Unpaved roads correspond to approximately 90% of Brazilian's highway. In most cases they are built without previous studies should be subject to a many problems. In this work was simulated unpaved roads ditch outlet spacing, using a software to design roads drainage system. It was used erodibility, critical shear stress and density values for different soils of roads located in the state of Goias, Brazil. Were simulated different scenarios considering changes in slope (1%, 5%, 10% and 15%) and in roads channel's cross section (1:1, 1:2, 1:5 and 1:10). The model answered favourably to slope and cross section of the channel and to soil resistance parameters. The spacing obtained indicated that roads with slopes of less than 5%, even high levels of erodibility allowed viable outlet spacing. However, 10% and 15% slopes presented reduced spacing turning them impractical, and so requiring channel protection or changes of the hydraulics features.
Hydrologic model; erosion; secondary roads
