Title: WG ECOSTAT report on common understanding of using mitigation measures for reaching Good Ecological Potential for heavily modified water bodies: Part 2: Impacted by flood protection structures
Publisher: Publications Office of the European Union
Publication Year: 2018
JRC N°: JRC110957
ISBN: 978-92-79-80289-8 (print)
978-92-79-80290-4 (pdf)
ISSN: 1018-5593 (print)
1831-9424 (online)
Other Identifiers: EUR 29131 EN
OP KJ-NA-29131-EN-C (print)
OP KJ-NA-29131-EN-N (online)
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC110957
DOI: 10.2760/875939
Type: EUR - Scientific and Technical Research Reports
Abstract: Hydromorphological alterations due to floods are among the most widespread pressures on water bodies in Europe. Along with storms, floods are the most relevant natural disaster in Europe, in terms of economic costs due to direct damage to infrastructure, property and agricultural land, and indirect losses. As such, flood protection structures and actions are among the main causes for hydromorphological alteration and ecological impairment. Moreover, mitigation measures options, in the case of HMWB for flood protection, are very limited. Any action for mitigation could in fact result into a weakening of flood protection, increasing risk for population and assets. However, in a substantial number of these water bodies, the effects of the alterations are expected to require some mitigation if good ecological potential (GEP) is to be achieved. One of the core activities for the CIS WG ECOSTAT between 2013 and 2017 has been to try to compare the ecological quality expected by different countries for water bodies impacted by flood protection. The process involved the use of a number of workshops and questionnaires to collect relevant information from European water managers. This report is based on information collected via a template on mitigation measures for water bodies impacted by flood defence structures, which was completed by 18 countries. The key findings of the exercise are as follows: • Comparing the mitigation expected for good ecological potential by different countries provided a good basis for identifying similarities and differences between those countries’ standards for good ecological potential. It also provided a valuable opportunity for the exchange of information. • Although not all Member States (MS) have developed a national hydromorphological assessment method, most of them answered that their assessment systems can detect the hydromorphological impacts due to flood defence structures and actions. • Regarding the scale of the impacts, it appears that in the case of flood defences, which work in longitudinal, lateral and vertical dimensions, a typical range of length of impacts cannot be found. • Some flood defence structures are not very common in some countries, which could explain why the assessment systems are not actually detecting them (e.g. grade control structures, groynes, etc.). • Few MS have already developed a national library of mitigation measures. Even if a national library for mitigation measures is present, MS may not have considered all the possible impacts from flood defences for different reasons. The reasons for not identifying the need for certain types of mitigation is mainly linked to the fact that in some countries, (e.g. mainly lowland), some flood defences are not used, and therefore the related impacts and measures are not considered. Another reason may be that some countries are lacking an appropriate assessment system to detect some types of impact. • The majority of MS consider measures aimed at enhancing longitudinal connectivity for fish and sediments and e-flows to be both highly effective and without an adverse effect on use. Fish passages and light bank protection structures seem to be considered as the most effective measures. • On the contrary, measures linked to enhancing lateral continuity or heterogeneity of banks and channel are deemed to have an adverse effect on use, lowering the level of protection from floods. • The most common reasons for ruling out mitigation measure options are significant effects on use or the wider environment. Some MS rule out mitigation measures that are technically infeasible and/or disproportionately costly.. • A general preliminary conclusion is that there is a need for a common language in order to understand what flood structures and actions are and their impacts in terms of scales and magnitude, on fluvial hydromorphology and biological processes. • Further development of the use of HMWB in respect to flood protection is also needed, with a better understanding of the effects of mitigation measures on hydromorphology and biota and of the potential adverse effects on the use. This requires close cooperation with experts working on the implementation of the Floods Directive and again calls for the need of a common language and understanding.
JRC Directorate:Sustainable Resources

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