Small Urban River Runoff Response to 2020 and 2021 Extreme Rainfalls on the Territory of Moscow.

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. [ABSTRACT FROM AUTHOR]