Foto: Vojta Herout
New Shape of the Morava River in the South of Olomouc
The Morava River in Olomouc has a new shape. From the confluence with the Mlýnský brook all the way to the railway bridge on the train line connecting Olomouc with Prostějov, it carries over water during flooding and is an important part of the flood protection system. A gradual cascade of shores allows the water to spill during torrential rain. Under normal conditions, passers-by can refresh themselves in the river. The evaporation of water cools down the local microclimate and, together with the surrounding nature, contributes to making the once inaccessible Morava River a popular place for recreation.
The Adaptation Journey
The positive impact
The flood control measures on the Morava River respond to the increasing instability of the weather - heavy rainfall, disturbed water regime in the landscape and flooding. Although the measure addresses in particular the risk of floods, it also has a positive impact on river life during the drought. New watercourse, lowered banks and being closer to the groundwater level create better conditions for permanent vegetation with good effects on the surroundings. It also partially alleviates the overheating of the town, the so-called thermal island effect, which affects Olomouc since it is a large intensively built up city surrounded by the agricultural area of Haná. New trees were planted as well and they contribute to improving the local microclimate with their shadows and evaporation.
How does it work?
The increase in the capacity of the Morava riverbed within the Stage II A of the project deals with a 1437 meter long stretch of the river. It starts at the confluence of the Morava with the Mlýnský brook and ends at the point where the river flows under the railway bridge of the Olomouc - Brno track. It includes elevation of the river banks by 80 centimeters. In narrow sections, the embankments were replaced by walls. At the same time, 625 meters of the right bank between the bridges Velkomoravská and U dětského domova and 100 meters of the left bank in front of the U Dětského domova bridge were lowered. The new level is thus 2 meters above the riverbed. This allows for a safe flow of the flooding river into the undeveloped landscape.
A movable closure on the Mlýnský creek, an increase in the volume of water that flows underneath the Velkomoravská Bridge without damaging it and the relocation of some civil engineering infrastructure were also a part of the project. In addition before the construction, 832 meters of the main sewer with a diameter of 1.8 meters had to be relocated to a new place outside the area of potential floods behind the riverbank.
The whole flood protection construction is not only a piece of technical work, it also has an ecological side to it. It includes the division of the edge of the banks, alternating calm and rapacious sections and construction of shelters for fish. Thanks to a new parallel riverbed, a 350-meter-long island was created.
Before the work began, the selected section of the Morava riverbed was able to safely transfer only a 20-year flood. The river was buried deeper in the terrain with difficult access to the shores separated from its surroundings.
Operation and maintenance
The correct function of flood protection is closely related to the maintenance of individual parts, walls, barriers and other technical objects and means of flood protection. This concerns both the maintenance of vegetation and their technical condition.
A lot more than before, the new routes along the revitalized section of the river are used by pedestrians to access the city center, as well as tourists, in-line skaters and cyclists. According to the 2017 traffic census, 669 cyclists per day were counted on the road.
Why was the measure chosen?
The modification of the Morava riverbed was a part of a complex project to restore the retention capacity of the floodplain of the lower Morava River and it was also included in the “General Plan for Flood Protection of the Morava River Basin”. The design was verified by calculation using a numerical model. Three options in the section of the right bank dam between the bridge „U dětského domova“ and the railway bridge were verified by hydrotechnical calculations. After negotiations with the owners of the neighbouring private gardens, the City of Olomouc, together with the administrators of Morava River Basin chose a combination of a bank and a flood wall.
Obstacles and challenges
The most important thing was to design a good project and finish it. The construction itself took place under normal conditions and there were no serious complications during the construction. The whole Stage II A was finished in time.
How much did it cost?
Total cost of the flood protection measures was 330 million CZK (13 million EUR). Povodí Moravy, s.p. as the administrators of the river basin, and the Statutory City of Olomouc contributed financially and funding was also provided by a grant by the Ministry of Agriculture aimed at supporting flood prevention. The estimated lifetime of the measure is 100 years.
Revitalization of water elements Városi növényzet Flood control measures Vlny horka a tepelný ostrov Povodně a přívalové srážky