Evaluation of the green flood mitigation measures in urban area in the frame of the sustainable city concept

The flood protection problem has always existed for the Ukrainian Carpathians. The floods that caused damage to urban areas occurred 10 times during the past 20 years in the basin of the Uzh River, ones were the cold period floods in most cases. The Uzh River passes through the central part of the Uzhhorod city, the river is crossed by five bridges, the embankment consists of “grey” flood protection structures: dams, concrete and stone walls. The central embankment was flooded by extreme floods only. At the same time auxiliary buildings and greenhouse in the Botanic Garden and the Bozdos Park area are flooded almost every two-three years. The purpose of the work is to update hydrological calculations, to calculate the flood water surface curve and assessment of the “green” flood mitigation measures in the central part of the city. Flood flow rate of 1% probability was calculated by processing continuous observations data for 72 years. Flood water levels of 1% probability were calculated using a 1D HEC-RAS model. Retention reservoirs, old river bed, mobile flood protection systems for local areas and buildings were considered as “green” flood control measures. Relocating embankments to make “room” for river within the existing buildings is not possible, but some stream widening has been preserved within the Botanic Garden by local flood protection of the single buildings and the central part of the garden. Calculation showed that the central part of the city is protected from flooding by the existing dykes, except for a few areas that would be protected by local mobile barriers. It is not possible to create an exclusively “green” flood control measures in the urban area, but the further development of flood risks management must be directed to the concept of a sustainable city development with minimization of the negative environment impact.