Zmiany natężenia transportu materiału zawieszonego w dolnym odcinku Obry
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Date
2007
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Wydawnictwo Poznańskiego Towarzystwa Przyjaciół Nauk
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Abstract
Research concerning changes of intensity of
suspended load transport was done in the lower
course of the Obra river near Miêdzyrzecz (Western
Poland). Hydrological measurements were
realized within 1 km long and 70–150 m wide
section of the Obra river valley, which is situated
about 3 km north-west of Miêdzyrzecz. Detailed
analysis of relation between suspended
sediment concentration and discharge afforded
possibility for preliminary determining the way
of suspended sediment supply to the river bed
during high water stages. It was supposed that
exposures of glacial and fluvioglacial sediments
in high concave banks could be an important
factor influencing the amount of delivery of suspended
material. On the other hand, normal
hysteretic loops (oriented clockwise) were observed
in cross-sections 4 and 5. That fact would
suggest that transported material originates
form the Obra river bed or its nearest neighborhood.
Besides, the process of sediment accretion
was observed on the fragment of drowned
floodplain during high water stages. This investigation
allowed to illustrate the mechanism of
forming floodplain sediments both at present
and in the past. The problem of changes of amount
of suspended load in longer time periods
also was discussed. On the basis of measurement
data and hydrological data from Miêdzyrzecz
water-gauge, annual amount of suspended
load was calculated for years 1971–1991.
The main factor, which influenced the amount
of sediment transport, was frequency of high
water stages and hydraulic conditions of flow in
the river bed. Flood events also were very important
because of increased possibilities of suspended
sediment supply from floodplain and
steep bank slopes.
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Citation
Badania Fizjograficzne, Seria A, Tom 58, 2007, s. 107-132
ISBN
978-83-7063-538-1