Sand-shaped stream
Sand-shaped stream is the name of a type of flowing water specified by LAWA in the north German lowlands (type 20). There is the subtype sand-shaped, tidal river of the lowlands (example: Lower Elbe ).
Water structure
These waters flow in wide, flat lowlands, often in glacial valleys . They are mostly winding to meandering, whereby the current can be sometimes weak, sometimes relatively strong. The river bed is next to sand and gravel often made of organic materials, as well as large quantities of dead wood, often overturned in the form of trees. Islands, deep channels and fords occur naturally . In some cases, large-scale relocations and splits take place. However, due to the straightening and embankment of most of the sand-shaped streams, this is hardly possible.
The catchment areas of the rivers are larger than 10,000 km².
Flora and fauna
Many different species of creatures can be found in sand-shaped streams. Species that require stable sand and gravel deposits are predominant. There are pea clams , various mayflies and dragonflies such as the common wedge maiden . Fish such as bream , barbel and bleak , which prefer flowing waters, as well as still water species such as tench , bitterling or mud whip , which live in the floodplains , are also found, as well as migratory fish such as salmon and sea lamprey depending on the season .
Knotted pondweed is predominant in the bank areas of these rivers , together with other floating leaf plants such as the floating pondweed . Plankton is also present in the waters, but its density depends heavily on the amount of runoff from the rivers.
Examples
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- Profile of the river type 20 on wasserblick.net (PDF file; 148 kB)