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River Form (river + form)

Distribution by Scientific Domains

Life Sciences	50%
Earth and Environmental Science	50%

Selected Abstracts

Optical remote mapping of rivers at sub-meter resolutions and watershed extents

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2008
W. Andrew Marcus
Abstract At watershed extents, our understanding of river form, process and function is largely based on locally intensive mapping of river reaches, or on spatially extensive but low density data scattered throughout a watershed (e.g. cross sections). The net effect has been to characterize streams as discontinuous systems. Recent advances in optical remote sensing of rivers indicate that it should now be possible to generate accurate and continuous maps of in-stream habitats, depths, algae, wood, stream power and other features at sub-meter resolutions across entire watersheds so long as the water is clear and the aerial view is unobstructed. Such maps would transform river science and management by providing improved data, better models and explanation, and enhanced applications. Obstacles to achieving this vision include variations in optics associated with shadows, water clarity, variable substrates and target,sun angle geometry. Logistical obstacles are primarily due to the reliance of existing ground validation procedures on time-of-flight field measurements, which are impossible to accomplish at watershed extents, particularly in large and difficult to access river basins. Philosophical issues must also be addressed that relate to the expectations around accuracy assessment, the need for and utility of physically based models to evaluate remote sensing results and the ethics of revealing information about river resources at fine spatial resolutions. Despite these obstacles and issues, catchment extent remote river mapping is now feasible, as is demonstrated by a proof-of-concept example for the Nueces River, Texas, and examples of how different image types (radar, lidar, thermal) could be merged with optical imagery. The greatest obstacle to development and implementation of more remote sensing, catchment scale ,river observatories' is the absence of broadly based funding initiatives to support collaborative research by multiple investigators in different river settings. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Taxonomic status of salmonids in the Bulgarian stretch of the Danube River and their bionomic strategy

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2008
J. Hol
Summary Analysis of salmonid fish samples from the Bulgarian stretch of the Danube resulted in the conclusion that this river segment is inhabited by the Black Sea salmon Salmo labrax Pallas, 1814 and not by the huchen Hucho hucho (Linnaeus, 1758), as originally believed. Occurrence of huchen in this stretch of the Danube River is improbable. It has also been suggested that the anadromous Black Sea salmon population does not exist. It remains to be determined if the salmon occurring in the Danube River and along the coast of the Turkish, Bulgarian, Romanian and Ukrainian coasts of the Black Sea represent the black trout, i.e. the brook form of the Black Sea salmon washed down from the tributaries or the specific potamodromous river form. [source]

A geomorphological framework for river characterization and habitat assessment

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2001
J.R. Thomson
Abstract 1.,Methods to assess the physical habitat available to aquatic organisms provide important tools for many aspects of river management, including river health monitoring, determination of river restoration/rehabilitation strategies, setting and evaluating environmental flows and as surrogates for biodiversity assessment. 2.,Procedures used to assess physical habitat need to be ecologically and geomorphologically meaningful, as well as practicable. A conceptual methodological procedure is presented that evaluates and links instream habitat and geomorphology. 3.,The heterogeneity of habitat potential is determined within geomorphic units (such as pools, runs, riffles) by assessing flow hydraulics and substrate character. These two variables are integrated as hydraulic units , patches of uniform flow and substrate. 4.,This methodology forms a logical extension of the River Styles framework that characterizes river form and behaviour at four inter-related scales: catchments, landscape units, River Styles (reaches) and geomorphic units. As geomorphic units constitute the basis to assess aquatic habitat availability, and they form the building blocks of river and floodplain systems, intact reaches of a particular River Style should have similar assemblages of instream and floodplain habitat. 5.,An application of the hydraulic unit procedure is demonstrated in gorge, partly-confined and alluvial River Styles from the Manning catchment in northern New South Wales, Australia. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Historical and ecological correlates of body shape in the brook stickleback, Culaea inconstans

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009
JESSICA LYN WARD
Using geometric morphometric methods, we evaluated the correlation between phenotypic variation and available historical and habitat information for two genetically differentiated, allopatric lineages of a widespread North American species, the brook stickleback (Culaea inconstans). The results obtained revealed strong patterns of structured phenotypic differentiation across the species range with extreme phenotypes occurring at the northwest and southeast range boundaries. Shape variation was broadly congruent with the distribution of two mitochondrial DNA lineages; a deep-bodied eastern form (Atlantic refugium) and a slim-bodied western form (Mississippian refugium); however, the two forms were not lineage-specific and phenotypic cladistic diversification is likely to be an artefact of underlying clinal variation associated with longitudinal and latitudinal gradients. In addition, we found little evidence of diagnosable lake and river forms across North America. Taken together, large-scale patterns of phenotypic diversity observed in C. inconstans suggest that relatively recent factors, such as continually varying natural selection across the range and/or potential local gene flow, may substantially mitigate the effects of historical separation or a generalized adaptive response to alternative habitats. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 769,783. [source]