Analysis of the performance of debris screens at culverts

Construction of a culvert will impact ambient hydraulic characteristics such that upstream flow depths may increase due to any constriction at the inlet. Exacerbating this, flow can be further restricted within a culvert due to internal blockage by debris. Screens to prevent debris entering a culvert may also cause blockages, thus heightening the flood risk. In response to this problem, the research reported in this paper made use of a Froude-scaled physical model to investigate how screen blockage by debris is influenced by the geometry and positioning of a screen. Analysis based on 105 000 debris passes is used to show that, as expected, the potential for screen blockage by debris increases as the ratio of debris length to bar spacing increases. Furthermore, screen angle and position is shown to have a significant influence on blockage potential. This research involved the development of a methodology that can be used to assess the efficiency of different trash screen configurations. To build upon the analysis from this initial research and continue working towards the development of a predictive model that can aid future screen design, the research needs to be extended to look at the process of cumulative debris build up on screens.