In situ observations of ripples on the surf zone of a beach

In situ observations of ripples on the surf zone of a beach
김무종; 이수환; 백영숙; 도종대; 임학수; 이희준
KIOST Author(s)
Lee, Su Hwan(이수환)Do, Jong Dae(도종대)Lim, Hak Soo(임학수)Lee, Hee Jun(이희준)
Publication Year
The ripple migration was observed on the surf zone of a beach in the eastern coast of Korea. A sonar sensor logging ripples and a current meter were placed together on a sand bar in water of 3.4 m for about 10 days in the spring of 2017. Bedloads were calculated from the records of the ripple geometry and migration and were compared with the estimates of a sediment transport model, SEDTRANS96.
The ripples observed ranged in height (Hr) and length (Lr) from 0.5 and 8.9 cm and from 11.4 and 125.3 cm, respectively. They were highly dependent upon the wave height (Hs) and thus wave-induced currents (Uc). The largest ripples (Hr = 3.64, Lr = 51.43 cm) occurred during waves of 1 m, the highest waves in the measurement period. In this spell, the current and ripple migration speeds (Uc and Ur) were 4.08 cm/s and 17.13 cm/h, respectively. Therefore, the bedloads were estimated at 5.785 kg/h/m. However, as Hs decreases to 0.5 m, the size and Ur of the ripples as well as Uc all together decreased simultaneously. At waves of 0.5 m, the values of Hr, Lr, Uc and Ur were 1.97, 18.82 cm, 2.72 cm/s, and 0.26 cm/h, respectively. The resulting bedloads were estimated at 0.047 kg/h/m.
The comparison of the measured and modelled bedloads indicates an overestimation of the model by a factor of 6-8. The model used the default values of 1 and 10 cm for the ripple height and length. This rather large discrepancy may be derived mainly from
Bibliographic Citation
3rd International Water Safety Symposium, pp.1, 2018
Related Researcher
Research Interests

Coastal Disaster Prevention,Coastal Erosion,Coastal Ocean Modeling,연안재해방재,연안침식,연안해양모델링

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