Suspended sediment budget and stability of the River Don Delta in the period from 1944 to 2020

Abstract The River Don Delta (RDB) and the adjacent estuary and land areas have significant ecological and economic value. RDB is the most eastern in the Mediterranean – Black Sea (MBS) basin delta, and it has similar problems with many other MBS deltas. So, the delta became sediment-starved due to the construction of dams upstream. Additionally, the geomorphological stability of RDB is threatened by regional climate changes over the sea and land, which became especially apparent starting from 1980th. In this study, we reconstructed suspended sediment budgets in different parts of the delta and the adjacent estuary and land areas in the period from 1944 to 2020 and analyzed the changes in the delta channel’s width and at the sea border starting from 1980th. We used the modelling framework, consisting of the modified hydrodynamic model HEC RAS and the large-scale sediment budget model, as well as satellite image analysis. We estimated suspended sediment balance in the front-delta, the delta channels, and the delta platform and at the adjacent land area for the three periods 1944–1973, 1974–1981, and 1982–2020, which are related to the construction of large dams in the River Don Basin. The sediment accumulation rates were similar to those of other MBS deltas. Suspended sediment budget dropped three times for the entire case study area from 1944–1973 to 1982–2020. At the same time, the percentage of accumulated sedimentation to the fluvial sediment delivery increased almost five times from the first to the third period. This proves that sea factors, seiches and storm surges, play a stabilizing role for the River Don Delta by increase in suspended sediment budget during the hydrological interaction of sea and river waters. Observed total annual channel width within the delta changes in line with sedimentation accumulation patterns in the delta channels for the period of environmental changes that started in 1980th. The delta’s sea border stabilizes in the period 1982–2020 due to the influence of the sea factors, seiches, and increased storm surges upon sedimentation patterns. Our findings allow us to conclude that engineering regulation of sedimentation is not necessary now in the River Don Delta.