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Differences in the reconstructions of the depositional environment of overbank sediments performed using the C/M diagram and cumulative curve analyses

Liro M.

Landform Analysis

2015

Vol. 29

35--40

In order to compare the results of the reconstructions of depositional environment of sediments performed using the C/M diagram (Passega, Byramjee 1969) and the cumulative curve analysis (Visher 1969), 49 samples of overbank sediment were collected in the valley of the Dunajec River. The samples were collected from the fill of an abandoned channel on the floodplain of the lower Dunajec (17 km from its mouth) and from the floodplain of the Dunajec in the backwater of the Czorsztyn Reservoir and analysed used the laser diffraction and sieve methods. A cumulative curve analysis of the samples located in the fields of dominant deposition from traction in the C/M diagram (Fields I, II, III, IX) showed that the dominant type of their transport prior to deposition was saltation and suspension (81%), while traction amounted to an average of 19%. In the fields of the C/M diagram corresponding to the deposition of graded suspension under the conditions of high (Field IV) and moderate turbulence (Field V), the dominant type of sediment transport before deposition was saltation, whose amounted to 78–86% (Field IV) and 50–76 % (Field V). In the fields of the C/M diagram indicating deposition from graded suspension transported in conditions of low turbulence (VI) and uniform suspension of varied grain size (VII), the dominant type of transport prior to deposition was suspension, amounting to 35–94%. Sediments located in the field of the C/M diagram corresponding to the finest uniform suspension and pelagic suspension (Field VIII) were in 91–95% transported in suspension prior to deposition.

Wpływ regulacji koryta na warunki sedymentacji osadów na równinie zalewowej dolnego Dunajca

Liro M.

Przegląd Geologiczny

2012

Vol. 60, nr 7

380--386

In the last century the Dunajec channel in its lower river course was considerably transformed due to channelization works. The former multi-thread river channel was replaced by a single one, resulting in abandonment of side channels. Groynes were constructed on both main and side channel. Quick filling up of the inter-groyne basins reduced channel width and capacity. In the study area, a side channel with groynes was abandoned and filled up. The aim of this study was to reconstruct the rate and depositional conditions of the sediments infilling the abandoned channel. These sediments are 215-222 cm thick and were deposited at an average rate of 5-5.2 cm/year. Their sedimentary environment was inferred based on a C/M diagram. The depositional conditions in the abandoned channel were determined by two major factors: distance to the active channel and difference in elevation between depositional surface and active channel. Close to the active channel, 61% of sediment was deposited from suspension and 39% by traction current. At a distance of 200 m to the active channel, 100% of sediment was deposited from suspension, with 25% falling from pelagic suspension. At an early stage of infilling of abandoned channel, the depositional flows are more energetic and the deposition rate is higher than in the later stage. The investigated sediments are an example of accumulation induced by channelization works. The spatial distribution of these fine-grained, quickly deposited sediments is determined by the course of the abandoned channel.