Characteristics of the drainage network of the Kosi Megafan, India and its interaction with the August 2008 flood flow
D. Majumder, P. Ghosh, 2018. "Characteristics of the drainage network of the Kosi Megafan, India and its interaction with the August 2008 flood flow", Geology and Geomorphology of Alluvial and Fluvial Fans: Terrestrial and Planetary Perspectives, D. Ventra, L. E. Clarke
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The Kosi River in India is well known in the fluvial fan literature because of its well-documented avulsive dynamics and because of the relationships between changes in the course of the river and megafan aggradational processes. The radial configuration of the Kosi drainage network was instrumental in the recognition of large, low-gradient, fluvial-dominated counterparts of alluvial fans, commonly defined as megafans, and the system forms a well-constrained example contributing to the recent development of the concept of distributive fluvial systems. A major flood inundated the Kosi Megafan in August 2008. The available data on the temporal evolution of the flood inundation patterns illustrate how the exceptional discharge event travelled across the megafan surface using the pre-existing distributary channel network, how the anthropogenic infrastructure affected the flood path and propagation, and the type of geomorphic changes that were induced by this catastrophic hydrological event. In spite of the large discharge involved in the flood, the fan drainage network appears not to have been significantly modified by the event, probably because the flood wave followed a pre-existing channel network for avulsion and down-fan propagation. Most of the evident aggradation took place on the proximal and medial domains along a well-defined, radially oriented sector of the fan. The observed pattern of flood propagation and associated sedimentation provide important clues to understanding the processes operating during exceptional discharge events, which are an integral part of the long-term, avulsion-dominated evolution of such systems.
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Alluvial and fluvial fans are the most widespread depositional landform bordering the margins of highland regions and actively subsiding continental basins, across a broad spectrum of tectonic and climatic settings. They are significant to the local morphodynamics of mountain regions and also to the evolution of sediment-routing systems, affecting the propagation and preservation of stratigraphic signals of environmental change over vast areas.
The volume presents case studies discussing the geology and geomorphology of alluvial and fluvial fans from both active systems and ancient ones preserved in the stratigraphic record. It brings together case studies from a range of continents, climatic and tectonic settings, some introducing innovative monitoring and analysis techniques, and it provides an overview of current debates in the field.
This volume will be of particular interest to geologists, geomorphologists, sedimentologists and the general reader with an interest in Earth science.