Study of the storm runoff mechanism (for discussion)

Summary

For the hydraulic calculation of surface runoff disposal networks in SP 32.13330.2018 «Sewerage. External Networks and Structures», a technique is applied that implements the method of «limiting intensities». Despite its notability and widespread use in practice, a number of authors point to a limited area of its use. However, there are no results of a quantitative assessment of the errors of this method in the technical literature. For this reason, the analysis of the degree of influence of the accepted assumptions on the results of hydraulic calculations was carried out. It has been established that with certain ratios of other factors, the use of the «limiting intensities» method can result in an underestimation (from 1.2 to 1.7 times) of the calculated wastewater flow rates. Taking into account the results obtained, two directions of work are formulated to eliminate the consequences of flooding in sewer basins. The first direction provides for the introduction of engineering measures aimed at increasing the reliability and efficiency of the sewer system operation, the second – the improvement of the construction regulations that exclude the creation of problem situations in the future.

Key words

drainage area , method of limiting intensities , climatic parameters , force of rain , rainfall duration , surface runoff disposal systems , travel time

UDC 628.221
DOI 10.35776/VST.2023.04.07

Volkov Sergei, Luk’ianchuk Maksim, Zhitenev A. I., Kuz’min Valentin, Rublevskaya O. N., Gvozdev V. A., Erofeev Vasilii, Kostenko I. G., IGNATCHIK V. S., Ignatchik S. Iu., Kuznetsova N. V., Seniukovich Mikhail

Methods and results of estimating calculated rain parameters for the surface runoff disposal systems of Saint-Petersburg Part 2. For hydraulic calculations in simulation

Summary

Urban surface runoff disposal systems need to be adapted to the changing climate with account of local conditions and schematic design features. In line with the world practice, one of the stages of the works in this area is the substantiation of the calculated parameters of rain for the considered climatic region. At the same time, to fulfill the design tasks adjusting the specified climatic parameters will be sufficient. However, justifying the solutions on the upgrade of the drainage systems using computational models, substantiating the profiles of calculated rains constituting the graphs of the temporal variations of their intensity is needed. While substantiating these profiles, the following requirements were taken into account: the maximum 10-minute amount of precipitation that can cause flooding in the wastewater disposal networks; the accumulative amount of atmospheric precipitation during 1 hour that can cause flooding in the tunnel sewers. It has been established that under these requirements, the temporal variation of the rain intensity representing the design rain profile can be expressed as a continuous analytical function with two parameters: i₀ – the maximum instantaneous rain intensity (mm/h) and the empirical parameter φ (min^–1). It has been experimentally determined that for St. Petersburg, for example, with a return period of p = 1 year, φ = 0.1837 min^–1, i₀ = 40.21924 mm/h.

Ключевые слова

surface runoff disposal systems , flooding , adaptation measures , calculated parameters of rains , rain profiles

UDC 628.221
DOI 10.35776/VST.2023.06.05

Volkov Sergei, Luk’ianchuk Maksim, Zhukova Anastasiia, Zhitenev A. I., Kuz’min Valentin, Rublevskaya O. N., Gvozdev V. A., Erofeev Vasilii, Kostenko I. G., IGNATCHIK V. S., Ignatchik S. Iu., Kuznetsova N. V., Fes’kova A. Ia.

Methods and results of estimating calculated rain parameters for the surface runoff disposal systems of Saint-Petersburg
Part 3. For hydraulic calculations in designing and modeling with account of the uneven distribution of rain intensities areally

Summary

Municipal surface runoff disposal systems need to be adapted to the changing climate with account of local conditions and schematic design features. In line with the world practice, one of the stages of the research in this area is the substantiation of the calculated parameters of rain for the considered climatic region. Herewith, to solve design problems, adjusting the standard climatic parameters is sufficient, whereas, to solve the problems related to the justification of decisions on the upgrade of wastewater disposal systems using calculation models, justifying the design rain profiles constituting graphs of the intensity variations over time is required. In addition, justifying the calculated parameters of rains with account of the spatial variability is needed. Beyond that, for large areas, the design rainfall parameters must be converted to average values. In world practice, this is done by multiplying the average rainfall intensity for a given duration, frequency and area by the appropriate reduction factor – areal reduction factor (ARF). In domestic practice, while designing, a similar reduction factor is also used called a correction factor that takes into account the uneven rainfall areally. However, the reliability of the values of these correction factors is very doubtful, since, for example, with a runoff area of less than 4km², the values are available only for the conditions of Moscow, whereas the origin of the values for a runoff area of more than 4km² is not known. For these reasons, in St. Petersburg, along with the assessment of the actual and prospective parameters of calculated rains used in design and modeling, the regularities of the distribution of rain intensity areally were additionally determined. As a result of the research, the hypothesis that areal and point precipitation have the same probability of exceeding was confirmed, as well as the type and parameters of the dependence were substantiated for estimating the actual values of the correction factors that take into account the unevenness of rainfall areally.

Key words

surface runoff disposal systems , flooding , adaptation measures , calculated parameters of rains , rain profiles

DOI 10.35776/VST.2022.07.07
UDC 628.221

Volkov Sergei, Luk’ianchuk Maksim, Zhitenev A. I., Rublevskaya O. N., Erofeev Vasilii, IGNATCHIK V. S., Ignatchik S. Iu., Kuznetsova N. V.

Systems for the removal of surface runoff: problems and solutions (for discussion)

Summary

For the hydraulic calculation of storm sewer networks removing surface runoff in our country, the concept of immediate removal of runoff formed as a result of rainfall has been used for more than 60 years. With this aim, the method of «limiting intensities» has been used up nowadays, implemented with the help of the methods laid down in Norms and Technical Conditions for Design 141-56, SNiP II-G.6-62, SNiP II-32-74, SNiP 2.04.03-85, SP 32.13330. 2012, CP 32.13330.2018. If we continue to be guided by this concept, then in order to adapt the operated systems to the current conditions, in most cases relaying all the networks with larger pipe diameters would be required, which is practically impossible not only from the economic, but also from the technical and social point of view. In the current situation, introducing alternative solutions for adapting storm sewer networks is needed, which, in comparison with relaying all the networks, are more economically justifiable. Among them, noteworthy are the solutions that provide for the detention and retention of water in sewers, and for reducing runoff coefficients. The effectiveness of these solutions is estimated using numerical modeling and analytical calculations.

Key words

drainage area , method of limiting intensities , climatic parameters , force of rain , rainfall duration , surface runoff disposal systems , travel time

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