Developing More Appropriate Culvert Blockage Factors for Use in Flood Modelling Studies on the Sunshine Coast

Culverts are often used to convey floodwaters under roadways and other obstacles during rainfall events. Vegetation and debris emanating from upstream urban catchment areas can become mobilised and transported downstream during rain events. This debris can often become trapped and cause blockages in the culvert, resulting in increased upstream water depths and flooding. Flood and hydrological modelling studies generally attempt to consider any impacts due to the implementation of culverts, and in particular, the extent of the flooding should the culvert become blocked. Current culvert design guidelines suggest that a blockage factor ranging from 10% to 50% blockage should be applied for typical storms with some guidelines recommending up to 100% blockage be applied for severe storms. This study in partnership with the Sunshine Coast Council investigated whether or not the current guidelines for the applied blockage factors used in hydrological models are appropriate for the Sunshine Coast region. This was achieved through the use of a Froude-scaled physical model of a real world site that was constructed on a specially design culvert testing rig at the University of the Sunshine Coast. A variety of flowrates and suitably scaled debris were tested.Submitted in the fulfilment of the requirements of the degree of Bachelor of Engineering (Civil Engineering), University of the Sunshine Coast, 2015