Controls on Sediment Bed Erodibility in a Muddy, Partially-Mixed Tidal Estuary

The objectives of this study are to better understand controls on bed erodibility in muddy estuaries, including the roles both sediment properties and recent hydrodynamic history. An extensive data set measurements, properties, information was utilized create statistical models predict bed. This includes >160 eroded mass versus applied stress profiles collected over 15 years along York River estuary, a system characterized by “depth-limited erosion,” such that critical for erosion increases rapidly with depth into For study, quantified two ways: at 0.2 Pa (a commonly produced tides York), normalized shape profile stresses between 0 0.56 Pa. In as response variable, explanatory variables strongest influence were (in descending order) tidal range squared averaged previous 8 days proxy bottom stress), salinity or past river discharge, organic content, water level anomalies, percent sand, clay, layering. Results support 1) deposition disturbance increasing 2) cohesion/consolidation erosion/winnowing fines decreasing erodibility. most important variable influencing Pa, more (vs. less) erodible cases exhibited straighter strongly curved) profiles. Overall, best predictors which, turn, predictor shape. suggests calculations position salt intrusion can serve useful empirical proxies consolidation state resulting uppermost seabed estuarine numerical models. Observed content top 1 cm poor erodibility, likely because typical suspend less than mm sediment. Future field sampling would benefit from higher resolution observations within bed’s few millimeters.