Erosion and urban sediment control using straw blankets woven from recycled plastic threads
Terezinha Cássia de Brito Galvão, Aloisio Rodrigues Pereira, Arnaldo Teixeira Coelho, Paula Rodrigues Pereira and Joaquim Fernandes Teixeira Coelho

Soil erosion and sediment transport represent invisible threats that, in small steps, impact severely on the existing infrastructure of roads and dams, and on the quality of air and water resources. In recent decades, a large amount of research has been devoted to erosion and sediment-transportation processes. However, it was mostly concentrated on agricultural areas, water impoundments for dams, and land conservation; very few projects were specifically devoted to urban areas. There is a lack of studies devoted to urban areas, combined with the need to diminish the amount of sediment originating from those areas that enters rivers and the atmosphere, in particular as airborne particulates. Traditionally, the costs associated with controlling erosion and sediments in urban areas are high, and, in some cases, out of the range of most developing countries. The main factors responsible for these high prices are the use of heavy equipment for soil grading and transportation, and the use of costly building materials. Also, there is the need to employ more specialized personnel. In the case of gullies in urban areas, another concern is to ensure proper equipment access to the study area. In this paper, a cost-effective method to remediate an extensive gully erosional area of about 11?000 m2 located in an urban area is presented. The estimated amount of sediment released from this area was about 66?000?000 tons. The bioengineering works were performed in 60 days, with almost no sediments generated outside the work area and grading. In this case, bioengineering techniques were applied by using a combination of rigid and biological products: including biologs; silt fences; biodegradable straw; and blankets made from plastic threads derived from recycled PET bottles. In addition to this, an efficient drainage system was designed in order to prevent upland flow, sub-seepage and seepage. Biologs were used as barrier to soil and sediment flow and as a filler for empty spaces. The works were performed in 60 days at a cost of US$0.89/m2, in comparison to traditional methods that would have cost US$2.92/m2. The airborne particulates and the overall visual aesthetics improved shortly after the implementation of the works, and, after six months, the vegetation was completely established. Monitoring was performed after twelve months, and no erosion and/ or sediment transport was visible.

The ease of implementation of the techniques without the need for specialized workers, in combination with low prices, makes this method a model for developing countries.

Key words: bioengineering techniques, erosion in tropics, gully erosion recovery, revegetation

Land Contamination & Reclamation, 18 (4), 383-388 (2011)

DOI 10.2462/09670513.1018

© EPP Publications Ltd 2011

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Article code 1018