Carbonate, fine to coarse material rich low mountain range

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River type 9.1: The Gera at the confluence of the Wilder and Zahmer Gera
The Aurach near Roth, subtype 9.1_K

The low mountain range river (type 9.1), rich in fine to coarse material, is one of the types of flowing water specified by LAWA as part of the implementation of the Water Framework Directive . Due to the special characteristics of the rivers in the Keuper area , the subtype 9.1_K exists for these waters: Carbonatic, fine to coarse material-rich low mountain rivers of the Keuper .

structure

The waters occur in limestone or chalk areas of the low mountain ranges. They mostly flow in a winding to meandering course in sole valleys . Their transverse profile is flat to moderately incised, impact and sliding slopes are pronounced. The flow speed changes strongly and regularly. The sole is made depending on the catchment area of stones, gravel or pebbles, partly sand comes in relatively large amounts. Box-shaped profiles with steep banks occur naturally in the Keuper areas. The bottom there consists mainly of sand or clay, the flow speed of the rivers is much slower. In the karst areas, the water has a blue hue, especially near the springs.

Due to the size of the catchment area of ​​100 to 1000 km², the carbonate low mountain rivers are separated from the fine or coarse material rich brooks of the low mountain range (type 6 or 7) on the one hand and the large rivers of the low mountain range (type 9.2) on the other. The low-lime variant is the silicate, medium-mountain river, rich in fine to coarse material .

Flora and fauna

The invertebrate inhabitants of these rivers have to be adapted to the predominantly fast currents and the hard substrates. There are mayflies - and caddis larvae before, in addition to larger stretches of sand shells as the river mussel . The fish are mainly represented by current-loving species such as grayling , chub or loach , but also by species that prefer calm water. In the waters of the Keuper, there are mainly undemanding species such as roach , bleak and perch .

The aquatic plants are represented by spawning herbs such as the streaky pondweed or the floating pondweed and other plants such as the simple hedgehog . In the Keuper areas there are mainly aquatic mosses and the crested pondweed .

Examples

swell