Vízügyi Közlemények, 1965 (47. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

'(44) During investigations into the roughness coefficient, close agreement was found under the particular experimental conditions between values calculated for the roughness coefficient by Agroskine's, Strickler—Manning's and Lindquist's method (Table IV

). For this reason it was found most convenient to use the formula of Strickler, Manning, Lindquist, С = A-jRV. for describing roughness. Subsequently, founding on results presented in Table III, as well as in Figs. 4 and 5, it is demonstrated that for the canal under study the value of к in the formula of Manning, Strickler, Lindquist is unaffected by the extent of bed-fullness. Investigations aiming at the practical determination of the roughness coefficient, with results summarized in Table V, led to the conclusion that each of the experimental sections denoted in Fig. 1 must be characterized with at least three cross sections to permit a reliable determination of the roughness coefficient with an accuracy of five figures. It was decided therefore to characterize in further calculations on the average each 300 m long section by a cross section, leading to further increased safety. Roughness coefficients obtained by this approach for individual sections are summarized in Table VI, from which certain conclusions of a generalized nature may be arrived at. As revealed by data tabulated, vegetation in the bed results in a considerable reduction of conveying capacity, even though the irrigation canal investigated must be classified large by Hungarian standards. Regular cleaning of the canals is therefore absolutely necessary, and all vegetation should be removed from the bed, with the exception of the wave protection strip of predetermined width where this is necessary. It was found further that the roughness coefficient used in dimensioning the canal — which was otherwise the same as commonly used in designing practice — related to a fully neglected bed covered with vegetation and lacking any maintenance. Therefore, assuming during planning adequate maintenance and thus using a roughness coefficient corresponding to a bed free of vegetation, considerable savings, over the present situation can be realized. BRIEF PUBLICATIONS AND REPORTS 1. Dr. Lampl, H., Eng. : Restoration of the Siófok Lock (for the Hungarian text see pp. 237) The navigation lock at the head of the Sió Canal draining Lake Balaton and discharging into the Danube river was constructed of concrete in 1943. Groundwater appeared at several places along the construction joints running horizontally on the walls of the lock chamber, and seepage occurred over 1 — 2 m long sections as a result of which concrete along the joints deteriorated (Fig. 1). For restoration the surface of the lock chamber wall facing the earth was made impervious by grouting a sealing material behind the wall. A 1: 1 mix of sodium silicate: water was used for grouting. Details of grouting operations are shown in Figs. 2, 4 and 5, while the success of grouting is demonstrated by comparing Figs. 1 and 6. 2. Illés, I., Eng. : Location oî sewage lifting pumping stations (for the Hungarian text see pp. 242) Investigations included the cases of one and two lifting stations (Figs, 2, 3 and 4) by taking into account a) investment cost only; b) investment cost varying with depth of canal only; c) investment and operating costs simultaneously. Changes in the slope of the sewer were also included. Results of the study are shown in Table II. Practical application of the method is illustrated for one and two lifting stations by a numerical example. 3. Bukovszkg, Gg., Eng. : Storage of floods on small watercourses (for the Hungarian text see pp. 257) In designing flood retention reservoirs design criteria include besides peak flood discharges, flood runoff volumes as well. Reservoirs designed for snowmelt are