Hydraulic sizing of forest road pipe culverts

This article presents guidelines for assessing the optimal dimensions of forest road pipe culverts, based on input of actual and experimental data to standard engineering techniques. In doing so, we assess the need for (i) changes in the parametrisation of inputs (i.e. culvert micro-catchment dimensions, rainfall and resultant culvert flow, and culvert flow rates during culvert hydraulic dimensioning), and (ii) the need to redesign culvert outlets in relation to flow speed. Our results demonstrate that values for most inputs presently used under current technical practice for forest road pipe culvert sizing are significantly higher than those achieved under experimental conditions. The data on outlet flow velocities strongly suggests that strengthening of culvert outlet aprons will be crucial for their future operation.