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Hydraulic calculations of alternative flushing of the left-side branch system of the Danube
Project Summary :
Planned timetable: May 2007 - September 2008
Coordination workplace: WRI Bratislava
Responsible researcher/coordinator: RNDr. Zuzana Capeková
Co-researchers: Ing. Katarína Holubová, PhD.
Coordination workplace: WRI Bratislava
Responsible researcher/coordinator: RNDr. Zuzana Capeková
Co-researchers: Ing. Katarína Holubová, PhD.
The main task was to check the alternative scenarios of flushing the branch system of the Danube, which would allow for the transport of created sediments and silt and would support an increase in infiltration of water through the bank line of the Danube branch system, i.e. defining the discharge conditions that would allow reaching a speed high enough to ensure lifted deposited sediments and their transport across the various lines up to the old Danube. By flushing not only reducing of the river-bed clogging should be achieved but in particular creating of soil conditions for elimination, reducing colmatage/ clogging process.
Within the task a rather extensive field measurements were made: - 67 riverbed section profiles were measured in the main branches of the river system, samples of river-bed sediments were collected and analysed as well as levels, velocities and discharges in different parts of the branch system.
Results of measurements of section profiles from 2007 were used to assess morphological changes over a period of 37 years (compared to year 1970). The results were used to identify areas with the most intense sedimentation and alluviation.
The analysis of flow dynamics was evaluated on the basis of the assessed topography of the main branches and one-dimensional hydrodynamic model (HEC-RAS) was created for conditions of steady and unsteady flow. The basic scenarios were defined with regard to the requirements of the sponsor and subject to the fulfilment of basic conditions, which can be achieved by transport of sediments along the branch system. The optimised process of flow conditions and eventually the best scenario was defined, which will be used for flushing the branch system in August 2009.
In addition, modifications of dams in some lines were designed, which enable to improve level regime for artificial floods.
Assembled hydrodynamic model adapted on the basis of acquired experience from planned flushing can be used for evaluation for other corrected measures in the branch system of the Danube.
Distribution of measured section profiles oriented in the branch system of the Danube
Within the task a rather extensive field measurements were made: - 67 riverbed section profiles were measured in the main branches of the river system, samples of river-bed sediments were collected and analysed as well as levels, velocities and discharges in different parts of the branch system.
Results of measurements of section profiles from 2007 were used to assess morphological changes over a period of 37 years (compared to year 1970). The results were used to identify areas with the most intense sedimentation and alluviation.
Development of the steady flow levels in the branch system for flow rates for 40 m3s-1 and 60 m3s-1 on the inflow object
The analysis of flow dynamics was evaluated on the basis of the assessed topography of the main branches and one-dimensional hydrodynamic model (HEC-RAS) was created for conditions of steady and unsteady flow. The basic scenarios were defined with regard to the requirements of the sponsor and subject to the fulfilment of basic conditions, which can be achieved by transport of sediments along the branch system. The optimised process of flow conditions and eventually the best scenario was defined, which will be used for flushing the branch system in August 2009.
In addition, modifications of dams in some lines were designed, which enable to improve level regime for artificial floods.
Flooded areas of the proposed measures at maximum levels of flood regime
Assembled hydrodynamic model adapted on the basis of acquired experience from planned flushing can be used for evaluation for other corrected measures in the branch system of the Danube.