With the onset of the warm period in the early Middle Ages, the Kuban' began to shift to the right (poleward). Accordingly, the "many islands" of the Taman' region disappeared and it became a peninsula. At this time the right branch of the river, the Protoka, developed considerably, and most of the discharge was into the Sea of Azov. During the third cold period (late Middle Ages) the river once again deviated to the left (equatorward), and then the main flow was through the Kiziltash and Bugas Lagoons to the Black Sea. Downstream from the Griven Protoka station the river changed course at this time, flowing to the west instead of north meridionally (a general equatorward shift). During the present warm period the Kuban' is shifting to the north. The studies of Kapitonov and Bramber (1958) verify that at the beginning of the last century the Kuban' emptied into the Black Sea. The influx of water to the Sea of Azov especially increased during the 1850's, however, and the old Kuban' channel leading to the Black Sea gradually became shallow.
The Don. In its lower reaches this river has a westerly course (Figure 11). Below Melikhovskaya stanitsa* the Don floodplain becomes much broader, forming a delta with a total width of up to 20 km, and the river divides into several branches and distributaries there. The largest of these are the Aksai, the Mertvyi Donets, the Kuter'ma, and the Kalancha. During the second cold period (antiquity), the Don tended to deviate to the left (equatorward). Consequently, the main flow was then along the southern branch, the Staryi Don [the Old Don]. It was on the bank of this well-watered distributary, not far from Elisavetskaya stanitsa, that the large Greco-Scythian trading city of Tanais prospered.
During the second warm period (early Middle Ages) the river deviated to the right (poleward), and most of the flow was along the northern branch (the Mertvyi Donets). A large port town, also named Tanais, is now being built on the bank of this branch, which is beginning to be well supplied with water once again. The new Tanais is not far from the present village of Nedvigovka. The old Tanais, which was located on the left bank, on the Staryi Don, has long since become a ruin.
"... the data for Nedvigovka begin just at the time when the data for the Elisavet settlement terminate... The reason for the move from the Elisavet settlement is quite clear: the previously navigable channel of the river on which the settlement was located, and on which the entire lite of this predominantly commercial town must have depended, became silted up... Beginning from the moment when traffic on the river (along which goods were transported) began to be hampered, it must have occurred to the inhabitants to move the main trading point to some place where condi tions were more favorable; the region of the present village of Nedvigovka must have been at that time just such a more suitable place" (Knipovich, 1934, p.195).
During the third cold period (late Middle Ages) the Don deviated to the left (equatorward). As noted by Samokhin (1958, p. 48), at the end of the twelfth century the Venetians founded their colony of Tana not on the Mertvyi Donets, which had already grown shallow by this time, but on the bank of the Staryi Don, which was better supplied with water. After being destroyed by Tamerlane, Tana was rebuilt on its previous site. Then, at the end of the fifteenth century, it was captured by the Turks, who gave it the name of Adzek or Assek (now Azov). Samokhin thinks that the town was shifted to a new site on account of a change in the states of the river channels.
During the third (present) warm period the river has tended to shift to the right (northward). The distributary on which Tana stood accordingly has become shallow, and at present the main flow is more to the north, via the middle branches of Kalancha and Kuter'ma. As a result, the central part of the Don delta is now advancing considerably. Belyayskii (1888) notes that all the southern branches of the river, including the Don (Staryi Don) branch, which was formerly the main branch, have become quite shallow.
The Dniester. In its lower reaches this river flows southeast and empties into the Dniester Estuary. The channel meanders over a broad floodplain, forming a great number of lakes. Through this line of lakes flows the deep Turunchuk River.
During the third cold period (late Middle Ages) the Dniester deviated to the right (southward), and as a result the supply of water to its left bank became insignificant. With the onset of the present warm period the river began to deviate to the left (northward), and the water supply to the left bank increased. In addition, bifurcation of the river took place: a left branch of the Dniester, the Turunchuk, was formed near the village of Chuburcha. The Turunchuk flows back into the Dniester again at Beloe Lake, which is 60 km from the bifurcation point along the Turunchuk and 130 km from it along the Dniester. Gradually the stream velocity of the Turunchuk began to increase, and its channel developed at the expense of the Dniester; sediment began to be deposited in the Dniester just down stream from the bifurcation point. At present the Turunchuk carries more than 70% of the discharge of the Dniester, which is beginning to show signs of senility. If the Turunchuk continues to develop in this way, then in time the "main" channel of the Dniester will become completely senile, as was the case with the Staryi Dniester [the Old Dniester] during the seventies of the last century. As noted by Kortatstsi (1923) the progressive reduction of the rate of flow of the Dniester and the deposition of sediment in it are resulting in a continually increased development of the Turunchuk at the expense of the Dniester.