Drainage Characteristics of Tectonically Active Areas: An Example from Rajasthan, India

Abstract

The morphotectonic studies help in deciphering the role of tectonics and neotectonics in morphological evolution of draiage basins. On the basis of remote sensing technique, the relationship betwcen morphology and tectonics have been investigated in Bundi-Indergarh sector of southeast Rajasthan. The area sclected for present study is drained by Mej river and its tributaries and occupies the southeastern part of the Aravalli Mountain Range (AMR). The course of Mej river is mostly controlled by the Great Boundary Thrust (GBT) and associated tectonic elements. GBT separatcs the folded, faulted and metamorphosed older rocks of the AMR in the west and relativcly undeformed Vindiyan rocks in the east. This study has been carried out using digital and hard copy product of IRS IC/ID LISS III geocoded FCC data. The morphometric and morphotectonic aspects have been studied for identification of present day tectonic activities in the area. The remote sensing data interpretation indicates that the landforms of the area are structurally controlled and mainly covered by linear and parallel strike ridges and valleys. These valleys indicate sign of stream rejuvenation and occasional presence of dynamic ravines. General morphometric parameters, bifurcation ratio, stream lengh and shape parameters have been computed. Longitudinal river profilcs can be quantificd by normalizing the elevation and the distance along rivers. Several parameters such as profile shape (concavity), gradient fluctuations, river grade and valley incision have been derived from longitudinal river profile. These quantified parameters and their interrelations are useful in comparing different drainage basins and also help drawing inferences on neotectonism. The computed values suggest that the area is covered by resistant rock and drainage network, affeced by tectonic disturbance. The valley floor ratio is very low, indicating channel down cutting vis-a-vis ground uplif. The gradient index is most commonly used to define relative diferences in uplift and erosion. The computed values for these parameters indicate ongoing tectonic activity in the area. Migration and/or rejuvenation of rivers, rotational/vertical/lateral movements of crustal blocks and several other evidences bear testimony to ongoing neotectonic activities in the region.