Vízügyi Közlemények, 1970 (52. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

but of course to be successful, consideration must be given to the natural conditions under which the particular relationship has been derived. Checks on relationships derived for bed-load transportation have revealed during the study of river stretches regulated earlier [2, 13] these relationships to be correct and valid. However, the results obtained by them are unreliable if the channel bottom is cemented and the discrepancy between theoretical and actual rates of bed-load transportation is especially wide where river regulation is accompanied by channel dredging. The volumes of bed-load set into movement under similar conditions may be greatly in excess of those indicated by the bed-load formulae. A combination of the regime theory and the equations derived on physical foundations is presented in the paper by Kotsheyev [7], in which the planning and design of ford-regulation is described. In the theoretical analysis spur dikes are regarded as submerged weirs, allowance is made for lateral contraction and the flow velocities in the condition after regulation are determined in this manner. In keeping with the classical approach to river regulation, his primary objective 1з to create velocities high enough to ensure the desired water depth in the ford-section. To estimate the critical velocity which causes already scouring of the channel bottom, the formula of Samow is recommended: v = 6-Yd-fH which is based on practical experience and is the result of a great number of field observations. Whereas in the paper of Kotsheyev the contracting influence and weir-like behaviour of spur-dikes is emphasized and adopted as the basis of estimation, the increase of bed roughness due to the spur dikes is considered by Kornatzky [61, who performed a series of experiments and observations in the field to determine the most effective spacing of spur dikes at which silting is produced in the fields between them. These investigations relate to the method of river regulation by spur dikes (the so-called German method of regulation) in contrast to the method used in Hungary (French regulation) in which the spur dikes are used only to control the concave bank [14, 15]. The conclusions arrived at are valuable in river regulation and were implicitly observed in earlier regulation work as well. According to the conclusions of Kornatzky, to obtain the desired silting effect the spur dikes should be spaced at distances corresponding approximately to one and half times the length of the dikes. In Hungarian river regulation practice each second or even each third of the contemplated spur dikes were only built in the first stage because of the uncertain influence of spur dike spacing. Those omitted have been added at a later date only, if the concave bank failed to develop in the desired manner under the influence of the dikes first built. 38