Andujar village sits on the right bank of Guadalquivir River. Its origin precedes the arrival of the Romans. During the 20th century, small hydroelectric power plants were built in its surroundings. The closest one is the Marmolejo reservoir, 16 km downstream from Andujar. It is a concrete dam regulated with gates, which raises about 20 m over the water level surface. It had a capacity of 11.4 hm(3). The operating water level places the reservoir tail in the Roman bridge of Andujar. In the 90s there were significant flood events in the Guadalquivir valley, which came to affect Andujar with floods that traditionally did not generate problems. The Guadalquivir Water Administration ("La Confederacion Hidrografica del Guadalquivir"), as the competent water Administration, carried out a series of measures, such as longitudinal weirs and dredging, with little success. CEDEX began to collaborate in this study, after the April 2013 flood event. A new 2D hydrodynamic model was carried out with Iber, considering the riverbed sediment evolution thanks to the available bathymetries of 1962, 1997, 2001, and 2014. In 1997 the reservoir had lost 81% of its capacity, and the accumulated sediment considerably raised the flood events water levels. Therefore, Andujar's first defense measure against flooding is to control the reservoir sediment level. It also was found that the flood events of 2010 and 2013 dragged a large amount of sediment, leaving the capacity at 65% of the initial one. This shows that the sedimentation process is reversible. To analyze the sedimentation process of the reservoir, six other bathymetries have been obtained since 2018. They have been carried out strategically, before and after flood events, or dry periods, in which the reservoir water level is maintained. Suspended sediment sampling campaigns are also being carried out. It has been found that the sediment concentration is very high mainly due to the high soil erosion. The reservoir basin has an area of 313,200 ha, of which 58% are olive plantations. ENDESA, the power plant operator, has collaborated in these works. Currently the sedimentation processes are being numerically simulated with the Ariathurai & Arulanandam model (1978) for cohesive materials. The evolution of the reservoir has been simulated in the periods between the different bathymetries, which has allowed to calibrate shear stresses of erosion and sedimentation in the model. The reservoir sedimentation is highly conditioned by its operation, during dry periods, which can sometimes last for years, the reservoir level remains at the operating level, favoring sedimentation. During flood events, a large amount of sediment is dragged. With the numerical model, the best management strategies are being studied, allowing to maintain the profitability of the hydroelectric power plant as well as maintaining low sediment levels that guarantee the safety of Andujar against floods.
