Evaluating episodic sediment deposition zones in freshwater mussel habitats across Missouri, USA

Point-source sedimentation, such as spills from construction-related activities, can introduce substantial sediments into streams in the short term, potentially leading to mussel burial. To estimate downstream areas where freshwater mussels might face threats from sediment burial within the mussel habitats of Missouri streams and rivers, we examined 49 reaches where both field measurements and gaging data are available. We established empirical relationships for three flow classes to represent general flow conditions of all reaches. Using these hydraulic data, we employed a Lagrangian particle tracking model to simulate sediment transport under each condition, employing two sediment size ranges covering very fine sands to small gravels, resulting in 72 simulated scenarios. The model results indicate that sediments with diameters exceeding a critical value, ranging from 0.041 to 1.975 mm for varying velocities (ranging from 0.124 to 2.191 m/s) and depths (ranging from 1 to 12 m), settle in downstream locations. Potential settling sites span from tens to hundreds of meters downstream. The mode, median, and mean of sediment distribution generally fall within the range of 10–200 m based on particle count, while these values typically range from 1 to 100 m based on sediment mass.