Sedimentation Processes and Asymmetric Development of the Godavari Delta, India
K. Nageswara Rao, N. Sadakata, B. Hema Malini, K. Takayasu, 2005. "Sedimentation Processes and Asymmetric Development of the Godavari Delta, India", River Deltas–Concepts, Models, and Examples, Liviu Giosan, Janok P. Bhattacharya
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The Godavari delta, on the east coast of India, is prograding into a microtidal and low to moderate wave environment, fed by a highly variable water discharge in a monsoon-driven hydrographic regime. Extensive strandplains that prograded 30 to 35 km across the continental shelf during the Middle to Late Holocene characterize the overall arcuate seaward bulge of the delta. At present, the delta has two lobes: the Gautami in the northeastern part and the Vasishta in the southwestern part, which have been active during the past one thousand years. Although the bigger size of the Gautami lobe with extensive mangrove swamps apparently indicates a larger riverine influence, both lobes, in fact, exhibit strong wave-influenced morphologies. As revealed by a series of historical maps, pronounced growth of spits characterizes the northern Gautami lobe. The 21-km-long Kakinada spit, which is prominent among all such sand bodies, had even deflected the Gautami distributary course in the initial stages of its growth under the influence of a strong northeastward longshore drift. Analysis of multi-date satellite images shows that spits are growing at the updrift sides of the mouths of the two terminal branches of Gautami, whereas erosion is dominant on their downdrift sides. On the downdrift side of the Vasishta mouth, development of mouth bars is followed by their emergence as barrier islands that migrate landward, and subsequent infilling of the backbarrier bays by riverine discharge, typical for wave-influenced asymmetric deltas. The nature of coastal landforms and sedimentation processes indicate prevalence of a northeastward drift at the Gautami lobe and a southwestward drift at the Vasishta lobe.
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Deltas are amongst the most environmentally and economically important coastal sedimentary environments. Studies of deltas lag behind research in both fluvial and deep-water depositional systems, as well as more geomorphologically oriented land studies. This knowledge lag reflects both a reorientation of the petroleum industry in the last two decades toward deep-water systems, as well as the difficulty of working across the shoreline with the traditional tools used for oceanographic or land-based work. However, deltaic studies are experiencing a renewed focus, because of their global importance in environmental and other societal concerns. This volume stems from a special session: Deltas: Old and New, held at the Annual Geological Society of America conference in October 2002, that was convened to highlight these new directions in deltaic research.