Analyzing the Drainage Networks Anomalies and its relation with Active Tectonics in the Basin of Northern Tabriz

Tectonic activity plays an important role in the development of drainage basin morphology. Drainage networks are the most active and sensitive elements which can be used as a powerful tool to understand the neotectonic activities of an area (Ahmed and Rao, 2016). The geomorphic indices are a tool for analyzing the landforms and evaluating the degree of tectonic activity in a given area (Keller, 1986; Guarnieri and Pirrotta, 2008). Calculation of parameters of the hierarchy of the hydrographic network such as bifurcation index (R), bifurcation ratio (Rb), hierarchical anomaly number (Ha),hierarchical anomaly index (Δa), drainage density (Dd) and drainage frequency (Df), allows us to define the influence of tectonics on the hydrographic network evolution (Guarnieri and Pirrotta, 2008). Several studies show that rivers necessarily flow from high to low elevations parallel to the maximum regional slope (regional topographic gradient). All deviations of stream flow direction from the regional topographic gradient Considered as anomalies related either to structural or lithological discontinuities (Deffonataines, 1990; Sedrette et al, 2016). Iran is located in an active tectonic zone due to its location in the belt of the Alp-Himalayan. Arabia and Eurasia shells convergence is the cause of active tectonic in Iran. There is a special complication of structure process on northwest of Iran. One of Azarbijan important faults that plays basic role in its structure evolution is Tabriz fault. It crosses the north of Tabriz city . North of Tabriz Fault (NTF) is collection of fault branches. This fault affects upon geology and geomorphology processes on region basins. Since drainage networks patterns present useful information about past and present region tectonic, so one of sensitive landforms to tectonic activities are rivers. In this way, the present study studies the effect of active tectonics of Tabriz fault on the hierarchical anomalies of the drainage network Varkesh Chay basin, Gamanaj Chay basin, Nahand Chay basin and Sarand Chay basin that located on north of Tabriz.
In this research for recognizing study region we have used from topography maps, geology maps 1:100000 ( Tabriz and Khoja) and DEM image with resolution of 30 meter. Also ARC GIS, EXCEL and SPSS soft wares were used for drawing region maps and parameter analysis. In this research studied Varkesh Chay basin, Gamanaj Chay basin, Nahand Chay basin and Sarand Chay basin that located on north of Tabriz. In this study used a quantitative method for calculation of stream's hierarchical anomaly number. Morphometric parameters to be used are hierarchal anomaly index (Δa), Density hierarchical anomaly index (ga), asymmetry factor (Af), basin Shape (Bs), basin length to mean width ratio (Bl/Bmw), bifurcation index (R), drainage density (Dd), drainage frequency (Df), Basin volume / Area index (VA), Basin elongation ratio index (Re), Circulatory ratio (CR) and Langbin Concavity index (IC).
Results show that the strong correlations exist between pairs Da-Re (R=0.99), Da-IC(R=0.91), Da-LSBW (R=-0.87), Da-BS (R=-0.87), Da-R(R=0.69), Da-CR (R=0.55). also the strong correlations exist between pairs ga-IC(R=0.95), ga-Re (R=0.93), ga-R(R=0.83), ga-LSBW(R=-0.94), ga-CR(R=0.65), ga-BS (R=-0.8). The results of the analyzes indicate that the indices Δa and ga are completely affected by the basins elongation caused by the active tectonic effect. In addition, Anomalies in drainage network of all northern basin of Tabriz are affected by the Langbin Concavity index (table1).
Table 1: Coefficients Pearson Correlation between morphometric index in study basins
IC Df Dd R VA LSBW CR Af BS Re
0.91 0.06 0.02 0.69 0.08- -0.87 0.55 0.33 0.85- o.99 Da
0.93 0.27 0.14 0.83 -0.27 -0.94 0.65 0.25 -0.80 0.95 ga
In this study used a quantitative method for calculation of stream's hierarchical anomaly number. Morphometric parameters to be used are hierarchal anomaly index (Δa), Density hierarchical anomaly index (ga), asymmetry factor (Af), basin Shape (Bs), basin length to mean width ratio (Bl/Bmw), bifurcation index (R), drainage density (Dd), drainage frequency (Df), Basin voulume / Area index (VA), Basin elongation ratio index (Re), Circulatory ratio (CR) and Langbin Concavity index (IC) . Results show that the strong correlations exist between pairs Da-Re (R=0.99), Da-IC(R=0.91), Da-LSBW (R=-0.87), Da-BS(R=-0.87), Da-R(R=0.69), Da-CR (R=0.55). also the strongcorrelations exist between pairs ga-IC(R=0.95), ga-Re (R=0.93), ga-R(R=0.83), ga-LSBW(R=-0.94), ga-CR(R=0.65), ga-BS(R=-08). The results of the analyzes indicate that the indices Δa and ga are completely affected by the basins elongation caused by the active tectonic effect. In addition, Anomalies in drainage network of all northern basin of Tabriz are affected by the Langbin Concavity index.