Abstract
In the Danube Delta, on the Sulina branch, the morphology, sediment, and bedform characteristics were investigated. Three-dimensional (3D) bathymetry, flow velocity, suspended-load concentration, and liquid and solid discharge data were acquired throughout several cross sections along the Sulina channel, in order to investigate the distribution of water and sediment discharges and their influence against the river bed. A single observation (in February 2007) was made regarding the geometry, sediment composition, and hydraulic conditions under which the dunes grew and degenerated. The investigation focuses here mostly on the geometrical parameters of these bedforms, such as height, length, as well as grain size characteristic of the sediment and water dynamics. Based on in-site measurements, different hydraulic parameters were calculated, such as bed shear stresses and Reynolds number. During the field campaign, the measured water mean velocity was from v = 0.22–1.13 m∙s−1. At the same time, the measured range of shear stresses within the dune field formation was from τ0 = 2.86 N·m−2 (on the cutoffs) to 8.62 N·m−2 (on the main channel). It was found that the correlation between height (H) and length (L) of the Sulina branch dunes describes the formula: H = 0.093L0.5268. The bedforms of the Sulina channel are, in general, developed in fine sand (D50 between 0.06 and 0.35 mm).
Highlights
Bedforms are the result of the interaction of the flow, sediment transport, and bed morphology [1,2,3,4].Multibeam measurements offer a very detailed description of the fluvial channel and a detailed characterization of the morphologic processes and dynamic interpretation can be performed
Multibeam sonar bathymetry data were collected along the Sulina channel during the field campaign on NIRD GeoEcoMar’s RV ISTROS, equipped with an ELAC Nautik SeaBeam 1050D
Bedforms are sediment storage bodies thatthat occur in theinchannel and are scaled
Summary
Bedforms are the result of the interaction of the flow, sediment transport, and bed morphology [1,2,3,4].Multibeam measurements offer a very detailed description of the fluvial channel and a detailed characterization of the morphologic processes and dynamic interpretation can be performed. Bedforms are the result of the interaction of the flow, sediment transport, and bed morphology [1,2,3,4]. Multibeam sonar bathymetry mapping methods and advances in sediment dynamics instrumentation [5,6,7,8,9,10,11,12], have enabled higher resolution studies of the morphology of sand ridges, and the quantification of the migration of bedforms and the hydrodynamic and sediment transport processes that cause this migration [11]. The fluvial environment was investigated by many authors in order to describe the bed morphology and bedforms migration [5,8,9,10,13]. Bedform geometry is shown to be influenced by transport stage [20,21,22], by sediment concentration in flow [23], and is dependent on how sediment is transported by flow [5,24]
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