Role of river transport and coastal abrasion in forming modern coastal and marine sediments in the Northwestern Black Sea

he Danube, the Dniester, the Southern Buh and the Dnipro rivers discharge into the north-western part of the Black Sea. Their total catchment area is 1,458 million km2. The length of the coastline with active abrasion processes in this segment is about 60 km. This is 26% of the total length of the coastline (from the estuary of the Danube, Odesa Oblast, to the city of Ochakiv, Mykolaiv Oblast). The article analyses the methodological basis for the calculation of solid river runoff and material entering the sea as a result of coastal destruction, summarizes their main characteristics and proposes an algorithm for quantitative calculations. For river runoff, it is based on the dependence of the amount suspended matter on the volume of water discharged per unit time. For quantitative calculations of coastal abrasion, data on the dynamics of changes in the configuration of the coast have been used with the help of GIS systems. It has been shown that one of the main factors influencing the removal of solid material from the land is the flow velocity, which also influences the volume of water per unit time. This leads to an increase in the mobility of terrigenouscomponents. An important factor is the mineral and physical condition of the rocks eroded along the river’s path. Man-made structures (hydroelectric plants, dams) significantly reduce the mobility of water and consequently the amount of material transported. They have the greatest effect on the transport of bottom constituents. One of the main factors influencing the intensity of abrasion is wave activity with wave heights exceeding 0.5 m. The average annual number of such waves is 165 days. The current total annual mass of sediment discharge from the Dniester (to the Dniester estuary) is 2,280 thousand tons, from the Southern Buh – 192 thousand tons (to the Dni- ester-Buh estuary) and from the Dnipro – 800 thousand tons (to the Dniester-Buh estuary). Most of this material is deposited in the estuaries and about 10% is discharged directly to the sea, which is (in thousand tons): suspended –11,981, bottom – 488. The Danube sediment discharge to the Black Sea is estimated at 12,143 thousand tons. The calculated total annual mass of material entering the sea through coastal abrasion in various parts of the coast is (in thousand tons): Lebedivka-Kurortne – 501.8; Karolino-Buhaz-Chornomorsk – 184.5; Kryzhanivka-Rybakivka – 201.6; Rybakivka-Ochakiv – 7.2, making a total of 895.1. About 158.8 thousand tons are involved in the formation of the particle size distribution of beach sediments.