On designing surface runoff control schemes (to be discussed)

Summary

The necessity of the rainfall flow rate and volume control before the treatment facilities is stipulated in Code of Practice 32.13330.2012. The recommendations given by NII VODGEO suggest three control schemes designed on the basis of the theoretic runoff hydrograph described by two curves (flow rate increase and decrease) expressed through the maximum flow rate. The given functions have been obtained with the use of the runoff flow rate equation following the method of limit intensities with a constant runoff coefficient which is a special case. Presented in the article is a proximate description of the theoretic runoff hydrograph with account of using a variable runoff coefficient which is a more general case. The analysis of the method of calculating the rainfall flow and volume control schemes is presented. A calculation example is considered, a comparative assessment of the results obtained is given. It is shown that when using the existing method of calculating surface runoff control systems and determining the capacity of pumping station tanks the calculations of the maximum flow rate of the design rainfall shall be carried out with the use of the variable surface runoff coefficient that provides for the maximum approximation to the theoretic runoff hydrograph.

Key words

design runoff hydrograph , rainfall flow rate and volume control scheme , runoff coefficient , pumping station tank capacity