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    Weirs and Canal Intakes: by Vaibhav Sharma 121665 D2

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    Vaibhavishappy
    asasas

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    Weirs and Canal Intakes: by Vaibhav Sharma 121665 D2

    Uploaded by

    Vaibhavishappy
    41 views13 pages
    asasas

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    121665

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    asasas

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    41 views13 pages

    Weirs and Canal Intakes: by Vaibhav Sharma 121665 D2

    Uploaded by

    Vaibhavishappy
    asasas

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 13

    Weirs and Canal

    Intakes
    By vaibhav sharma
    121665 D2

    Weirs and Canal Intakes


    Main Types of Weirs
    Sharp Crested Weir
    Broad Crested Weir
    V-Notch Weir

    Main Types of Canal Intakes


    Lateral Intake
    Bottom Intake
    Overhead Intake (Inlets in piers are used for water intake)

    Weirs and Canal Intakes


    Lateral Intake with damming
    Uses a Weir or similar hydraulic control structure to maintain a
    minimum stage
    Allows the off take structure to continue operating regardless of
    river conditions
    Harder to design and build than a lateral intake without damming
    Will have a higher environmental impact than a lateral intake
    without damming

    Weirs and Canal Intakes


    V-notch weirs
    Found all over the world because construction and installment is
    very straightforward
    Used primarily as a simple flow measurement device
    A relationship between flow height through the notch and
    discharge is easily developed and measurable in the field
    Q=(g/2)1/2*yc5/2
    Where: Q is discharge, g is gravity, and yc is the height of the water
    through the notch

    V-notch weir used for flow measurement

    Weirs and Canal Intakes


    Weirs can also be used to improve fishing conditions
    Fishing weirs found all over the world, some are very simple and
    some involve complex engineering
    Backup of water upstream of weir creates a holding place for fish

    Fishing weir used to trap fish in a bay near Taiwan

    Weirs and Canal Intakes


    Bendway weirs are used to redirect flow in meander bends in
    rivers
    The objective of the bendway weirs is to improve navigation
    through tight bends.
    Usually angled 20-30 upstream
    The weirs are low enough that ships can pass even in low flow
    They are high enough so that they significantly control nearbed velocities and redirect near-bed streamlines
    Built in sets of approximately 4-14 weirs per bend

    Weirs and Canal Intakes


    Bendway Weir:

    Weirs and Canal Intakes


    Recreational uses:
    Weirs are often built to create pools for swimming and recreation

    Swimmers enjoying the pools created by a weir

    The water drop created by a weir on the downstream side can be


    used for boating and tubing

    Kayaker surfing downstream of a weir

    Weirs and Canal Intakes


    Habitat considerations:
    A large drop off the downstream edge of a weir can create a
    barrier to upstream fish passage
    Weirs can be built so that they maintain or enhance fish habitat
    Rock ramps on the downstream end of weirs create riffle habitat
    instead of a small waterfall

    This weir on the South Platte creates a


    backwater condition to slow velocities and
    prevent bridge pool scour, but also creates riffle
    habitat and does not impede upstream fish
    passage

    Weirs and Canal Intakes


    One type of habitat-enhancing weir is a Newbury Riffle
    Newbury Riffles are installed as a combination grade control
    structure/habitat improvement
    The weir backs up water into a pool, and the riffle maintains
    fish passage

    Series of Newbury Riffles

    Weirs and Canal Intakes


    Weir Construction:
    One simple way to construct a weir is to use sheet piles driven
    into the river bed to a depth 2-3 times the maximum scour rate
    Regardless of the construction material, the sides of the weir
    must be tied into the banks with riprap or sheet pile to keep the
    water from getting around the weir
    For weirs with ramps on the downstream side, rocks must be
    placed carefully to maintain desired slope over backside of weir
    When multiple weirs are used for grade control, they must be
    constructed so that the energy slope in between structures
    matches that needed for sediment control

    Weirs and Canal Intakes


    Weir Failures:
    When weirs are not adequately constructed or not tied back into
    the bank, failure can occur
    Failed weirs can cause dangerous situations for animals,
    navigation, and recreation

    Failed concrete weir on Clear Creek

    Weir lacking adequate tie-back

    Weirs and Canal Intakes


    Conclusions:
    Weirs and Canal Intakes have a huge range of uses and designs
    They must be designed properly so that they function as intended

    The triple weir on the Avon River in Bath (There


    is a lock on the right side to allow for navigation)

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