3. Fundamentals of Sediment Transport

The goals of this chapter are to (1) describe the processes that govern the transport of sediment in surface waters, (2) provide guidance for use in assessing and/or quantify sediment transport, and (3) describe the procedure to use in modeling sediment transport. A basic knowledge of these topics is requisite to understanding many of the contaminant transport processes important in sediments due to the strong particle associations of most contaminants of concern. This chapter starts with brief overviews of sediment transport – sedimentation related problems and how sediment in surface waters responds to the forces that cause water movement. Basic sediment transport processes are also defined. Section 3.2 describes pertinent properties of sediments, and transport processes for cohesive sediments. Section 3.3 provides guidance to use to assess and/or quantify sediment transport. It is often necessary for remedial project managers to conduct a Sediment Transport Assessment in support of a remedial alternatives evaluation for contaminated sediment Superfund sites. The assessment involves using a systematic approach that (1) identifies the processes and mechanisms that might result in erosion, (2) determines the most appropriate methods to use to assess sediment resuspension and deposition, and (3) quantifies sediment resuspension and deposition rates under varying flow conditions. Section 3.4 provides an overview of the procedures following in performing a sediment transport modeling study. These procedures or steps include: (1) model selection and setup, (2) hydrodynamic modeling, (3) sediment transport modeling, (4) calibration and validation of the models, and (5) analyzing model results.