Produção de sedimentos em áreas urbanas: o caso da Microbacia do Córrego do Pau DAlho. Guarulhos, SP

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This work presents the research results about sediment yield related to actual land use in Pau dAlho watershed, about 0, 51 km2, located at Cabuçu region, Guarulhos, SP. The research was conducted by an Engineering Geology approach encompassing technogenic sediment deposits survey, the environment characterization and the history of land use that originated such deposits. Field recognitions were done to estimate sediment produced and erosion volumes in source areas and inhabitants interviews to land use history recover. Laboratory analyses were done to determine sediment grain sizes and bulk densities, and remote sensing interpretations of different surveys to understand the land use evolution. The results revealed the occurrence of a rural and an urban deposits, indicating the existence of 4 main phases of sediment yield evolution: a natural, previous occupation phase; a land agricultural use phase; an urban phase with deposition of the sediment and another one, the current one, with the deposits river incision. For the rural phase, it was esteem, on the basis of the volume of the deposit and in the time of land agricultural use, about 24 years of chayote of culture, a 61 m3/year (or 91 t/year), that corresponds to an specific sediment yield of about 120 m3/km2.year (or 180 t/km2.year). For the urban phase, a volume of 29.288 m3 total erosion was estimated, for laminar process (or diffuse) and linear (gullies) in source areas, corresponding to urban implantation (20.678 m3) and 8.610 m3 related to the incision of the Pau d Alho stream. Part of the sediments was deposited in the valley bottom forming an urban deposit of 5.593 m3 volume, before the incision. The remaining sediment delivery correspond to 1.185 m3/year (or 1777 t/km2.year) sediment yield, throughout the last 20 years, and specific values of 2.320 m3/km2.year (or 3.484 t/km2.year). The relation between the sediment yield and total erosion indicates 81% sediment delivery ratio, that can be considered very high, however compatible with the small size of the watershed. Although the complexity of watershed land use transformations and the hypotheses adoption of volumes and related times periods to estimate sediment yields, results can be considered compatible with sediment yield values resented in bibliography. Finally, the importance of studies based on current hydrological and sediment instrumentation was indicated by the erosive processes that remain intense in the watershed.

ASSUNTO(S)

depósitos tecnogênicos guarulhos produção de sedimentos uso urbano do solo guarulhos urban land use atershed technogenic deposits microbacia sediment yeild geociencias

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