Chapter 4: Basic Coastal Sediment Transport Mechanisms

The following sections are included:

• Introduction

• Boundary Layers and Bed Shear Stresses

  • Coastal bottom boundary layers

  • Shear stresses on rippled beds

  • Shear stresses over flat movable beds

  • The log law for steady flow

  • The wave friction factor

  • Time dependent bed shear stresses

• Sediment Parameters and Sediment Mobility

  • Introduction

  • Sediment characteristics

  • Forces on sediment particles

  • The mobility number

  • The Shields parameter

  • Sleath's acceleration parameter

  • Infiltration effects

  • Initiation of sediment motion

• Bedload and Sheet Flow

  • Introduction

  • What is bedload?

  • Dispersive stress and the amount of bedload

  • Meyer–Peter and Müller type bedload formulae

  • The average speed of the bedload

  • Energy dissipation and bedload

  • Velocity moment formulae for sediment flux

  • Bedload and sheetflow transport in arbitrary flows

• Bedforms and Hydraulic Roughness

  • Introduction

  • Bedform growth and migration

    • Migration of natural bedforms

    • The continuity equation applied to bedforms

    • Bedforms migrating with constant form

    • Migration and growth of sinusoidal bedforms

    • Numerical issues with bed updating

  • Vortex ripples

  • Megaripples

  • Bedforms in combined wave current flows

  • Hydraulic roughness

• The Motion of Suspended Particles

  • Sediment velocities and sediment orbits

  • Equation of motion for a suspended particle or bubble

  • The time scale of particle acceleration

  • Suspended particles in wave flows

  • Particles or bubbles suspended in vortices

  • Turbulence effects on settling of particles or the rise of bubbles

  • Reduced particle velocity variance due to selective sampling

• Sediment Suspensions

  • What is suspended load?

  • The modeling framework for sediment suspensions

  • Near-bed reference concentrations

  • Sediment pickup functions

  • Sediment distribution modeling

    • The mixing length approach

    • Mixing length model of u(z) and c(z) for l_m = λ_z and w_m = γ^u*

    • Suspension under waves

  • Suspensions of cohesive sediments

• Basic Sediment Transport Model Building

  • Introduction

  • Two different families of transport models

• Sediment Transport Outside the Surf Zone

  • Shorenormal transport

  • Shoreparallel transport outside the surf zone

• Surf Zone Sediment Transport

  • Shorenormal transport

  • Shoreparallel transport

• Swash Zone Sediment Transport

  • Swash sediment transport and the beach watertable

• Concluding Remarks on Sediment Transport Modeling

• References