River engineering#Channelization
At a flow straightening the naturally occurring meander of a river are pierced at their necks. The river course becomes shorter and straighter; the water flows faster. In places where a river runs into an arm two arms often shut down. River regulation is a measure of river engineering.
Objective
Frequently river regulation serve to make the river for shipping available. Sometimes there is also the land reclamation or the permanent establishment of provincial, municipal and land boundaries in the foreground. If the river defined structurally, can - with appropriate hydraulic engineering measures, such as scheduled flooded areas - even a flood protection can be achieved. Due to silting, as a result of river regulation and other reclamation of swamps, malaria in the 1960s could be eradicated in Germany.
Usually, the flow loops or circulating mountains was only a relatively low embankments often performed by means of fascines, which was below the high water line in sediment-rich rivers next to the piercing. At high tide, the river could spread over the floodplain, decreased speed, the debris sedimented and increased the land behind the dam. Only when such a sufficient increase of the hinterland has been reached, a flood dam was created.
Known examples of a flow straightening the Jura water correction in the Swiss Zealand and the straightening of some Rhine - sections.
Disadvantages
Most rivers in the lowlands have a natural tendency to the formation of meanders and therefore to slow flow, which in lateral brownfields a natural flood protection brings. Occasionally the river breaks through its continuously extended loops and then look for a new bed. Also in some water gap may occur this is when the meander get too close to either side of the so-called circulation mountain.
Artificial straightening or too tight flow control can cause downstream flood risk increased. Due to the higher flow rate, it happens that now submit several feeder her ( coming quickly ) flood at the same time in the lower reaches. In this way, the significant accumulation of Elbe floods of recent times is to explain. For similar reasons, straightening in the mountain areas close to the source are made largely responsible for high water. In some places, therefore underway to them to undo what easier to manage than the large-scale adjustments in the middle or lower reaches.
From an ecological perspective river regulation are considered extremely problematic because they can affect entire ecosystems or even destroy it. Many and living in the water animals like fish, otters, shellfish or water birds and many species of plants can lose water flows, their habitat or parts thereof.