The author presents the results of his investigations of the basic problems of the so called systematic geomorphology; the article is a summary of the methodical part of his doctor’s thesis presented at the Department of Geography and Regional Studies of Warsaw University, in 1983. It has been meant as his opinion in the discussion on the following, as yet unsolved, theoretical problems: - the problem of principles of the choice and evaluation of classification criteria; - the problem of principles and methods in constructing classification systems; - the problem of principles and methods in distinguishing the links of those systems (topologic units). Geomorphologic objects (Earth’s sufrace forms) may be classified according to various criteria. The main groups of criteria used in geomorphologic classification systems are: physionomic criteria, morphometric criteria, hypsometric (orographic) criteria, morphogenetic criteria, morphochronological criteria, lithological criteria. Among the above named groups of criteria same reflect the causes of a given surface form (morphogenetic criteria) while others enable to classify the effects (physionomic, orographic, morphometric criteria). Some help in tracing the limits of geomorphologic units (physionomic criteria), others determine the rank of those units (orographic, morphometric, morphogenetic and morphochronological criteria). All these groups of criteria serve the systematic characterization of the distingui shed units having determined limits and rank. Depending on the number of criteria used, on their choice or selection it is possible to build different classification systems. Classification based on one criterion is called simple, if it is based on a number of criteria, we call it complex classification. If the selected criteria belong to only one of the mentioned groups the classification based on them is said to be homogeneous. As the number and differentiation of criteria increases, the degree of complexity of the classification system also grows. As a consequence of a definite choice of a criterion or of the selection of a group of criteria the classification may be vertical, horizontal or combined (vertical-horizontal). Largely developed vertical-horizontal classification is called here many-membered classification. In vertical classification units distinguished according to a given criterion or a group of criteria are successively attributed lower (higher) ranks determined by the classification level; in horizontal classification - the same rank, while in combined classification we distinguish both-units of different rank (depending on the classification level) and units of the same rank (with one level of classification). Criteria used in complex classification (vertical and horizontal) are constant and equally treated within the whole classification. Instead, in combined classification (vertical-horizontal) the criteria must be evaluated. Usually the leading criterion or group of criteria is the base of the vertical structure of a part of classification and serves as determinant of classification levels which qualify the rank of distinguished units. Complementary criteria serve to disinguish units within the particular classification levels. Geomorphologic classification systems use taxonomic and typological units, while cartographic typological studies, basing on definite classification systems, use spatial typological units. There are four principal methods of unit distinction: - The first consists in defining the basic unit of high rank comprising the whole analysed collection and then in dividing it into units of lower rank according to the assumed criteria. - The second also consists in defining the basic unit of high rank comprising the whole analysed collection, then in the isolation, within this unit, of lower-rank units, according to assumed criteria. In the first use we have a complete repartition of the analyzed space while in the second case only some elements of that space are isolated. - The third way consists in dividing the given collection into basic units of the lowest rank, and then in connecting them ito units of higher rank. - The fourth way (applicable only together with one of the previously named) consists in the description - in more precise characteristics - of units of higher rank through units of lower rank. An intermediate way is also used; it connects the division method with the method of isolation. Typological units created through the method of division, isolation and connection really exist in the geographical space, they can therefore be consideredas spatial typological units; instead typological units formed through additional description occur only in systematic or descriptive elaboration. The above theoretical considerations have been applied in the proposed system of classification of natural geomorphological objects constituting the surface forms of lowland postglacial areas. The system is connected with the general classification of the Earth’s surface forms. In the presented terminology it is a vertical-horizontal (many-membered) system. It uses groups of units of various cathegories, distinguished by the methods of division, isolation, connection and additional description (the use of a definite method depends on the level of classification). Therefore it takes into consideration superior forms which have a bearing on the general character of the configutaion of the surface of lowland postglacial areas, and it distinguishes, within them, forms of lower rank affecting the character of superior forms. In a further stage of classification it divides groups of still lower forms of relief with definite guiding features, and in the lowest level of classification it distinguishes the particular inferior forms having definite individual features. This system fullfils the requirements of a full, well-ordered description of relief, based on criteria of physionomy, orography and morphometry, of morphogenesis and morphochronology with the evaluation of the degree of transformation of primitive forms, as well as on criteria of structure of geomorphologic objects. These criteria are systematized in relation to their classificatory values (leading and complementary) and in relation to their function (distinguishing taxonomic units, typological units and determining the limits of spatial typological units). The rightness of these structural principles of the above-presented classificatory system was confirmed at the time of drawing the typological geomorphologic map of the areas between the Narew and the Bug rivers.
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