Fluvial Geomorphology Assessment for Somerton Bridge

Overview Tamworth Regional Council is seeking a consultant to undertake a fluvial geomorphology assessment for Somerton Bridge, to inform two proposed repair treatments addressing flood-related erosion of the bridge abutment and upstream riverbank. Purpose The purpose of the assessment is not to determine the hydraulic capacity of the bridge, as the structure's general capacity and current constructed configuration are not being questioned or changed. The purpose of the study is to determine the geomorphology of the river and the effects future flood events will have on the waterway, particularly the upstream riverbanks, and how that will likely impact the operational function of the two proposed repair treatments: Reinstatement of the washed-out bridge approach and installation of substantial scour protection around the abutment and upstream riverbank to withstand floodwater erosion of the abutment and road approach Extending the bridge another span to move the bridge abutment and road approach past the riverbank hinge point to protect the structure from floodwater erosion, with only isolated erosion protection required around the cutting of the new abutment and bridge span Historical imaging of the site shows the riverbank is naturally migrating towards the north after each flood event. Therefore, with flood events naturally causing the migration of the Peel River, the repair treatment chosen needs to be designed to best mitigate these changes to ensure continued operational function of Council's assets. The historical images can be seen in the attached Appendix F. Scope The following items are anticipated for the assessment: Site visit to the location for data collection and site awareness Preliminary assessment based on provided information and data from the site visit If the preliminary assessment is undetermined, undertake a detailed analysis using the detailed survey model provided to generate a model showing the fluvial geomorphology of the river and predict the future migration path of the north riverbank and the potential impacts that migration will have on the bridge Detailed assessment report identifying the high impact areas of the northern riverbank and the mitigation measures required to reduce the migration of the riverbank from impacting the bridge