Satellite image processing sedimentology and geophysical studies to identify and map palaeochannels in a part of south eastern India

Abstract

Palaeochannels have long been recognized as important newlinegeomorphic units and as potential sources of groundwater economic minerals newlineand placer deposits They are also good repository of palaeoclimate data To newlineexploit such resources the first essential step would be to identify and map newlinethe palaeochannels This thesis presents an integrated and systematic study newlinecarried out using certain recent satellite image processing techniques newlinesedimentology electrical resistivity surveys and GPR surveys to identify and newlinemap the palaeochannels newlineThe study area in the southeastern part of India Andhra Pradesh newlineand Tamilnadu states is characterized by numerous palaeodrainages due the newlineuplift of land along the Mulki Pulicat Axis and the consequent migration of newlinethe Pennar Swarnamukhi Palar and Cauvery rivers A few palaeochannels newlineare readily visible in the satellite images while most of them are not newlineImage enhancement techniques such as linear contrast enhancement newlineand fusion of multisensor image was attempted Fusion included Landsat 7 newlineETM multispectral images and PAN images fused using PCA method and newlineLandsat ETM Thermal and PAN images fused using the Brovey tansform newlinemethod The Brovey transform approach resulted in images which were newlinevisually appealing and contain a host of information about the palaeochannels newlinethat exist in the area Hill shading techniques with specific combinations of newlineSunAzimuth and SunElevation applied to the satellite derived DEM further newlineenhanced the appearance of the palaeochannels especially the exposed ones newlinewith a gently undulating surface expression across the palaeovalley newlineThe mapped palaeochannels were later validated by spatial profiling of newlineDEM ground check sedimentology electrical resistivity and GPR surveys newlineFrom the spatial profiling of the DEM the topographic lows between two newlinepoints across the opposite banks were identified and the existence of a newlinepalaeochannel is validated Sedimentological analysis sieving Miola and newlineWieser plot Friedmans curve of borehole samples collected from the newlinemapped palaeochannels reveals newline