DSC07965

122 E. Niedziałkowski!

a.s.l.) are characterized by steep slopes and deeply (600 — 700 m) incised va||e_v whcreas the foothill zonę (330 — 550 m a.s.l.) is narrow (Starkel 1972), *|y summer maximum of precipitation is pronounced, as well as the high diurnal precipitation amounts. Conscqucntly, the Vistula has a snowy-rainy hydro logical regime (Punzet 1983).

Man*s activity is responsible for the most marked changes in the co^. position of the natural vegetation cover (changes in tree species, forest clearance) and in the naturę of the river channels. The Wisłoka channel ig non-regulated. The first channel correction was undertaken on the Vistula in the 1930s. Successive channel works undertaken in the mountainous and foothill sections included the construction of concrete banks and weirs. This caused both the current velocity and the rates of incision to increase (Klimek 1983). Furthermore, gravel extraction from the river channel led to its loca]

Fig. 3. Schematic geomorphological map showing the upper Vistula valley

/ — Holocene floodplain; 2 — Vis(u)ian terrace łevel — alluvial Tan; 3 — valley-sides. 4 — distribution ofsites examined:5 of modern flood-formed deposits; 6 — location of gravet bars examined: 7 — sections