نتایج جستجو برای: bed sediments

تعداد نتایج: 77010  

Journal: :Journal of Marine Science and Engineering 2022

The Krone–Partheniades (K-P) framework has been used for decades to quantify and analyze the sediment exchange at a water–bed interface. Measuring erosion deposition parameters that are part of this requires time-consuming field observations. Additionally, measured independently parameters, while in reality they coupled. In numerical models applying K-P these often assumed be constant time mutu...

Journal: :Journal of Hydrology and Hydromechanics 2022

Abstract This study presents the results of 32 laboratory experiments on local scour at a single pile and 1 × 4 group for both uniform non-uniform sediments under clear water conditions. The present aims to evaluate effects different sediment beds made up mixtures sand gravel (four-bed configurations) in d 50 (1–3.5 mm) gradation (1.4–3) ranges depth flow discharges depths. Further, findings ar...

2013
A. C. Fowler M. Spagnolo C. D. Clark C. R. Stokes

We provide a mechanistic explanation for observed metrics for drumlins, which represent their sizes and shapes. Our explanation is based on a concept of drumlin growth occurring through a process of instability, whereby small amplitude wave forms first grow as ice slides over a bed of deformable sediments, following by a coarsening process, in which the wavelength as well as the relief of the d...

2016
F Richard Hauer Harvey Locke Victoria J Dreitz Mark Hebblewhite Winsor H Lowe Clint C Muhlfeld Cara R Nelson Michael F Proctor Stewart B Rood

Gravel-bed river floodplains in mountain landscapes disproportionately concentrate diverse habitats, nutrient cycling, productivity of biota, and species interactions. Although stream ecologists know that river channel and floodplain habitats used by aquatic organisms are maintained by hydrologic regimes that mobilize gravel-bed sediments, terrestrial ecologists have largely been unaware of the...

2017
Romain Marti Sébastien Ribun Jean-Baptiste Aubin Céline Colinon Stéphanie Petit Laurence Marjolet Michèle Gourmelon Laurent Schmitt Pascal Breil Marylise Cottet Benoit Cournoyer

Rivers are often challenged by fecal contaminations. The barrier effect of sediments against fecal bacteria was investigated through the use of a microbial source tracking (MST) toolbox, and by Next Generation Sequencing (NGS) of V5-V6 16S rRNA gene (rrs) sequences. Non-metric multi-dimensional scaling analysis of V5-V6 16S rRNA gene sequences differentiated bacteriomes according to their compa...

M.R Majdzadeh Tabatabai S.H Ghoreishi

Sediment flushing of reservoirs is an operational technique, whereby previously accumulated sediments in the reservoirs are hydraulically removed by accelerated flow when the bottom desiltingoutlets of the dam are opened. In this research, the process of sediment flushing is simulated by a three dimensional numerical model in which sediment and flow interaction are reflected in the reservoirs. ...

2012
Jana Nabelkova Dana Kominkova

Trace metals (TMs) are still a serious problem in urban streams because of their toxicity and continuing significant levels in the aquatic environment, especially in bed sediments. Concentrations of Cd, Cr, Cu, Ni, Pb and Zn were monitored in the sediments of several small streams in the Prague area. These streams differ in the main source of pollution (combined sewer overflow CSO, storm water ...

2003
D.C.W. Sanderson P. Bishop M. T. Stark J. Q. Spencer

This paper presents a case study in the analysis of anthropogenically reset sedimentary materials, through work undertaken to identify and date sediments in an ancient canal in the Mekong Delta, Cambodia. The emergence of rice cultivating communities, utilising canals for both hydraulic management and transport, represents an important stage in the social evolution of southeast Asia. The emerge...

Journal: :Global change biology 2015
Elisa Capuzzo David Stephens Tiago Silva Jon Barry Rodney M Forster

Light in the marine environment is a key environmental variable coupling physics to marine biogeochemistry and ecology. Weak light penetration reduces light available for photosynthesis, changing energy fluxes through the marine food web. Based on published and unpublished data, this study shows that the central and southern North Sea has become significantly less clear over the second half of ...

2001
C. K. JAIN

A laboratory study was performed to study the effects of various operating factors, viz. initial metal ion concentration, solution pH, amount of sediment, contact time, particle size and temperature on the adsorption of zinc ions onto the bed sediments of the River Ganga (India). The equilibrium time was found to be of the order of 60 min. The adsorption curves are smooth and continuous leading...

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