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River
 

River

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this ppt is related to all stages of river.

this ppt is related to all stages of river.

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    River River Presentation Transcript

    • River Mr. Dhawale Ganesh Madhukar S.P.College,pune-30
    • Hydrologic cycle - the movement and interchange of water between the sea, air, and land – Evaporation • Solar radiation provides energy – Precipitation • Rain or snow – Hydrologic cycle – the movement and interchange of water between the sea, air, and land. – Transpiration • Evaporation from plants – Runoff • Water flowing over land surface – Infiltration • Water soaking into the ground Click to view animation
    • • Stream – a body of running water that is confined in a channel and moves downhill under the influence of gravity. Water velocity is the key factor in stream erosion, transportation, and deposition. • Stream velocity – the distance water travels in a stream per unit time. – Expressed in ft./sec. – The stream reaches its maximum velocity near the middle of the channel.
    • Types of River Perennial River Non-Perennial River
    • What processes occur in a river? There are 3 processes taking place in every river. These are: Erosion (The wearing away of the land) Transportation (The movement of eroded material) Deposition (The laying down of eroded material) There are also two other processes that shape the river valley. These are weathering and mass movement.
    • deposition
    • Ganga river- Length :-2,525 km Discharge( Farakka Barrage ) - average 12,500 m3/s
    • Shaping the river valley. There are also two other processes that shape the river valley. These are weathering and mass movement. Weathering = the breakdown of rock material. Mass movement = the movement downslope of broken down rock material due to gravity.
    • Erosion Processes . Abrasion (Corrasion) is when the river is loaded with material in suspension and scours away at the river banks. (Sandpaper effect) Hydraulic Action is the shear force of the river impacting on the sides of the river banks. Corrosion is substances carried in solution such as acids. They dissolve rocks away over long periods of time. Attrition is when bed load collides into each other with the current flow and breaks down into smaller particles.
    • Key words - Transportation. • Traction – where large rocks and boulders are rolled along the river bed. Happens most in times of flood, when the current is strongest. • Saltation – where smaller stones are bounced along the river bed in a leap frogging motion • Suspension – where very small grains of sand or silt are carried along with the water • Solution – where some material is dissolved (like sugar in a cup of tea) and is carried downstream. Occurs often in limestone landscapes where the water if very acidic.
    • Transportation (4 ways)
    • Methods of transportation. Shows the rate of flow needed Traction Saltation Suspension Solution
    • What is a drainage basin? Mouth Where the river flows into the sea, or sometimes a lake. Tributary A river which joins a larger river. Watershed The boundary dividing one drainage basin from another- a ridge of high land. Confluence The point at which two rivers join. Catchment The area from which water drains into a particular drainage basin. Source The upland area where the river begins.
    • Long Profile A Upper Course 0 50 100 150 200 250 Height above sea level in meters. Gradient/slope decreasing Velocity/flow increasing Cumecs/discharge increasing B Middle Course 35 30 25 Energy increases 20 15 10 Distance from sea in Kms. 5 C Lower Course 0
    • Valley & Channel Cross-Sections A B Upper Course Middle Course C Lower Course
    • The Work of Rivers The work of a river depends on its energy Energy a function of a. Volume of water b. Speed of water flow (dependent on gradient) c. Types of rocks
    • The Upper Course of a river Learning Objectives: •To know and understand the formation of landforms in a river’s upper course. •To understand the processes that operate in a river’s upper course
    • Upper valley characteristics “V”shape valley, vertical erosion dominant Interlocking spurs Slumping and landslides very active hill slopes Narrow, shallow channel, low velocity and discharge Large bed load derived from upstream and from valley sides
    • 1 2 3 4
    • Gorge of Ganga River
    • Interlocking spurs A typical upper course V-Shaped valley with interlocking spurs, steep valley sides and active slope processes. The diagram below shows the formation of interlocking spurs.
    • Waterfall formation Look at the diagram, How is a waterfall formed?
    • Water fall on Sharawati River
    • Formation of Rapids
    • Upper valley characteristics -River load Material that is transported by a river is called its load.
    • River load in upper course Why are they rounded? Boulders are large and semi-rounded, due to attrition within the load and abrasion with the stream bed and banks
    • The Middle and Lower Course of a River Learning Objectives •To understand the main processes that operate in the middle and lower course of a river. •To understand how meanders and oxbow lakes are formed.
    • Processes operating in the middle course of a river Erosion is still an important process. The river is now flowing over flatter land and so the dominant direction of erosion is lateral (from side to side). The river has a greater discharge and so has more energy to transport material. Material that is transported by a river is called its load. Deposition is also an important process and occurs when the velocity of the river decreases or if the discharge falls due to a dry spell of weather.
    • 1 2 Meanders 3
    • Direction of meander migration Floodplain Slip-Off Slope Erosion on the outer bend where there is faster flow. It creates a river cliff Deposits on the inner meander bend where there is low energy
    • Ox Bow Lake Formation Can you look at the diagram & explain the formation of ox-bow lakes?
    • Ox Bow lake on Mississippi
    • The Lower Course of a River Learning Objectives: To be able to describe and explain the formation of a flood plain, levees, delta .
    • Defintions Flood plains • A flood plain is the wide, flat area of land on either side of the river in its middle and lower course. Levees • Levees are natural embankments of silt along the banks of a river, which are often several metres higher than the flood plain.
    • Floodplain & Levee formation 1. 2. 3. 4. 5. Floodplains and leveés are formed by deposition in times of river flood. The river’s load is composed of different sized particles. When a river floods, the river water overflows the banks of the river and immediately slows down due to friction. This drops the larger particles first, building up a raised river bank called a LEVEÉ. The sands, silts and clays are similarly sorted with the sands being deposited next, then the silts and finally the lightest clays. This builds up the floodplain.
    • Levee formation
    • Delta Formation Deltas form at the mouths of many of the world’s larger rivers, e.g the Nile (Egypt), the Ganges (Bangladesh), the Mississippi (USA). A delta is a flat area of sand and silt built into the sea. It is formed by deposition. 1. When a river enters a sea or lake carrying large volumes of fine material, the velocity slows and causes the load to be deposited in layers. 2. Over time, the deposited material blocks channels and forms small islands separated by river channels called distributaries.
    • Deltas Deltas – a body of sediment deposited at the mouth of a river when the river’s velocity decreases. – A stream flowing into quiet water usually builds a delta. – The surface is usually marked by distributaries – small, shifting channels that carry water away from the main river channel and distributes it over the surface of the delta.
    • Mississippi Delta
    • Alluvial Fans
    • Human Aspects of Rivers :1. Chief highway of commerce and transport 2. Fertile soil 3. Generation of hydro-electric power 4. Construct dams (for irrigation, power generation, control on flood) 5. Fresh water – fishing, domestic consumption, sewerage, and industrial purpose 6. Political boundaries
    • Flooding
    • Human Interference: Urbanization, Industrialization, Water Pollution, Dam Construction- (Disturbing present ecosystem), Festival (Ganesh Utsav), Sand Mafiya. Ganga Action Plan  Launched in April 1986 in order to reduce the pollution load on the river. Spending Rs 901.71 Crores. Withdrawn on 31 March 2000. Phase-II of the program was approved in stages from 1993 onwards, and included the following tributaries of the Ganges: Yamuna, Gomti, Damodar and Mahananda.
    • Water pollution
    • Festival (Ganesh Utsav) Kumbha Mela