Vízügyi Közlemények, 1970 (52. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

Agavnadsori section thereof. Repeated checks have revealed, however that a critical Q, value can be determined for each river, below which Eq. (11) looses its validity. This phenomenon is likely to be related, beyond the aggradation of the bed, to hydrological characteristics of the catchment area, erosion conditions, the composition of sediment, etc. This conclusion is corroborated also by the investigations of Razoumyniha, К. V. [9] into the applicability of various formulae suggested for the estimation of sediment transporting capacity. A comparison the result computed from the formulae suggested by E. A. Zamarine [25], Gostounskyi, A. M. [19] and A. V. Karaoushev [20] with actually observed data revealed as one of the main cause of the difference between theoretical and observed data the failure to observe the granulometric composition of the bottom layer, i. е., the determination of the composition of suspended sediment in the vicinity of the bottom is omitted. The results observed by Karaoushev [20] on several plain-land rivers of the Soviet Union, the regime of which shows a single high-water peak in spring, indicated a very good agreement with the results obtained by the formula с = 150 N G (12) h* suggested by him. In the formula N = a coefficient depending on the С coefficient of the Chézy formula, and G = a coefficient, the magnitude of which depends on the granulometric composition of the sediment, the morphological, erosional and meteorological, etc. conditions of the catchment area. Hydrometeorological and morphological conditions were found to necessitate the classification of rivers into at least three groups. Within individual groups the magnitude of the correction factor must be determined in terms of the duration, time of occurrence, magnitude and number of the flood waves (sometimes distinctions must be made even for the rising and falling branches of flood hydrographs). The significant influence of hydrometeorological and erosion conditions in the catchment is emphasised also in the paper by I. V. Bogoly oubova [2], who processed the 20-year long record of observations performed on the Mzoumte river in the Caucasus mountains and concluded therefrom that a positive correlation can be demonstrated to exist between sediment composition and the rate of streamflow. By analysing the composition of the material settled along reservoirs it is observed that the particle sizes decrease towards the dam section and that they can be classified broadly into three typical groups. All bed-load, forming about 45% of the total sediment discharge, was settled in the reservoir and beyond this, 24% of the suspended load was also retained thereein. 74