FLOOD PROTECTION IN THE UPPER OPAVA RIVER BASIN WITH FOCUS ON NEAR NATURAL FLOOD CONTROL MEASURES

The Czech Republic was badly affected by the catastrophic floods in 1997. The Opava river basin was particularly heavily afflicted by these floods resulting in enormous material damages as well as human casualties. This year was a turning point in perceiving the necessity to take measures that would not only eliminate the immediate consequences but also reduce the risk of losses in the future. In the following period, the professional as well as general public considered and widely discussed a number of flood control options.

An example of the flood protection measures in the upper part of the Opava river basin can demonstrate a long-term process of searching a generally acceptable flood control concept. The approach should be built upon systematic preparation of underlying data, if a viable solution is to be found. Dozens of studies, expert opinions and conceptual documents were progressively developed in the period up to 2008. By a resolution adopted in 2008, the Government of the Czech Republic approved the final variant of measures reducing the flood risks in the upper Opava river basin. The published information and data are based on documents of the Upper Opava river basin flood protection project – preparation works 2008 -2010 which in certain parts continued until 2012. Its complexity has necessitated provision of extensive set of background documents including feasibility studies, geodetic and geological survey of the area of interest, cadastral and property data, hydrological data, expert studies and opinions, research deliverables, sets of documents related to the environmental impact assessment (EIA) and others.

The set of flood control measures in the upper Opava river basin can be considered as an example of a comprehensive approach to flood protection in a particular area. Functionality and sufficient efficacy of this project were proven by the underlying works. After the adoption of the final concept, the state-owned company Povodí Odry (Odra River Authority) was commissioned by the Czech government to ensure its preparation and implementation.

This presentation aims to give brief information regarding reasons for preparing a set of measures for flood risk mitigation in the upper Opava river basin, development and contents of the adopted concept, and in more detail it deals with the near natural flood control measures. The presentation is divided into 4 sections and each of them into sub-themes:

1. Area of interest and flood protection

Flood control measures focus on specific area with its specific conditions. Decisions on the concept of flood protection must conform to local conditions, functionality of the system should be ensured and other important aspects in the decision-making process should be taken into account.

• The River Odra basin and area of upper part of the Opava river basin
• History of floods and flood protection measures in territory
• Flood events of 1996, 1997, searching for conception
• Information on the current flood risk
• Selection of a flood protection concept

2. Set of flood control measures in the upper Opava river basin

A comprehensive conception for the area of interest has been developed. The system includes construction of a new dam as a key measure in synergy with other technical and near natural measures, the project also covers other organisational and compensatory elements and measures supporting the future development opportunities as well.

• Functionality of the system
• Investment plan processing
• Main data of individual packages according to the Investment plan
• Main administrative and decision milestones (resolutions of the Government, EIA)

3. Nature-friendly approaches adopted in the Upper Opava project

A wide set of activities was executed during the preparatory phase of the project. Besides the design and survey it included a qualitative analyses focused on the aquatic environment and climate, specialised studies on specific environmental issues, evaluation, documentation and all other activities related to the EIA, data processing for the purposes of land use planning and compensation for property and others. The objective was to incorporate appropriate compensations for the documented impacts on the environment and land into the project aiming to prevent from the deterioration of water environment and, where possible, to initiate improvement of the conditions along the Opava River reach from the municipality of Karlovice to Krnov including floodplains.

• The evolution of the Opava riverbeds upstream the Nové Heřminovy site
• Nové Heřminovy dam - revitalisation of the retention reservoir bottom
• Appropriate integration of the Nové Heřminovy reservoir in the landscape
• Fishway – the Nové Heřminovy reservoir bypass
• Sediment regime along the Opava River and affects by the Nové Heřminovy reservoir
• River training using revitalisation principles downstream the Nové Heřminovy dam, passing through the municipalities of Zátor, Brantice, Kostelec - Krnov
• River revitalisations outside built-up areas
• Flood protection measures in the municipality of Krnov, downstream Krnov and influences on the Polish territory
• System of polders and its appropriate integration into the landscape, land use modification
• Resolving of obstacles for the fish migration and water tourism from Kunov weir to the Krnov municipality

4. Resume

Flood control measures usually interfere with property rights and cause serious environmental impacts. At the same time, the level of protection determines the framework for development in the far future. The set of flood control measures designed for the Upper Opava river basin represents a comprehensive project in a particular area utilising close natural measures as far possible.

The last section provides information on the status of preparation and implementation at the end of 2014.

Individual sub-themes of this presentation are available only in Czech language.

More detailed information can be provided by Odra River Authority acting as the investor of flood control measures in the Upper Opava river basin. You are invited to use special mailbox noveherminovy@pod.cz. Kindly share your contact information.

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