Morphologic development, relative sea level rise and sustainable management of water and sediment in the Ebre Delta, Spain

• Published in: Journal of coastal conservation 1997-09, Vol.3 (2), p.191-202
• Main Authors: Ibanez, C. (Barcelona Univ. (Spain). Dept. d'Ecologia), Canicio, A, Day, J.W, Curco, A
• Format: Article
• Language: English
• Subjects: Accretion; Coastal; Dam construction; Dams; DELTA; DELTAS; Deposition; Dikes; Discharge; Embankments; ESPAGNE; ESPANA; Eustatic changes; Freshwater; GESTION DES EAUX; Hydroelectric power; Inland water environment; Levees; MAR MEDITERRANEO; Marine; Mean sea level; MEDITERRANEAN SEA; MER MEDITERRANEE; NIVEAU DE LA MER; NIVEL DEL MAR; Offsets; ORDENACION DE AGUAS; Oryza sativa; Reservoirs; Rice; Rice fields; River deltas; River mouth; River mouths; Rivers; Salt marshes; Saltmarshes; SEA LEVEL; Sea level changes; Sea level rise; Sediment; SEDIMENTACION; SEDIMENTATION; Sediments; SPAIN; Stocks; Subsidence; Sustainability management; Sustainable agriculture; Topographical elevation; WATER MANAGEMENT; Waterlogging; Watersheds; Wetlands
• ISSN: 1400-0350; 1874-7841
• DOI: 10.1007/BF02905244

The Ebre (Ebro) Delta is one of the most important wetland areas in the western Mediterranean. Ca. 40% of the delta plain is less than 0.5 m above mean sea level and part of the southern margin of the delta is at mean sea level in an area protected by dikes. Both mean rates of secular subsidence in the Ebre Delta and eustatic sea level rise are ca. 1 - 2 mm/yr. Thus, the present annual relative sea level rise (RSLR) rate in the Ebre Delta may be at least 3 mm/yr. Measured accretion rates in the delta range from 4 mm/yr in the wetlands surrounding the river mouth to 99% of the riverine sediments are retained in the reservoirs and rice fields are losing ca. 0.2 mm/yr. Future management plans should take RSLR into account and include control of freshwater and sediment flows from the river in order to offset negative effects from waterlogging and salt intrusion, and maintain land elevation. This will include the partial removal of sediments trapped behind the Ribarroja and Mequinença dams. Stocks and inputs of sediments in the corresponding reservoirs are large enough for land elevation of ca. 50 cm in the whole delta plain. Advantages of this solution include (1) new sediments to the delta to offset subsidence (via rice fields) and coastal retreat, (2) enhanced functioning of the delta (productivity and nutrient processing), (3) avoidance of accumulation of sediments in the reservoirs. Hence, it is important to manage river discharges at the dams from an integrated viewpoint, whereas currently only hydropower and agricultural requirements are considered. It is also crucial to maintain periods of high discharge, to have enough river energy to transport as much sediments as possible.