Author(s)

J. A. Mintegui Aguirre, J. C. Robredo Sánchez, L. Mao & M. A. Lenzi

Abstract

The Arroyo del Partido is a small stream flowing into the Doñana National Park marsh. In its lower part, the stream used to flow in a wide, low-gradient area, where the channel was highly dynamic with frequent avulsions. As a result of a channel rectification, the subsequent floods heavily eroded the artificial banks and created over time a depositional fan within the Doñana marsh. The bedload dynamic at the annual scale was estimated from the expansion of the sedimentation fan, assessed from aerial photographs analysis and repetitive topographic surveys. The bedload transport ranged from 3.7×106 to 2.1×103 m3 per year, depending on the sequences of occurring floods and on the changing geometrical conditions of the main channel. The progressive erosion of the artificial banks led to self-established cross-sections and slope geometry, which reduced shear stress acting on the bed and favoured sediment deposition on the floodplains, reducing overtime the expansion of the sedimentation fan. This evidence has been used to plan a restoration strategy for the fan and floodplains, aimed to mitigate the effect of the embankment and to improve the overall functionality of the stream. As a result of the restoration, an artificial levee was eliminated and a wide floodplain area was recreated as a free-meandering floodplain. Keywords: channel rectification, sedimentation fan, sediment transport, aerial photographs, topographical surveys, channel restoration.

Keywords

channel rectification, sedimentation fan, sediment transport, aerial photographs, topographical surveys, channel restoration