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.

No abstract

No abstract

Broad-crested weirs (BCW) are often used in hydraulic engineering and water management. The most complex factor that affects the discharge capacity of BCW is the discharge coefficient. In Ukrainian engineering practice, the flow rate of BCW is defined as a function of the relative height of the spillway wall, while in the most common European methods – as a function of the relative length of the weir. The experimental dependences of the discharge coefficient of rectangular sharp-edged BCW with vertical inlet and outlet walls with the ratio of the weir length and height d/Р = 2; 4 are obtained. A comparison of the obtained results with the values of the discharge coefficient of the same BCW using the methods of Kumin and Hager indicates that this coefficient depends on both the height of the wall and the length of the weir. The corresponding empirical power law dependences are obtained. At the same values of the relative height of the wall, the discharge coefficient for the weir with the ratio d/Р = 4 is significantly lower comparing the weir with d/Р = 2, that can be explained by the more significant effect of friction resistance for the weir with longer threshold.

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 p ef =(p tot ) 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 n 1 =1.308 and n 2 =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 km 2 semi-urban watershed in Marion County,