Fluvial Geomorphology Jagdish

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Gondia Education Society's C.J. Patel College, Tirora , Dist.- Gondia 441911. Subject : FLUVIAL GEOMORPHOLOGY Topic long Profile of River 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 .

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Long Profile of River: As water flows along the channel of a river, its long profile will be determined by several factors, which include geology, structure, original slope, discharge, etc. In the source region, the limited catchment supplies little volume of water whence erosion is limited. As the river precedes downstream the volume increases and erosion gains momentum. Nearer the mouth, however, because of low gradient deposition exceeds erosion. Because of such varying degrees of erosion, the long profile becomes concave.

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Long Profile: The long profile is a section drawn along the river gradient from source to mouth. Cross Profile: cross profile is a cross section drawn across the river valley at intervals along the course. Long Profile

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Long Profile Cross Profile

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Energy of a River Energy is required to move water and load along the channel. The energy of a river is represented by its velocity, which is determined by: Internal Friction (ii) Bed Friction/Channel Roughness (iii) Gradient (iv) Discharge (v) Size/Shape of Channel Erosion and transport can only take place when there is sufficient energy in the system to do the work. However, deposition of material occurs as a rivers loses energy ie . its velocity increases and/or discharge or an increase in load occurs.

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River Long Profile The general form of the profile is a concave upward curve but the degree of concavity varies considerably depending on the overall steepness of the gradient.

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The degree of regularity of the concave curve varies between different rivers. Some may show regular concave sections separated by even convex sections.

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Most long profile show considerable irregularities, in this case there is evidence that overtime the river is establishing an equilibrium by eroding the knick points, and filling in the lakes be deposition which will ‘iron out’ the irregularities.

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Factors which control the shape of long profile The base level i.e. the lowest point of any stream- usually the sea, but lakes can cause local base levels to occurs. The increase in discharge downstream which is usually greater than the load increase. Increasing discharge means that a given load, and in a most a larger load, can be moved with the same velocity over a lower angel of slope.

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Decrease in the load size downstream, so that a given mass of load can be transported over gentler slopes. Increasing discharge implies an increasing cross-sectional area which, assuming no channel x section change, means an increase in efficiency. greater depth and finer load leading to a smoother channel bed downstream, so that energy transformation caused by turbulence will decrease.

References:

References Geomorphology Savindra Singh Fluvial Geomorphology www.rusnature.co.org.

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Thank you…

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