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    River System 23-24

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    hadnmade14

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    © All Rights Reserved
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    River System 23-24

    Uploaded by

    hadnmade14
    13 views26 pages

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    © © All Rights Reserved

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    PDF, TXT or read online from Scribd

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    Copyright:

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    13 views26 pages

    River System 23-24

    Uploaded by

    hadnmade14

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
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    You are on page 1of 26

    River Systems

    You will learn:


    • Where do rivers begin?
    • How are river systems formed?
    • What are the parts of a river system?
    • What is a drainage basin?
    Rivers and
    Hydrologic cycle
    The Course of a River
    •A river is a natural stream of water flowing in a
    channel
    • The source is the place at which a river begins
    • It may be melting snow from the top of a mountain
    or a lake with a stream flowing out from it
    • Due to gravity, the river flows downhill from its
    source
    • The path that a river follows is called its course
    • The part of the river near the source is called the
    upper course
    • The middle part of the river is called the
    middle course
    • Near the end of the river is the lower
    course
    • Theplace where the river flows into the
    sea or ocean is called the river mouth
    The River System
    • Streams or other rivers may join the course
    of a river
    • They are called tributaries
    • The point at which a tributary joins the main
    river is called the confluence
    • The river and its tributaries form the river
    system
    The Drainage Basin
    • Rivers
    drain the surrounding area by collecting
    surface run-off and directing it to seas or
    oceans
    • The area that is drained by the river and its
    tributaries is called the drainage basin
    • The boundary of a drainage basin is marked by
    surrounding highlands and is called the
    watershed
    The Drainage Basin (cont’d)

    • The watershed
    separates one
    drainage basin
    from another and
    is also known as
    a divide
    Action of Rivers
    •Ariver and the sediments it carries can
    erode the river bed and its banks
    • Over time, a channel is cut into the
    land
    • The
    channel eventually deepens to
    form a valley
    Valleys
    • One of the results of the action of rivers
    • The shape of a valley depends on how the
    river cuts into the land
    • In the upper course, the
    river is flowing down very
    steep slopes
    • Enough energy to cause
    great erosion
    • Cuts deep into the land and a V-shaped valley
    forms
    • A steep-sided valley with river flowing at the bottom
    is called a canyon
    • Inthe middle course, the river
    flows across less steep land
    • Cuts less deeply into the
    land
    • Erodes the land sideways and
    downwards
    • Starts to deposit sediments
    • Sides of valley becomes wider
    • In
    the lower course, the land is
    almost flat
    • Bends in the river are very
    pronounced
    • More sediments deposited
    • Erosion of bends continues
    • Deposition of sediments along its
    channel results in a wide, flat-floored
    valley
    Rapids and Waterfalls
    • River flows over alternating
    bands of hard and soft rocks
    • Soft rocks erode faster
    • Hard rocks jut out
    • A series of small and short falls
    develop
    • These falls are known as rapids
    •A waterfall is a vertical
    flow of fast-moving water
    from a great height
    Rapids and Waterfalls (cont’d)

    •A waterfall usually forms when a river flows


    over hard and soft rocks
    • The soft rock is eroded more quickly
    •A ledge is formed over which water falls
    • The
    force of the water is so great that it cuts
    a depression or plunge pool at the bottom
    Meanders
    • Curves and bends in the lower course of
    the river
    • Formed when the river erodes sideways
    and deposits sediments on the opposite
    banks of the curves
    Deltas
    •A river deposits its sediments when it flows
    into the sea or a lake
    • The
    deposits build up and block any further
    movement of the river
    •A river has to follow other routes called
    distributaries
    • Distributaries branch out from a river
    Deltas (cont’d)
    • A delta is a flat, low-lying area where layers of
    sediments have been deposited over time
    • For a delta to form
    • The river must be carrying a lot of sediments

    ◼Currents along
    the coast must
    not be too strong
    to carry away the
    sediments faster
    than they can be
    deposited
    GROUP ACTIVITY
    GROUP ACTIVITY

    Explain and justify why you


    decided to position your river
    system in that way.

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