Valley floor
A relatively wide, flat area on the course of the river in a valley is referred to as a valley floor , valley floor or valley floor .
Forms and names
The valley floor is usually created by erosion and subsequent filling with sediments or other loose rock ( Sohlental in general), in the case of the explicit trough valley (with rock bed) also through direct glacier excavation, in the Kastental or Muldental through secondary erosion . In the case of a narrow valley floor, on the other hand, one speaks of the valley line , in the case of a short, particularly wide valley widening of a basin , in the case of more extensive valleys of basins ( landscape ) , or generally of river plain .
Expressions for smaller valley floors - also in the sense of regional landforms - are for example Tobel or Kar . Soils that are not hydrographically conditioned are the sinkholes of the karst or volcanic calderas .
Origin and use
Wide valley floors are particularly found in alpine trough or U-valleys , which often also have valley shoulders at medium altitude . They generally go back to the erosion of Ice Age glaciers . Many mountain valleys formed by glaciers are divided lengthways by a series of valley steps into which the meltwater streams cut gorges . At the gorge exits at the foot of the steps, in particular, small valley floors from deposited river gravel formed early on . The valley floor can be built up from gravel of widely varying grain size . In addition to the river bed, there may be flat terraces, backwaters and temporarily flooded alluvial forests . These fluvial sedimented valley fillings have often been partially removed again by renewed erosion processes. Of the resulting valley races , mostly only the lowest is included in the valley floor.
With a suitable altitude, near-surface water balance and microclimate, valley floors represent economic core areas of mountains, as they can be relatively easily populated and used for agriculture. The valley settlements can be found - depending on regional building tradition , tanning or any environmental hazards - partly in the valley floor itself, but mostly on the higher terraces or the debris cones of the side streams or on sunny flat surfaces in the lower slope area. The valley floors of high alpine valleys are often threatened by avalanches or landslides , while the lower areas are more threatened by torrents and debris flows . Post- glacial silting processes have often led to the formation of wetlands that are used as alpine pastures or, less often, as orchards . In some have raised bogs can develop that have become as rare habitats mostly now under protection are.
Occasionally the suffix -boden is also used to identify locations on the valley floor (e.g. Bodenbauer or Mooser- und Seeboden ) or location-specific companies (e.g. Talboden-Immobilien or Raiffeisenkasse Lienzertalboden ).
Traces of former valley floors
In high valleys in the east of the Alps or in the inland basins, there is gravel known as Augensteingerölle . They show that before the elevation of the Alps (mostly since the Miocene ), today's high altitudes may have been valley floors, such as the Miesboden in the Kemet Mountains (Styria), some flat areas near the Rax and Schneealpe (Lower Austria) or the South Tyrolean Fanes group .
For large alpine valleys such as Inn , Eisack / Etsch , Salzach , the trough bottoms of the older, great ice ages ( Mindel , Riss ), in which the rivers have once again carved themselves and which were drained again below by the later glaciers ( Würm ), according to the Tyroleans, are characteristic Low mountain ranges or the high-lying exits of the Tauern valleys .
See also
Web links
- The old valley floor of the Etsch (South Tyrol)
- Glacial geomorphology in Austria
- The valley floor of the Wutach Gorge
- Lienzer Talboden region, Hohe Tauern National Park
- Flood protection in the Uri valley floor (PDF file; 2.78 MB)
Remarks
- ↑ Valley line is also the orographic technical term for the line model of the valley, which mostly, but not necessarily, corresponds to the course of the river as a two-dimensional object. The valley line and the ridge line form the orographic terrain profile .
- ↑ All of these terms include the designation for the landform including its characteristic slope shapes.
- ↑ cf. for this the expressions old and young moraine