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 = 0.093L^0.5268. The bedforms of the Sulina channel are, in general, developed in fine sand (D₅₀ between 0.06 and 0.35 mm).

We present geochemical analyses (major, such as CaCO₃, TOC, Fe₂O₃, and minors such as MnO and TiO₂) and trace elements, as well as some trace elements with genetic significance (Rb, Sr, Zr) or toxic and potentially affected by anthropic influences (Cu, pb, Zn, Cd, Cr, V, Ni, Co) of the superficial bed sediments of the St. George distributary which is the most sinuous and morphologically dynamic branch of the Danube River. Bed sediment samples were collected onboard of R.V. Istros, in June 2017. The dataset is useful to evaluate the distribution of the sediment along the fluvial channel, the present ecological state of the environment and, the effects of artificial intervention on the fluvial channel (the cutoff of the natural channels by navigational canals between 1984 and 1988). The data are presented as tabular format.

Hydrological and sedimentological data were collected on several cross-sections of both natural and artificial canals of three cutoff meanders (Mahmudia, Dunavăţul de Sus, and Dunavăţul de Jos meanders) of the Sfântu Gheorghe branch at the beginning of June 2017. The hydrological data shows a heterogeneous distribution of water discharges: on the meanders of Mahmudia and Dunavăţul de Jos, most of the liquid flow passes through artificial channels. In the case of the Dunavăţul de Sus meander, the cut meander is the main transport channel for the liquid flow. The statistical analysis of chemical data evidenced an excellent quality of the bottom sediments, with few parameters exceeding the limits (for Ni, Cu, and Cr). These results correlated with the hydrological measurements made on each investigated cross-section.

The study presents a detailed analyse of the morpho-dynamic processes of the main two bifurcations of the Danube River within its delta, at Ceatal Izmail and Ceatal St. George. The first bifurcation of the Danube, called Ceatal Izmail; here the river divides into two distributaries: a northern one, the Chilia (Kilia), and a southern one, the Tulcea. Forking to the right at Ceatal Izmail (Mile 43), the Tulcea distributary stretches further to 17 km to the second main hydrographic knot Ceatal Sfantu Gheorghe (St. George) at Mile 33.84 (km 62.2). Here, the Tulcea branch divides into two main distributaries: Sulina on the left and Sfantu Gheorghe (St. George) on the right. More than a century ago, these two bifurcations were submitted to hydro-technical works producing morphological changes of the fluvial bed, as well as redistribution of water and sediment flows between the three main distributaries. The history, morphology and hydrodynamics were studied in detail. On each bifurcation, hydrological, sedimentological and morphological measurements were performed on nine crosssections distributed upstream and downstream of the bifurcation in August 2021. The bifurcation angles, the slope, the flow separation zones and the velocities were investigated to understand the distribution of the water flow and bed morphology of both bifurcations.