Restoration of a degraded torrential stream by means of a flood control system: the case of Arroyo del Partido stream (Spain)

摘要

The Arroyo del Partido is a small torrential stream (307.67 km~2), draining into the El Rocio marsh, in the Donana National Park (Spain). The DNP was declared a UNESCO Heritage site (1994), since it has an important role for bird migration between Europe and Africa. The last reach (7 km) of the stream was channelized in 1981, thereby the flowing conditions during floods changed. This fact caused the formation of a large alluvial fan over the wetland surface during the period 1982-200; covering an area of 4.31 km; with a volume of 4.48 × 10~6 m~3. In order to contain the advance of the fan into the marsh a flood control system was used. This control system consists of two check dams, one of them placed on the channelized reach, and a second one placed on a different stream, which receives the surplus flows of the Arroyo del Partido during floods. Between both streams a flood plain was reserved for sediments deposition and flood attenuation purposes. Reconstruction works were carried out in the summer of 2006. During the period 2007-09, works were monitored and adjusted on the basis of their behaviour in flood events, with the objective of restoring the former hydrological regime before the channelization.