The present paper aimed to evaluate the size sediment effects on runout area damaged by debris flow by using Kanako-2D in Böni Watershed, Serra Gaucha. This watershed presents a vast history of natural disasters, highlighting the events occurred in 1982 and 2000. The sediment sizes considered in the simulations and evaluated in terms of erosion, deposition and reached area were 0.15, 0.30, 0.50, 1.0, 1.3, 2.0 and 3.0 m. The sediment size strongly influenced on the erosion, deposition and total area reached by debris flow. Fine-grained sediments presented higher mobility, traveling greater distances and reaching larger areas than coarse-grained sediments. The obtained results confirm that Kanako-2D can be an important tool to predict susceptible areas to debris flow.
