Bedform Morphology in the Area of the Confluence of the Negro and Solimões-Amazon Rivers, Brazil

Abstract

Confluences are common components of all riverine systems, characterized by converging flow streamlines and the mixing of separate flows. The fluid dynamics of confluences possesses a highly complex structure with several common types of flow features observed. A field study was recently conducted in the area of the confluence of the Negro and Solimões/Amazon Rivers, Brazil, collecting a series of Acoustic Doppler Current Profiler (ADCP) transects in different flow conditions. These data were used to investigate the morphology of the bedforms observed in that area. First, the bedforms were mostly classified as large and very large dunes according to Ashley et al. (1990), with an observed maximum wavelength and wave height of 350 and 12 m, respectively. Second, a comparison between low flow and relatively high flow conditions showed that wavelength and wave height increased as the river discharge increased in agreement with previous literature studies. Third, the lee side angle was consistently below 10°, with an average value of about 3.0°, without flow separation confirming past findings on low-angle dunes. Finally, a comparison between the bedform sizes and past literature studies on large rivers suggested that while several dunes were in equilibrium with the flow, several largest bedforms were found to be probably adapting to discharge changes in the river.

Analyzing Sedimentary Rocks to Evaluate Paleo Dimensions and Flow Dynamics of Permian Barakar River of Rajmahal Gondwana Sub-Basin of Eastern India

“…On the other hand, ref. [23] who used the data from the Rio Parana (Argentina) and those from the Lower Rhine (The Netherland) and Negro (Brazil) obtained relationship between bed form height and length which affords another assessment of the bed form length.…”

Bulk Drag Predictions of Riparian Arundo donax Stands through UAV-Acquired Multispectral Images

“…The presence of aquatic vegetation inside vegetated open channels has a strong impact on flood hazards in urban areas [1][2][3]. The identification of the riparian vegetation traits affecting flow resistance is one of the most relevant topics of both modeling and experimental analyses in ecohydraulics [4,5]. Riparian plants behave differently depending on their bio-mechanical and morphometric traits, and on their submergence.…”

Turbulence and Flow–Sediment Interactions in Open-Channel Flows

“…The investigation of the interactions between flow and sediments in natural bed streams is one of the most fascinating research topic in the field of fluvial hydraulics, especially if the issues to be addressed are focused on the role of turbulence and its main characteristics in the sediment erosion, deposition and transport processes [1][2][3][4][5], as well as in the presence of vegetation [6]. Similarly, a comprehensive understanding of the flow dynamics in the near-bed flow zone is crucial for many different practical applications, such as bridge pier scour, pipeline scour, scour at bed sills, and other situations in which anthropization affects the behavior of water flow, turbulence, and sediment transport [7][8][9][10].…”

“…The Special Issue comprises ten original papers on turbulence and flow-sediment interactions in open-channel flows, which can be divided into two main categories: experimental [1][2][3][4][6][7][8]10] and field [5,9] studies. At the same time, among the experimental studies, it is possible to make another distinction on the basis of the instrumentation adopted.…”

“…Indeed, two different sophisticated technologies were used to capture the instantaneous velocity field: the first one is based upon the Doppler shift effect (Acoustic Doppler Velocimeter, ADV) [2,[6][7][8] and the second is an optical method of flow visualization (Particle Image Velocimetry, PIV) [1,3,4,10]. As regards the field studies [5,9], the Acoustic Doppler Current Profiler (ADCP) was employed, which is based on the Doppler effect as well as the ADV. From the viewpoint of turbulence analyses, all the contributions present in-depth and detailed statistical investigations.…”