The Role of Dykes in Shaping Stream Junction Angles: A Case Study of the Rangavali River Basin, Northern Maharashtra

Abstract

Dyke swarms frequently act as natural barriers, obstructing or deflecting stream courses. Streams tend to flow along the outcrop ridges of dykes, resulting in acute junction angles. Dykes serve as structural controls by influencing the orientation of streams. The relationship between stream junction angles and dyke orientation is a significant factor in stream confluences. Terrain plays a crucial role in directing the river’s flow path and shaping its characteristics. This research paper investigates the impact of dyke orientation on stream junction angles through stream hierarchy analysis. The Rangavali River, a left-bank tributary of the Tapi River, flows for a distance of 45.65 km, crossing 21 East-West (E-W) trending dykes within a 215.95 km 2 basin, which forms part of the Deccan Traps. To examine the relationship between dyke orientation and stream junction angles, inputs from Google Earth imagery, LISS III images, SOI topographical maps, quadrangle maps, and Cartosat DEM were used to delineate the Rangavali basin and extract dyke features. The Rangavali River basin is a sixth-order drainage system that exhibits a superimposed drainage pattern within the Tapi dyke swarm zone. The prominent linear dyke ridges are predominantly aligned in an East-West direction (average angle N81˚), with a dyke density of 0.51 km/km 2 . The average junction angle of streams within 100 m upstream and downstream of the dyke ridges is 81˚, compared to an average of 78˚ in non-dyke areas. The trend of acute junction angles is attributed to the orientation of the dykes and the distance of streams from the parallel-aligned dyke ridges. This study demonstrates that dyke ridges not only redirect stream flow but also control drainage density and network development. The findings have broader implications for watershed management, flood risk assessment, infrastructure planning, and groundwater exploration in basaltic terrains and contribute significantly to the understanding of fluvial-structural interactions in volcanic landscapes.