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Hydromorphological pressures other than continuity interruption and examples of measures

Except for physical structures which interrupt longitudinal continuity (via barriers on the river network), humans have made many other physical changes to rivers, lakes and estuaries. Examples are changes to the size and shape of natural river channels for land drainage and navigation, modifications to beds (via either concrete or change in sedimentation/erosion), the banks and shores of water bodies. These modifications alter natural flow levels and sediment dynamics in surface water bodies and lead to the loss of habitats and recreational uses.

Almost 60 % of the water bodies which are impacted by hydromophological pressures are affected by physical alterations in the channel, bed, riparian zone or shore. The main drivers for the physical alterations reported for water bodies in the second RBMPs are flood protection and agriculture.

Restoration of bank structures, reconnection of backwaters or floodplains and wetland restoration are among the most common measures applied to achieve hydromorphological improvements. In many rivers, habitat quality at the river banks is poor due to bank fixation. Removal of bank fixation is a prerequisite for many other measures like re-meandering or widening as well as initiating later channel migration and dynamics. Also tree-planting and/or preserving riparian zones aim to reverse the impacts of land use change by improving channel stability, aquatic habitat and terrestrial biodiversity.

Especially, wetlands and the floodplains play an important role in the ecological integrity of aquatic ecosystems and they are of significant importance when it comes to ensuring/achieving good ecological status of adjacent water bodies. Wetlands/floodplains also play a significant role for flood retention. The current situation for European floodplains is critical with 95% of the original floodplain area converted to other uses. Many of the remaining European floodplains are far from pristine and have lost most of their natural functions. For example, of the former 26 000 km² of floodplain area along the Danube and its major tributaries, about 20 000 km² are isolated by levees (summary by Tockner et al, 2008).

Reconnecting backwaters, such as oxbows and side channels, and wetlands aims to restore the lateral connectivity between the main river channel, the riparian area and the wider floodplain and to re-vitalise natural processes.

Also activities for the implementation of the Floods Directive and the elaboration of the Flood Risk Management Plans can significantly contribute to the restoration of disconnected wetlands and floodplains. Table 6.5 illustrates examples of measures implemented during the last years.

Table 6.5: Examples of measures address other hydromorphological pressures.

Source ICPR: River basin management plan 2015. Available at http://www.iksr.org/en/water-framework-directive/river-basin-management-plan-2015/index.html – Section 7.1.1 Restoration of biological river continuity, increase of habitat diversity.

ICPDR 2015; http://www.icpdr.org/main/activities-projects/river-basin-management-plan-update-2015

Austria national RBMP 2015: https://www.bmlfuw.gv.at/wasser/wisa/fachinformation/ngp/ngp-2015/text/textdokument_ngp2015.html

Rhône Mediterranée district 2016: Tableau de bord adopté par le comité de bassin du 27/05/2016. http://www.rhone-mediterranee.eaufrance.fr/gestion/sdage2016/tableau-de-bord.php

Scotland 2^nd RBMP: https://www.sepa.org.uk/environment/water/river-basin-management-planning/the-current-plans/