Granulometric Composition of Abrasion-Accumulative Jumpers of Volgograd Reservoir Bays as an Indicator of Sediment-Forming Currents’ Speeds

Abstract

Separation of bays from the main water area of Volgograd Reservoir by abrasion-accumulative jumpers is one of the regional problems now. This process arises due to alongshore sediment transport. Granulometric composition describes the movement of sediments of abrasion-accumulative jumpers under the influence of alongshore currents. We determined granulometric parameters of jumpers, and we made evaluative calculation of sediment-forming currents’ speeds based on materials of 2019–2020. We studied 82 samples from 24 right-coast and left-coast bays. Field (sediment sampling, visual characteristic of the coast’s lithological composition) and analytical (granulometric analysis, graphic and mathematical methods) research methods were applied. We have established that size of sediments participating in the construction of abrasion-accumulative jumpers is from 100–50 mm (coarse pebble) to 0.05 mm or less (small dusty particles). All studied particles turned out to be rounded or well rounded. This gives grounds to classify them as sediments. There are differences in the granulometric composition of jumpers’ sediments on the right and left coasts of the Reservoir. Coarse pebble (100–50 mm) and medium pebble (50–20 mm) or medium sand (0.5–0.2 mm) and fine sand (0.2–0.1 mm) dominates in sediments’ composition of right-coast bays jumpers. Medium sand (0.5–0.2 mm) prevails in sediments’ composition of left-coast bays jumpers. Here was registered size of sediment particles less than 0.05 mm. The currents’ speeds forming abrasion-accumulative jumpers are from 0.47 to 3.45 m/s in the right coast and from 0.47 to 1.63 m/s in the left coast. Sediment samples of estuarine jumpers have different degree of sorting (1.13–14.40). This attests about differences in currents’ speeds forming these landforms in different time periods. The granulometric composition of sediments is an indirect sign of the dynamics of already formed jumpers. It is an indicator of sediment-forming currents’ speeds. Sedimentation of sediments in the Volgograd Reservoir occurs at a close distance from the source of their income.