The term derives from the river known to the ancient Greeks as (?aia?d???) Maiandros or Maeander, characterised by a very convoluted path along the lower reach. The Meander River is located in present-day Turkey.

Meander is composed of upper branch (upstream), arch and lower branch (downstream). Between two branches is spur or penninsula, which is connected with surrounding land by neck of meander.

There are two banks of meander:

Outer bank - water flows fastest on the outer bank of the river where the channel is deeper and there is less friction. This is due to water being flung towards the outer bend as it flows around the meander, this causes greater erosion which deepens the channel, in turn the reduction in friction and increase in energy results in greater erosion. This lateral erosion results in undercutting of the river bank and the formation of a steep sided river cliff.

Inner bank - on the inner bank water is slow flowing, due to it being a low energy zone, deposition occurs resulting in a shallower channel. This increased friction further reduces the velocity (thus further reducing energy), encouraging further deposition.  

 

Formation of meander:

Dicect flow of stream or river may assume a meandering course, then starts erosion of sediments from the outer bank and depositing them on the inner bank. As the outer banks of a meander continue to be eroded through processes such as hydraulic action the neck of the meander becomes narrow and narrower. Eventually due to the narrowing of the neck, the two outer bends meet and the river cuts through the neck of the meander. The water now takes its shortest route rather than flowing around the bend. The old meander bend is called abandoned meander. Deposition gradually seals off the old meander bend forming a new straighter river channel. Due to deposition the old meander bend is left isolated from the main channel as an ox-bow lake. Over time this feature may fill up with sediment and may gradually dry up (except for periods of heavy rain). When the water dries up, the feature left behind is knwon as a meander scar.  

Meandering progress depends on the conditions of the river flow, and on the rock surface its valley is made of. In areas that consist of material of low morphological valence (a non-consolidated material or that its consolidation quality is low, so that the erosion and alluvium processes act in an easier manner), meander development occur more frequently. Meanders that develop in a non-consolidated environment are called free meanders, because they are free to relocate their path from one river bank to the other. Solid rock areas, with a high morphological valence, support the development of "enclosed" meanders, their movement is limited and the stream erodes downwards, its established meandering pattern will remain as a deep valley known as an incised or entrenched meander.

  

Ke splnení této Earthcache musíte najít odpovedi na následující otázky a poslat mailem pres muj profil:

  

Zastavení 1 -  MOST (N 49° 46.820 E 018° 25.050) - postavte se na most a pri pohledu po proudu reky zjistete, který typ brehu je na levé a pravé strane toku (jesep nebo výsep)?