An important trend of modern development is the concentration of population in urban agglomerations, where a specific meso- and micro-climate is created under conditions of dramatically transformed natural landscapes. In the present paper, the long-term statistical analysis of intense rainfalls and annual daily precipitation maxima was carried out based on the Moscow region weather stations timeseries for the period of 1966-2021. An increase in the variability of intense precipitation over the Moscow region corresponding to the formation of significant floods was revealed in some years. The COSMO-CLM model simulated extreme precipitation for the basin of the Setun' River (190 km2), the largest right-bank tributary of the Moskva River within the Moscow city, which was recorded over Moscow in May 2020 and June 2021. Maximum precipitation was registered over the Setun' River basin during 45-90 minutes and induced rainfall floods that exceeded the spring flood by two times. The estimated basin travel time was 6-8 hours. Rainfalls form a multistep hydrograph inheriting the shower precipitation structure on small rivers.

The Agrakhan Bay of the Caspian Sea is a unique hydrographic and environmentally valuable object at the mouth of the Terek River. At the beginning of the 20th century, it was a typical sea bay; however, by the 21st century, it lost the features of a marine area and a single water body and was divided into two parts with their specific hydrographic network, water regime, landscapes, biota, and anthropogenic load. Rehabilitation of the wetlands of the former sea bay requires urgent and scientifically grounded measures, as well as good knowledge of the causes and features of its rapid degradation and data on its current hydrological-morphological and hydroecological state. In 2018–2020, the authors carried out a series of field reconnaissance, geodetic, hydrometric, botanical, and hydrochemical works in this part of the mouth, created a network of stations, took numerous water samples and bottom soil samples, and analyzed them in laboratories. A vast array of data from Roshydromet (Russian Hydrometeorological Service) stations, as well as multi-temporal cartographic materials and satellite images, have been accumulated and studied; a multilayer GIS and various maps, empirical dependencies, diagrams, and graphs have been constructed; the results of studies by outside specialists have been considered. This study has made it possible to comprehensively describe the current state of the former Agrakhan Bay, build a depth map, a landscape map, a map of bottom sediments, a map of macrophytes, and a map of hydrochemical parameters, describe the water regime and water balance of the main water bodies of the former bay, determine the relationships between the main hydrological and morphological characteristics, etc. Patterns, causes, long-term stages, and parameters of the unfavorable morphodynamics of the Agrakhan Bay in the 20th century and at the very beginning of the 21st century have been studied. This has made it possible to justify measures for partial restoration of the hydrological and ecological potential of the water bodies of the former Agrakhan Bay.

Significant degradation of the Agrakhan Bay on the eastern coast of the Terek River delta has occurred in the course of the 20th century as a result of the combined action of natural and anthropogenic factors. Comprehensive studies conducted by the authors in 2018–2020 have made it possible to describe the main causes of this degradation, characterize the current state of the reservoir, and establish scientific bases under recommendations for its improvement. It has been demonstrated that as a result of partial drying and reduction of water surface area the bay has lost its former importance as a spawning and rearing water body providing the West Caspian region with the younglings of valuable commercial fish species. By 2018, the catches decreased by ten times compared to the early 20th century with sturgeons having almost totally disappeared. The state of the northern part of the bay, which has transformed into a group of shallow water bodies almost entirely separated from each other and from the sea is particularly unfavourable. The study of hydrological and morphological, hydrobiological, fishery-related and hydrochemical parameters has shown that the improvement of the wetlands at the former bay site is possible. Detailed analysis of the water balance using multivariate limnological calculations has shown that there is enough water for watering and partial restoration of the water bodies of the Agrakhan Bay hydrographic system. Clearing of silted and overgrown canals, deepening and berming of the remaining water bodies, and directing the necessary amounts of river water into Northern and Southern Agrakhan Bay (in accordance with the calculated delivery schedule) will allow reduction of the overgrowing and siltation of water bodies, restore the water exchange between them, improve water quality, revive the fishery industry in the region, improve the habitats of many rare and protected animal species, and increase the recreational attractiveness of the region.

The Zakharkovskaya floodplain of the Moscow River is located directly above the Moscow Ring Road. It is an example of a natural structure that is spontaneously restored after long-term economic use (hayfields, pastures, long-term plowing, summer cottege settlements, drainage and irrigation channels, silt sites, etc.) under conditions of cessation of intensive anthropogenic impact. The article deals with the history of the formation and development of the Zakharkovskaya floodplain in prehistoric times (late Holocene), in the early historical period (beginning-middle of the second millennium AD), and in the late historical period-XIX-XXI centuries. The regulation of water flow, which has occurred in recent decades, is accompanied by a relative stabilization of the Moscow riverbed, turning it into a canal, reducing the intensity of channel deformations, leveling the bottom relief with its general deepening. As in other floodplain plots, the territory of floodplain leaves the flood zone; depressions are filled in, lakes are degraded, and man-made terrain is formed. At the same time, the current restrictions on access to the territory of the Zakharkovskaya floodplain for 10-15 years have created conditions for the restoration of natural structures, in particular, forest and shrub tracts, and increased the landscape and ecological attractiveness of floodplain lands.

The study was based, firstly, on the diverse data collected during field work in 2018 – 2020 in the eastern part of the Terek River delta and long-term hydrological monitoring data on the Roshydromet gauges. Secondly, on a profound comparative analysis of multi-temporal cartographic materials and multiple satellite images, laboratory analysis of water and sediment samples and other research groups’ field data. The performed analysis resulted in unprecedented complex and profound assessment of the contemporary hydrological, morphological and ecological state of the former Agrakhan Bay of the Caspian Sea. The drivers, dependencies and parameters of hydrological and morphological degradation were described; a multi-layer large-scale GIS was created to design multiple illustrations. The performed assessment allowed for development of measures for partial restoration of the hydrological and ecological potential of the former Agrakhan Bay.

The procedure for assessment developed in the paper for the conditions of northwestern, central, and southern European Russia is an efficient means for comparative analysis of power lines in terms of individual and integral impact of hazardous hydrological and slope processes on their vulnerability, for determining of the periodicity of monitoring observations and the composition of such studies.