Author(s): Maria M. Botcheva; Vania D. Ioncheva

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Abstract: The formation of rivers’beds is a self-adjustable processwhich is directly related to the ability of the flow to transportsediment materiais.Depending on the rivers′water-sediment regime,the granulometric composition of bottom deposits and the basiccharacteristics of the flow,this process has different intensityboth in separate rivers and in various regions of the same river aswell as during different time periods.In Bulgarian rivers,whichare mountain ones,characterized by great variations in their waterand sediment outfilow,the bed-forming processes are distinguishedby the appearance of considerable erosion-accumulative effectsresulting in deformarions of the river beds not only in the verticaldirection but also along the meanders.The activation of theanthropogenic factor,and more particularly,the removal of largedeposit quantities for subsequent applications as inert naterials inconstruction,has an adverse effect on the natural formation of theriver beds.In order to restrict the undesirable bed deformations,river training is most often carried out,consisting in straighten-ing of the beds,formation of trapezium-shaped cross-sections andconstruction of protective engineering structures.The establishmentof the dimensions of rivers'cross-sections upon training is basedon the relationships between the geometrical and the hydraulicparameters of the flows and the size and quantity of the transport-ed bed-load sediments.

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Year: 1989