Nature and Landscape Management

Nature Conservation 3/2008 — 24. 6. 2008 — Nature and Landscape Management

Making a Blanice River Cut-Off Meander Flowing – An Important Facility for the European Freshwater P

významná stavba k ochraně perlorodky říční

autorka: Magda Růžičková

The Blanice River National Nature Monument is one of eight sites in the Czech Republic, where the European Freshwater Pearl Mussel (Margaritifera margaritifera) Recovery Programme/Action Plan has been implemented.

In a cut-off meander and partially also in the Blanice River mainstream beds, the most important European Freshwater Pearl Mussel's population in Central Europe lives, having reached 46,000 individuals in 2003. In summer 2006, three floods occurred in the Bla-nice River, causing huge damages within the cut-off meander. Thus, the mussel's population was directly strongly affected by emergency conditions of the dams. Consequent weir restoration includes building a stable, composite trapezium profile of the bed which ensures that even the minimal streamflow in the Blanice River is divided into its own riverbed and the cut-off meander, the latter serving also for juvenile mussels´ rearing. The bed in the vicinity of the weir was restored to na-tural shape corresponding to that more upstream and the banks were improved by willow fascine cylinders. The facility which was financed by the Ministry of the Environment of the Czech Republic's River System Restoration Programme through the Agency for Nature Conservation and Landscape Protection of the Czech Republic was built in October to December 2007, totalling 3.8 million CZK (152,000 euros). The first winter and spring period after its finishing the facility confirmed that the measures implemented stabilized the bed even in the case of greater floods, improved hydraulic conditions for float material and sediment transport, troublemaking ice phenomenon has been eliminated and what is also important – building technologies used there have not affected the unique European Freshwater Pearl Mussel's population in the cut-off meander.