Analysis of confluence angle of drainages and its relation to morphometric properties of drainage basins in the Zagros Simply Folded Belt, Iran

Abstract

Quantitative analysis of drainage network properties plays an important role in the identification of active tectonics and their spatial variations. The purpose of this study is to analyze the drainage's confluence angle (α) in relation to tectonic activity and morphometric characteristics of drainage basins. A total of 23 drainage basins in the Zagros Simply Folded Belt were selected and then the values of α were calculated for 7829 drainage junctions. The relationship between α and other morphometric indexes such as basin area, perimeter, slope, asymmetry factor, shape, circularity, drainage density, ratio of the 1st-order streams to the total number of streams of all orders, and density of drainage's hierarchical anomaly were analyzed. Results show that mean of α increases as the order of stream junctions increases. Basins with higher values of elongation, the ratio of the 1st-order streams to the total number of streams of all orders, and density of drainage's hierarchical anomaly have higher α values. Results also show that the lateral and vertical growth of anticlines, axes of anticlines, trends of faults and drainage patterns influenced by folds growth strongly control the confluence angles of drainage channels in the studied basins.