Re-Examination of the Wash Load Concept: Role of Physicochemical Processes

The term "wash load" is often used to describe the fine sediment fraction in rivers, but the term lacks a clear definition. The concept of wash load has been employed variously by scientists and engineers in the fields of hydraulics, geomorphology, and sediment transport. Some fields use definitions based on qualitative field observations while others are based on quantitative scaling analyses. All existing definitions consider only the physical properties of the sediment. However, chemical and electrostatic interactions ("cohesive forces") will often influence the transport of these fine sediments. Existing definitions of wash load will be examined and reinterpreted with a consideration of physicochemical particle-particle interactions.