Vízügyi Közlemények, 1970 (52. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

EFFECT OF SEDIMENT CONDITIONS ON THE DEVELOPMENT OF RIVER-TRAINING METHODS by J. S AB AT H I EL

1 The development of water management entailed an expansion of the scope of river regulation, and the changes in flow regime resulting from river canalization frequently necessitated the reregulation of these rivers. The usual effect of weirs and barrages was to reduce the original river slope and consequently, in the development of the new bed the silt settling from suspended sediment assumed a role of an importance comparable to that of bed-load. The problems associated with suspended sediment demanded increasing attention in river regulation and promoted theoretical as well as practical statistical investigations into the origin, transportation and settling of suspended load. In earlier studies concerned with river bed development the role of suspended sediment was usually considered as of secondary importance. While it was recognized that considerable sediment volumes are carried in suspension, its influence on bed development was known to be small, affecting no more than sedimentation of the flood plain and the raising of river banks. At the beginning of the last century the common belief shared by all fluvial engineers was that suspended sediment passes almost imperceptibly down the rivers. And this was actually the case with the exception of estuarine reaches. The theoretical and physical laws governing the movement of bedload were more readily recognized and relationships describing bed-lead transportation were more readily established than in the case of suspended sediment (of course here, too, simplifying assumptions had to be introduced, respectively seme factors had to be neglected). The volume of suspended sediment depends much more on erosion and consequently on a variety of catchment properties, whereas bed-load transportation could be considered in terms of phenomena and forces occurring in the channel itself. Yet at the same time, considerable difficulties have been encountered when attempting to observe bed-load by accurate methods 1 Professor of Hydraulic Engineering, Technical University, Budapest, Hungary 3* 35