Possibility of Assessment of the Slope of Siltation Based on the Some Hydraulic Characteristics of the Torrential Flows

Abstract

Slope of siltation is a very important parameter necessary in the designing of torrential flow regulation works. There is a series of formulas for its determination, and most of them are based on well-known Thiéry's formula boundary water velocity for bed load movement. Due to some difficulties in determining the acceptable amounts of the parameters, all the methods are rather unsuitable in practical calculations.
That is why, in the forecasting of slope of siltation the most exact results are obtained from analytical correlations determined on the basis of really formed slope of siltation in the field.
Based on the study of the slope of siltation on 35 check dams in the torrents in South-East Serbia the significant correlation between the slope of siltation and the some hydraulic characteristics of torrential flows (torrent-bed slope and the bed-load size in torrential flows) has been observed.
The natural torrent-bed slope (J_t) and the bed-load sizes have been considered as the hydraulic characteristics. Bed-load sizes have been expressed by the sizes of the characteristics diameters: d₁₀, d₃₀, d₅₀, d₆₀ as well as the value of the coefficient of bed-load, heterogeneousness-U.
U=d₆₀/d₁₀
Based on the statistical analysis, the paper represents regional analytical correlations for the forecast of the slope of siltation (J_z) depending on the torrent-bed slope (J_t) and the bed-load size in torrential flows: the following analytical correlations have been suggested:
a) J_z=0.46877J_t+0.21226
b) J_z=0.46514J_t+0.00673U+0.20278
c) J_z=0.45746J_t-0.01298d₁₀+0.01611d₃₀-0.00797d₅₀+0.52412
d) J_z=0.45912J_t-0.0135d₁₀+0.01666d₃₀-0.00872d₅₀-0.00444U+0.61838
The expression under “a” should be preferred.