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D. C. Diaconu
13.2.1 Modifications of the Water Course
The Danube channel, or the navigable Danube, is today the entire river sector ranging
from km 237 to km 175. During the last century, this main channel undoubtedly
suffered the greatest changes in both morphology and the toponymy used for the
different sections which make it up. The name under which this channel was known
in the past, or at least its southern half, was the Cremenea channel. In 1910, the name
of the Cremenea channel referred to the entire section between the bifurcation of the
downstream river Giurgeni (km 237) and the confluence in the Gropeni area with the
Valciu channel (km 196). But map 28 made by the Romanian Hydrographic Service
in 1934 limits the extension to downstream of this channel to its confluence with
the secondary channel Pasca (km 210), now known as the Orbu channel. Today this
toponym refers exclusively to the secondary channel bounded between km 226 and
km 216.
Another particularly important hydromorphological process took place between
1934 and 1963, and that is the increase in the liquid and obvious flow rate of the
former Pasca channel which, on the section between km 226 and km 216, became
navigable and is currently associated with the hydronim Danube waterway. The
geomorphological phenomena are also of great importance, taking place along this
channel and having important consequences on river navigation. From those, special
attention should be given to the accumulation of sediment produced in the Danube
bed in the critical area of Gropeni (Km 196), at the confluence of the Danube and
Valciu branches and further downstream in the Tichilesti area (km 190–191). Due to
these phenomena, in the last decades, at least during periods of low water levels of the
river, it was necessary to direct the river navigation on the secondary channel Caleia
(Calia). The predominantly cumulative sedimentary regime on the Cravia branch led
to the appearance of the small island, Chiciul Cucului, alongside the channel, before
1963 (and especially after 1934). Sequentially it led to the disappearance of the little
Brancusi’s secondary channel after 1963, which led to the affixation of the island to
Mount Fundu Mare, as well as to the small island of Popa Vasile on the right bank
of the river.
The Valciu channel represents the second main branch of the studied hydrographic
network. Removed from the Macin channel just 1.5–2 km downstream of the Vadu
Oii bifurcation, this channel is transported over a length of approximately 40 km
to its confluence with the channel called the navigable Danube located in the area
of Gropeni (km 196) approx. 21% of the total flow of the river. The width of the
Válciu river bed varies between 160 and 440 m, and the bank shares have values
between 5 and 6 m determined in the Black Sea—Sulina (MN-S) altimetric system.
An exception is the upstream section of its right bank, where the intense alluvial
activity of the channel has led to the formation of several tall beams which have
allowed the settlement of the population and the development of several localities:
Marasu, Bandoiu, and Tacau, whose existence is still registered from the beginning
of the last century. Also on the left bank of the Valciu branch are the tributaries Plange
Bani and Noua Nebuni, which represent the natural channels of communication and
D. C. Diaconu
13.2.1 Modifications of the Water Course
The Danube channel, or the navigable Danube, is today the entire river sector ranging
from km 237 to km 175. During the last century, this main channel undoubtedly
suffered the greatest changes in both morphology and the toponymy used for the
different sections which make it up. The name under which this channel was known
in the past, or at least its southern half, was the Cremenea channel. In 1910, the name
of the Cremenea channel referred to the entire section between the bifurcation of the
downstream river Giurgeni (km 237) and the confluence in the Gropeni area with the
Valciu channel (km 196). But map 28 made by the Romanian Hydrographic Service
in 1934 limits the extension to downstream of this channel to its confluence with
the secondary channel Pasca (km 210), now known as the Orbu channel. Today this
toponym refers exclusively to the secondary channel bounded between km 226 and
km 216.
Another particularly important hydromorphological process took place between
1934 and 1963, and that is the increase in the liquid and obvious flow rate of the
former Pasca channel which, on the section between km 226 and km 216, became
navigable and is currently associated with the hydronim Danube waterway. The
geomorphological phenomena are also of great importance, taking place along this
channel and having important consequences on river navigation. From those, special
attention should be given to the accumulation of sediment produced in the Danube
bed in the critical area of Gropeni (Km 196), at the confluence of the Danube and
Valciu branches and further downstream in the Tichilesti area (km 190–191). Due to
these phenomena, in the last decades, at least during periods of low water levels of the
river, it was necessary to direct the river navigation on the secondary channel Caleia
(Calia). The predominantly cumulative sedimentary regime on the Cravia branch led
to the appearance of the small island, Chiciul Cucului, alongside the channel, before
1963 (and especially after 1934). Sequentially it led to the disappearance of the little
Brancusi’s secondary channel after 1963, which led to the affixation of the island to
Mount Fundu Mare, as well as to the small island of Popa Vasile on the right bank
of the river.
The Valciu channel represents the second main branch of the studied hydrographic
network. Removed from the Macin channel just 1.5–2 km downstream of the Vadu
Oii bifurcation, this channel is transported over a length of approximately 40 km
to its confluence with the channel called the navigable Danube located in the area
of Gropeni (km 196) approx. 21% of the total flow of the river. The width of the
Válciu river bed varies between 160 and 440 m, and the bank shares have values
between 5 and 6 m determined in the Black Sea—Sulina (MN-S) altimetric system.
An exception is the upstream section of its right bank, where the intense alluvial
activity of the channel has led to the formation of several tall beams which have
allowed the settlement of the population and the development of several localities:
Marasu, Bandoiu, and Tacau, whose existence is still registered from the beginning
of the last century. Also on the left bank of the Valciu branch are the tributaries Plange
Bani and Noua Nebuni, which represent the natural channels of communication and