Sediment Transport J.P

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HPT ARTS & RYK SCIENCE COLLEGE NASIK SUBJECT :- Gg-220:-Fluvial Geomorphology Topic :- Sediment Transport Sub Topic :-Suspended & Bedload Is Presented By Patil Jayesh Ramesh (M.A-l Roll No 16) Guidance by Prof – Kudnar Sir


Gondia Education Society's C.J. Patel College, Tirora , Dist.- Gondia 441911. Subject : FLUVIAL GEOMORPHOLOGY Topic Flow And Types of Flow 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:- Sediment Load of river refers of the total amount of sediment of various sizes carried away by a river as suspended & bedload where in suspended load refers to the amount of fine sediments such as clay, silt & fine sands which are carried by the river in suspension off the bottom. The bedload comprised of sand, gravel, pebbles & cobbles is carried by the river water close to the channel floor. It may be pointed out that human activities mainly land use changes, Urbanization, Constructional works, Farming practices, Overgrazing etc.


Bed load and suspended load:- The Separation of bed and suspended load has often been quite arbitrary. Workers in the field are agreed that suspended load in rivers is that portion of the load borne by the up ward momentum or flux of momentum in turbulent eddies in the flow. Bed load, although variously used in engineering practice, applies to the sediment that moves by sliding, rolling, or salt ring on or very near the bed. Bed material includes the sizes of material found in the bed.


Types Of Load - River Load Sediment Load and sediment yield Types Of River Load - When we consider the river transport Process, it is possible to divide sediment load in to two main types Solution load & solid Particulate load Solid load is further differentiated according to the mode of transportation as suspended load and bed load with an intermediate type that includes saltating or hopping sediments.


A) Solution Load- The dissolved or solution load is usually not important in terms of the amount carried. It becomes important in areas where rocks are soluble. For example, a stream flowing through a limestone terrain will carry a large amount of solution load. The major elements that are transported in solution include calcium, silica, iron, alumina & other elements.


B) Solid or particulate load :- The mode of transportation of solid load changes with flow velocity. The sediment grains first have to be picked up from their position of rest on banks, bars, channel bed, etc. The velocity at which the grains of a given size begin to be deposited, indicating the end of transportation, is known as settling or all velocity. Thus, for very small particles, the erosional velocity is high, but the fall velocity is low. In comparison, sand grains (0.06 to 2mm) are eroded first as they lack adhesion. Clasts coarser than sand such as pebbles, cobbles, and boulders are eroded at higher velocity


because of their size. The coarser they are, the bigger is the velocity of entrainment. However, they settle rapidly once the velocity decreases, again because of their fall velocity is higher. There fore, Cobbles and boulders move only at very high velocities, I.e., during floods, but are deposited soon.


Suspended Load :- Suspended load can be defined after Bagnold as that part of the total load of a stream whose immersed weight is carried by the fluid i.e. it floats in the water. Transport of suspended load is largely a function of river discharge. Suspended sediment always increases with an increase in discharge at a cross-section. Suspended load in a river has the following characteristics: Suspended load increases directly with discharge.


2) The vertical distribution of suspended load in a arrives before the peak of the hydrograph unless there is an abundance of sediment. 3) Suspended load my exhibit a loop where for the same discharge, the rising limb of the hydrograph carry more sediment than the falling limb . The size of particles carried in suspension is usually clay, silt, and fine sand, which may range up to coarser sand depending on flow condition. In very high floods, instances of pebbles and fine cobles in suspension have been postulated by modeling.


Bed Load :- Bed load is that part of the load which moves downstream along the bed of the river in rolling or sliding fashion. For a given flow velocity, particles are too large to be picked up and entrained. They are too large to be picked up and entrained. They are, however, moved along the bed by the force of water. The force at which bed load starts to move is known as the critical tractive force. Bed load is very difficult to measure, and is commonly estimated from theoretical bed load functions such as the shields, the Du Boys, or the Einstein bed load function.


Material on bed moves in there ways:- Rounded or sub rounded material can be rolled. Any type of grain can be dragged by sliding or slipping along the bed. Small grains can salt ate, i.e. move in progressively decreasing hope after beings hit by another grains which is moving. The size of saltating load varies with flow velocity. During large flows, for example, even boulders can move in this fashion and during very low flows. Sand saltates.


References Book’s 1) Introduction to Geomorphology -Vishwas Kale. 2) Geomorphology -Savindra Singh


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