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Soil erosion and land degradation are global problems and pose major issues in many countries. Both soil erosion and mass movement are two forms of land degradation and humans play important roles in these geomorphological processes. This paper reviews slope processes associated with mass movement and soil erosion and contributory factors, including physical and human agents. Acting together, these cause diverse geomorphological features. Slope processes are illustrated by reference to case studies from Brazil and UK. The causes and impacts of erosion are discussed, along with appropriate remedial bioengineering methods and the potential of the measures to prevent these types of environmental degradation. Although there are several agents of erosion, water is the most important one. Cultivation can promote soil erosion, due to ploughing and harvesting, which moves soil down slopes. Soil erosion and mass movement data would inform the viability of soil conservation practices. Integrated management of drainage basins offers a promising way forward for effective soil conservation and soil remedial bioengineering in Brazil and UK

Field and laboratory studies indicate that utilisation of biological geotextiles constructed from palm-leaves and other selected organic materials are an effective, sustainable and economically viable soil conservation technique. The three-year plus

This paper analyses the contribution of biological geotextiles to gully stabilization\ud in the urban area of Sa˜o Luis City (Sacave´m District). Biological geotextile mats\ud were constructed from palm leaves. At Sacave´m, gully rehabilitation included the following\ud techniques: (1) installation of Buriti geotextiles, in association with barriers of\ud wooden stakes and the construction of contoured terraces; (2) analysis of sediment particle\ud size and (3) photograph comparison of the development of vegetal cover. Rehabilitation\ud used *30 kg of grass seeds (Brachiaria decumbens) on slopes, in combination with\ud geotextiles. Besides recuperating a degraded area, income has been generated to poor\ud people, who live around Sacave´m gully, either by producing the geotextiles or by applying\ud them on the soil, together with grass seeds, lime and NPK to improve soil properties

Preliminary investigations suggest biological geotextiles could be an effective and inexpensive soil conservation method, with enormous global potential. However, limited quantitative data are available on the erosion-reducing effects of biological geotextiles. Therefore, the objective is to evaluate the effectiveness of biological geotextiles in reducing runoff and soil loss under controlled laboratory conditions and under field conditions reflecting continental, temperate and tropical environments. In laboratory experiments, interrill runoff, interrill erosion and concentrated flow erosion were simulated using various rainfall intensities, flow shear stresses and slope gradients. Field plot data on the effects of biological geotextiles on sheet and rill erosion were collected in several countries (UK, Hungary, Lithuania, South Africa, Brazil, China and Thailand) under natural rainfall. Overall, based on the field plot data, the tested biological geotextiles reduce runoff depth and soil loss rates on average by 46 per cent and 79 per cent, respectively, compared to the values for bare soil. For the field and laboratory data of all tested geotextiles combined, no significant difference in relative runoff depth between field measurements and interrill laboratory experiments is observed. However, relative soil loss rate for the concentrated flow laboratory experiments are significantly higher compared to the interrill laboratory experiments and the field plot measurements. Although this study points to some shortcomings of conducting laboratory experiments to represent true field conditions, it can be concluded that the range and the mean relative runoff depth and soil loss rate as observed with the field measurements is similar to those as observed with the interrill laboratory experiments.

Available studies do not allow comparison and quantification of the effects of biological geotextiles on runoff and water erosion rates under different agro-environmental conditions. Hence, this paper addresses this issue by comparing runoff and soil loss data obtained from field experiments (using different types of biological geotextiles) conducted in the United Kingdom, Hungary, South Africa, China, Thailand and Vietnam. Palm leaf mats (Borassus and Buriti mats) were used in the European countries. In the UK, Borassus mats were used as whole plot cover (area coverage $76 per cent; termed Borassus completely covered to differentiate from the Borassus buffer strip plots) and as buffer zones (area coverage $10 per cent), whereas Buriti mats were used only as buffer zones (area coverage $10 per cent). Only Lala mats were used in South Africa. Elsewhere (China, Thailand and Vietnam) biological geotextiles were constructed using other indigenous local materials, such as bamboo, rice straw and maize stalks. Biological geotextiles were used on bare plots in South Africa and the European countries. In the UK, plots were maintained bare by need based herbicide spraying. However, in South Asia, different crops were grown on the geotextile-covered plots. Results suggest that biological geotextiles were very effective for soil erosion control in all locations and the effectiveness for decreasing soil erosion rates by water was in the range of $67-99 per cent. The effectiveness of biological geotextiles in reducing runoff volume was in the range of $26-81 per cent. In the UK, total runoff and soil loss (during 8 January 2007-6 May 2008; total precipitation ¼ 1145.8 mm) from the Borassus (one metre wide) buffer zone plots (cover percentage $7.6 per cent) were, respectively, $81 and $93 per cent less than bare plots. In Hungary and China, plots with $38 and 22 per cent geotextile-cover, respectively, had $88 and 96 per cent less soil loss, than bare plots. In most months with low precipitation (depth) in Hungary and the UK, runoff volume was greater from plots with geotextile-cover than from bare soils. However, complete data sets indicate that in the UK and Hungary, runoff reduction by different treatments over bare plots ranged between $26 and 81 per cent. Results from the UK showed that plots with buffer strips of Borassus and Buriti mats had similar effects in reducing soil losses as completely covered plots of the Borassus mats. Thus, foreseeing biological geotextilecover on vulnerable segments of the landscape is highly effective for soil erosion control.

This paper assesses the role of biological geotextiles on non-agricultural erosion environments, based on studies in the mine tailings Gauteng Province (South Africa) and urban area of São Luis City (Brazil). Gauteng Province (South Africa) has suffered immense problems related to sustainable rehabilitation of mine dumps. This is a huge challenge, as wastes are highly susceptible to both water and wind erosion. Establishing a grass cover to reduce erosion is the dominant reclamation method. Covering the slopes with biological geotextiles might constitute another option for mining companies to reduce erosion and aid natural re-vegetation. The objective of the waste part of this study was to determine the beneficial effect of palm mat cover on erosion control, using rainfall simulation. Results clearly illustrated that application of palm-mats more than halved the sediment load in runoff, thereby having the potential to effectively stabilize tailing dam slopes. Covering tailings with palm-mats did not reduce runoff or improve water infiltration, however. In São Luis City, biological geotextile mats were constructed from palm leaves which are an effective, sustainable and economically-viable soil conservation technique. At Sacavém Community biological geotextile mats were used in association with barriers of wooden stakes and the construction of terraces along contour lines. The aim is to minimize soil erosion, by intercepting rainfall, retarding runoff velocity and sediment loss.

Artigo recebido em 15/06/2011 e aceito para publicação em 07/02/2012 RESUMO:Faz-se neste artigo uma análise sobre a relação entre o potencial matricial e a cobertura vegetal em uma estação experimental na Fazenda do Glória, Uberlândia-MG, com base nos dados obtidos nos tensiômetros e na fotocomparação. Foram adotados os seguintes procedimentos: a. Construção de duas parcelas de 10 m 2 cada, uma com Solo Exposto (SE) e outra com Geotêxteis e Gramíneas (SG); b. A análise granulométrica dos sedimentos foi baseada na proposta da EMBRAPA; c. Monitoramento de duas baterias de tensiômetros nas parcelas com solo exposto e com geotêxteis em diferentes profundidades (15, 30, 80 e 120 cm), com o auxílio de um tensímetro digital INFIELD 5; e d. Fotocomparação com classificação supervisionada usando software de sensoriamento remoto. Os resultados foram divididos em três fases: 1. na fase 1, a ocupação da cobertura vegetal variou entre 0 a 6,4%, destacando-se o tensiômetro de 120 cm cm na parcela com geotêxteis, que atingiu -20 kPa; 2. na fase 2, com uma taxa de ocupação variando entre 15,2% a 59,4 % na parcela com geotêxteis e gramíneas, o potencial matricial chegou a -32,4 kPa na profundidade de 15 cm; e 3. na fase 3, com uma taxa de ocupação da gramínea entre 63,9% a 100% , cita-se o tensiômetro de 30 cm, que chegou a -67 kPa. Palavras-chave: Potencial matricial, cobertura vegetal e geotêxteis. ABSTRACT:The aim of this research is to analyse the relationship between soil matrix potential and vegetation cover on an experimental station in the Gloria Farm, Uberlândia Municipality, Minas Gerais State, taking into consideration the data from tensiometers and photo comparison. We have been using the following procedures: a. two plots were set up, with 10 m square, one with bare soil and another one with geotextile and grass; b. Granulometric analyse was based on EMBRAPA; c. Monitoring of two tensiometers sets on geotextile and grass plot in different depths (15, 30, 80 e 120 cm), it was used the INFIELD 5 digital tensimeter; and d. Photo comparison data from supervised classification using remote sensing software. The results were split up into three periods: the first one, vegetation cover index ranged from 0 to 6.4% and soil matrix potential reached -20 kPa in 120 cm depth on geotextile plot; the second one, grass cover