Quantitative analysis of hierarchical anomaly of drainage system and its relevance to tectonic, case study: 10 catchments in Zagros



In this research, hierarchical anomaly index (∆a) and density of hierarchical anomaly (ga) for 10 catchments were calculated and then their relationship with percent of asymmetry factor of basin (PAF), elongation ratio (Bs), circularity ratio (CR), bifurcation index of drainage (R), bifurcation ratio(Rb), drainage density (Dd) and drainage frequency (Df) were analyzed. Results of this study reveal that the highest value of ∆a is associated with catchment 7 (3.4) and the lowest value is related to catchment 1 (0.64). The highest value of ga is associated with catchment 6 (12.1) and the lowest value is related to catchment 10 (1.54). Analysis of relations between different parameters demonstrates that ∆a and ga as indicators of drainage system anomaly are more influenced by PAF, Bs and Cr factors. This means that drainage system anomaly of studied basins is more influenced by the percent of basin asymmetry as well as by basin shapes so that catchments that are more tilted and elongated have highest values of ∆a and ga. Data show that drainage density and frequency don’t have considerable effect on the rates of ∆a and ga indexes. Results demonstrate that the rate of fold’s compaction, uplifting and trend is controls the basins shape and tilting and the drainage system anomaly. Since the Zagros catchment's tilting and shapes are controlled by folds characteristics, it can be concluded that tectonic is a determinative factor in the values of ∆a and ga indexes.