12 Jan 2023
 | 12 Jan 2023

Modelling ocean wave conditions at a shallow coast under scarce data availability – A case study at the western coast of the Mekong Delta, Vietnam

Moritz Zemann, Roderick van der Linden, Dan Trinh Cong, Duong Hoang Thai Vu, Nguyet Minh Nguyen, Frank Seidel, Peter Oberle, Franz Nestmann, and Andreas H. Fink

Abstract. Against the background of the rising sea level and land subsidence, protecting the progressively eroding coast along the Vietnam Mekong Delta becomes of tremendous importance. Within the presented work, design conditions for breakwaters were derived from offshore climate reanalysis data (ERA5), which were transferred to the nearshore by two numerical approaches, i.e. SwanOne and Delft3D, for different average and extreme wave and weather conditions. Within this process, design wave heights and periods at the nearshore could be determined for 10- to 100-year recurrence intervals. Both models thereby showed sufficient accuracy according to measurements in the field. Limitations must be made regarding the available spatio-temporal resolution, where reanalysis data showed a lack of short but high peak values compared to the observed measurements. Both numerical approaches showed their capabilities, where SwanOne offers a simple and fast calculation method, while it lacks of continuous effects like wind-generated swell or bottom friction. The Delft3D software on the other hand provides a more complete representation, not only of wave but also current dynamics, while it requires a much broader amount of input parameters and more complex boundary conditions. Within this study, the advantages and disadvantages of both models could be demonstrated, whereas for the final calculation of nearshore wave characteristics, only SwanOne was applicable based on the input parameters extracted from statistical analysis of long term ERA5 data.

Moritz Zemann et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1447', Anonymous Referee #1, 02 Feb 2023
    • AC1: 'Reply on RC1', Moritz Zemann, 01 Apr 2023
  • RC2: 'Comment on egusphere-2022-1447', Anonymous Referee #2, 06 Feb 2023
    • AC2: 'Reply on RC2', Moritz Zemann, 01 Apr 2023

Moritz Zemann et al.


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Short summary
The study investigates the possibility to predict wave heights close to the coast of the Mekong Delta based on long time climate model wave heights which are only availabe offshore. Due to severe coastal erosion in the Mekong Delta with average land loss rates of up to 10m per year, the coast needs to be protected from wave attacks e.g. by breakwaters. To design a breakwater in the right dimensions for the local conditions, the knowledge of wave heights is essential to the performing engineer.