The effects of unpaved roads on suspended sediment concentration at varying spatial scales – a case study from Southern Brazil

Unpaved roads may induce adverse effects on downstream water resources by increasing suspended sediment concentration (SSC). This study documents the localized impacts on stream SSC of six unpaved road–stream crossings in the rural Guabiroba River Catchment, in southern Brazil. Results demonstrated that SSC values downstream of road–stream crossings was between 3.5 and 10 times higher than upstream SSC at all third‐ and fourth‐order stream locations. However, downstream values were statistically undistinguishable from those collected upstream of road–stream crossings at fifth‐order sampling sites. These findings suggest that localized road effects on stream SSCs are scale‐dependent in that these are important for low‐order headwater streams yet undetectable for their higher order counterparts. Findings point to the importance of low‐order stream crossings in increasing SSC and the need to further explore the role of unpaved roads as agents of water quality degradation in agriculturally active rural settings.