Changes in meander geometry over the last 250 years along the lower Guadalquivir River (southern Spain) in response to hydrological and human factors

Abstract

Meandering rivers and their morphological changes have been extensively investigated in fluvial geomorphology, but little knowledge is available on the meander geometry response in rivers heavily impacted by dams and their relative importance compared to natural hydrological and climatic variability. Understanding the causes of planimetric changes has several implications for assessing channel dynamics hazards and alterations of physical habitats and ecosystems. A multi-temporal analysis of meandering changes along the lower Guadalquivir River over the last 250 years was conducted with the aim of investigating possible climatic and human factors. Changes in controlling factors were investigated by hydrological analysis. A sequence of historical maps and aerial photos, and data analysis by GIS were used to analyse changes in meander geometry at the bend scale and planform parameters at the segment scale. The results showed two periods of changes in meander geometry influenced by different factors: (i) a historical period (1750–1915) of dynamic oscillations during a period of high concentration of floods; (ii) the period 1915–2010, with a drastic reduction in meandering size and sinuosity and a fragmentation of the active band, representing a rapid response to the extensive construction of dams in the catchment and the associated flow regime and sediment transfer alterations.