Water Replenishment of the Blue Zone and Flood Management on the Urban Area

Climate change has led to the temperature rising, the river flow decreasing during the summer months, and to the flood frequency increasing up to ten times a year in the mountainous Carpathian region. Reducing the harmful effects of droughts and extreme floods has become a pressing issue today. It is possible to increase the water levels in the dry season and to replenish floodplain areas (green-blue islands) in urban areas by creating the backwater in the riverbed. The purpose of the work is to assess the water replenish possibilities of the blue-green zone, taking into account the extreme flood to improve the management of water resources on the urban area. Simulations were carried out with the backwater creation by flap gate, weir and riffles and their impact on the extreme flood levels and a spring seasonal flood during the mean year was estimated for the central part of the city. The calculations showed a negligible effect of the backwater structures on the rise of the water level during the extreme flood. The ability to operate the flap gate with dropping down to the foundation let to maintenance the constant water level during the spring flood.