scholarly journals DUNE MIGRATION AND SAND TRANSPORT RATES IN TIDAL ESTUARIES: THE EXAMPLE OF THE RIVER ELBE

2011 ◽  
Vol 1 (32) ◽  
pp. 38
Author(s):  
Anna Christina Zorndt ◽  
Andreas Wurpts ◽  
Torsten Schlurmann ◽  
Nino Ohle ◽  
Thomas Strotmann
Keyword(s):  
Sand Dunes ◽  
Offshore Structures ◽  
Sand Transport ◽  
Correlation Technique ◽  
Data Set ◽  
Migration Patterns ◽  
River Elbe ◽  
Tidal Estuaries ◽  
Dune Migration ◽  
And Migration

Large parts of the tidal estuary of river Elbe (Germany) are characterized by regular patterns of sand dunes. They are presumed to evolve due to complex sand transport mechanisms and show multi-faceted migration patterns. Direction and magnitude of their migration are influenced by hydrodynamic boundary conditions such as river runoff and tides. Dune Migration can lead to residual sand transport rates, depending on its direction and magnitude and the dune’s characteristics. The understanding of dune migration patterns and associated sand transport is the basis of an effective sediment management as well as an important requirement for planning offshore structures. This study focuses on methods for computing migration and sand transport rates in automated ways. In a comparison and validation of different approaches, a cross-correlation technique was found to produce best results. From a unique data set of up to six annual bathymetrical multi-beam soundings between 1995 and 2010, dune characteristics and migration rates were processed and analysed autonomously. The findings show that in a long perspective, average dune migration and sand transport rates in the present study reach are directed upstream.

Dunes and associated sand transport in a tidally influenced sand-bed channel: Fraser River, British Columbia

2003 ◽  
Vol 40 (1) ◽  
pp. 115-130 ◽  
Author(s):  
P V Villard ◽  
M Church
Keyword(s):  
British Columbia ◽  
Rapid Change ◽  
Sand Transport ◽  
Fraser River ◽  
Flow Conditions ◽  
Material Transport ◽  
Coefficients Of Variation ◽  
Dune Migration ◽  
And Migration ◽  
Dune Height

Dunes form annually on the sand bed of the tidally influenced South Arm of Fraser River, British Columbia. Bathymetric surveys along the center of the main channel throughout a snow-melt freshet provided measurements of dune geometry and migration. Dune length, height, and steepness all increase with river discharge. However, lag between the highest flow conditions and development of the largest, steepest dunes reflects the influence of antecedent flow conditions on dune geometry. Population averages of dune height and steepness ratio change more rapidly than dune length, whilst coefficients of variation of dune height, length, and steepness ratio indicate high variability in dune geometry within the estuarine reach during periods of dune growth and decay. Unlike dune geometry, dune migration rates display little lag with flow conditions. The largest coefficients of variation for dune migration occur during periods of rapid change in discharge and tidal fall, corresponding to the onset of rapid change in dune geometry on both rising and falling limbs. Migration rate estimates and geometry measurements are used to estimate associated sand transport. In the absence of hydraulic measurements in the estuary, Mission and Hope discharges are adopted to drive simple statistical models of sand transport as a function of discharge and tidal fall. The models cover 65–70% of the transport, and tidal fall is only marginally significant. Comparison with historical direct measurements indicates that the dune-associated transport coincides with bed-load transport in the estuary, and arguments are made that it constitutes the preponderance of all bed-material transport.

Population trends and migration patterns in the critically endangered Yellow-breasted Bunting (Emberiza aureola) in the Republic of Korea

2020 ◽  
Vol 27 (1) ◽  
pp. 56-63
Author(s):  
Jong-Gil Park ◽  
Chang-uk Park ◽  
Kyoung-Soon Jin ◽  
Yang-Mo Kim ◽  
Hee-Young Kim ◽  
...  
Keyword(s):  
Population Trends ◽  
Critically Endangered ◽  
Republic Of Korea ◽  
Migration Patterns ◽  
The Republic ◽  
And Migration

scholarly journals Spatial and space-time correlations in systems of subpopulations with genetic drift and migration.

Genetics ◽  
1993 ◽  
Vol 133 (3) ◽  
pp. 711-727
Author(s):  
B K Epperson
Keyword(s):  
Population Genetics ◽  
Time Correlation ◽  
Space Time ◽  
Spatial Correlations ◽  
Gene Frequencies ◽  
Migration Patterns ◽  
Migration Rates ◽  
Space And Time ◽  
Time Correlations ◽  
And Migration

Abstract The geographic distribution of genetic variation is an important theoretical and experimental component of population genetics. Previous characterizations of genetic structure of populations have used measures of spatial variance and spatial correlations. Yet a full understanding of the causes and consequences of spatial structure requires complete characterization of the underlying space-time system. This paper examines important interactions between processes and spatial structure in systems of subpopulations with migration and drift, by analyzing correlations of gene frequencies over space and time. We develop methods for studying important features of the complete set of space-time correlations of gene frequencies for the first time in population genetics. These methods also provide a new alternative for studying the purely spatial correlations and the variance, for models with general spatial dimensionalities and migration patterns. These results are obtained by employing theorems, previously unused in population genetics, for space-time autoregressive (STAR) stochastic spatial time series. We include results on systems with subpopulation interactions that have time delay lags (temporal orders) greater than one. We use the space-time correlation structure to develop novel estimators for migration rates that are based on space-time data (samples collected over space and time) rather than on purely spatial data, for real systems. We examine the space-time and spatial correlations for some specific stepping stone migration models. One focus is on the effects of anisotropic migration rates. Partial space-time correlation coefficients can be used for identifying migration patterns. Using STAR models, the spatial, space-time, and partial space-time correlations together provide a framework with an unprecedented level of detail for characterizing, predicting and contrasting space-time theoretical distributions of gene frequencies, and for identifying features such as the pattern of migration and estimating migration rates in experimental studies of genetic variation over space and time.

scholarly journals Vielfalt and diversité: how local actors in France and Germany evaluate immigration and socio-cultural heterogeneity

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Maria Schiller ◽  
Christine Lang ◽  
Karen Schönwälder ◽  
Michalis Moutselos
Keyword(s):  
Local Politics ◽  
Original Data ◽  
National Politics ◽  
Data Set ◽  
Large Cities ◽  
Cultural Heterogeneity ◽  
Societal Actors ◽  
Local Actors ◽  
Urban Level ◽  
And Migration

AbstractIn both Germany and France, perceptions of immigration, diversity and their societal consequences have undergone important transformations in the past two decades. However, existing research has only partially captured such processes. The “grand narratives” of national approaches, while still influential, no longer explain contemporary realities. Further, analyses of national politics and discourses may not sufficiently reflect the realities across localities and society more broadly. While emerging in different national contexts, little is known about how diversity is actually perceived by political stakeholders at the urban level. Given the key role of immigration and diversity in current conflicts over Europe’s future, it is imperative to assess present-day conceptualisations of migration-related diversity among important societal actors.This article investigates perceptions and evaluations of socio-cultural heterogeneity by important societal actors in large cities. We contribute to existing literature by capturing an unusually broad set of actors from state and civil society. We also present data drawn from an unusually large number of cities. How influential is the perception of current society as heterogeneous, and what forms of heterogeneity are salient? And is socio-cultural and migration-related heterogeneity evaluated as threatening or rather as beneficial? Based on an original data set, this study explores the shared and contested ideas, the cognitive roadmaps of state and non-state actors involved in local politics.We argue that, in both German and French cities, socio-cultural heterogeneity is nowadays widely recognized as marking cities and often positively connoted. At the same time, perceptions of the main features of diversity and of the benefits and challenges attached to it vary. We find commonalities between French and German local actors, but also clear differences. In concluding, we suggest how and why national contexts importantly shape evaluations of diversity.

Lake Sturgeon Geographic Range, Distribution, and Migration Patterns in the Saskatchewan River

2014 ◽  
Vol 143 (6) ◽  
pp. 1555-1561 ◽  
Author(s):  
Van Wishingrad ◽  
Meghan K. Carr ◽  
Michael S. Pollock ◽  
Maud C. O. Ferrari ◽  
Douglas P. Chivers
Keyword(s):  
Geographic Range ◽  
Lake Sturgeon ◽  
Migration Patterns ◽  
Range Distribution ◽  
And Migration

Variations in the distribution and migration of centriole duplexes in mitotic PtK2 cells studied by immunofluorescence microscopy

1980 ◽  
Vol 43 (1) ◽  
pp. 177-194 ◽  
Author(s):  
J.E. Aubin ◽  
M. Osborn ◽  
K. Weber
Keyword(s):  
Nuclear Membrane ◽  
Immunofluorescence Microscopy ◽  
Cytoplasmic Microtubule ◽  
Migration Patterns ◽  
Large Variability ◽  
Membrane Breakdown ◽  
Large Populations ◽  
Tubulin Antibodies ◽  
Cytoplasmic Microtubules ◽  
And Migration

The localization and migration of centriole duplexes have been studied in PtK2 cells by indirect immunofluorescence microscopy using specific tubulin antibodies. The study demonstrated the usefulness of the immunofluorescence technique to quantitate studies of centriole migration and concomitant events such as cytoplasmic microtubule breakdown in large populations of cells. Centriole duplex locations in normal and Colcemid-treated interphase populations have been compared with duplex locations in prophase cells. A higher percentage of duplexes were found close to the nucleus in prophase than in interphase cells, but approximately 5% of the duplexes remained in the cytoplasm far removed from the nucleus in prophase and throughout the course of duplex separation. Duplex separation occurred along a wide variety of paths and duplexes did not have to be closely juxtaposed to the nuclear envelope for separation to occur. Some duplexes separated in the cytoplasm with no detectable nuclear attachment, with spindles forming far to the side of the condensing chromosomes. The timing of duplex separation did not always coincide either with chromosome condensation or with nuclear membrane breakdown, and in a small percentage of the cells separation occurred as late as prometaphase. These data suggest that normal spindle formation can occur despite the large variability in initial and final centriole duplex location, their migration patterns, and the timing of the different events. Breakdown of cytoplasmic microtubules began in prophase and progressed until prometaphase; the last cytoplasmic microtubules disappeared soon after the loss of the nuclear membrane.

Sign in / Sign up

Export Citation Format

Share Document