Cause Analysis of Erosion-Induced Resort Washout on Cua Dai Beach, Vietnam

Hung, N.T.; Vinh, B.T.; Nam, S.Y., and Lee, J.L., 2017. Cause analysis of erosion-induced resort washout on Cua Dai Beach, Vietnam. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 214–218. Coconut Creek (Florida), ISSN 0749-0208. On an eroding beach, high waves can completely wash out beaches, swimming pools, and resorts. Cua Dai shore, which is located immediately north of Thu Bon river mouth in central Vietnam, has eroded on the order of hundreds of meters in beach width. The present study estimated the erosion rate of sediment volume into the estuary through the Thu Bon river mouth by using recent satellite images, and utilized a shoreline change model to reproduce the erosion of shoreline near the river mouth. Results are in good agreement with observed data. The numerical model is modified by including the equilibrium angles that were obtained from a static shoreline equation of parabolic shape. Through the sediment conservation rule, the main cause of shore retreat is found to be sediment loss in the Thu Bon river estuary with the reduction in river sediment. The possible causes for this type of sediment loss are mining in the estuary and reduction of river flow action against waves in the river mouth with the reduced sediment supply. Proper management of Cua Dai beach requires the development of a monitoring system to fully understand beach dynamics and to mitigate the further resort washout owing to background erosion.