Author(s): Papanicolaou N. Athanasios; Tsakiris G. Achilleas
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Keywords: Cluster; Microforms; Fractal; Box-counting; Characteristic scales; Irregularity
Abstract: Cluster microforms in gravel bed rivers are organized groupings of particles, which sit on top of the river bed. Their interaction with the flow field properties, sediment transport and reach morphology is well documented but least understood, due to the dynamic nature of the interaction, the high 3D irregularity of the bed and the inability of the traditional measures to describe it with parsimony. The fractal geometry is able to quantify the degree of spatial complexity of an irregular feature with the concept of the fractal dimension D. It has also been proven to be able to capture the characteristic scales of a feature, at which the underlying processes for the feature formation are most pronounced. In the current study, the ability of the fractal dimension D to act as a descriptive measure of the bed microtopography is investigated. To the completion of the objective, the cell-counting method as implemented in the commercial software ImageJ is first tested against a series of synthetic data and then applied for the calculation of the fractal dimension for a series of clustered beds and of the individual clusters developed in laboratory experiments under various flow and sediment availability conditions. In parallel, the discrete clusters are classified in terms of shape and their properties are acquired. The results of the methodology, suggest that the fractal dimension D possesses the ability to characterize the microtopography of different clustered beds and yield valuable insight into the degree of expression of the dominant processes, responsible for their spatial arrangement.
Year: 2007