On the beach you can find several types of ripples, such as wave ripples, current ripples and mega ripples. Already before waves break at the shore, their orbital motion reaches the bottom. The velocity under the wave crest is in the landward direction, in contrast to the velocity under the wave trough, which is directed seaward. Near the bed, where the vertical orbital motions are dampened, solely these oscillating horizontal motions remain and induce the formation of ripples.
A current with one constant direction can result in the formation of current ripples, which can be recognized by their asymmetric shapes. The shape of these ripples is different from wave ripples. Wave ripples are symmetric with elongated crests parallel to the shore. Stronger currents, like rip currents (in Dutch the so called "muistroom") or strong alongshore currents, can result in the formation of mega ripples.
A current with one constant direction can result in the formation of current ripples, which can be recognized by their asymmetric shapes. The shape of these ripples is different from wave ripples. Wave ripples are symmetric with elongated crests parallel to the shore. Stronger currents, like rip currents (in Dutch the so called "muistroom") or strong alongshore currents, can result in the formation of mega ripples.
During the field campaign at the Sand Motor, we encountered all types of ripples, but they are not always present at the beach. You might wonder why ripples would be relevant. All these morphological structures are affecting the flow structures and velocities and thereby sediment transport. For my MSc research I'm investigating the effect of these ripples on the magnitude and direction of sediment transport.
Marieke
Marieke