Detecting the Paleochannels Based on Optical Data and High-Resolution Radar Data for Periyar River

A separated buried river channel from the active river by the activities of cutoff or abandonment is called paleochannels and later they may be filled with the sediments of young unconsolidated or semi-consolidated. Additionally, it is impacted by geomorphological influences, lineament alterations, and other factors. The aim of this study is to identify the paleochannels in Periyar River Basin for the year 2023. Those channels have high probability in the presence of natural resources including gold, platinum, tin, and uranium. Numerous techniques are used to map the paleochannel. Using the optical data, satellite images were collected from various sources which comprise multispectral satellite images from which indices such as normalized difference vegetation index (NDVI), normalized difference water index (NDWI), soil adjusted vegetative index (SAVI) and thematic layers, such as lithology, stream network, and lineament were prepared. Weights are assigned to each layer based on its importance and overlay analysis has been done which concluded that the northwest region of the area has shown some paleochannel patterns. The results were cross-verified using the results obtained using microwave data. Using Sentinel data, SAR Image was extracted from ESA portal, preprocessed it using SNAP 6.0. In addition to that, polarimetric decomposition technique has been incorporated to detect the paleochannels based on its scattering property. Further, principal component analysis has been done for enhanced output imagery. Results obtained from optical and microwave radar data were compared and the location of paleochannels was detected. Six paleochannels in the study area were identified out of which three paleochannels were validated with the existing data published by Department of Geology and Environmental Science, Kerala. The other three paleochannels were newly detected with the help of SARimage.