Water ecosystems comprise above two thirds of our planet and play an important role in stabilization of global climate, and also provide a wide range of services to the rapidly increasing society. A number of scientific works are devoted to the study of environmental safety. Water is a basis of life on our planet, and the issue of rivers protection should be of top priority. Unfortunately, a considerable number of surface water reservoirs undergo anthropological influence. The analysis of the research allows us to note that surface water reservoirs, lakes, rivers and their floodplain suffer from human-made pollution. At the time of total use of plastics in all spheres of life, its presence in rivers is detected at the micro-level. The aim of our study is the analysis of landscape-forming factors of ecological safety of the river Styr within the city of Lutsk (Ukraine). The volume of discharge of untreated return water into the river Styr within the city of Lutsk during the last years tends to decrease: in 2018 – 427 000 m3; 2019 – 424.9 000 m3; 2020 – 423 000 m3. It is established that the quality of water of the river Styr in the range line above the city are affected by the pollution from the river Ikva housing-communal enterprise “Mlynivske” and state communal enterprise “Dubnivske”, and also waste waters transferred from Lviv region – communal enterprise “Radekhiv water sewage enterprise” (through the river Ostrivka) and communal enterprise “Brodyvodokanal” (through the river Bovdurka). The quality of water in the range line below the city undergoes the influence of the waste waters from communal enterprise “Lutskvodokanal”. In order to assess transformation of ecological conditions within urban floodplain, it is proposed to run biomonitoring on the basis of fluctuating asymmetry (FA) of a leaf of a plant, which is informative in case of description of the peculiarities of formation of vegetation.