This research presents a proposal for experimental determination of the soil viscosity in order to evaluate the development of debris flows. This rheology parameter is important for determining not only the velocity values, but also to delimitate the area to be affected by a debris flow. For this, a device was developed from adaptations in slump test, used for studies on concrete, and established a standard methodology to be used in tests aimed at determining the viscosity in soils. In possession of the shear rate, which varies depending on soil moisture, obtained as a result of the test performed on the equipment developed rheological tests were performed on plate-plate rheometer and Brookfield viscometer. After that, correlations of the soil moisture, the shear rate and the viscosity of each sample were established. At total, four different lithologies of soil were analyzed, which allowed a good spatial distribution of the results, culminating in the determination of an equation in which the viscosity can be estimated as a function of the shear rate.