Flood Events in the Rhine Basin: Genesis,Influences and Mitigation   总被引：4，自引：1，他引：4  

Disse  Markus  Engel  Heinz 《Natural Hazards》2001,23(2-3):271-290

The paper analyses the hydrological regime of the Rhine catchment,the genesis of recent floods,and recommends some research and practical activities to mitigate flood damage. The catchment of the Rhine River can be divided into four main subcatchments: the alpine region with the Aare River as its main tributary and downstream the lower mountain regions of the tributaries Neckar, Main and Moselle. These four basins generate very different hydrographs. Due to the geographical conditions, the average discharge maximums shift from summer to winter downstream the Rhine. Moreover, the spatial and temporalprecipitation patterns of each river have a strong influence on the individual flood events. Some recent extraordinary floods are used to illustrate the parameters that have influenced these events.A strong relationship between recent climate change observationsand the occurrence of flood levels cannot be proven. However, the consequences of human interventions and the resulting changes to the river system (the Rhine and its tributaries) for the hydrograph can be quantified precisely.The influences of different land-use and climatic scenarios on flood conditions in the Rhine basin have not yet been separately identified. Thus, the Dutch-German project LAHoR was established. The primary aim of this project is to giveadvice for the ``Action Plan on Flood Defence' of the International Commission for the Protection of the Rhine (IKSR). In this plan a multidisciplinary approach to mitigating floods is suggested.It is anticipated that the plan willgenerate synergistic effects between flood prevention, water management, regional planning, agriculture, forestry and ecological demands.  相似文献   

Yearly changes in the seasonal frequency and duration of short-term acid pulses in some Nova Scotia, Canada streams   总被引：1，自引：0，他引：1  

T. A. Clair  A. Ghosh Bobba  Krista Miller 《Environmental Geology》2001,40(4-5):582-591

 The seasonal frequency and duration of low pH events at three sites located in southwestern Nova Scotia were analyzed using measured and synthetic daily pH data. The basins varied in size from 0.3 to 300 km² and were subject to frequent snowmelt events in winter and spring, as well as occasional runoff events during summer and fall. Results showed that, in order to fill in missing data from periods where collection was interrupted, statistical approximations using discharge were not totally acceptable, as generated data consistently missed the extreme values measured. Despite a lack of totally accurate event pH estimates for periods where daily data were missing, analysis showed that in this region, low pH episodes can occur year-round including summer. The highest probabilities of low pH episodes nevertheless occurred in the winter and spring when snowmelts were frequent. Received: 12 November 1999 · Accepted: 18 July 2000  相似文献   

Sources, distribution and storage of heavy metals in the Río Pilcomayo, Bolivia     

Karen A. Hudson-Edwards  Mark G. Macklin  Jerry R. Miller  Paul J. Lechler 《Journal of Geochemical Exploration》2001,72(3)

The Río Pilcomayo rises on the Cerro Rico de Potosí precious metal-polymetallic tin deposits of Bolivia, and flows in a southeasterly direction for ca. 600 km to Bolivia's southern border with Argentina. Mining of the Potosí deposits has occurred continuously since 1545, generating large quantities of waste materials in the headwater of the basin. In addition, a tailings dam breach at the Porco mine in 1996 released an estimated 235 000 m³ of tailings and fluid into the upper reaches of the Río Pilaya, the largest tributary to the Pilcomayo.Concentrations of As, Sb, Cd, Cu, Pb, Hg, Ag, Tl and Zn in contemporary channel sediments upstream of the Pilaya confluence are significantly elevated above background values. Elevated levels appear to be associated with pyrite- and other sulphide mineral-bearing tailings materials transported more than 200 km downstream of the Potosí mines. Significant downstream declines in elemental concentrations occur within 15 km, and again between 150 and 200 km, from the mines. The initial decrease in concentrations is due to the rapid dilution of nearly pure tailings effluent released to the river from milling facilities near Potosí. The latter decrease results from a combination of geomorphic processes including the storage of sediment-borne metals within the channel bed and the influx of ‘clean’ sediment from several large tributaries. Downstream of the Pilaya confluence, concentrations of Cu, Pb, Hg and Zn are only slightly elevated above background values, and Ag, Cd, Sb and Tl cannot be distinguished from background levels. These data suggest that while the Porco tailings spill may have had a significant short-term impact on sediment and water quality along the lower reaches of the Río Pilcomayo, its longer-term impacts were limited. Metals stored and eroded from alluvial deposits of historical age in upstream reaches appear to be an important source of metals to the river today. An additional, and perhaps more significant source, is the release of tailings effluent to the river from modern milling operations. The transport of these contaminants downstream of Icla (203 km from Potosí) appears to be restricted by aggradational processes occurring in the vicinity of Puente Sucre. In addition, downstream of the confluence of the Río Pilaya, inputs of large amounts of ‘clean’ sediment have caused dilution of the metal contaminants. Data from other studies where similar geomorphic processes have occurred suggest that the metals in the upper Pilcomayo may eventually be moved downvalley as the aggradational processes are reversed and channel stabilisation occurs. Thus, the most significant impacts of metal contamination may not be realised in downstream areas for decades.  相似文献   

Microphytobenthos: The ecological role of the “secret garden” of unvegetated,shallow-water marine habitats. II. role in sediment stability and shallow-water food webs     

Douglas C. Miller  Richard J. Geider  Hugh L. MacIntyre 《Estuaries and Coasts》1996,19(2):202-212

The microphytobenthos form an important component of all shallow-water ecosystems where enough light reaches the sediment surface to support appreciable primary production. Although less conspicuous than macroalgae or vascular plants, the microphytobenthos can contribute significantly to primary production and can modify habitat characteristics. The microphytobenthos alter sediment properties (e.g., erodibility) both directly, in the extreme forming a mat or scum on the sediment surface, and indirectly by modifying the activities of benthic infauna (e.g., pelletization, burrowing, tube building, and sediment tracking). Carbon dioxide fixed by the microphytobenthos supports higher, grazing trophic levels. These include deposit-feeding and suspension-feeding macrofauna as well as meiofauna and microfauna. Quantitative relations between the feeding and growth rates of macrofauna and the abundance of microphytobenthos and suspended organic matter (i.e., functional responses) are reviewed. Given the current state of knowledge of the direct and indirect interactions involving trophic dynamics, sediment properties, and benthic microalgae, we argue for reductionist studies of particular interactions as distinct entities. This is a prerequisite for the emergence of a comprehensive picture of unvegetated ecosystems and the ability to predict their responses to man’s activities. *** DIRECT SUPPORT *** A01BY074 00005  相似文献   

Editorial     

Gerhard Furrer  Bernhard Wehrli  Heinz Gamsjäger 《Aquatic Sciences - Research Across Boundaries》1993,55(4):229-229

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Thermal analysis in the laser-heated diamond anvil cell     

Jeffrey S. Sweeney  Dion L. Heinz 《Pure and Applied Geophysics》1993,141(2-4):497-507

A new technique actively controls thermal radiation and monitors sample properties during laser-heating in a diamond anvil cell. The technique can be described as a qualitative application of thermal analysis. Discontinuities in temperature, laser power, visible thermal radiation, or in their derivatives as functions of time can be associated with the enthalpy of phase transitions (such as melting) or with changes in maternal properties (such as emissivity).The technique is illustrated with melting experiments on iron-magnesium-silicate perovskite. Temperature corrections associated with these experiments are discussed and the results are briefly reviewed.  相似文献   

Stochastic perturbation analysis of groundwater flow. Spatially variable soils,semi-infinite domains and large fluctuations     

G. Christakos  C. T. Miller  D. Oliver 《Stochastic Environmental Research and Risk Assessment (SERRA)》1993,7(3):213-239

As is well known, a complete stochastic solution of the stochastic differential equation governing saturated groundwater flow leads to an infinite hierarchy of equations in terms of higher-order moments. Perturbation techniques are commonly used to close this hierarchy, using power-series expansions. These methods are applied by truncating the series after a finite number of terms, and products of random gradients of conductivity and head potential are neglected. Uncertainty regarding the number or terms required to yield a sufficiently accurate result is a significant drawback with the application of power series-based perturbation methods for such problems. Low-order series truncation may be incapable of representing fundamental characteristics of flow and can lead to physically unreasonable and inaccurate solutions of the stochastic flow equation. To support this argument, one-dimensional, steady-state, saturated groundwater flow is examined, for the case of a spatially distributed hydraulic conductivity field. An ordinary power-series perturbation method is used to approximate the mean head, using second-order statistics to characterize the conductivity field. Then an interactive perturbation approach is introduced, which yields improved results compared to low-order, power-series perturbation methods for situations where strong interactions exist between terms in such approximations. The interactive perturbation concept is further developed using Feynman-type diagrams and graph theory, which reduce the original stochastic flow problem to a closed set of equations for the mean and the covariance functions. Both theoretical and practical advantages of diagrammatic solutions are discussed; these include the study of bounded domains and large fluctuations.  相似文献   

Bestimmung systematischer Korrektionen für die Rektaszensionen des revidierten 3. Fundamentalkatalogs des Berliner Astronomischen Jahrbuches (FK3R)     

Heinz Enslin 《Ocean Dynamics》1960,13(1):28-33

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Bemerkungen über den Einfluss der Verwitterungsschicht auf das Spektrum seismischer Wellen     

Heinz Menzel  Otto Rosenbach 《Pure and Applied Geophysics》1958,40(1):36-40

Zusammenfassung In Fortfühung einer früheren Arbeit der Autoren werden einige weitere theoretische Untersuchungen skizziert, bei denen die elastischen Eigenschaften der Verwitterungschicht geeignet abgeändert sind. Bei Anregung der Schicht durch einen momentanen Impuls (Nadelimpuls) ergibt sich, daß die Frequenz der seismischen Welle nicht durch den Gradienten der Geschwindigkeit, sondern durch den Gradienten des Schallwiderstandes bestimmt wird.

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Summary Continuating an earlier paper the authors present some further theoretical investigations on the influence of the weathering layer; the assumptions with regard to the elastic nature of the layer are properly modified. The result is as follows: If the layer is acted on by a momentary pulse (needle pulse) then the frequency of the seismic wave is determined by the gradient of the acoustical resistance, not by the gradient of the velocity of propagation.

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Beitrag zur Gliederung des Präkambriums in Minas Gerais     

Heinz Ebert 《International Journal of Earth Sciences》1957,45(3):471-521

Zusammenfassung Aufnahmen im Kristallin südostwärts und südlich der EsphinhaÇo-Zone, ausgedehnt bis an die Südgrenze des Staates Minas Gerais, ergaben eine neue stratigraphische und tektonische Gliederung. Große Gebiete, die bisher als tiefstes Archaikum galten, erhielten ihre metamorphe Überprägung erst in der assyntischen Phase. Auch die vormetamorphe sedimentäre Substanz ist weithin algonkischen, wahrscheinlich neo-algonkischen Alters. Im Inneren besitzen diese Sedimente nur schwache epizonale Metamorphose und erlauben weitgehende stratigraphische Gliederung (Formationen Tiradentes, Carandaí, Barroso, Prados). Sie sind Überwiegend klastisch. Küstenwärts folgen die sedimentär-lithologisch gleichen, aber stärker (mesozonal) metamorphe Andrelandia-Serie und die katazonalen Juiz de Fora- bzw. Paraíba-Serien (Metamorphose charnockitisch bzw. mikroklingranitisch). Die Küstenzone stellt daher eine kristalline Zentralzone dar, von der aus die Bewegungen binnenwärts gerichtet sind. An der Westgrenze des Arbeitsgebietes erfolgt eine Virgation der Faltenzüge in Araxaiden und Paraibiden. Das ordovizische Alter der Füllung des Beckens des Rio SÃo Francisco (Bambuí) ist zu bezweifeln. Die EsphinhaÇo-Zone ist algomisch konsolidiert, die alt-algonkische Minas-Serie auf diese Zone beschränkt. Sie bildet, zusammen mit dem Bambuí-Becken, das Vorland der assyntischen Faltenzüge. Eine Aufgliederung des Archaikums ist begonnen; im bisher untersuchten Gebiet sind die archäischen Strukturen co-axial den jüngeren.  相似文献