low Level Waste Repository Site, West Cumbria

This report describes the GSI3D model of the superficial geology of the ground seaward of the Drigg Low Level Waste Repository site, West Cumbria. This geological model is based on the GSI3D geophysical model described in IR/12/071: Callaghan, E, Kearsey, T, Finlayson, A and Auton, C.A. 2012. Model metadata repport for the GSI3D model of shallow geophysical surveys of the ground seaward of the Drigg Low Level Waste Repository Site, West Cumbria. British Geological Survey Internal Report, IR/12/071. 16pp. The geophysical model was built to show resistivity characteristics of Quaternary sequences overlying sandstone bedrock and was commissioned by the National Nuclear Laboratory (NNL) for Low Level Waste Repository Ltd (LLWR) and is Commercial in Confidence. The superficial geological model is not Commercial in Confidence

Structural and stochastical modelling of possible contaminant pathways below nuclear installations

Structural and stochastical modelling of possible contaminant pathways below nuclear installations 1Richard Haslam, 1Stuart Clarke, 1Peter Styles & 2Clive Auton 1Earth Sciences and Geography, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire, ST5 5BG, United Kingdom 2British Geological Survey, Murchison House, West Mains Road, Edinburgh, EH9 3LA, United Kingdom Dounreay Nuclear Power station is situated on the northern coast of Caithness, Scotland on complex normally faulted Devonian sedimentary rocks with a thin, intermittent cover of superficial deposits, predominantly comprising glacial tills of varying provenance. Bedrock structure, fracture patterns and the relationships between bedrock and the superficial deposits have a considerable impact on the transmissivity of any possible contaminants. Consequently, an understanding of the bedrock-superficial boundary and how fractures and faults influence and control the transport of fluids are a key concern. The principal aims of this work are to gain an understanding of the processes and controls on fluid flow pathways within such complex geological terrains, and develop methods of stochastatically evaluating likely contamination transport within the subsurface. This work focuses on the near-surface bedrock geology and superficial deposits. The near surface geology of the Dounreay site comprises cyclic sequences of lacustrine rocks; their cyclicity has enabled a reference stratigraphy to be created and correlated across the site. This stratigraphy, the coastal exposures and the extensive amount of borehole data available, provide a unique opportunity to construct and constrain a three-dimensional bedrock model; the interpretive element of which has been robustly test using structural restoration techniques. In the bedrock of Dounreay, three principal fracture sets have been identified. The first two sets of fractures are approximately orthogonal, trending north-northwest and west-southwest respectively; they represent the regional fracture set. It is proposed that these fractures where produced during loading and burial of the Devonian sediments. The final fracture set is predominantly parallel to bedding of the laminated sediments; it gives the Caithness Flagstones their ‘flaggy’ nature. The regional fracture sets are approximately constant over the site area and vary little with depth, whereas the bedding parallel fracture set shows a marked decrease in the number of fractures per meter with depth, on a logarithmic trend. This relationship is also visible in the Rock Quality Designation (RQD) values and hydraulic conductivity data from boreholes. It follows that the bedding parallel fractures are the major controlling factor of flow in the shallow subsurface and that the RQD values can be used as a proxy for fracture density. RQD values are a commonly collected during borehole drilling and the relationship between hydraulic conductivity and RQD values offer a method for stochastically populating a 3D geological model with hydraulic conductivity values. Current geological interpretations of the superficial deposits are based primarily on their genesis. Consequently, subdivisions based on the origin of the sediments do not relate directly to their fluid transmissivity. The superficial deposits generally have a very low hydraulic conductivity, compared to that of the bedrock, impeding the flow of water from the surface to the groundwater system at depth. A combination of driller’s description and comparisons of grain-size distribution enables subdivisions of the Quaternary strata to be established based on their properties instead of their genesis. These properties can then be stochastically interpolated throughout the 3D geological model. This work provides a framework from which likely contamination scenarios can be modelled, both in the well-constrained subsurface of Dounreay, and at other nuclear installations where the nature of the subsurface is less well constrained

Graphene Triangular Ballistic Rectifier: Fabrication and Characterisation

It has been shown that graphene can demonstrate ballistic transport at room temperature. This opens up a range of practical applications that do not require graphene to have a band gap, which is one of the most significant challenges for its use in the electronics industry. Here, the very latest high mobility graphene (>100,000 cm2 V−1 s−1) fabrication techniques will be demonstrated so that one such device, called the triangular ballistic rectifier (TBR), can be characterised. The TBR is a four-terminal device with a triangular anti-dot at their intersection; two sides of the triangle are positioned and angled such that ballistic carriers from the two input electrodes are redirected like billiard balls to one of the two output contacts irrespective of the instantaneous polarity of the input. A responsivity of 2400 mV mW−1 is demonstrated at room temperature from a low-frequency input signal. The ballistic nature of the device is justified and explained in more detail with low-temperature measurements

The relationship of soil and woodland cover on soil hydraulic conductivity at a hillslope scale and local flood management in the Scottish Borders

An important criteria in Natural Flood Management (NFM) is understanding and improving the surface soil permeability (or field, saturated hydraulic conductivity, Kfs; Talsma, 1987) of natural ground surfaces with the view of increasing rainfall infiltration and storage capacity (Marshall et al., 2009). At the local scale infiltrability and soil hydraulic conductivity (Ks) are key soil properties as they activate surface and near-surface flow paths that influence runoff generation (Elsenbeer, 2001; Bonell et al., 2010)

Bubble Lift-off Size in Forced Convective Subcooled Boiling Flow

Forced convective subcooled boiling flow experiments were conducted in a BWR-scaled vertical upward annular channel. Water was used as the testing fluid, and the tests were performed at atmospheric pressure. A high-speed digital video camera was applied to capture the dynamics of the bubble nucleation process. Bubble lift-off diameters were obtained from the images for a total of 91 test conditions. A force balance analysis of a growing bubble was performed to predict the bubble lift-off size. The dimensionless form of the bubble lift-off diameter was formulated to be a function of Jacob number and Prandtl number. The proposed model agreed well with the experimental data within the averaged relative deviation of ±35.2 %

Genetic recombination is targeted towards gene promoter regions in dogs

The identification of the H3K4 trimethylase, PRDM9, as the gene responsible for recombination hotspot localization has provided considerable insight into the mechanisms by which recombination is initiated in mammals. However, uniquely amongst mammals, canids appear to lack a functional version of PRDM9 and may therefore provide a model for understanding recombination that occurs in the absence of PRDM9, and thus how PRDM9 functions to shape the recombination landscape. We have constructed a fine-scale genetic map from patterns of linkage disequilibrium assessed using high-throughput sequence data from 51 free-ranging dogs, Canis lupus familiaris. While broad-scale properties of recombination appear similar to other mammalian species, our fine-scale estimates indicate that canine highly elevated recombination rates are observed in the vicinity of CpG rich regions including gene promoter regions, but show little association with H3K4 trimethylation marks identified in spermatocytes. By comparison to genomic data from the Andean fox, Lycalopex culpaeus, we show that biased gene conversion is a plausible mechanism by which the high CpG content of the dog genome could have occurred.Comment: Updated version, with significant revision

Negative local resistance caused by viscous electron backflow in graphene

Graphene hosts a unique electron system in which electron-phonon scattering is extremely weak but electron-electron collisions are sufficiently frequent to provide local equilibrium above liquid nitrogen temperature. Under these conditions, electrons can behave as a viscous liquid and exhibit hydrodynamic phenomena similar to classical liquids. Here we report strong evidence for this transport regime. We find that doped graphene exhibits an anomalous (negative) voltage drop near current injection contacts, which is attributed to the formation of submicrometer-size whirlpools in the electron flow. The viscosity of graphene's electron liquid is found to be ~0.1 m$^2$ /s, an order of magnitude larger than that of honey, in agreement with many-body theory. Our work shows a possibility to study electron hydrodynamics using high quality graphene

Scaling approach to tight-binding transport in realistic graphene devices:the case of transverse magnetic focusing

Ultraclean graphene sheets encapsulated between hexagonal boron nitride crystals host two-dimensional electron systems in which low-temperature transport is solely limited by the sample size. We revisit the theoretical problem of carrying out microscopic calculations of nonlocal ballistic transport in such micron-scale devices. By employing the Landauer-Büttiker scattering theory, we propose a scaling approach to tight-binding nonlocal transport in realistic graphene devices. We test our numerical method against experimental data on transverse magnetic focusing (TMF), a textbook example of nonlocal ballistic transport in the presence of a transverse magnetic field. This comparison enables a clear physical interpretation of all the observed features of the TMF signal, including its oscillating sign