Assessment of the possibility of local object to be flooded in megalopolis as a result of a hydraulic system breakage in the area of a transport tunnel

In the article is observed the approach to assessing the safety of the downstream of retaining waterworks in the conditions of the existing urban infrastructure of the metropolis and the transport tunnel built on the border of the water system. Also are described the peculiarities of the methodology for determining the size of probable harm in the event of a hydrological accident of a low-pressure hydroelectric megalopolis complex, the lower pool of which is filled up, the watercourse is taken into the collector. The position of the groundwater level causes flooding of the territory, increasing the hazard indicator due to the activation of included processes (change in soil properties, suffusion, appearance a source of local flooding of an urbanized area, etc.). The results of a numerical experiment to assess changes in the position of the ground water level in the territory in contact with the Mikhalkovsky tunnel in Moscow are presented. It is shown that if the drainage system fails near the tunnel, a significant rise in the ground water level (more than 1 m) may occur, which will cause flooding of the surrounding area and residential buildings. To improve the efficiency of drainage in the lower reaches of the hydroelectric system, it is proposed to create an additional drainage system, including from the collector of the Zhabenka river. Calculation also shows that the emergency situation which may occur due to hydrological crash with implementation of the most difficult and simultaneously the most likely of several possible crash scenario with overtopping of the dam and the formation of the closure channel on the waterworks of Moscow is not likely to occur. The damage in the probable and most severe scenario of a hypothetical hydrological accident is close to zero. Therefore, there will be no damage on most ponds in the megalopolis where the downstream is filled in, planned, fortified, or the diverting section of the watercourse is taken into the collector.