Barrage (dam)
A barrage is a system for damming a river to control the water level upstream and downstream. Mostly located in a impounded river section after another several barrages.
It is - in contrast to a dam - a dam that blocks the flow only and not the entire valley width substantially. It consists of military and, if necessary, a power plant and a ship lock system. Above a barrage is the impoundment, which is occasionally a lake-like expansion ( reservoir) and is bounded laterally depending on the terrain of impoundment dams.
The main shut-off is usually a defense, rarely a dam or a dam. Depending on the design, a distinction between different weirs:
- Controllable (Portable ) Weirs:
- Non-taxable (fixed ) Weirs:
The shape of the weir crest can be performed open-crowned, rounded streamlined or sharp-edged. The shape affects both the discharge capacity at a given upper water level and possible underwater influences.
On the weir crest is generally a flow change from streams for shooting a. This flow change goes hand in hand with an acceleration of the outflow on the defensive backs. In some circumstances, provide a backwater on the weir crest in larger drains and / or at low weir heights of the relatively high lower water level. The ideally perfect ( through underwater undisturbed ) attack then proceeds in an imperfect raid, with an increase of the water level in the headwater.
Larger weirs are usually armed with several fields equipped with military closures (regulatory bodies ), which can be operated separately. For security reasons, weirs should have a field more than necessary (n- 1 rule), so a risk can fail during flood events due to revision or Verklausung.
On navigable waters have barrages via locks to allow the shipping overcoming the height difference.
In order to ensure the continuity of the flowing water for aquatic organisms, increasingly bypass channels and fish ladders are ordered or carried out a part of the fortification as a gently dipping ramp rough.
Examples of regulated by barrages navigable rivers are:
- Upper Rhine between Basel and Iffezheim
- Main, see List of Main barrages
- Mosel, see List of Mosel barrages
- Elbe above Ústí ( Ústí nad Labem )
- Danube between Vienna and Jochenstein (details: Austrian Donaukraftwerke AG)
- Neckar, between the mouth of the Rhine and Plochingen
Very small barrages are used to discharge measurement (level). The height of the water level above the transfer case provides information on the amount of water flowing. The attack of a level usually contains a triangular cut-out for small amounts of water.
In the sloppy sound of radio hosts a barrage is an indicator of a traffic jam on the road.