Revision as of 09:20, 9 July 2010

Link flood reduction with ecological restoration

Link flood reduction with ecological restoration03. Flow dynamics improvement

General description

The measures for ecological restoration projects in Europe on the River floodplains before the issue of WFD have been addressed to one or two river floodplain functions/services: water storage for flood mitigation, nature/biodiversity conservation or both (Marin et al., 1997; Vadineanu et al.,1998; Schiemer, 1999; Smits et al., 2000; Hughes F.M.R, 2000; Klijn and Duel, 2000; Cals and Drimmelen., 2000; Morris et al., 2005), nutrient cycling (Heiler et al.,1995) and less to the multiple ecological objectives as river system integrity and ecological status. More emphases was given to measures aiming to restore lateral connectivity between rivers and floodplains since 2001, aiming to improve ecological status and integrity of the rivers but also to restore water storage function of the floodplains. Concepts as ,,fluvial territory”, ,,room for rivers” ” or ,, free space for rivers”, ,,espace de liberté fluvial”, ,,erodible corridor”, or simply ,,wetland (or floodplain) restoration”, have been developed across Europe, supporting restoration of the connectivity between the river and its floodplain for multiple purposes, including flood reduction. The concept ,,Room for Rivers” was promoted in the Netherlands in 1996 as an alternative to a new round of dike raising to prevent floods (Silva et al., 2001; Buijse et al., 2002; Vis et al., 2003), whereas the term ,,Fluvial Territory” is related to the Spanish River Restoration Strategy, 2007 (Ollero et al., 2007; Ollero et al., 2009) which is an adaptation of the French ,,espace de liberte fluvial” and ,,erodible corridor”(Piegay et al., 1996; Malavoi et al., 1998; Piégay et al., 2005). Similarely, the Italian term ,,fascia di pertinenza fluvial” (Govi and Turitto, 1994). All these terms define flood strategies based on enlargement of the fluvial space that includes river bed, riparian corridor and the floodplain in their dynamics.

Applicability

The large-river floodplain restoration projects are long term undertakings. Beside the complexity of the floodplain ecosystems, the present land use and the degree of adverse effect of restoration works on economic activities or flood defense structures could hamper implementation. When looking at the reconstruction of a floodplain, first the function must be defined (Plateew et al., 2001). However, experience shows that political and socio-economical conditions (property, status of the area, political decision-makers) play a far more important role in implementation of floodplain restoration projects than the actual land use (Gunther-Diringer D., 2000). The private ownership is often a serious constraint for implementation and a limitation of the dimension in space.

Expected effect of measure on (including literature citations):

• HYMO (general and specified per HYMO element)
• physico � chemical parameters
• Biota (general and specified per Biological quality elements)

All the concepts described aim, to reduce floods in a natural way reducing the peak flows by overflowing inside the riparian and floodplain areas what slows down the wave of flood, mitigating the risk and saving in defences and compensations. It is, in fact, a new defence system, a resiliency strategy, opposite to the traditional resistance strategies (dikes, embankments, etc.). This strategy is in line with both EU Water and Floods Directive requirements. The effects of ecological restoration on the river hydrology were subject to sound hydraulic modelling exercises and predictions of reducing flood peaks downstream of creating storage room for floodwater (Nielsen et al., 1991 ; Hooijer A., 1996 ; Plateew et al., 2001). An assessment by WWF International of the four pilot implemented floodplain restoration projects in Europe, has confirmed the effect on mitigation of flood (Zockler et al. 2000).

Temporal and spatial response

Pressures that can be addressed by this measure

• Hydrological regime modification
• Alteration of instream habitat

Cost-efficiency

Case studies where this measure has been applied

• Millingerwaard - Floodplain rehabilitation
• Vreugderijkerwaard - Side channel
• Rijkelse Bemden - River bed widening
• Thur
• Low reach of River Cinca
• Warta Middle River Valley
• Vallacuera ravine. Removal of a dyke.
• Drava - Kleblach
• Enns - Aich
• Polder Ingelheim – Restoring former floodplains (INTERREG Sustainable Development of Floodplains)
• Hondsbroeksche Pleij – Restoring former floodplains (INTERREG Sustainable Development of Floodplains)
• Bemmelse Waard – Restoring former floodplains (INTERREG Sustainable Development of Floodplains)
• Niederwerrieser Weg - Optimisation of the pSCI “Lippe floodplain between Hamm and Hangfort” (LIFE05/NAT/D/000057)
• Oberwerries - Optimisation of the pSCI “Lippe floodplain between Hamm and Hangfort” (LIFE05/NAT/D/000057)
• Ahlen-Dolberg - Optimisation of the pSCI “Lippe floodplain between Hamm and Hangfort” (LIFE05/NAT/D/000057)
• Soest - Optimisation of the pSCI “Lippe floodplain between Hamm and Hangfort” (LIFE05/NAT/D/000057)
• IJssel
• Scheldt - Vallei Grote Nete
• Rhine - Meinerswijk
• Rhine - Polder Altenheim
• Drava - River Widening Amlach/St. Peter
• Drava - River Widening Obergottesfeld
• Drava - River Widening Rosenheim
• Rhine - Nebenrinne Bislich-Vahnum (LIFE08 NAT/D/000007)
• Rhine - Ontpoldering Noordwaard
• Rhine - Emmericher Ward (LIFE10 NAT/DE/000010)
• Lower Traun

Useful references

Other relevant information