12 Sediment Management in River Basins: An Essential Element …
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represented by two groups of riverbed forms: micro- and mesoforms [83]. The former
constitutes a dynamic surface layer of mesoforms. Due to their small size (several
centimetres high and wide, several meters long), and their tendency to permanently
relocate and transform, they’re inherently difficult to research outside of the lab. The
said forms are commonly referred to as river bars, and their size usually corresponds
to channel width or exceeds it, whereas their surface height coincides with average
water levels—MWL [83]. They have a tendency to be stable and inert and may maintain their form over many seasons showing variable hydrological regime. They have
a tendency to occur as individual, large sandy-gravel swells or bars and are typically
accompanied by negative forms—pools.
The authors were ready to pursue the study objective by means of employing
methods based on their experience [17, 27, 40]. In the case of big rivers, e.g. the
Vistula, they involve performing measurements of sandbar dynamics at the selected
segments of the river, as well as measurements of river load accumulation growth in
delta zone of the Gda´ nsk Bay. The data were supported by depth maps of the selected
segments and analysis of aerial pictures collected between 1989 and 2015. The
method takes into a count within the monitoring of river bar dynamics and comparison
of depth changes on bathymetric maps allows for estimating bed sediment transport
capacity in cubic meters. In order to calculate the load weight, it was assumed that
1 m
3 of sandy sediments weighs approx. 1.8 tons. Investigation on river bars dynamics
was conducted in the years 1981–2014 over a 220 km-long fragment of the Vistula.
The detailed research occurred at a characteristic part of the riverbed (Fig. 12.5),
which is partially channel training and features a single dam. Movement of sandbars
was made on the basis of own field methods (Fig. 12.7), including geodetic surveys
carried out at the unregulated reach near the Warsaw (K˛ epa Polska section), as well
as at the sediment deficit fragment downstream the dam in Włocławek. The second,
25 km far from Włocławek, a section in Nieszawa village (km 700.00). Nieszawa
river section constitutes a maximum range of an erosive reach of channel. The third
study fragment runs through the Toru´ n, 60 km downstream of the dam. It represents
an initial, training section of the Vistula with a similar width and alternate diagonal
river bars. The last fragment is located near the Swiecie, it is 140 km downstream of
the dam. In this analysis, both cross—and longitudinal profiles of the channel proved
to be greatly helpful in preparing the depths maps of the riverbed. The study was
supplemented with sediment sampling and granulometric analysis composition of
the river bars.
Systematic research on river bars led to the development of a model of dynamics of
these forms and allowed for the estimation of river bedload transport. Field research
and the analysis of available aerial pictures allowed for the identification of the
following river bars in the Vistula: at the training section—lateral bars and midchannel bars. The elevation of their surface corresponds with the average annual water
stages. The linguoid bars, whose elevation coincides with average low water stage and
alternate-diagonal bars that in terms of elevation fall between the abovementioned
forms. Generally, each increase in water flows corresponds to a proportional increase
in the river bars dynamics and vice versa. The analysis of riverbed fragments featuring
different development levels shows that the front of river bars of the same kind moves
281
represented by two groups of riverbed forms: micro- and mesoforms [83]. The former
constitutes a dynamic surface layer of mesoforms. Due to their small size (several
centimetres high and wide, several meters long), and their tendency to permanently
relocate and transform, they’re inherently difficult to research outside of the lab. The
said forms are commonly referred to as river bars, and their size usually corresponds
to channel width or exceeds it, whereas their surface height coincides with average
water levels—MWL [83]. They have a tendency to be stable and inert and may maintain their form over many seasons showing variable hydrological regime. They have
a tendency to occur as individual, large sandy-gravel swells or bars and are typically
accompanied by negative forms—pools.
The authors were ready to pursue the study objective by means of employing
methods based on their experience [17, 27, 40]. In the case of big rivers, e.g. the
Vistula, they involve performing measurements of sandbar dynamics at the selected
segments of the river, as well as measurements of river load accumulation growth in
delta zone of the Gda´ nsk Bay. The data were supported by depth maps of the selected
segments and analysis of aerial pictures collected between 1989 and 2015. The
method takes into a count within the monitoring of river bar dynamics and comparison
of depth changes on bathymetric maps allows for estimating bed sediment transport
capacity in cubic meters. In order to calculate the load weight, it was assumed that
1 m
3 of sandy sediments weighs approx. 1.8 tons. Investigation on river bars dynamics
was conducted in the years 1981–2014 over a 220 km-long fragment of the Vistula.
The detailed research occurred at a characteristic part of the riverbed (Fig. 12.5),
which is partially channel training and features a single dam. Movement of sandbars
was made on the basis of own field methods (Fig. 12.7), including geodetic surveys
carried out at the unregulated reach near the Warsaw (K˛ epa Polska section), as well
as at the sediment deficit fragment downstream the dam in Włocławek. The second,
25 km far from Włocławek, a section in Nieszawa village (km 700.00). Nieszawa
river section constitutes a maximum range of an erosive reach of channel. The third
study fragment runs through the Toru´ n, 60 km downstream of the dam. It represents
an initial, training section of the Vistula with a similar width and alternate diagonal
river bars. The last fragment is located near the Swiecie, it is 140 km downstream of
the dam. In this analysis, both cross—and longitudinal profiles of the channel proved
to be greatly helpful in preparing the depths maps of the riverbed. The study was
supplemented with sediment sampling and granulometric analysis composition of
the river bars.
Systematic research on river bars led to the development of a model of dynamics of
these forms and allowed for the estimation of river bedload transport. Field research
and the analysis of available aerial pictures allowed for the identification of the
following river bars in the Vistula: at the training section—lateral bars and midchannel bars. The elevation of their surface corresponds with the average annual water
stages. The linguoid bars, whose elevation coincides with average low water stage and
alternate-diagonal bars that in terms of elevation fall between the abovementioned
forms. Generally, each increase in water flows corresponds to a proportional increase
in the river bars dynamics and vice versa. The analysis of riverbed fragments featuring
different development levels shows that the front of river bars of the same kind moves