About 1/3 of the world’s population live near the coast, mostly with shallow water. These are affected by sediment transport and erosion.
Some important examples:
- Erosion of beaches and sandstone rocks/cliffs
- Difficulties for ships to approach harbours – dredging
- Flooding – destruction of urban and agricultural areas filled with sediments
- Transport of Pollution
Concept: Waves and current induced drag forces on the sea bottom. This leads to that bottom sediments (such as sand) is being transported.
This process takes place on the beach, near the beach (swashzone and and surfzone) and to water depths up to typically 70m.
Transport Modus:
Bedload
Bed-load means that the sediments are transported (“dragged”) along the bottom. Another name of the sea bottom is seabed; hence the name bedload. You can think of bed-load as small stones or sand grains that are sliding and rolling along the bottom.
Suspended Load
If the sediments are fine enough, they may be lifted up from the bottom so that they mix with the water. This is called suspended sediments and measured in unit concentration.
Sheet Flow
This is a form for sediment transport that takes place under strong drag forces (strong waves or current). The sediments are moving like a carpet on the bottom. A similar phenomenon can be observed with snow a winters day with a little wind, the snow is moving as a carpet on the ground.
Source: Coastal Engineering Lecture Notes
