Regulation of mountain streams versus ecological balance as illustrated by the example of the upper Vistula basin (part II)

Streams of the Polish Carpathians are characterized by a high gradient as well as a great changeability of their volume and velocity of flow. The processes which take place in these streams are those connected with lateral, bottom and channel erosion. In order to reduce those types of erosion, various methods of channel regulation are used. In mountain streams these are mainly: river bars, drop hydraulic structuresand anti-debris dams. Regulation works (straightening of the stream channel and hydraulic structures), changes in the use of the river basin, reduction in debris supplies and exploitation of river alluvia have led to a signifi cant deepening of channels. This increases the risk of flooding associated with higher flows. Regulation works conducted within the channels and anthropogenic pressure in the areas adjacent to watercourses exert a negative effect on biotic communities. In most cases, changes in the structure of flows, in the stability of the river bottom and in the variety of habitats as well as disruption of the river continnum affect living conditions and diversity of vertebrates and invertebrates. The attempts at improving the ecological status of Carpathian watercourses through changes in hydromorphological conditions are connected with the implementation of European Union directives. Such actions include, among other things, replacement of traditional hydraulic structures by biotechnical ones, which are more eco-friendly. Their usefulness, however, still requires long-term monitorin