engleski

Solving the Flood Control Problem of the City of Rijeka by Using Mathematical Flood Modelling

Largest Croatian port at the Adriatic is in the city of Rijeka. This is a very old city, dating back to Roman times, and it nowadays represents a very important regional economic center of Croatia. City core and most signifcant economic features are placed next to the riverbed of Rjecina torrential river, at its very Adriatic mouth. The river is 18.3 km long and has an orographic catchment area size of 218 sq.km. Its water flow can oscillate from 0 - 400 m3/s during the year. On many occasions throughout the history Rjecina river endangered the city by its floods, particularly its most important parts at the very mouth. Torrential character of those floods and a relatively narrow available corndor for the evacuation of flood waves demand a specific approach to solving the flood control problem here. Traditional principles of riverbed regulation and protective dam construction are acceptible just in part here. Protective dam construction cannot be taken into consideration in the urbanized city core, till the problem itself carmot be solved only by riverbed regulation. Therefore, regarding the existing situation, the use of unstructural flood protection measures is purposeful within the endangered city area, while physical measures for reduction and detention of flood waters can be applied in the upper catchment part. In order to define unstructural flood protection measures within the endangered city area, it is necessary to know the propagation and duration of floods with different occurrence probabilites, whereas to establish the effciency of possible physical measures in the upper catchment part, it is necessary to analyze whether the reduced high waters will still spill over the endangered area from the riverbed or the reduction sucesfuly. For the purpose of solving these problems, a mathematical model of flood waves propagation within riverbed has been developed, as well as a model of flood waters propagation within the endangered area. That model enables examination of various scenarios of possible floods as well as varying of different parameters that directly impact the flood occurrence. The paper show flood model results obtained with assumptions of different incidences and durations of heavy torrential rains and high tide occurrence at the river mouth. Results for presumed different conditions of watercourse riverbed regulation are also demonstrated. These results create a quality base for reaching decisions on future protection measures of the endangered area. Potential (possible) structural and unstructural protection measures that are analyzed are also specified on the poster.

Flood water; propagation; mathematical modelling; flood control measures.

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