The procedure of designing drainage rates and geologic safety threshold in case of urban industrial area underflooding

Summary

The regulatory documents specify the indicators of the ground water critical state depending on the development pattern of urban industrial areas. Dividing the areas according to the development pattern is presented in general without regard to the RF Town Planning Code. The analysis of published data and regulatory requirements showed the necessity of specifying the geologic safety threshold in case of underflooding in order to validate the drainage rate of the urban industrial areas. The concept of designing geologic safety threshold on the basis of the geohazard risk theory with the evaluation of underflooding negative effect level is set out. The design functional connections were obtained and the procedure of designing drainage rates, acceptable ground water levels and geologic safety threshold in case of underflooding of different urban industrial areas classified as provided by the RF Town Planning Code was developed.

Key words

risk assessment , drainage rates , geologic safety threshold , negative effect level , territory underflooding

Justification of the optimum alternative of the wastewater disposal system of St. Petersburg adapting to the conditions of the joint effect of urbanization and climate change.
Part 1. Program-method for justification of the optimal alternative

Summary

The wastewater disposal system of Saint-Petersburg has been operating under the conditions that differ from the design ones owing to main reasons. The first reason is the process of urbanization that involves water flow rate decreasing in dry weather because of the water consumption reduction, and water flow rate increasing during rainy periods due to the increasing share of watertight coverages. The second reason is the increasing intensity and frequency of rain showers. In this regard, adapting the wastewater disposal system to the conditions that arise under the joint effect of urbanization and climate change became a necessity. The consequence of the new operating conditions is the presence of two undesirable phenomena: flooding of territories and overflows of storm drains, emergency outfalls, emergency outlets and bypass lines of the treatment facilities. Justification of the optimal solution for adapting the Saint-Petersburg wastewater disposal system to the conditions of the joint effect of urbanization and climate change should provide for the solution of a double criterion optimization problem: search for an economically feasible option for the system reconstruction to eliminate floodings in the city during rainfall with a frequency of Р > Р_opt; search for an economically feasible option to ensure minimal discharges through overflows during rainfall with a frequency of Р > Р_opt during the operation after the reconstruction. From a mathematical point of view, the search for an economically justified reconstruction option comes down to determining such a period of rain frequency P_opt, where one of two equivalent conditions is met: either the minimum cost of damage from flooding and the cost of preventing it is achieved; or the maximum difference between the amount of prevented damage from flooding and the costs of preventing it is achieved.

Key words

territory underflooding , surface runoff disposal system , adaptation measures , calculated parameters of rains , urbanization , climate change

Designing drainage systems of flooded areas on the basis of computer simulation

Summary

To make hydrogeological calculations of drainage systems for protecting territories from floods the methods of analogy, analytical and computer simulation are used. The method of computer simulation as applied to designing drainage systems on the territory of the Imeretinskaia Lowland of the Krasnodar Area is closely considered. The analysis of the model map of ground water depth after territory upfilling and building development provided for identifying the areas to construct the systems of engineering protection from flooding. The basic design solution of reducing ground water level on the flooded territories is constructing horizontal subsoil pipe drainage with filtering bedding or radial horizontal drainage. Depending on the results of the mathematical simulation of the hydrogeological conditions on the protected area and hydrogeological calculations pipe drainages of perimeter, linear or systematic (areal) type are constructed. Ground water by gravity is diverted into open-channel flows provided the proper ecological justification is available. As may be required automated drainage pumping over stations are established. The developed concept allows reducing and maintaining ground water level at the permissible depth.

Key words

filtration , drainage system , numerical simulation , territory underflooding , ground water , hydroisohypses