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3.2.2        Loss of lateral connectivity (flood protection and drainage on floodplains)

Overview

Wetlands and floodplains play a particularly important role in the ecological integrity of aquatic ecosystems. By providing habitats for life stages of aquatic organisms, they are significant in ensuring or achieving the good ecological status of adjacent water bodies. Wetlands and floodplains also play a significant role in flood retention (EEA, 2018).

Studies have shown however that 70-90 % of European floodplains have been environmentally degraded as a result of structural flood protection, river straightening, disconnection of floodplain wetlands, agricultural land use and urbanisation over the past two centuries. The largest pressures on floodplains are linked to hydromorphological pressures, land use and pollution (EEA, 2019).

Flood protection structures play a key role in this context. Flood events are one of the most common and most dangerous natural hazards affecting European society with almost 3 700 flood events having occurred in Europe between 1980 and 2015 (EEA, 2016). Since decades, European countries have taken flood protection measures that mostly involve conventional engineering flood protection structures to mitigate the catastrophic consequences of floods. At the same time, flood protection structures and measures (such as levees, retention basins, channel straightening, removal of vegetation and sediment) are among the main causes for hydromorphological alteration and ecological impairment of rivers, in particular by disconnecting river channels from the floodplains and modifying riparian zones. 

Further pressure on the river-floodplain system is exerted by activities that drain excess water from the soil to increase areas suitable for crop production. Land areas may also be drained to serve for forestry or coastal and urban development. Drainage for agriculture has led to major losses of wetlands throughout Europe and is related to several hydromorphological pressures such as channelization of rivers and channel deepening (Vartia et al., 2018). In Europe, 35 % of wetland loss between 2000 and 2006 was due to conversion to agriculture (EEA, 2012); only in south-western Sweden, almost 70 % of wetlands have been lost due to drainage over the last 50 years (Franzén et al. 2016). In many European countries mainly in northern and central Europe, more than 40 % and up to 100 % of farmland is being drained (based on data from ICID, undated).[5] [5] http://www.icid.org/imp_data.pdf

In the second RBMPs under the WFD, almost 15 000 surface water bodies (about 10 % of total) are affected by physical alterations of their channel, bed, or riparian area due to flood protection and/or agriculture in 21 of the WFD countries. In addition, flood protection and/or drainage for agriculture are the reasons for designating almost 7 500 water bodies as heavily modified in 26 European countries.

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