Main determinants of the grain size distribution of overbank deposits in Poland – an overview of literature on models of sedimentation

Jacek Szmańda

Abstract


The article describes the most important features of the grain size distribution of overbank deposits (madas) of Polish rivers. The most important characteristics of their deposition and the factors determining the variability of the grain size distribution of overbank deposits are indicated. Almost all grain fractions distinguished in nature, i.e. cobbles, gravels, sands, silts, and clays, occur in the overbank deposits of Polish rivers. The sandy fraction dominates in overbank sediments, which contradicts their widespread recognition as silty-clayey (mud) sediments. The change in the proportion of these fractions (the formation of different types of lithological overbank deposits) is caused by a change in the conditions of sediment transport dependent on six factors: (1) decrease in water flow velocity over a floodplain along with an increase in the distance from the river channel, (2) change in water flow velocity during a single flood (stages of a flood), (3) the diversity of the floodplain relief, (4) changes in the forest cover of the river basin (catchment), (5) change in the longitudinal slope and (6) width of floodplains.


Keywords


sedimentology; overbank deposits; grain size distribution; models of deposition

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