Comparison between two rivers and rivers’ basin in the light of the evidence of tectonic activity: Chel and Neora Manna Dipanwita1,*, Ghosh Kapil2,** 1ICSSR Centrally Administered Full Term Doctoral Fellow, Department of Geography, Diamond Harbour Women’s University, Sarisha-743368, West Bengal, India 2Assistant Professor and HoD, Department of Geography, Diamond Harbour Women’s University, Sarisha-743368, West Bengal, India (*Corresponding author) email id: dipanwitamanna114@gmail.com
**ghoshk.geo@gmail.com
Online Published on 23 April, 2024. Abstract The present study is focused on showing the relationship between structural control and drainage characteristics for establishing active tectonic influence on the drainage network in the piedmont zone of the Sikkimese-Bhutanese Himalaya, between the Chel and Neora rivers. The entire area is divided into two parts, based on the tributaries and the main river- one is the Chel river basin and the other is the Neora river basin. Two dissected fan surfaces are present- the Gorubathan-Rangamati fan surface and the Matiali-Chalsa fan surface. Satellite images and DEM data have been processed using different softwares. Lineaments and scarps have been identified based on the flow path of the rivers. Topographic cross sections and long profiles have been generated from the DEM. Rivers have been digitized from satellite images, watersheds and thalwegs have been generated from the DEM, and drainage patterns have been mapped to observe their relation with relief. A morphometric study has been conducted by observing the mountain front sinuosity (Smf), valley floor width to height ratio (Vf), asymmetry factor of the river basin (AF), concavity and slope of the river channel, hypsometric curve, sinuosity index (SI), and stream length gradient index (SL) index which differ significantly in different parts of the study area. The values of the morphometric indices in the Chel basin are Smf>4<5, AF>21<22, Concavity>0.011<0.012 indicating that this basin is tectonically inactive, asymmetric and the river is in a senile state. On the other hand the values in the Neora river basin are- Smf<2, AF<11, Concavity<0.05 which indicates that it is slightly tectonically active with a marked break of slope in the long profile of the Neora river- This river basin is nearly symmetric and possibly eroded in nature. The SI and SL indices also yield significant results, consistent with the outcomes of the previous morphometric indices. In many parts of the study area, stream courses are directed and influenced by lineaments. Any changes in tectonics of this region may have an influence on the development of the drainage network. Top Keywords Mountain front sinuosity, Valley floor width to height ratio, Concavity, Hypsometric integral, Sinuosity index, Stream length-gradient index. Top |