Measuring streambank erosion due to ground water seepage: correlation to bank pore water pressure,precipitation and stream stage   总被引：1，自引：0，他引：1  

Garey A. Fox  Glenn V. Wilson  Andrew Simon  Eddy J. Langendoen  Onur Akay  John W. Fuchs 《地球表面变化过程与地形》2007,32(10):1558-1573

Limited information exists on one of the mechanisms governing sediment input to streams: streambank erosion by ground water seepage. The objective of this research was to demonstrate the importance of streambank composition and stratigraphy in controlling seepage flow and to quantify correlation of seepage flow/erosion with precipitation, stream stage and soil pore water pressure. The streambank site was located in Northern Mississippi in the Goodwin Creek watershed. Soil samples from layers on the streambank face suggested less than an order of magnitude difference in vertical hydraulic conductivity (K_s) with depth, but differences between lateral K_s of a concretion layer and the vertical K_s of the underlying layers contributed to the propensity for lateral flow. Goodwin Creek seeps were not similar to other seeps reported in the literature, in that eroded sediment originated from layers underneath the primary seepage layer. Subsurface flow and sediment load, quantified using 50 cm wide collection pans, were dependent on the type of seep: intermittent low‐flow (LF) seeps (flow rates typically less than 0·05 L min^?1), persistent high‐flow (HF) seeps (average flow rate of 0·39 L min^?1) and buried seeps, which eroded unconsolidated bank material from previous bank failures. The timing of LF seeps correlated to river stage and precipitation. The HF seeps at Goodwin Creek began after rainfall events resulted in the adjacent streambank reaching near saturation (i.e. soil pore water pressures greater than ?5 kPa). Seep discharge from HF seeps reached a maximum of 1·0 L min^?1 and sediment concentrations commonly approached 100 g L^?1. Buried seeps were intermittent but exhibited the most significant erosion rates (738 g min^?1) and sediment concentrations (989 g L^?1). In cases where perched water table conditions exist and persistent HF seeps occur, seepage erosion and bank collapse of streambank sediment may be significant. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

GROSSULAR IN THE ALLENDE (TYPE III CARBONACEOUS) METEORITE*     

Louis H. Fuchs 《Meteoritics & planetary science》1974,9(1):11-18

Grossular garnet has been observed in several white inclusions in the Allende meteorite. Compositions range from Gro_9sPy₅ to Gro₈₈Py₁₂ in five inclusions. Its mottled appearance indicates that it crystallized from a glass of near-grossular composition and not by a solid state reaction between wollastonite, anorthite and melilite. These grossular-bearing inclusions either condensed directly as metastable liquids from the solar nebula or if initial solid condensates were liquefied by some subsequent heating process. In either case, a prolonged residence time in a thermal blanket appears necessary to effect crystallization of the grossular.  相似文献   

Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari,Botswana) during Marine Isotope Stage 5 inferred from diatoms     

Mareike Schmidt  Markus Fuchs  Andrew C. G. Henderson  Annette Kossler  Melanie J. Leng  Anson W. Mackay  Elisha Shemang  Frank Riedel 《Journal of Paleolimnology》2017,58(3):373-390

The Makgadikgadi–Okavango–Zambezi basin (MOZB) is a structural depression in the south-western branch of the East African Rift System of the northern and middle Kalahari, central southern Africa. In the present day, the mainly dry subbasins of the MOZB are part of a long-lived lacustrine system that has likely existed since Early Pleistocene and from which an extant freshwater fish radiation emerged seeding all major river systems of southern Africa. During hydrologically favourable periods the subbasins were connected as a single mega-lake termed Lake Palaeo-Makgadikgadi. Previous geomorphological studies and OSL dates have provided evidence for repeated mega-lake periods since approximately 300 ka. The environmental and climatic implications of such large scale late Quaternary lake-level fluctuations are controversial, with the duration of mega-lake phases poorly constrained. Here, we present the first evidence for a Marine Isotope Stage (MIS) 5 mega-lake period (about 935–940 m a.s.l.) reconstructed from a diatom-rich, 30-cm-thick lacustrine sediment section, exposed close to a palaeo-shoreline of the Makgadikgadi Basin. Based upon the environmental setting and in comparison with sedimentation rates of other similar lake environments, we tentatively estimated that the highstand lasted approximately 1 ka during MIS 5d–b. The 30-cm section was sampled in 0.5-cm steps. Diatom species diversity ranges from 19 to 30 through the section. The dominant species are Pseudostaurosira brevistriata, Rhopalodia gibberula, Cyclotella meneghiniana and Epithemia sorex. The total of 60 sediment samples provide us with a record at decadal to bi-decadal resolution. Based on diatom assemblages and their oxygen isotope composition (δ¹⁸O) we infer an alkaline and mostly oligohaline lake with shallow water conditions prevailing in MIS 5, and is potentially analogous to a Heinrich event. The climate over southern Africa during MIS 5 has been considered very arid but the hydromorphological context of our sediment section indicates that we captured a mega-lake period providing evidence that short-term excursions to significantly higher humidity existed. A hydrologically more favourable environment during MIS 5 than formerly presumed is in line with the early human occupation of the Kalahari.  相似文献   

Rockfall in the Port Hills of Christchurch: Seismic and non‐seismic fatality risk on roads          下载免费PDF全文

Stefan Unterrader  Peter Almond  Sven Fuchs 《New Zealand geographer》2018,74(1):3-14

Numerous rockfalls released during the 2010–2011 Canterbury earthquake sequence affected vital road sections for local commuters. We quantified rockfall fatality risk on two main routes by adapting a risk approach for roads originally developed for snow avalanche risk. We present results of the collective and individual fatality risks for traffic flow and waiting traffic. Waiting traffic scenarios particularly address the critical spatial‐temporal dynamics of risk, which should be acknowledged in operational risk management. Comparing our results with other risks commonly experienced in New Zealand indicates that local rockfall risk is close to tolerability thresholds and likely exceeds acceptable risk.  相似文献   

Faint Stars and the Structure of the Galaxy     

S. Phleps  K. Meisenheimer  C. Wolf  B. Fuchs  H. Jahreiss 《Astrophysics and Space Science》1999,265(1-4):231-232

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E. W. MIELKE: Geometrodynamics of Gauge Fields. On the Geometry of Yang-Mills and Gravitational Gauge Theories. Physical Research Vol. 3. Akademie-Verlag Berlin, 1987. Preis: DM 45     

H. Fuchs 《Astronomische Nachrichten》1988,309(3):196-196

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A modeling language to support the interoperability of global navigation satellite systems     

Daniele Gianni  Joachim Fuchs  Pierluigi De Simone  Marco Lisi 《GPS Solutions》2013,17(2):175-198

The availability of multiple Global Navigation Satellite Systems (GNSS) will offer the opportunity to provide seamless navigation services and improved positioning performance. However, before this opportunity can be exploited, a number of issues need to be solved to ensure the compatibility and interoperability of existing GNSS. In particular, the GNSS interoperability can be technically defined as the capability of receivers to compute their global position using two or more GNSS signals. This capability can be more effectively achieved if Signal-In-Space interface specifications are available in a consistent, unambiguous, and possibly standard format, which can support engineers to design interoperable receivers. We aim to support the design of interoperable receivers with the introduction of the Interface Communication Modeling Language (ICML), a graphical language for the formal specification of Signal-In-Space interfaces. The ICML language enables receiver engineers to specify these interfaces at different levels of abstraction, such as analog signal or binary data. In addition, the ICML language also supports the specification of conversion routines between adjacent levels, for the representation of the dynamic aspects—e.g., convolution and encryption processes—of the interface specification. As such, the ICML language proposes an alternative format to textual-based interface specifications and can possibly integrate with the ongoing trend of the Model-based Systems Engineering approaches. We present the structure of the framework implementing the language and an example ICML-based specification for a simplified and reduced version of the Galileo Freely Accessible Navigation (F/NAV) message. The language metamodel is also attached for technical reference. An important caveat: no endorsement is made for the use of the ICML language for the official Galileo Signal-In-Space interface specification.  相似文献   

An Integrated Approach to Germanic Place Names in the American Midwest     

Stephan Fuchs 《The Professional geographer》2013,65(3):330-341

Place names represent an established topic in sociocultural and critical scholarship on human space and place. Based on a comprehensive data set of Germanic names in the American Midwest, this article explores the value of a novel approach integrating advanced spatio-statistical measures with critical interpretation to revitalize the field of toponomy on a concerted methodological and theoretical level. Processed in a geographic information system (GIS) environment, the regional toponymic pattern provides a broad and reliable framework that evokes interpretative discussion of underlying structures and processes. This characterizes Germanic toponyms as versatile sociodemographic, political, and ethnocultural indicators.  相似文献   

Deep 3D thermal modelling for the city of Berlin (Germany)   总被引：1，自引：1，他引：0  

Judith Sippel  Sven Fuchs  Mauro Cacace  Anna Braatz  Oliver Kastner  Ernst Huenges  Magdalena Scheck-Wenderoth 《Environmental Earth Sciences》2013,70(8):3545-3566

This study predicts the subsurface temperature distribution of Germany’s capital Berlin. For this purpose, a data-based lithosphere-scale 3D structural model is developed incorporating 21 individual geological units. This model shows a horizontal grid resolution of (500 × 500) m and provides the geometric base for two different approaches of 3D thermal simulations: (1) calculations of the steady-state purely conductive thermal field and (2) simulations of coupled fluid flow and heat transport. The results point out fundamentally different structural and thermal configurations for potential geothermal target units. The top of the Triassic Middle Buntsandstein strongly varies in depth (159–2,470 m below sea level) and predicted temperatures (15–95 °C), mostly because of the complex geometry of the underlying Permian Zechstein salt. The top of the sub-salt Sedimentary Rotliegend is rather flat (2,890–3,785 m below sea level) and reveals temperatures of 85–139 °C. The predicted 70 °C-isotherm is located at depths of about 1,500–2,200 m, cutting the Middle Buntsandstein over large parts of Berlin. The 110 °C-isotherm at 2,900–3,700 m depth widely crosscuts the Sedimentary Rotliegend. Groundwater flow results in subsurface cooling the extent of which is strongly controlled by the geometry and the distribution of the Tertiary Rupelian Clay. The cooling effect is strongest where this clay-rich aquitard is thinnest or missing, thus facilitating deep-reaching forced convective flow. The differences between the purely conductive and coupled models highlight the need for investigations of the complex interrelation of flow- and thermal fields to properly predict temperatures in sedimentary systems.  相似文献   

Exploring the method of optical dating and comparison of optical and 14C ages of Late Weichselian coversands in the southern Netherlands     

D. Vandenberghe  C. Kasse  S. M. Hossain  F. De Corte  P. Van Den Haute  M. Fuchs  A. S. Murray 《第四纪科学杂志》2004,19(1):73-86

A study was made of the applicability of three different techniques for equivalent dose (D_e) determination in the optical dating of quartz: the single‐aliquot regenerative‐dose technique (SAR), the single‐aliquot additive‐dose technique (SAAD) and the multiple‐aliquot additive‐dose technique (MAAD). For this purpose, quartz grains were extracted from a sequence of Upper Pleniglacial to Late‐glacial coversands exposed at the locality of Ossendrecht in the southwestern Netherlands, a site for which both radiocarbon and earlier luminescence dates are available, providing independent age control. Upon testing the different assumptions underlying each of the three OSL techniques investigated, the SAR protocol was found to be the technique of choice. The optical ages obtained with this protocol were in good agreement with the chronostratigraphical position of the sediments investigated and with the available chronostratigraphical information on the same and equivalent deposits. This confirms the suitability of the SAR technique for dating coversands. Furthermore, a small laboratory intercomparison of SAR‐based D_e determinations yielded results that were in fair overall agreement. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献