Large floods in the lower Vistula River

Internal structure and sources of selected ice jams on the lower Vistula River

“…Ice jams' internal structure studies conducted in the 1980s by Grześ () show that the filling of the cross section with ice (I) at 60–70% is quite frequent in the lower Vistula, especially in its unmanaged stretches. The maximum value measured during the ice jam of January 1982 was 82% (ice dam compact and firm accumulation).…”

“…Generally, it is considered that one of the major reasons behind the occurrence of ice jams on the Vistula River is the river's channel morphology (Grześ, ). From 1995 to 2014, the ice filling of the Vistula River channel was examined on the basis of nearly 80 cross sections, whose geometric types were then determined using Milne () Within the managed stretches of the river, the most frequent types were asymmetric with a more central thalweg and asymmetric with a more central sand bar.…”

“…During frazil slush penetration testing, changes in the ice deposits' compactness were recorded with a precision of 5 cm. Three grades of hanging dam compactness were adopted: loose accumulations ( L ), when the sounder penetrates the accumulation driven by its own weight; compact accumulation ( C ), when the sounder stands upright in the slush; firm accumulation ( F f ‐F , with or without ice floes), when the sounder must be driven by force (ice floe occurrence requires additional piercing); approximate density, on the basis of earlier studies using the frazil slush sounding core (Grześ, ), determined as ‘the dry density of the slush’ (Bealtos and Dean, , Beltaos ), for distinguished grades was as follows: L – density between 100 and 200 kg/m 3 , C – 200 and 500 kg/m 3 , F – 300 and 500 kg/m 3 or more. …”

“…At the damming height of about 3 m, water overflowed the side dams of the reservoir. More than 100 km 2 of the valley was then flooded (Grześ, ).…”