Scouring-sedimentation balance for gully reaches affected by check dams in Mediterranean environments

Abstract

Many of the geomorphological impacts caused by check dams are usually fairly common in torrential channels (bed agradation upstream into the sedimentary wedges, deepening and narrowing of the bankfull channel downstream, etc). Nevertheless, the extent of these impacts and consequently the degree of effectiveness of the crossstructures is very different depending on the environmental characteristics of the catchments and on the hydrological rectification systems (spatial distribution of check dams, location, number and type of work). A clear indicator of such an influence is the channel response to the deficit and overfeeding of sediments (Brandt, 2000; Lenzi et al., 2003; Marion et al., 2006; Comiti et al., 2005). In such a way, this study has as its objective to show the influence of staggered check dams of gabions on the scouring-sedi-mentation balance in Mediterranean ephemeral gullies submitted to Projects of Hydrological Forest Restoration (PHFR). For areas of study, two semiarid gullied catchments with a strong tendency to dry up have been chosen: Torrecilla and Cárcavo catchments (South-east Spain). The Torrecilla catchment (15.5 km2) shows a gullied area develo-ped on metamorphic materials (slates, phyllites, schists and quartzites), while the Cárcavo catchment (34.8 km2) is drained by ephemeral channels and gullies that dissect deeply the Miocene marls and Quaternary pediments. The hydrological rectification projects undertaken are similar in both catchments: 33 and 40 check dam series were constructed respectively during the 1970s, the majority of them with gabions.