ANÁLISE da IMPERMEABILIZAÇÃO DOS SOLOS e AUMENTO DOS PICOS de VAZÃO de CHEIAS em BACIAS HIDROGRÁFICAS URBANAS

Abstract

The main idea of this work is to apply one hydrological model to evaluate the relationship between rainfall and runoff of medium size basins. Data treatment and thematically maps made under GIS environment were used to quantify the spatial distribution of several hydrological components. The hydrological model created considers proper characteristics of the area under study and it was based on urbanization impact over drainage systems, where simulated peaks of discharge obtained quantify areas of impermeable surfaces. Cartographic bases of surface covering of land of 1962, 1980 and 2000 were accomplished by digital photogrammetry technique. For the digital photointerpretation, the software Erdas Imagine 8.6 ("Stereo Analyst" function) was run to obtain surface covering maps. The increases of runoff coefficient and maximum discharge were quantified using a modification of Rational Equation. In order to run these calculations, some hydrological parameters were established: rainfall intensity, basin physical characteristics including size, talvegue length, concentration time, soil hydrologic groups, soil antecedence humity, declivity land surface, effective precipitation, potential maximum retention (S), time of hydrogram pick, reduction factor of hydrogram and runoff coefficient (C). During GIS step a data set containing thematic information of basin surface combining maps confectioned and tables of information by algebric operations were created. Simulations of maximum discharge were performed applying several thematic maps of soil, geology, land declivity, surface covering, potential maximum retention and runoff indices, all created by digital methods. All the parameters considered were analyzed together and integrated in GIS environmental considering a multi-temporal overview and a future projection. As a final result, by quantification and mapping for potential maximum retention of the soils were obtained, runoff coefficient and maximum discharge. The methodology developed here (based in digital photogrametria and GIS) seems to be an interesting alternative for analyzing spatial distribution of hydrologie parameters and estimate maximum discharge in hydrographic basins of medium size not containing fluviometric data.