Vízügyi Közlemények, 2003 (85. évfolyam)
3. füzet - Rövidebb tanulmányok, közlemények, beszámolók
Szigetképzőilés és -fejlőilés a Maros határszakaszán 495 Picgay H.-Gurnell A. M.: Large woody debris and river geomorphological pattern: examples from S.E. France and S. England. Geomorphology 19. 1997. Rosgen I). L.\ A classification of natural rivers. Catena, 22, 1994. Somogyi S. (szerk.): A XIX. századi folyószabályozások és ármentesítések földrajzi és ökológiai hatásai Magyarországon. MTA FKI. Budapest. 2000. Tóth F. (szerk): Makó Monográfiája 1. Makó régi térképei. Makó, 1992. * * * Generation and development of islands in the River Maros at the Hungarian-Romanian border by György SIROS geographer and Dr. Timea KISS professor of biology and geography Before the river regulation works of the 19 t h Century islands were generated in a great number in Hungarian rivers, reflecting their energy and flow conditions. Upon the impact of the large scale river training activities most of these formations have disappeared and the morphological changes came along with the degradation of river habitats as well. One exemption in this context is the River Maros within river kilometres (r.km) 30 and 50, where nearly half of this river reach was straightened by the regulation works, which resulted in a new flow pattern and the generation of an increasing number of islands. There were islands in the River Maros even before the regulation, but they were mostly located along the inner arches of the river-bends and thus could be considered as bank-line sandbars, rather than actual middle-river islands. In the river reach investigated we identified the widened parts ot the channel (called here the "noduses"), which are the main locations of island generation. Among these locations the most complex one was the island and sand-bar system of Apátfalva and the related findings were the basis of important conclusions. The objective of this study was to investigate the impact of the river regulation activities of the 19" 1 Century in terms of the reactions of a relatively "abandoned" river reach in forming islands. In doing so we applied several techniques; géomorphologie mapping, dendrologic analysis and other GIS techniques. The results of the analysis can be summarized as follows: The géomorphologie analysis of the system of islands and sand-bars of the channel widening of Apátfalva indicated that the rate of the falling limb of hydrographs basically determines the shape and size of these formations. In this study area the formation of islands started from the mid-channel sand bars, subject to the rapid growth of vegetation and also to the longer lasting flood free periods. Subsequently the islands may move at a rate of 5-10 m/year. The formation and development of islands is a cyclic process in which the coreislands of the nodal points convert to real islands and later, with the shifting of the main streamline, will connect to one of the river banks. The main streamline changes frequently and this results in the opening or blocking of side channel arms. While aerial photographs and GPS surveys provided exact spatial data, the dendrological measurements could provide for the tracing of the development of the islands; Thus the two methods supplement each other in a remarkable way. The river reach is further divided by nodal sections into several segments in which the above mentioned processes can also be observed. On the b; isis of the rate of these processes the channel widenings can be split into two groups. In the upper part of the river reach investigated the nodal sections and the islands within them arc older slowly changing units, while in the lower part younger and more dynamic formations can be found. Thus one may conclude that the formations and the development of islands move towards downstream. In
