summer. The typhoons have destroyed the banks and much coastal erosion has
therefore occurred locally. In winter, because the precipitation is low, sedimentation is insufficient; and therefore coastal erosion occurs.
The tidal effect needs to be considered. However the time of the satellite images
could not be obtained. The tide amplitudes were 1.1–3 m in September 30, 1994;
1.3–2.3 m in February 9, 1995; 1.3–2.9 m in September 17, 1995; 1.8–2.1 m in
January 27, 1996; 0.8–3.2 m January 13, 1997; 2–2.5 m October 4, 1997; 1–2.9 m in
February 13, 1998; 1.7–2.7 m September 21, 1998. The tide amplitude was large
only on January 13, 1997. The other dates had narrow tide amplitudes. The
coastline changes because of the tide are narrow, while the coastline changes due
to erosion are larger than those resulting from the tidal change. Additionally, Thuy
et al. (2012) analyzed the coastline change in Hai Hau area by satellite data,
determining the times of high, middle and low tides. The results showed the
coastline is apparently less affected by the tide than by erosion and deposition.
10.4.4 Coastal Erosion Risk Map
By using the CDIs, banks, and, heights of land, the authors classified the 74 coastal
meshes. The coastline was divided into four large clusters (Fig. 10.3). The CPCC
(cophenetic correlation coefficient) was 0.941. The features of those four groups are
as follows: Group I – regardless of CDIs, most parts of the banks in each mesh are
not over 4 m; Group II – coastal erosion occurs, land level is below sea level; Group
III – coastal erosion or small deposition occurs, the land level is above sea level;
Group IV – large deposition occurs. Therefore, the construction of a coastal erosion
risk map was possible (Fig. 10.4).
10.4.5 Risk Map of Coastal Erosion
By using the CDIs, banks, and, heights of land, the authors classified the 74 coastal
meshes. The coastline was divided into four large clusters (Fig. 10.5). The CPCC
(cophenetic correlation coefficient) was 0.941. The features of those four groups are
as follows: Group I – regardless of CDIs, the greater part of the banks in each mesh
are not over 4 m; Group II – coastal erosion occurs; land level is below sea level;
Group III – coastal erosion or small deposition occurs; the land level is above sea
level; Group IV – large deposition occurs. Therefore, the construction of a coastal
erosion risk map was possible (Fig. 10.4)
10 Mapping Coastal Erosion Risk in the Southern Red River Delta, Vietnam
211
therefore occurred locally. In winter, because the precipitation is low, sedimentation is insufficient; and therefore coastal erosion occurs.
The tidal effect needs to be considered. However the time of the satellite images
could not be obtained. The tide amplitudes were 1.1–3 m in September 30, 1994;
1.3–2.3 m in February 9, 1995; 1.3–2.9 m in September 17, 1995; 1.8–2.1 m in
January 27, 1996; 0.8–3.2 m January 13, 1997; 2–2.5 m October 4, 1997; 1–2.9 m in
February 13, 1998; 1.7–2.7 m September 21, 1998. The tide amplitude was large
only on January 13, 1997. The other dates had narrow tide amplitudes. The
coastline changes because of the tide are narrow, while the coastline changes due
to erosion are larger than those resulting from the tidal change. Additionally, Thuy
et al. (2012) analyzed the coastline change in Hai Hau area by satellite data,
determining the times of high, middle and low tides. The results showed the
coastline is apparently less affected by the tide than by erosion and deposition.
10.4.4 Coastal Erosion Risk Map
By using the CDIs, banks, and, heights of land, the authors classified the 74 coastal
meshes. The coastline was divided into four large clusters (Fig. 10.3). The CPCC
(cophenetic correlation coefficient) was 0.941. The features of those four groups are
as follows: Group I – regardless of CDIs, most parts of the banks in each mesh are
not over 4 m; Group II – coastal erosion occurs, land level is below sea level; Group
III – coastal erosion or small deposition occurs, the land level is above sea level;
Group IV – large deposition occurs. Therefore, the construction of a coastal erosion
risk map was possible (Fig. 10.4).
10.4.5 Risk Map of Coastal Erosion
By using the CDIs, banks, and, heights of land, the authors classified the 74 coastal
meshes. The coastline was divided into four large clusters (Fig. 10.5). The CPCC
(cophenetic correlation coefficient) was 0.941. The features of those four groups are
as follows: Group I – regardless of CDIs, the greater part of the banks in each mesh
are not over 4 m; Group II – coastal erosion occurs; land level is below sea level;
Group III – coastal erosion or small deposition occurs; the land level is above sea
level; Group IV – large deposition occurs. Therefore, the construction of a coastal
erosion risk map was possible (Fig. 10.4)
10 Mapping Coastal Erosion Risk in the Southern Red River Delta, Vietnam
211