Sediment dispersal during ne monsoon over northern Bay of Bengal: preliminary results using IRS-P4 OCM data

Abstract

False Color Composite (FCC) from the sequential satellite images of Indian Remote Sensing Satellite IRS-P4 OCM (bands around 443, 555 and 845 nm) together with sea truth data acquisition at 42 stations along the Orissa coast have been used to reconstruct the sediment dispersal patterns in the northern Bay of Bengal during the NE monsoon. Our preliminary results suggest a south-southwesterly dispersal of the fluvial plumes of Ganga-Brahmaputra along the coast during October 1999 through January 2000. The suspended sediment load is observed to be higher in November. An increased discharge off the mouth of Ganga-Brahmputra feeds the coastal sediment plumes off coastal waters of Orissa, and these sediments are transported for long distance in a short span of one week along the coast. These results demonstrate a teleconnection between enhanced discharge of Ganga-Brahmaputra and coastal turbidity. Higher influx of suspended load off the Sand Head feeds the coastal plumes, which move into the shallow coastal waters. These sediments appear to sink along the coastal stretches of southern Orissa and Northern A.P. It has also been observed development of offshore curl in the deeper waters. This curl enhances with an increase in the width and augmentation of suspended loads in the Ganga-Brahmaputra plumes, and dies down rapidly. From the images of 10-12 November 1999, it is also apparent that the plumes of high concentration act as feeder and contribute towards the generation of this feature. From these preliminary results, it is tentatively deduced that the suspended sediment discharge of the Ganga-Brahmaputra system continues to influence the coastal processes with much higher temporal and spatial variability along and across the continental margin.