Influence of land use and occupation in runoff in the city of Ji-Paraná-RO, Western Amazon

No municipio de Ji-Parana/RO, a ocupacao urbana ocorreu de forma desordenada as margens dos rios Urupa e Machado, tornando parte da area urbana suscetivel a inundacoes. O presente estudo teve como objetivo a caracterizacao do uso recente do solo em seis bacias hidrograficas que integram o perimetro urbano de Ji-Parana, a partir da utilizacao do processamento digital de imagens (PDI), sendo verificado que todas elas possuem mais de 20% de sua area impermeabilizada. Tambem foi verificada a influencia da urbanizacao das bacias no escoamento superficial, com base nos dados provenientes da analise de chuvas intensas, sendo mensurado o tempo de concentracao (tc) pelo metodo de George Ribeiro, Kirpich e Kirpich Modificado; o coeficiente de escoamento superficial (C) pelos metodos de Horner e Fantoli; e as vazoes maximas de projeto (Q) pelo metodo racional; cujos resultados nao diferiram estatisticamente. A B S T R A C T Urban occupation in the city of Ji-Parana/RO occurred on the banks of Urupa river and Machado river in a disorderly manner, making part of the urban area susceptible to floods. This study aimed to characterize the current land use in six watersheds that comprise the urban perimeter of Ji-Parana using the digital image processing (DIP). It was found that all of them have more than 20% of its area impermeable. The influence of urbanization of watersheds in the runoff was observed based on data from the analysis of heavy rainfalls, and the time of concentration (tc) was measured by the method of George Ribeiro, Kirpich and Kirpich Modified; the runoff coefficient (C) by the methods of Horner and Fantoli; and the project peak flows (Q) by the rational method; the results were not statistically different. Keywords: Watershed, Digital Image Processing, Heavy rainfall, Concentration Time, Peak Flow.