DSC07937 (2)

T. Sokołowski

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0.64 m in 1937—1976 upstream the Dunajec mouth had been stated du-ring the secondary levelling survey of the inter-embankment area (Dembowski 1981). Thus, the raean ratę is 0.8—1.6 cm/yr. This smali deepe-ning can be explained by a fairly smali channel shortening during the channelization.

According to Kociszewska-Musiał studies (1969) and those of the aut hor, the sand fraction is the dominant one among the coarse materiał transported in the channel at present. Mean grain diameter varies from —0,3 to 2.3 0 (1.2—0.2 mm) and sorting is poor and very poor (Fig. 6).

The petrographic composition of alluvia is morę interesting because the human impact is very pronounced here. The latter is evidenced by the presence of coal pieces in the coarse grain deposits and by the in-creased content of heavy metals in the fine grain deposits.

In the first case, the coal concentrations are at riffles only, or morę precisely in shadows behind the plant thickets. Depending on the grain size composition the coal content can constitute up to 80% (Fig. 7 — Strojców B, Maniów B). Amount of coal in the sediment deposited in the river current is smali or even minimum (Fig. 7 — Strojców A, Ma-

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Fig. 7. Contens of coal clasts in recent Vistula deposits as a function of siae gr*®* i — oaartz clasts; 2 — flysch sandstone clasts; 3 — coal clasts; i =— other clasts

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