Vízügyi Közlemények, 1970 (52. évfolyam)
4. füzet - Rövidebb közlemények és beszámolók
total work is minimum, since over each elementary length the work performed is proportionate to the square of the change in direction occurring at that point. The resulting configurations are composed of sinusoidal curves which actually represent a fair approximation to meandering rivers. The shape of the channel cross-section is also an important factor in river regulation. The channel shape is preferably characterized by the ratio of surface width and water depth. A certain required depth must in the majority of cases be ensured in the interest of navigation. Experiments performed at several laboratories, with results checked against field observations, have led to the conclusion that a relationship of the form (5) ]h(Bi\ l •Di IBJ is bound to exist between the original water depth Ц L and surface width Bi, as well as the corresponding values D 2 and B 2 applying to the constricted section, where © must be greater than 9/14, but smaller than 6/7. These relationships have been derived under the assumption that the constricted bed should be capable of conveying the original discharge by an appropriate increase of depth. Changes in the channel which are the objective of river regulation must be designed essentially on the basis of the ratio of the actually transported sediment load and. the sediment carrying capacity of the watercourse. This can be attained by relying on the sediment balance equation or by applying purely hydraulic relationships, or else the relationships describing sediment transportation itself may be taken into consideration. Whichever method is adopted allowance should be made for the fact whether the channel may be regarded as stable, or it is of a degrading or aggrading character. Essentially the objective of regulation is to attain that the sediment carrying capacity of the regulated channel should equal the actual sediment load transported by the river. Here again the result leads to a relationship between the width and depth of the regulated channel as well as the actual width and depth in the original condition. The construction of weirs or minor fixed pondage dams presents obviously special problems in river regulation. Special attention should be paid in these cases to the upper portion of the backwater reach and to the section downstream of the weir to avoid adverse sediment conditions there. 2. Effect of sediment conditions on the development of river-training Contemporary river regulation meeting all requirements is impossible unless the influence of suspended sediment is taken into consideration with a weight equal to that of bedload. The suspended sediment load of watercourses depends primarily on the availability of sediment, that is on the catchment area, and to a lesser it
