Bugs in engineering? Understanding the transport of cohesive sediment in aquatic systems

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More and more, computers are being used to help predict the environmental impacts of proposed infrastructure projects, such as the removal of dams or the building of bridges.  However, the usefulness of computer modelling is still limited by our understanding of how natural systems work and our knowledge and experience with how to represent nature with numbers. Hydrodynamic and sediment transport modelling is a powerful tool to better understand the relationship between the hydrodynamic environment (water velocity, direction, etc.) and the erosion and deposition of material from a river channel.       The proposed research seeks to further the understanding of the dynamic erosional properties of biologically-rich mudflats in Shepody Bay near the Petitcodiac River Estuary.  These mudflats are considered as important sites internationally, as they are visited every year by more than two million migratory birds that feast on the abundant mudshrimp.  The proposed partial opening of the Petitcodiac River causeway will increase the tidal energy within the estuary and may have impacts on the mudflats; this site will be used as a case study to support the research.  Previous attempts to numerically model the opening of the causeway have not considered the presence of biological organisms on the eroding or building-up of mudflats downstream of the causeway.  As a result, there is a limit to the usefulness for environmental protection planning.   The proposed research has two components: 1) to investigate the impact of the presence of macro-organisms on the erosion rate of cohesive estuarine sediments; 2) to advance the development of predictive transport models for simulating the erosion and fate of fine cohesive sediments, and in particular incorporate the impact of the presence of biological organisms.  The research will enhance our understanding of these processes, leading to a more comprehensive and accurate model that can better support decision makers and planners.