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Gondia Education Society’s C.J. Patel College, Tirora , Dist.- Gondia 441911. Subject : FLUVIAL GEOMORPHOLOGY Topic Relation of discharge with width, depth, velocity and gradient. Is presented by Dr. Nanabhau S. Kudnar M.A., B.Ed., SET, NET, Ph.D., M.B.A . Head, Department of Geography C.J . Patel College Tirora .


INTRODUCTION-: Channel morphology or river channel morphology includes the consideration of a) channel geometry ( e.g. channel length, channel width, channel depth, wetted perimeter, channel slope, channel bends) b) channel fluid dynamics ( e.g. discharge, velocity etc.) c) Hydraulic geometry d) channels types v) channel patterns etc. HYDRAULIC GEOMETRY-: Definition-: The analysis of the relationships among streams discharge, velocity, channel shape, sediment load, channel width, channel depth, channel slope etc. is called hydraulic geometry of a river channel.


DISCHARGE-: The product of mean velocity and the cross-sectional area (width * depth) defines the discharge of a streams. It is the volume of water passing through a cross-section during a fixed of time, and is expressed in cubic metres per second . Formula, Q = w d v Where, Q = Discharge w= channel width d= channel depth v = channel velocity Discharge increase downstream for most streams .However, some rivers experience rapid downstreams decrease in discharge due to high transmission losses due to evoporation and seepage.


A river channel represents water course of a river confined within the limits of valley walls on both the sides. The channel thalweg represents the line that connects all the points of maximum depth of water from the source to the mouth of the river along the channel in downstream direction. Sinuosity refers to deviation of actual channel path from expected theoretical (straight) path while ‘ radius of curvature’ nomenclature ,rm, is the radius of a circle drawn through the apex of the bend and the two crossover means midpoints.


Channel length denotes the distance of channel from source to the mouth of the river and connects all the mid-points across the channel . Channel width (W) is he mean of measurements taken at the crossovers.( M.Morisawa,1985 ) wherein crossover means straight line joining two points across the channel. The depth of channel denotes vertical distance from the water in the channel to the channel bed. Maximum channel depth is measured from the level of water bankfull stage of the river to the lowest point of the channel bed.


VELOCITY- Is the measure of the speed & direction of an object (to be very simple the speed the river is travelling) It is commonly believed that the velocity of rivers is faster than the upper course: however, this is not true, the velocity of the river actually increases as you near the mouth as shown in the Bradshaw model above. This because the cross-section of the source so there smaller near the source so there is greater than friction and the discharge is smaller. Nearer the mouth the discharge of the river increases as does the rivers cross-section. We measure velocity with the formula :- speed=distance / time.


CHANNEL GRADIENT-: a) The shape of channel of a river from source to mouth is considered as longitudinal profile or simply long profile which is generally a concave upward profile in the case of perennial rivers. The gradient or slope channel in downstream direction is called channel gradient . b) Gradient means how steep something is the gradient of the river will normally get less step as it travels from the source to the mouth.





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