Estabilização de taludes marginais com técnicas de bioengenharia de solos no Baixo São Francisco

Abstract

RESUMOOs taludes marginais no baixo curso do Rio São Francisco, dominados por solos de baixa coesão sofrem com o avanço da erosão que causa recuo da margem e assoreamento do canal. A proposta deste trabalho foi estudar a aplicação da bioengenharia de solos visando ao controle da erosão por meio da estabilização dos taludes marginais, para posterior recuperação da vegetação ciliar. A área experimental foi dividida em dois tratamentos com 3 repetições, sendo o tratamento sem uso de bioengenharia (testemunha) implantado à montante do fluxo da água e o tratamento com uso de bioengenharia, à jusante. A técnica de bioengenharia de solos foi caracterizada pela associação do geotêxtil Fibrax® 400 BF com gramínea Brachiaria decumbens, e retentores de sedimentos (Bermalongas®) ao longo da linha d'água. Para avaliação do comportamento do talude realizou-se levantamento topográfico planialtimétrico aos 30, 180, 360 e 540 dias de implantação do experimento. No tratamento sem proteção de bioengenharia (testemunha) ocorreram variações significativas no perfil topográfico, enquanto no talude protegido com bioengenharia ocorreram movimentos de massa pouco expressivos. Palavras-chave: erosão marginal, Rio São Francisco, geotêxtilRiverbank stabilization with soil bioengineering techniques at the Lower São Francisco River ABSTRACTThe river banks of the Lower São Francisco River, which mostly present low cohesion soils, have suffered with the increase in erosion, leading to margin retreat and sedimentation. The purpose of this work was to study the application of a soil bioengineering technique in order to control the riverbank erosion by its stabilization aiming toward the riparian vegetation recovery. The experimental area was divided in two different assays, with three replications. The test assay (without the soil bioengineering technique) was installed upstream, and the assay with soil bioengineering was installed downsteam. The soil bioengineering technique was characterized by the association of the biotextile screen under the trade name Fibrax® 400BF, associated with Brachiaria decumbens grass and sediment retainers under the trade name Bermalonga®, installed along the river bank base. In order to evaluate the riverbank changes, direct topographic measures was used. The data was collected 30, 180, 360 and 540 days after the beginning of the study. At the assay without soil bioengineering protection, strong slope soil mass movement occurred. The opposite behavior occurred in the assay with soil bioengineering, with a very little soil movement.

Biotechnical Potential of Paspalum Submitted to Simple Superphosphate Doses and Moisture Content

“…The reinforcement promoted by the root system of the plants promotes the aggregation of alluvial soils, which are generally less cohesive, reducing the particle drag, resulting in a lower rate of erosion and reducing the sedimentation of watercourses (HOLANDA et al, 2008).…”

Environmental Services Associated With the Reclamation of Areas Degraded by Mining: Potential for Payments for Environmental Services

“…(2008) Reduction in quantity of water reaching the soil; reduction of positive pore pressure / elevation of suction pressure; increased soil-root cohesion Lemes (2001) Development facilitation for riparian vegetation Holanda, Rocha and Oliveira (2008) Source: Constructed by the authors, through bibliographic research and content analysis.…”

“…Pinheiro (1971), Coelho (2005), Galas (2006), Lemes (2001), and Holanda, Rocha and Oliveira (2008) have described the ES associated with soil bioengineering which are related to improvements in the soil conditions. Holanda, Rocha and Oliveira (2008) have in addition highlighted ES related to the facilitation of the development of land coverage by vegetation, which can be associated with soil bioengineering techniques. The ES identified in the studies that examined soil bioengineering as a measure in RDA are presented in Table 2.…”

Meteorological and hydrological variables on occurrence of riverbank erosion along lower São Francisco river

“…In the study area (geographic Universal Transverse Mercator (UTM) coordinates: 8868.461,918 N/744.301,092 E, SAD69 Zone 24S), a large concentration of erosion occurrences have been previously identified on the almost completely deforested banks, specifically on a slope with approximate dimensions of 127 m length, 11 m width, and mean slope of 43.03%; the area and perimeter were approximately 1.397 m² and 276 m, respectively (Holanda et al, 2008).…”

“…Coops et al (1996) compared the effects of waves on artificial streams in the case of treatments with and without the protective vegetation and concluded that the erosion values for the unprotected banks were higher. Similarly Holanda et al (2008) conducted studies along the Lower São Francisco River and attributed the changes in the cross-sections mainly to the actions of the shock waves at the base of the riverbank slopes.…”