Preprints
https://doi.org/10.5194/egusphere-2022-1447
https://doi.org/10.5194/egusphere-2022-1447
 
12 Jan 2023
12 Jan 2023
Status: this preprint is open for discussion.

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 Zemann1,2, Roderick van der Linden3, Dan Trinh Cong1, Duong Hoang Thai Vu1, Nguyet Minh Nguyen4, Frank Seidel1, Peter Oberle1, Franz Nestmann1, and Andreas H. Fink3 Moritz Zemann et al.
  • 1Karlsruher Institut of Technology, Institute of Water and River Basin Management, Hydraulic Engineering and Water Resources Management, Kaiserallee 12, 76131 Karlsruhe
  • 2Disy Informationssysteme GmbH, Ludwig-Erhard-Allee 6, 76131 Karlsruhe
  • 3Karlsruher Institut of Technology, Institute of Meteorology and Climate Research, Kaiserallee 12, 76131 Karlsruhe
  • 4Souther Institute of Water Ressources Research (SIWRR), Q.5, 658 Đ. Võ Văn Kiệt, Phường 1, Quận 5, Thành phố Hồ Chí Minh, Vietnam

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: open (until 09 Mar 2023)

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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.