Flood dam

A flood dam is colloquially a dam along a river , while the word dike is the technical term for this structure. In landlocked countries, however , dykes are mostly associated with engineering structures on the seashore .

Dams on the Inn near Bever

Flood protection

Protection against flooding is usually provided by earth dams parallel to the river, the core of which can also be reinforced by large stones or concrete.

Dams on the Rhine near Schaan / Vaduz

While large rivers mainly have continuous protective structures, there are often dams on flat banks that protect individual villages or lowlands - for example at the Oderbruch . In the case of smaller rivers, hydraulic engineering is sometimes limited to such variants in order to avoid unnecessary effort and excessive interference with nature.

An absolute flood protection is not technically possible - you calculate statistically mostly with events such as 50- or 100-year floods , possibly also with probabilities over several centuries . If other unexpectedly large floods, the dam is also with sandbags or by dredging zoom geschafften boulders amplified (a so-called Aufkadung ). However, these makeshift measures only protect to a limited extent against very long infiltration of river water, as the dam breach on the Austrian-Slovak border river March showed in April 2006.

Hydraulic engineering

Many flood dams are provided with additional facilities, e.g. B. with pumping stations , sluices or other regulations for the overflow , for example to floodplains. Often they are combined with retention basins , or in nature conservation for doping wetlands . For several decades, care has also been taken to ensure that river regulation does not lead to a falling groundwater level in the surrounding area.

Decreasing strength of dams or too much seepage water can be stabilized by sealing walls . After prolonged floods they will i. d. Usually checked for stability and tightness or special seals can be obtained by injections. Insights into stability and possible reductions obtained also periodic leveling along the dam crest.

More functions

Road on a dam on the Buna in Northern Albania

Many flood dams have other functions besides their main purpose. You can e.g. B. serve as a road embankment (e.g. Hubertusdamm near Vienna), be combined with locks and other hydraulic engineering facilities , designed as green strips on their edges or delimit a nature reserve from the surrounding area, such as on the Rhine or the March and Danube floodplains . In the latter, they are also used for the targeted doping of the wetlands with river water in order to prevent the risk of their drying out.

Most of the wider dams also have hiking trails , such as the flood dams on the Danube, Inn, Elbe, etc. The banks of the Rhine or various cycle path networks in Germany, Switzerland, Austria and the Czech Republic are of special tourist importance .

Disadvantages to large river barriers

In severe floods, dams can also have detrimental consequences, especially for sections of the river downstream. During the Elbe floods in 2002, it became clear that the strong river barriers in the upper reaches (Czech Republic) and in larger tributaries (in Germany mainly the Weißeritz and Mulde ) significantly increased the Elbe floods. The main reason is that most of the earlier floodplains in the flat lines of the upper reaches of the river have fallen victim to construction. As a result, floods can hardly be "stored" any longer, the flow speed increases sharply - and the problem is shifted to the underflow. If, therefore, several large tributaries swell at the same time (for example in the case of widespread heavy rain like 2002), a catastrophic flood is the result.

Individual evidence

↑ cf. Definition of "river dike" according to DIN 19712

[1] . Definition of "river dike" according to DIN 19712