CQCN Culvert Renewals
Assessment of culverts against flood immunity criteria.
Culverts on the Blackwater, Goonyella, North Coast and Moura Lines were condition assessed and found to be in a poor state requiring replacement, maintenance or upgrade. As part of this work 31 culverts required hydraulic assessment to determine rail embankment flood immunity, and make recommendations for removal, remedial works, replacements or upgrades.
To evaluate the flood immunity of the culverts, we developed hydrologic and hydraulic models. We developed a hydrologic model (WBNM) for the catchment contributing to each culvert, and a 2D hydraulic model (TUFLOW) for each culvert. We used these models to determine flood heights, with 20% blockage for each culvert, for a range of design flood events. We assessed the flood profiles for each culvert under a series of “what if” scenarios including complete blockage/removal and diversion of upstream flows, and duplication of the existing culvert.
Preferred solutions were developed for each culvert location. These solutions ensure that the structural integrity of the railway infrastructure is maintained whilst providing an adequate level of flood immunity, and minimising upstream and downstream drainage impacts for adjacent land owners. In addition to this, we were also able to inform Aurizon of locations where the standard flood immunity was not achieved which helped identify section of rail at risk of more frequent floods or overtopping, causing rail closure.