INTRODUÇÃONas ultimas décadas, o processo de urbanização nas cidades vem ocorrendo de forma acelerada e, muitas vezes, sem um planejamento adequado. Este fato, influência na alteração do ciclo hidrológico das bacias hidrográficas, como por exemplo, a diminuição da infiltração da água na superfície e, consequentemente, no aumento do escoamento superficial das águas pluviais que fluem através das obras hidráulicas (MONTES; LEITE, 2009). O aumento do volume do escoamento superficial provoca o aumento da vazão de cheia dos cursos d'água, o que pode ocasionar alagamentos, podendo deixar muitas pessoas desabrigadas e gerar altos prejuízos econômicos para os municípios (PORTO, 1995;TUCCI, 2016).
Geomatics applied to drainage urban ABSTRACTUrban growth, inadequate land use and lack of infrastructure alter the hydrological cycle by decreasing the infiltration of water into the soil and increasing the runoff of rainwater. Thus, it is necessary to know the maximum flow and capacity of the basin to support it, aiming at an appropriate design of the hydraulic works. One of the methods used to estimate flows of hydraulic works is the Rational Method, whose main parameter is the runoff coefficient (C). In this context, the objective of this work was to obtain the value of C for the return periods of 2, 5, 10 and 25 years for the Cohab neighborhood located in the municipality of Itaqui-RS, using techniques of Geomatics science. In this way, a planialtimetric survey and subsequent data processing were carried out to generate a Digital Elevation Model (MDE), which helped to obtain the slope. The classes of land use and cover were also determined through the supervised classification of a satellite image. Finally, the spatialized values of C were estimated from the overlapping of slope maps and land use and cover, considering the different periods of return under analysis.