The Ramsar Convention's resources on Wetland Restoration

The STRP Expert Working Group on Wetland Restoration

Restoration Approach: Prescribed flooding

Wetland type: River floodplain wetlands that have been degraded by the construction of upstream dams and water diversions.

Background: On a global scale, floodplain wetlands have been severely degraded by changes in the magnitude, timing, duration, and frequency of flooding events resulting from the management of upstream dams and water diversions. Re-establishing the physical and biological connections between the river channel and associated floodplain wetlands is essential to the rehabilitation of river-floodplain systems. In Africa, artificial flood releases below large dams are being tested as a means of wetland management and sustainable development. In Nigeria, for example, artificial flood releases from the Tiga and Challawa Gorge Dams have been promising and could be used further to help restore the Komadugu-Yobe basin's ecosystems. In the Senegal River basin, studies have demonstrated that floodplain conditions below Manantali Dam would be improved with only a small reduction in hydropower, and that the cost of the lost hydropower is substantially outweighed by the economic benefits to agriculture and fisheries. In the Zambezi River basin, research is demonstrating that prescribed flood releases from Cahora Bassa dam could provide millions of dollars in benefit from increased shrimp production, improved quality of wildlife grazing lands, restored floodplain fisheries, and other social and ecological benefits.

Advantages: Prescribed flood releases may be the only way to reintroduce the natural timing, duration, magnitude, and frequency of floodwaters in flood-dependent wetland systems, using natural processes to restore wetland diversity and heterogeneity; numerous studies suggest that the economic benefits of improved flood management may outweigh the costs in terms of other potential water uses; efforts may benefit both human and ecological communities.

Disadvantages: Involves an often complex political process to gain local and institutional support for flood releases from among competing demands for water among river basin stakeholders, particularly in larger river-floodplain systems; flood releases may not solve other problems associated with dams and diversions such as reduced floodplain siltation or poor water quality; some of the changes in wetlands systems caused by water regulation may not be readily reversed by mimicking former hydrological conditions, requiring other complementary restoration practices; some dams may not be designed to enable planned flood releases.

Further information: The World Commission on Dams Web site <www.dams.org> includes comprehensive information on the impact of dams on floodplain wetlands and the potential benefits of prescribed flooding.

References:

• Acreman, M. 1994. The role of artificial flooding in the integrated development of river basins in Africa. p. 35-44 In C. Kirby and W.R. White (eds.) Integrated River Basin Development. John Wiley and Sons, Chichester, UK.
• Bayley, P.B. 1991. The flood pulse advantage and the restoration of river-floodplain systems. Regulated Rivers: Research and Management 6:75-86.
• Bayley, P.B. 1995. Understanding large river-floodplain ecosystems. Bioscience 45:153-158.
• Beilfuss, R.D. and B.R. Davies. 1999. Prescribed flooding and the rehabilitation of the Zambezi Delta, Mozambique. Pages 143-158 in W.J. Streever, ed, An International Perspective on Wetland Rehabilitation. Kluwer Academic Publishers, the Netherlands.
• Bruwer, C., C. Poultney, and Z. Nyathi. 1997. Community based hydrological management of the Phongolo floodplain. p. 199-212 In M. Acreman and G.E. Hollis (eds.). IUCN/The World Conservation Union, Gland, Switzerland.
• Gammelsrod, T. 1996. Effect of Zambezi River management on the prawn fishery of the Sofala Bank. p. 119-124 In M.C. Acreman and G.E. Hollis (eds.) Water Management and Wetlands in Sub-Saharan Africa. IUCN, Gland, Switzerland.
• Horowitz, M.M. 1994. The management of an African river basin: alternative scenarios for environmentally sustainable economic development and poverty alleviation. p. 73-82 In Koblenz (ed.) Proceedings of the International UNESCO symposium: Water resources planning in a changing world. International Hydrological Program of UNESCO/OHP National Committee of Germany, Karlsrue, Germany.
• Junk, W.J., P.B. Bayley, and R. Sparks. 1989. The flood pulse concept in river-floodplain systems. p. 110-127 In D.P. Dodge (ed.) Proceedings of the International Large River Symposium, Canadian Special Publications in Fish. and Aquatic Science. v. 106.
• Scudder, T. and M.C. Acreman. 1996. Water management for the conservation of the Kafue wetlands, Zambia and the practicalities of artificial flood releases. p. 101-106 In M.C. Acreman and G.E. Hollis (eds.) Water Management and Wetlands in Sub-Saharan Africa. IUCN, Gland, Switzerland.
• Stanford, J.A., J.V. Ward, W.J. Liss, C.A. Frissell, R.N. Williams, J.A. Lichatowich, and C.C. Coutant. 1996. A general protocol for restoration of regulated rivers. Regulated Rivers 12: 391-413.
• Vaselaar, R.T. 1997. Opening the flood gates: the 1996 Glen Canyon Dam experiment. Restoration and Management Notes 15(2):119-125.
• Welcomme, R.L. 1995. Relationships between fisheries and the integrity of river systems. Regulated Rivers 11(1):121-136.
• Wesseling, J.W., E. Naah. C.A. Drijver, and D. Ngantou. 1996. Rehabilitation of Logone floodplain, Cameroon, through hydrological management. p. 185-198 In M.C. Acreman and G.E. Hollis (eds.) Water Management and Wetlands in Sub-Saharan Africa. IUCN, Gland, Switzerland.

-- Contributed by Richard Beilfuss, International Crane Foundation

Flood release from one of eight sluice gates on Cahora Bassa Dam in Mozambique

 Flood releases may be necessary to re-establish the hydrological link between river and floodplain, flushing out abandoned waterways and reversing the spread of less flood-tolerant species in the wetland. 

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For further information about the Ramsar Convention on Wetlands, please contact the Ramsar Convention Bureau, Rue Mauverney 28, CH-1196 Gland, Switzerland (tel +41 22 999 0170, fax +41 22 999 0169, e-mail ). Posted 15 February 2002, Bill Streever and Dwight Peck.