# Quantitative Assessment of the Environmental Impacts of Dredging and Dumping Activities at Sea
## 3 Results  
### Calibration and Validation Spectral Wind-Wave (SW) Model  
#### 3.1.1 Establishing Mesh in SW 2D Model  
To evaluate wave propagation in the study area, the bathymetry within the wave mesh was surveyed and expanded to a wide area. The computation grid is an unstructured grid of the whole study area. The computation mesh had a total of 9083 grids and 4857 nodes. The computation mesh can produce detailed results in the study area with its small and smooth grids while reducing computation steps with the use of more sparse grids offshore. An unstructured grid was established for the offshore zone with the maximum mesh size 3000 m and for the coastal area with the minimum mesh size 50 m (Figure 3b). It was then used to create the wave mesh for the study area (Figure 3a). Based on topographic features of the study area, the wave in the South China Sea hardly propagates in the Quy Nhon port. The wave at Quy Nhon port is normally generated from the wind. As the wind speed and velocity are relatively small, the wave in the port is small as well. The front of the port (the east of the port) is hardly affected by waves. Parameters were chosen based on the interaction between outside and inside the study area to outline its border (Figure 3b). The northern boundary of the study area ranges from 14\({}^{\circ}\)00\({}^{\prime}\) N, 109\({}^{\circ}\)15\({}^{\prime}\) E to 14\({}^{\circ}\)00\({}^{\prime}\) N, 109\({}^{\circ}\)30\({}^{\prime}\) E, the southern boundary ranges from 13\({}^{\circ}\)30\({}^{\prime}\) N, 109\({}^{\circ}\)30\({}^{\prime}\) E to 13\({}^{\circ}\)30\({}^{\prime}\) N, 109\({}^{\circ}\)15\({}^{\prime}\) E, and the eastern boundary ranges from 14\({}^{\circ}\)00\({}^{\prime}\) N, 109\({}^{\circ}\)30\({}^{\prime}\) E to 13\({}^{\circ}\)30\({}^{\prime}\) N, 109\({}^{\circ}\)30\({}^{\prime}\) E (Figure 3b).  
Nowadays, the application of the products of meteorological models such as Global Forecast System (GFS), Weather Research and Forecasting (WRF) as input for hydrological and hydraulic 2D models is increasingly popular and effective [40; 47; 48]. The wind statistics are produced from the NOAA GFS model, with a resolution of 0.5 degrees and a time span of 3 h at [[ftp://nomads.ncdc.noaa.gov/GFS/Grid4](ftp://nomads.ncdc.noaa.gov/GFS/Grid4)]([ftp://nomads.ncdc.noaa.gov/GFS/Grid4](ftp://nomads.ncdc.noaa.gov/GFS/Grid4)). The Climate Data Operators (CDO) tool and Grid Analysis and Display System (GraDs) were used to produce wind direction and velocity to provide input data for a simulation spectral wind-wave model (SW). The simulation results were produced from 1 September 2017 to 31 October 2017.  
The collected wind data at Ly Son station was used to evaluate the simulation results (wind direction and velocity) produced from the numerical weather prediction at the study area. The wind statistics from the GFS model are highly reliable, with the modification of real data from global ocean observing stations. The data is suitable for the simulation of the wave regime in the study area. The results of the wave field were used to produce input data for the hydraulic model MIKE 21 HD.