Frequency Distribution Curves as an Indicator of Evolutionary Trends in Geomorphological Systems: A Case Study from the Northwestern Part of Hrvatsko Zagorje (Croatia)

Abstract

Frequency distribution curves can be indicative of the dynamics and evolutionary development of geomorphological systems. Normally distributed geomorphological data are a reliable indicator of the
equilibrium fluctuations prevalent within such systems. This occurs, for example, when a delicate balance is established between various types of landforms and geomorphological processes. Landforms that exist in this geomorphological steady state can be properly called "equilibrium" structures. They show no permanent trends of either growth or destruction. On the contrary, a positively skewed frequency distribution curve indicates a type of non-equilibrium conditions and non -linear relationships within geomorphological systems, which may be the result of major external energy inputs (particularly from tectonic uplift ). This in turn gives rise to new and more complex higher-order landforms. These represent structures of growth or evolution. Alternatively, a negatively skewed frequency distribution curve, also being a consequence of non-equilibrium conditions, indicates a lack of free energy in the system, which induces destruction of the existing landforms. Such landforms represent strucres of degeneration. The fluvial landscape in the northwestern part of Hrvatsko Zagorje, portrayed in terms of an open system, has been used as the geomorphological framework for this study, the primary purpose of which was to apply frequency distribution curves in the interpretation of the processes influencing the creation and destruction of the landscape. Horizontal and vertical dissection, slope and other morphometric characterictics reflect the specific dynamics of the geomorphological processes, which relate a variety of landforms to their geologic framework and climate in the study area.