Geographia Polonica (1988) vol. 53
Morphometry and morphodynamics of the lower Vistula channel mesoforms
Geographia Polonica (1988) vol. 53, pp. 85-100 | Full text
Mesoforms are of major importance in the study of channel processes defined byPopov (1977) as an unsteady continuous movement of the river channel bed under theinfluence of flowing water. Kondratiev et al. (1982: p. 23) account for this in a specialway. They have stated explicitly that "the study of mesoforms is a way by means ofwhich the fundamental principles of a typical channel process may be discovered and itslogic may be understood". Following earlier suggestions (Kurpianov and Kopaljani1979), they also state that the channel process is chiefly conditioned by a mechanism forload transport and they establish certain relationships between them. These relationshipshave also been built up by Schumm (after Shen 1982; p. 13) and by Winkley et al.(1984: p. 84). From these data it can be inferred that a channel pattern (channel process)and an adequate system of mesoforms depend on the quantity and quality of thetransportée load.Accordng to Rzhanitsin (1984: p. 130), the mechanism for load transport is acomplex process. It occurs continuously in one case or takes place in a series of jerks tobecome cyclical in another case. Continuous load transport leads to the formation ofdunes and sand ripple marks, i.e. microforms, whereas discontinuous transport results incentral and lateral bars (islands), i.e. mesoforms.The term channel mesoforms refers to forms, the size of which corresponds with thechannel width and high stability of which is determined by hydraulic geometry of astream (Kondratiev and Popov 1967; Antropovski 1969). They usually comprise singlelarge sand-gravel waves and fixed lateral bars, the surface of which lies in a zone ofaverage Wcter stages although they are formed at high water stages.British-Vmerican investigators, for example Church «and Jones (1982), Cant andWalker (1978), Ferguson and Werritty (1983), Kellerhals et al. (1976), Schumm (1985),use a broaler typology of mesoforms. According to Znamenskaya (1976: p. 9), it ispartly basel on variations of identical forms. N. D. Smith (1978: Table 1) provides acomprehensive description of channel mesoform divisions and nomenclature. He uses asmany as 32 terms referring to forms of bar type, which are based on the morphologicalcriterion.Kondratiev and Popov (1967), as well as Znamenskaya (1976) group mesoforms intolongitudinal sand waves, lateral and central bars, depending on channel conditions.A different ;lassification of bars dependent on the degree of form stability (Fig. 11.4) and based on the relationship between form morphology and functions of stream hydraulicresistance and the amount of load (Table 11.2) has been given by Church and Jones(1982). The above divisions and classifications supplemented by other studies, includingthose by Krigstrom (1962), Task Force (1966), Collinson (1970), Kellerhals et al. (1976),Barwis (1978), Cant and Walker (1978), Levey (1978), Ferguson and Werritty (1983),Carson (1984) and Schumm (1985), are presented as a scheme in Figure 1. Recurrence ofnames in a variety of systems in the scheme is due to the complexity of load transportand to the naming of different forms with identical words by different investigators.
, Institute of Geography and Spatial Organization, Polish Academy of Sciences, Toruń, Poland