Comparative analysis of the performance of mixed terraces and level and graded terraces/Analise comparativa do desempenho de terracos mistos com terracos em nivel e com gradiente

• Published in: Acta scientiarum. Agronomy 2012-10, Vol.34 (4), p.351-357
• Main Authors: de Oliveira, Josiane Rosa Silva, Pruski, Fernando Falco, da Silva, Jose Marcio Alves, da Silva, Danilo Paulucio
• Format: Article
• Language: eng ; spa
• Subjects: conservação de água e solo; control of water erosion; controle da erosão hídrica; soil and water conservation; terraces; terraços
• ISSN: 1679-9275; 1807-8621
• DOI: 10.4025/actasciagron.v34i4.14755

The terracing of agricultural land is the most widespread mechanical practice used among farmers in the control of water erosion. The objective of this paper was to carry out a comparative analysis between mixed terraces and level and graded terraces. The dimensioning of level terraces was carried out based on the surface runoff volume, while the graded terrace dimensions were based on the maximum runoff flow rate. For the mixed terraces, the dimensioning was carried by considering two surface runoff hydrographs, one for the determination of the terrace channel capacity and another to estimate the flow rate at the extremity of the terrace channel. Therefore, in order to contain and transport the excess volume, an additional value was calculated and added to the depth of the channel. A case study was performed for the Uberaba, Minas Gerais State (Brazil) rainfall conditions, considering events with return periods of 10, 30, and 50 years. The obtained results provided quantitative evidence that mixed terraces have a lower height than level terraces and a higher level than the graded terraces, resulting in direct consequences for the soil movement for the terrace construction. Keywords: terraces, soil and water conservation, control of water erosion. O terraceamento de terras agricolas consiste na pratica mecanica mais difundida entre os agricultores no controle da erosao hidrica. O objetivo deste trabalho foi proceder a analise comparativa do desempenho de terracos mistos com terracos em nivel e com gradiente. O dimensionamento de terracos em nivel foi feito com base no volume de escoamento superficial, enquanto o de terracos com gradiente foi baseado na vazao maxima de escoamento superficial. Para o dimensionamento de terracos mistos sao utilizados dois hidrogramas de escoamento superficial, sendo um para a determinacao da capacidade de armazenamento do terraco e o outro para a estimativa da vazao que escoa na extremidade do canal do terraco. Assim, de maneira a conter e transportar o excesso de volume escoado, um valor adicional foi calculado e somado a altura do canal. Um estudo de caso foi realizado para condicoes de precipitacao de Uberaba, Estado de Minas Gerais (Brasil), considerando eventos de precipitacao com periodo de retorno de 10, 30 e 50 anos. Os resultados obtidos permitiram evidenciar, quantitativamente, que terracos mistos requerem menor altura do que os terracos em nivel e maior que os com gradiente, o que traz consequencias diretas na movi