Holocene evolution of meander bends in lowland river valley formed in complex geological conditions (the Obra River,Poland)

Ground‐penetrating radar surveys, coring and the analyses of satellite and aerial images have been carried out to study differences in the evolution of meander bends formed in various geological conditions. The research was conducted in the lower course of the Obra River (western Poland) characterized by a complex geology: particular sections of the valley were formed in glacial, stagnant water and fluvioglacial deposits. The research was conducted in four detailed study sites representing different formation conditions for the meander bends. Four types of meanders were distinguished: laterally migrating bends characterized by frequent changes of migration direction accompanied by river bed avulsions and cutoffs; bends with traces of continuous migration limited by stagnant water basin deposits; confined meanders in a narrow valley formed in glacial till characterized by the occurrence of mid‐channel islands; and meanders with traces of complex changes of the river bed migration influenced by anthropogenic intervention followed by intensive overbank deposition. Moreover, traces of an early development of the Obra valley and remains of multi‐channel pattern were discovered. The results also show that despite being formed in different geological conditions, a similar number of the meander migration phases were recorded in the floodplain architecture during the last 7000 years at each of the sites. It is also found that the development of the studied meanders was slow compared with cases of actively migrating meandering rivers.