Fractal analysis of the Oyo River, cave systems, and topography of the Gunungsewu karst area, central Java, Indonesia |
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| Authors: | Sari B Kusumayudha M T Zen Sudarto Notosiswoyo Rudy Sayoga Gautama |
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| Institution: | (1) Geology Department UPN “Veteran” Yogyakarta, Jl. Lingkar Utara Condongcatur Yogyakarta 55283, Indonesia Fax: +62-274-566800 e-mail: saribk@indosat.net.id, ID;(2) Geophysical Engineering Department, Bandung Institute of Technology, Jl. Ganesha 10 Bandung 40135, Indonesia, ID;(3) Mining Engineering Department, Bandung Institute of Technology, Jl. Ganesha 10 Bandung 40135, Indonesia, ID |
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| Abstract: | Gunungsewu, the southernmost subzone of the Southern Mountains, central Java, is a classic karst terrain, bounded by the
Oyo River on the north and the Indian Ocean on the south. In this study, the Oyo River, the main drainage in the area, is
divided into 14 segments, and the fractal dimension of each segment is determined by the box-counting method. The 14 segments
show various values of fractal dimensions, which are controlled by lithology and geologic structures of the area that is being
dissected by the river. Easily eroded lithologies have larger fractal dimensions, and the value changes abruptly when the
river crosses faults. Fractal dimensions of six underground rivers in the Bribin, Sodong, Semuluh, Jomblang, Soga, and Sumurup
caves, and the surface topography above the caves were also determined. The caves have fractal dimensions that range from
1.043 ±0.01 to 1.08±0.01; the surface topography has fractal dimensions that range from 1.49±0.01 to 1.732±0.01. The fractal
dimension of an underground river is proportional to the fractal dimension of the surface topography over the passage. Larger
fractal dimensions of underground rivers are associated with smaller flow rates of the rivers.
Received, June 1998Revised, March 1999, August 1999, February 2000Accepted, February 2000 |
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| Keywords: | karst Indonesia fractals geomorphology |
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