Search results for "rivers"
showing 10 items of 222 documents
Fluvial eco-hydraulics and morphodynamics: New insights and challenges
2015
The paper concerns the mechanisms underlying the distribution of the bed shear stress in meandering bends. Literature indicates that cross-stream circulation strongly affects the redistribution of the downstream velocity, but the feedback between them is still poorly understood. The aim of this paper is to gain some insight into how the momentum transport by cross-stream circulation contributes to the bed shear stress redistribution. Experimental analysis, based on a detailed dataset collected in a large-amplitude meandering laboratory flume, is presented. From these data an evaluation is made of the terms in the depth-averaged momentum equations and the analysis is especially devoted to te…
Cross sectional flow in a meandering laboratory channel with vegetated bed
2016
As it is known, the outer-bank of a meander wave is considerably vulnerable to the erosion processes. Literature indicates that cross-stream circulation strongly affects the redistribution of the downstream velocity and boundary shear stress in curved channels. In steep outside bends, beside a central-region circulation cell, a counter-rotating circulation cell often forms in the upper part of the outer-bank region. Accurate understanding of the role of these circulation cells on velocity redistribution in bends is important to define protective measures of the outer-bank. Literature also shows that vegetation could modify flow velocity and turbulent structure. This work reports preliminary…
A New Method to Reconstruct Quantitative Food Webs and Nutrient Flows from Isotope Tracer Addition Experiments
2020
Understanding how nutrients flow through food webs is central in ecosystem ecology. Tracer addition experiments are powerful tools to reconstruct nutrient flows by adding an isotopically enriched element into an ecosystem and tracking its fate through time. Historically, the design and analysis of tracer studies have varied widely, ranging from descriptive studies to modeling approaches of varying complexity. Increasingly, isotope tracer data are being used to compare ecosystems and analyze experimental manipulations. Currently, a formal statistical framework for analyzing such experiments is lacking, making it impossible to calculate the estimation errors associated with the model fit, the…
Effect of Vegetation on Fluvial Erosion Processes: Experimental Analysis in a Laboratory Flume
2013
Abstract The plane evolution of a meander wave is determined by the erosion processes at the banks. Particularly, the outer- bank is considerably vulnerable to the erosion processes. Indirect techniques, which act upon the reduction of the effect of the cross-circulation motion, have been recently proposed to limit the outer-bank erosion. This paper shows preliminary results on the role played by vegetation on cross-circulation motion. The analysis is conducted on the basis of experimental data collected in a large amplitude meandering channel constructed at the hydraulic laboratory of DICAM. Maps describing the cross-stream flow, both over the no-vegetated bed and over the vegetated bed, a…
Flood pattern changes in the rivers of the Baltic countries
2015
Estimation of both the frequency and variation of spring floods is a key issue for the assessment and management of flood risks. Changes in river floods in Estonia, Latvia and Lithuania have been investigated in few national studies. However, there are no studies of the changes of flood patterns by using a common methodology for the rivers of this region. In this study flood pattern changes in the rivers of the Baltic countries were estimated applying trend and frequency analysis for the periods of 1922–2010, 1922–1960, 1961–2010 and 1991–2010, i.e. for the whole spring flood data sets, periods before and after 1960 (this year was considered as the beginning of the remarkable climate change…
Characterization and source identification of polycyclic aromatic hydrocarbons (PAHs) in river bank soils.
2008
Elevated PAH concentrations were detected in bank soils along the Mosel and Saar Rivers in Germany. Information on the identification of PAH sources in this area however remains unclear. This study was able to characterize the PAH sources by application of several approaches, including consideration of the distribution patterns of 45 PAHs (including 16 EPA PAHs and some alkyl PAHs), specific PAH ratios, distribution patterns of n-alkanes and principal component analysis (PCA). In addition, the efficiency of the tested approaches was assessed. The results from the application of the various source identification methods showed that pyrogenic PAHs dominate soil samples collected upstream of t…
Bundle generation for last-mile delivery with occasional drivers
2022
In this paper, we present the vehicle routing problem (VRP) with occasional drivers (OD) and order bundles (OB). The problem VRP-OD-OB is an extension of the VRP-OD, where instead of assigning one customer per driver, drivers are assigned bundles of customers. To deal with the bundle-to-driver assignment, a bidding system is exploited, in which a company offers a set of bundles and the drivers raise their bids. These bids depend on features such as the drivers’ destination, flexibility in deviating from the shortest path, and willingness to offer service. To generate valuable bundles of customers, we propose two strategies: (i) an innovative approach based on the creation of corridors, and …
Research data sharing in Spain: Exploring determinants, practices, and perceptions
2020
This work provides an overview of a Spanish survey on research data, which was carried out within the framework of the project Datasea at the beginning of 2015. It is covered by the objectives of sustainable development (goal 9) to support the research. The purpose of the study was to identify the habits and current experiences of Spanish researchers in the health sciences in relation to the management and sharing of raw research data. Method: An electronic questionnaire composed of 40 questions divided into three blocks was designed. The three Section s contained questions on the following aspects: (A) personal information
Short-term occupations at high elevation during the Middle Paleolithic at Kalavan 2 (Republic of Armenia).
2021
The Armenian highlands encompasses rugged and environmentally diverse landscapes and is characterized by a mosaic of distinct ecological niches and large temperature gradients. Strong seasonal fluctuations in resource availability along topographic gradients likely prompted Pleistocene hominin groups to adapt by adjusting their mobility strategies. However, the role that elevated landscapes played in hunter-gatherer settlement systems during the Late Pleistocene (Middle Palaeolithic [MP]) remains poorly understood. At 1640 m above sea level, the MP site of Kalavan 2 (Armenia) is ideally positioned for testing hypotheses involving elevation-dependent seasonal mobility and subsistence strateg…