Vízügyi Közlemények, 1948 (30. évfolyam)

2. szám - VII. Szakirodalom

(42) of the crossings are far from being identical. Therefore it is impossible to lay down hard and fast rules, applicable to all sections, the alignment of the channel must always conform to the neighbouring sound sections. Generally speaking, it is advisable to avoid straight reaches, as easy curves offer various advantages; but on naturally long, almost straight reaches one should not force the increase the number of crossings by inserting short bends. The best way to increase the depth of a ford is the narrowing of the channel by appropriate alignment. On the Tisza, however, it is not enough to erect different constructional works of improvement below the low water level (groynes, longitudinal dykes), but at the passages from one curve to another the entire river bed has to be made narrower. On the Tisza the low water discharge namely is in itself not sufficient to form the channel. On the river during low water sections of greater and smaller slope of surface succeed each other (Fig. No. 9). The former correspond to the, places of shallow depth, the latter to the, places of deep water, mostly bends. At regulated fords the shape of the minor bed improves, thereby increasing the depth, decreasing the friction, improving the discharge capacity of the minor bed and consequently lessening the slope of surface necessary for the river discharge. This lowers the water level, which affects the section of the river above the ford as well. In case of a regulation of a longer section (including several subsequent fords) through summarisation of the water level sinkings, fords which previously were deep enough, have to be regulated too. The disadvantageous effect of the regulation carried out in the lower section is first of all felt in the imperfect fords, which can be avoided by the extension of the works. But when the depth diminishes below the projected measure at the irreproachably shaped passages, we have reached the limit of the technical possibilities of regulation. The Tisza at Szolnok discharges 65 cubic metres per second at its lowest water, and at bankfidl stage 900 cubic metres per second, and as the latter discharge forms the river bed, by low water regulation one cannot at will procure any desired depth of water. All that can be done is to secure for the other fords the same depth as is found in the naturally good fords. One need not fear that by narrowing the bed at low and at mean water, the deposit will be set moving in such a way, which might result in raising the level of the bottom and of the water level in the lower courses of the river. This is decisively proved by the fact that the numerous cut-affs, which were carried out during the regulation, nowhere resulted in the river bed being silted up. (To be continued.) LA RÉGULARISATION A BASSES EAUX DE LA TISZA. Par В. IVÁNYI. (Première partie.) (Figures et tableaux voir pp. 131 à 159 du texte hongrois.) 1. Généralités. D. C. 627.42 (282.243.742) + 627.15 La rivière de la Tisza, après avoir rassemblé les eaux de la partie orientale du bassin des Carpathes, se déverse dans le Danube. Son bassin collecteur est de 157,186 km

2. Les données caractéristiques de cette rivière ressortent des figures 1 et 2. En raison de la longueur relativement considérable de son secteur inférieur serpentant darts la Grande Plaine hongroise ainsi que de sa pente minime, elle ressemble, au point de vue hydraulique, au Mississippi Inférieur et aux fleuves des grandes plaines de l'Amérique du Sud, des Indes et de la Chine. La vallée de la Tisza, une plaine, pour ainsi dire, sans pente, a formé jadis le fond d'une mer, de sorte qu'elle est caractérisée par un champs d'inondation très large atteignant quelquefois 50 km. Du fait des inondations très fréquentés