Drainage Characteristics of Tectonically Active Areas: An Examplefrom Rajasthan, India

Abstract

The morphotectonic studies help in deciphering the role of tectonics and neotectonics in morphologicalevolution of drainage basins. On the basis of remote sensing technique, the relationship between morphology andtectonics have been investigated in Bundi-Indergarh sector of southeast Rajasthan. The area selected for present studyis 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. GBTseparates the folded, faulted and metamorphosed older rocks of the AMR in the west and relatively undeformedVindhyan rocks in the east. This study has been carried out using digital and hard copy product of IRS 1C/1D LISS IIIgeocoded FCC data. The morphometric and morphotectonic aspects have been studied for identification of present daytectonic activities in the area. The remote sensing data interpretation indicates that the landforms of the area arestructurally controlled and mainly covered by linear and parallel strike ridges and valleys. These valleys indicate sign ofstream rejuvenation and occasional presence of dynamic ravines. General morphometric parameters, bifurcation ratio,stream length and shape parameters have been computed. Longitudinal river profiles can be quantified by normalizingthe 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 theirinterrelations are useful in comparing different drainage basins and also help drawing inferences on neotectonism. Thecomputed values suggest that the area is covered by resistant rock and drainage network, affected by tectonic distur-bance. The valley floor ratio is very low, indicating channel down cutting vis-a-vis ground uplift. The gradient index ismost commonly used to define relative differences in uplift and erosion. The computed values for these parametersindicate ongoing tectonic activity in the area. Migration and/or rejuvenation of rivers, rotational/vertical/lateral move-ments of crustal blocks and several other evidences bear testimony to ongoing neotectonic activities in the region.