Vízügyi Közlemények, 1970 (52. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

The regulation of major navigable streams presents always a highly complex problem. The difficulty is especially great on sections where great volumes of sediment are transported and in the loose alluvial bed considerable sand-bar travel occurs. Over similar sections the alternation of scouring and silting sections, the development of shallow fords are the causes which make the required navigation depth and width difficult to maintain. The regulation of the Hungarian Upper Danube and especially the development of the low-water channel can be traced for more than hundred years back and is thus a source of valuable empirical information. It should be noted here that studies and investigations of this nature are still rare, although it is exactly the comparison of regulation methods and the consequences resulting therefrom in the field which may offer the greatest help in selecting the efficient method of regulation. In planning river regulation measures the correct solution of detailed problems is almost as important as the development of the general concept. One example for these is the determination of the most effective spacing and crest elevation of regulation spur dikes. Especially on great streams the spur dikes are very expensive and to be economical their number should be minimized. Recent investigations have shown that the spur dikes can be built at greater distances without impairing their efficiency. The same applies to the crest elevation of spur dikes which should be built, it seems, to a height somewhere between mean low stage and annual mean stage. As will be appreciated from the foregoing it is impossible to select the most efficient method of regulation, unless sediment conditions are properly understood. Thus it follows that studies and research capable of offering the required design criteria are necessary before regulation can be attempted. It should be obvious, however, that besides the knowledge of sediment conditions other information is also necessary. Information on river regime is obtained from hydrological studies while investigations into river training are essential for selecting the appropriate regulation method. Consideration of flood control problems along the river is also necessary while biological research is required in connection with the quality and supply of water in abandoned branches and beds created by regulation. A great number of questions requires to be cleared also in connection with construction work associated with regulation. 3. Theory of boundary conditions of sediment movement Most important information on the phenomenon of sediment transportation can be gained perhaps by studies into the boundary conditions of incipient sediment movement. Studies into this critical condition are all the more so justified since substantially all of the current problems are intimately related thereto. It should be appreciated that the development and variation of bed configurations (ripples, dunes, antidunes, etc.), the movement and distribution 13