Author(s): M. D. Bejarano; M. Gonzalez Del Tanago; M. Marchamalo; D. Garcia De Jalon
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Abstract: Flow stabilization by reducing frequency of high flows and modification of natural intrannual flow fluctuations because of dams, are considered to be an important cause of altered riparian corridors and floodplain forests. Periodically, in natural conditions, the floodplain is disturbed by floods which cause channel movement, and provides water, sediment and organic debris. As a result, potential regeneration sites increase, and delivery and establishment of seeds and vegetative regeneration processes are favoured. Rooting, germination and survival of vegetation are also dependent on seasonal water levels and fall and raise flow rates. In order to assess such effects, in this paper, an investigation of the changes of structure, composition and abundance of woody vegetation at islands, banks and floodplains bellow Rosarito dam (Tietar river, Spain) was carried out. Regeneration and succesional patterns were also taken into account. The study combined pre and post dam construction aerial photo comparisons and field surveys at one kilometer length reaches along 65 kilometers of river bellow dam. Several photo and field variables were computed and the complete dataset was statistically processed. Results showed an increase of suitable areas for plant colonization and a general increase of vegetation coverage. Regulation initiated new vegetation successional patterns in new areas and it was detected that certain species regeneration, survival and development were favoured by new hydrological conditions while others were not. A downstream trend of such changes was found out.
Year: 2009