International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage

Multilingual Technical Dictionary (MTD)
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Term No.Term Name/Term DescriptionAction
2266
Crib weir
A permeable weir formed by timber cribs. Cribs are constructed of round timbers in a block-house like fashion, sometimes with transverse walls. The timbers are joined together at their intersection with clamps, nails, or bolts. The cribs are filled with gravel and stones......
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2267
Brushwood weir
A permeable weir whose body is formed by brushwood, round timber and gravel.
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2268
Falling crest weir, or Falling shutter weir
A weir having falling shutters fitted along its crest that may be put down to pass floods. Falling crest arrangement is installed in both permeable and impermeable weirs......
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2269
Movable weir, or Collapsible weir
1 - A general term used to denote all barriers that may be opened in whole or in part. The movable part may consist of gates, stoplogs, needles, wickets or any other device whereby the area of flow through or over the weir or dam may be controlled. 2 - In Sudan, this term is used only for a special type of regulator consisting of a weir-shaped prof.....
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2270
Shutter weir
A weir fitted with shutters.
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2271
Rolling weir
1 - A weir with roller gates fitted on its crest. 2 - See 2957.
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2272
Segment gate weir
A weir fitted with segment gates on its crest.
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2273
Flap weir, Flash board weir, or Tilting gate weir
A type of movable weir in which a hinged leaf gate rotating about a horizontal axis is installed at the weir crest. Also called `flash board weir`......
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2274
Inflatable weir
A weir constructed of neoprene reinforced with nylon and anchored to a concrete foundation. The weir inflates by water pressure and automatically deflates when the upstream water reaches a prescribed level......
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2275
Flash weir
A device provided on rolling gates on weirs to increase freeboard or to prevent the passage of ice or trash over the top or to protect it from the effect of waves in closed position......
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2276
Needle weir
A movable weir where the headwater level is manipulated with the help of `needles` (See 2891).
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2278
Weir head
1 - The vertical height from the crest of a weir (apex of a V-notch weir) to the water surface in the forebay above the weir. It does not include the head due to velocity of approach. 2 - The energy head of the water referred to the crest of the weir that does not include the velocity head due to the velocity of approach......
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2279
Designed maximum head across the weir
The maximum difference in elevations that may occur under any set of conditions between the upstream and downstream water levels of a weir......
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2302
Vertical drop weir, or Overfall weir
A weir when the flowing water nappe separates from the weir body at the crest.
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2303
Step weir, or Cascade weir
A type of drop weir, when the drop is broken into a number of smaller drops.
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2304
Side weir
A weir over which water flows approximately parallel to the crest.
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2305
Ogee weir
A weir having a crest with an ogee shape (See 2747).
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2306
Irregular weir
A weir with irregular or zigzag crest as seen in plan (illustrated).
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2307
Oblique weir, or Skew weir
A weir with its crest inclined to the direction of flow as seen in the plan (illustrated).
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2308
Inclined crested weir
A weir with a sloping crest from one side to the other (illustrated).
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2309
Narrow-crested inclined weir
A weir formed by projecting an inclined wall (upstream or downstream) from the bed of the channel. Briefly, these are called `inclined weirs` (illustrated)......
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2310
Curved weir
A weir having a curved crest as seen in plan.
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2311
Parabolic weir
A measuring weir whose notch is bounded on the sides by parabolas (illustrated).
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2312
Circular weir
A measuring weir having a circular crest (illustrated).
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2313
Weir with linear flow characteristics, or Proportional weir
A weir, where the rate of flow is simply proportional to the head over the weir, i.e. Q = ha where Q = discharge, h = head over the weir, a = a constant depending on the weir dimensions and the sharpness of the weir plate. The shape is determined by the equation .....
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