Studies on the geomorphic processes of overland flow and mass movements in the brazilian geomorphology

Abstract

There have been sharp changes in Brazilian geomorphological studies, from the fifties to the seventies of the twentieth century, due to new theoretical developments that have been opposed to the Davisian paradigm. Such studies of deposits correlative to erosional episodes in the Cenozoic stimulated investigation and interpretation with new techniques of weathered, pedogenetic and colluvial materials. They led to constitution of researcher teams under the leadership, among others, of Ab'Saber, Bigarella and Tricart. At the time, other research was already under way on the estimation of losses by erosion in Brazilian agricultural soils. Geomorphologic research on a broader scale was much influenced, during the seventies, by several external factors, such as techniques of remote sensing, new publications stressing the role of tropical and subtropical process studies, relating forms, materials and processes, catastrophic landslides in Sao Paulo and Rio de Janeiro, in the 1966/67 summer, new knowledge of quantification, geochemistry, soil mechanics, meteorology and climatology of atmospheric circulation on the South Atlantic, forest clearing, draughts and fight against soil erosion. The visits of professor Yan De Ploey from the Catholic University of Leuven, Belgium, in 1977/78/79, fostered much Brazilian research on the dynamics of natural geomorphic processes happening on hillslopes, plains and coasts of tropical humid areas, such as overland and channel flow, and mass movements. De Ploey influenced and brought about remarkable changes in several geomorphological trends, always linked to field experimentation, such as the application of troughs to collect pluvial waters on slopes, or studies on the movement of the thick weathered materials and colluvia using sheargraph, or still detection of gullied risk areas and measurements of fluvial waters velocity and transportation power. In the eighties and nineties, attention to erosional phenomena indicated that natural processes are becoming faster, influenced by anthropic dynamics which interferes with nature. The consolidation of the Brazilian Geomorphology Union confirms the wish for more participation of geomorphologists in the study of contemporary serious environmental problems.