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Watershed Morphometry on Quaternary Volcanic Terrain in Southern Margin of The Bandung Basin: Its Implication in Distribution of Flood Area
Emi Sukiyah
Lecturer
Dept. of Geology, Faculty of Mathematic and Natural Sciences, University of Padjadjaran,,
Indonesia
Email: ifaamelia@yahoo.com
Adjat Sudradjat
Dept. of Geology
Faculty of Mathematic and Natural Sciences
University of Padjadjaran
Bandung
R. Febri Hirnawan
Dept. of Geology
Faculty of Mathematic and Natural Sciences
University of Padjadjaran
Bandung
Indonesia
Dicky Muslim
Dept. of Geology
Faculty of Mathematic and Natural Sciences
University of Padjadjaran
Bandung
Indonesia
Nana Sulaksana
Dept. of Geology
Faculty of Mathematic and Natural Sciences
University of Padjadjaran
Bandung
Indonesia
Djadjang Sukarna, Centre of Geological Survey, Geology Agency, Energy and Mineral Resources Ministry, Republic of Indonesia
Southern margin of the Bandung Basin is hilly and mountaineous terrain that composed of Quaternary volcanic rock. Volcanic terrain, mainly maturity stage, show tendency to have irregular pattern compared with the other, i.e. karst terrain. This condition exposed on similar drainage patterns in the terrain. Watershed morphometry is a part of many parameters of geomorphologic aspects to understand the characteristic of flood area. Some criteria of watershed morphometry i.e. river degree, length of river segment, cummulative total of river segments, bifurcation ratio (Rb), ratio of Lu average toward Lu+1 average. The research methods used are quantitative method for calculation of numerical data of watershed characteristic, probabilistic method for analysis of correlation among parameters of watershed morphometry with flood area distribution, and Geographic Information System (GIS) method for geo-spatial data analysis. The analysis of some morphometry indices of this area show that some parameters are related to each other. Based on deduction that river length are controlled by slope degree, lithology characteristic and tectonic so there are correlations among length of river segment and its river degree. On graphic of polynomial regression correlation among cummulative total of river segments (v1) and cummulative total of length of river segments (v2) toward river degree (v3), the region of flood vulnerable is shown by pattern of curve lines to be far apart. The non vulnerable area will be indicated by pattern of curve lines to be very close together. Statistically, there are real correlation among variables of river grade with flood area distribution. This correlation be shown by correlation grade (r) on graphic of regression correlation are 0.676 to 0.999. This phenomena shows Quaternary volcanic terrain have a little regularity of patterns to explain flood vulnerable area. Key-words: volcanic terrain, morphometry, river grade, flood area distribution, GIS, and graphic of regression correlation
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