ASSESSMENT OF ACTUAL HYDRODYNAMICAL AND SEDIMENTOLOGICAL CONDITIONS OF THE SULINA CHANNEL, DANUBE DELTA.

This article presents the results of studies of the hydrodynamical and sedimentological conditions of the Sulina Channel, the middle distributary of the Danube within its delta. One field campaign (at low waters) in September 2019 was conducted to analyse the geometry, the sediment composition and hydraulic conditions of the channel. During the field campaign, the measured water mean velocity was from v = 0.01–0.54 m.s-1 for a water discharge (measured upstream, at the bifurcation, knot Ceatal St. George) of 698 m3 .s-1 . Based on in-site measurements, different hydraulic parameters were calculated, such as stream power and bed shear stresses. The specific stream power has been situated below 1 W.m-2 (between 0.002 and 0.34 W.m-2 ) for all the investigated crosssections. The mean shear stress (τ0) has been situated between 0.284 and 1.518 N.m-2 . Sediment samples have been acquired throughout several cross-sections, in order to investigate the bed sediment characteristics. Grain size parameters (such as Median, Standard deviation, Skewness) showed the predominance of fine fraction (medium and fine sand, and silt), moderately and poorly sorted (the mean, D50 = 0.24 mm). The mean grain size showed a very slight linear decrease from upstream to downstream who could indicate the refinement of the bottom sediments. On the Sulina Channel, this trend is influenced by the presence of the groynes, which plays an important role on the downstream grain size distribution. The characterization of the grain size was fulfilled by the use of the Hjulström diagram [1], to represent the boundaries among erosion, transportation, and deposition. We asses that the upstream sector represent the most morpho-hydro-sedimentary dynamic sector of the Sulina channel. [ABSTRACT FROM AUTHOR]