Episodic transport of organic-rich sediment was examined in the Ortega/Cedar estuary system in Florida using a newly developed 2D horizontal model for fine cohesive sediment transport. Bed sediment samples were analyzed to provide information on organic content, settling velocity, erodibility and consolidation for inclusion in the model. Only a rudimentary calibration of the model was possible due to lack of data. Nevertheless the model reproduced the main tidal and sediment transport features of the estuary system, including the predominantly depositional nature of the system. In a more sophisticated version of the model, sediment erosion and deposition were manipulated by implementing organic content dependent functions, derived from the analysis of data from several sites. This allowed the model to be used to investigate the sensitivity of the sediment transport to the organic content. The changes in deposition rates caused by varying the organic content were found to be significant during large river discharge events, but during normal discharges they were insignificant. At approximately 40% organic content, there is a tendency for sediment accumulation rates to decrease and, in places, erosion becomes the dominant sediment transport process. © 2002 Elsevier B.V. All rights reserved.