Fluvial lakes are a very important part of the natural or quasi-natural river valleys. Although their origin is usually identified with the process of cutting off the meandering neck, there is also a large number of other processes responsible for floodplain basin creation. The first classifications of the floodplain lakes were very simple. All the lakes were considered as a homogenous group of oxbows, and their division was mainly based on shape. Hydrological studies of floodplain lakes have been more popular since 1990, with two phases of the lakes functioning being pointed out; inundation or potamophase and isolation or limnophase. The next step in floodplain lakes research was the division into hydrological types; evaporation-dominated, flood-dominated, and exchange-dominated. Moreover, those types of confluent, contrafluent or profundal lakes were distinguished with regard to the supply direction (with reference to the river). A hydrochemical classification of floodplain lakes was published in 2005. Three types of lakes, extra-zonal, inter-zonal and mix-zonal, and three kinds of each type were distinguished. Taking into consideration all the processes in the river valleys, a few feedback loops can be indicated, regardless of the climatic zone or intensity of the processes.