Hydrologic and land-use change influence landscape diversity in the Ebro River (NE Spain)

The landscape dynamics (1927–2003) of one reach at the Middle Ebro River (NE Spain) was examined using aerial pictures and GIS techniques. Moreover, changes in the natural flow regime and anthropic activities within the river-floodplain system were investigated. Our results indicate that hydrological and landscape patterns have been dramatically changed during the last century as a consequence of human alteration of the fluvial dynamics within the studied reach, as well as the overall basin. The magnitude and variability of river discharge events have decreased, especially since 1981, and flood protection structures have disrupted the river floodplain connectivity. As a result, the succesional pathways of riparian ecotopes have been heavily modified because natural rejuvenation no longer takes place, resulting in decreased landscape diversity. It is apparent from these data that floodplain restoration must be incorporated as a significant factor into river management plans if a more natural functioning wants to be retrieved. The ecotope structure and dynamics of the 1927–1957 should be adopted as the guiding image, whereas hydrologic and landscape (dykes, raised surfaces) patters should be considered. Under the current socio-economic context, the more realistic option seems to create a dynamic river corridor reallocating dykes and lowering floodplain heights. The extent of this river corridor should adapt to the restored flow regime, although periodic economic investments could be an option if the desired self-sustained dynamism is not reached.