Abstract

Slope of siltation is the slope of the upper surface of the deposited material, which can be considered as the equilibrium bed slope in the specific conditions of the torrent channels with the constructed dams. The formation of siltation is a complex process which is influenced by many factors, most significant being: natural bed slope, competent velocity, depth of flow, density of torrential water and sediment particle-size distribution. The assessment, that is, the forecast of the slope of siltation is a major issue in the practice of torrent management, significant in the selection of the site for dam construction and the decisive factor in the computation of the distance between the dams when they are designed in the system. The need for practical solution of this problem resulted in many formulas for the calculation of the slope of siltation. This paper analyses and verifies some of the most frequently applied formulas in practice, on the explicit example of the siltation of the dam No. 7 in the River Vidovačka. Slightest deviation from the actual, measured values for the slope of siltation is obtained using the Velojić-multiple i Kostadinov calculation formulas, or by regional analytical dependencies. The forecast of the slope of siltation should be carried out by the regional analytical dependences, which should be based on field research on already formed slopes of siltation and should include, in addition to bed slope, an independent variable that characterises the sediment. They would have a regional character with parameters adopted to local conditions.

Key words: Slope of siltation, natural bed slope, sediment particle-size distribution.