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Discharge Coefficient of Rectangular Broad-Crested Weirs in Narrow Channels with High Relative Length of the Threshold

Zhuk Volodymyr, Vovk Lesya, Popadiuk Ihor, Matlai Ivan

Ecological Engineering & Environmental Technology

2021

Vol. 22, iss. 6

11--16

Broad-crested weirs (BCW) are commonly used elements of stormwater systems and different open-channel hydraulic structures. Specific features of stormwater drainage channels are small width, low flow depths and, accordingly, small overflow heads at weirs. Dependences of the discharge coefficient of narrow (b = 0.224 m) rectangular sharp-edged broad-crested weirs with vertical walls, threshold height of 0.05 m and threshold length of 0.05–0.2 m were obtained experimentally. The experimental values of the discharge coefficient were approximated by the power-law functions of relative length of the weir. At large values of the relative length of the threshold (L/h> 10), for all weirs was obtained the same tendency of decreasing the discharge coefficient with increasing L/h ratio that can be explained by the enlargement of the hydraulic friction along the weir with increasing L/h ratio.

Dependency Between the Total and Effective Imperviousness for Residential Quarters of the Lviv City

Zhuk Volodymyr, Vovk Lesya, Matlai Ivan, Popadiuk Ihor, Mysak Ihor, Fasuliak Vadym

Journal of Ecological Engineering

2020

Vol. 21, nr 5

56--62

A detailed hydrologic analysis was performed using geographic information systems and field investigations for thirty residential quarters in the Franko district of the Lviv city, Ukraine. All investigated quarters are located at the territory of the Baltic Sea catchment of the Lviv city, and the surface runoff from this area flows to the Lviv wastewater treatment plant. The total area of the investigated sub-catchment is 348.5 ha, including 58.46 % of impervious covers, 41.17 % of green spaces and 0.37 % of water bodies. The share of total impervious surfaces for each of the 30 analyzed quarters varies from 0.329 to 0.929, and the effective imperviousness – from 0.222 to 0.917. The correlation between the total and effective imperviousness was described by the power law dependency pef=(ptot) n. Two approaches were used to describe the relationship between the total and the effective imperviousness: 1) using all 30 empirical results for each quarter; 2) using the average values of the imperviousness of the total subcatchment. The obtained values of the power law exponent for these two empirical approaches are n1=1.308 and n2=1.275, respectively or 7.2 % and 9.6 % less, respectively, comparing to the corresponding value n=1.41 in the Livingston’s & Veenhuis’ approximation, obtained for 14 different highly urbanized quarters of Denver city. On the other hand, the power law exponents are 3.9% and 1.3% higher, respectively, comparing to the corresponding value n=1.259 in the approximation for the 900 km2 semi-urban watershed in Marion County, Georgia, USA.