HYDROMORPHOLOGICAL STUDY OF THE RIVER , KOSI IN A SELECTED REACH USING EXTREMAL HYPOTHESES AND SATELLITE DATA

Abstract

A river is a dynamic system. It adjusts its channel roughness, geometry, pattern and profile with changing climatic, geological, hydrological, hydraulic, sediment and man-made. constraints. Thus fluvial hydraulics and river morphology form one of the most complicated subjects._x000D_ The plan-form of a reach of an alluvial river reflects the hydrodynamics_x000D_ of flow within the channel and the associated process of sediment transport and energy -dissipation. Braided streams occur in high energy environments with large and variable discharges carrying heavy sediment loads on steeper gradients. These streams are characterized . by a random pattern of multi-thread channel network due to appearance of braided bars within the overall waterway of the river. The presence of braid bars increases the total flow resistance and the energy losses along the boundary, thereby promoting the development of a network of hydraulically inefficient channels._x000D_ The river Kosi is one of the largest braided streams of the world. The_x000D_ river discharge varies to 10 times of its mean- 'annual discharge during the monsoon and carries a very high concentration of sediment load. Th6 river has shifted 115 Km West wards between 1736-1950. It has been confined -by-=t-he construction of eastern and western and embankments in 1-959 and a •barrage in_x000D_ 1963 at Bhimnagar.. It is still shifting its bed within the embankments and can be termed as unstable....