Investigating the Tectonic and Structural Controls on the Geomorphic Evolution of Shiriya River Basin, Southern India

Abstract

Morphotectonic analysis of a river basin using geomorphic indices helps to identify tectonic deformation. The aim of the present work is to determine geomorphic indices from the digital elevation model and to examine the extent to which structural characteristics of the Shiriya River Basin (SRB) have influenced its drainage morphology. GIS techniques are used to calculate geomorphic indices of the SRB. Morphotectonic and geomorphic analyses were carried out, which included evaluating various geomorphic indices. Hypsometric curve and hypsometric integral (0.46) indicate youth stage of the basin, asymmetry factor (43.23) and transverse topographic symmetry factor (0.37) indicate asymmetry of the basin, basin shape index (2.05) depicts the basin as elongated, sinuosity index (1.47) indicate the sinuous nature of the basin, valley floor width to height ratio is 10.21 and stream length gradient index is 113.75. The entire basin is divided into 18 fourth-order sub-basins for detailed analysis of morphotectonics. Relative active tectonic indices are calculated to identify the subbasin that had undergone pronounced structural disturbance. Out of 18 subbasins 13 subbasin belongs to moderate tectonic active category (class-2) and 5 subbasin belongs to active category (class 2). From the morpho structural analysis following results were arrived, all of which point towards significant structural control: Lower-order streams have an orientation in accordance with significant structural elements of the basin, such as foliations and lineations (E-W). Similarly, the alignment of higher-order streams follows the direction of the major lineaments of the basin (NW-SE). Eight waterfalls/cascades are positioned within the basin, all directed in accordance with the lineament (NW-SE), earthquake recorded near the basin, asymmetry of the basin, acute bending of streams, entrenched meanders, changes in the sinuous river path in several locations where lineament intersect the stream and shrinkage of estuary area indicate neotectonics and structural control over the development of drainage system in the SRB. These findings are essential for understanding the development of river drainage and landform evolution.