Sediment

As fluvial or fluvial ( Latin for " caused by rivers "; fluvius Latin for "river" ) sediments ( colloquially flow deposit ) is called in the geosciences by flowing waters entrained crushed rock.

Other Sedimentationsformen by hot water fluvioglazial ( hybrid of River / Glacier) and limnic and marine sediment ( lake or marine sediments ).

Fluvial transported sediments are usually well rounded and can include almost all rocks that occur in the catchment of each river or stream. They have grain sizes - depending on the location in the lower or the upper reaches of the water - fine sand to gravel -rich ( 0.1 mm to about 20 cm).

Variants

In fluvial transported sediments distinction is made between freight solution, suspended or suspending cargo and debris or sediment load.

Solution freight is the proportion of the total load that is transported dissolved in the water. The solids loading is not dissolved in water and is either jumping ( saltierend ) or rolling - sliding transported. Suspended solids are suspended due to their weight freely in the water column.

By transporting original edges are abraded. Water quantity and speed determine the size of the cargo in a stream section. A measure of this is the transport capacity of the flowing water. If the transport capacity from at constant bed load, the material is deposited ( sedimentation).

Whether in a stream section erosion prevails (machining of material) or sedimentation (deposition ), is expressed with a load ratio. This numbers indicate > 1 sedimentation, <1 erosion, and 1 balance.

Erosion occurs in the formation of river valleys in mountainous or hilly terrain, for example. In the sideways shift from meandering rivers occurs during cut bank erosion ( scour or subsurface erosion ) and the slip face in the deposition.

Effects

The fluvial transport can lead to significant deposits of sediments that accumulate eg in river terraces and in above or underground gravel banks - important sources of raw materials for gravel pits.

Most and most rocks are transported in rainy periods, especially during ice ages and floods. In the ice ages of the fluvial transport has led to the formation of many river terraces that characterize wide landscapes - such as in the Danube countries in the catchment area of the Rhine or in Poland and Russia. Floods can still lead to displacement of rivers, when a flood leading river sediment deposits be in a flat meander and blocked the way so even today.

Ecologically significant is in many rivers with low gradients that their mud at high tide in the riparian regions represents an important doping with nutrients. Examples are the former - to the construction of the Aswan Dam - annually taking place Nile floods, which were deposited the fertile Nile mud on the riverside fields and thus helped Egypt to intensive agriculture. The same is true for the major rivers in China, and this effect has also eliminated by the Three Gorges Dam in the Yangtze River; similar reasons for the alleged attack impoundment is criticized in the headwaters of the Euphrates.

The absence of regular floods can also - such as lead to the deepening of the river bed and lower the water table significantly - in the Danube regulation.