The authors define a total of 686 meshes and use the same clustering calculation
as coastal 74 meshes. The coastal meshes are assigned to clusters which were
calculated in a previous paragraph. The inland meshes are identified as the same
group of the nearest coastline meshes. The meshes which are on the opposite side of
the Day River are identified as those whose CDIs are small. If a mesh is on the
coastline, the distance is 0 km from the sea; otherwise, the distance is calculated in
km by multiplying the number of meshes to the coastline by the length of the
diagonal line or side line.
10.3.5.2 Land Use
Current land use is important is assessing the coastal erosion risk due to human
factors as well as to natural factors. In this study, the authors used the land use data
by the Ministry of Agriculture and Rural Development in 1996. Five types of land
use are classified as follows: village, rice paddy, rush field, saltpan, and mangrove
forest. The village has been destroyed by coastal erosion; and houses, churches and
other buildings ceased to exist. The people living there had to move to another area.
Then, the importance of the villages is assigned as the highest, 4. The paddy fields
were also destroyed or contaminated by salty sea water. Because the produce of the
paddies is very valuable, damage to them entails serious economic loss. Therefore,
the importance of the paddy field is assigned as 3. The saltpan uses sea water, and
salt is not so expensive so the importance of a saltpan is assigned as 2. There are
rush forests in the deposition area because the rush is highly resistant to salt water;
and the produce of the rush forests is less valuable than that of the paddies. There
are mangrove forests in some areas, but the mangroves are not salable. The
importance of rush field and mangrove forest are assigned as 1, the lowest. The
land use mesh map is Fig. 10.8 below.
10.4 Results
10.4.1 Altitude Map
An altitude map of the southern Red River Delta was constructed (Fig. 10.1). The
delta is very flat and low with an altitude varying from 0–5 m. There are some
patchy areas of 0 m. The Red River and Day River are partly raised bed rivers.
Upstream of the Red River and Day River, the altitude of the rivers is higher than
that of the surrounding area.
There are some sand ridges which are perpendicular to the rivers. The sand
ridges show how the delta has been expanded. The Giao Thuy area has been formed
by the Red River and Hai Hau, The Nghia Hung and Kim Son areas have been
formed by the Day River and Ninh Co River. There are islands formed by
10 Mapping Coastal Erosion Risk in the Southern Red River Delta, Vietnam
207
as coastal 74 meshes. The coastal meshes are assigned to clusters which were
calculated in a previous paragraph. The inland meshes are identified as the same
group of the nearest coastline meshes. The meshes which are on the opposite side of
the Day River are identified as those whose CDIs are small. If a mesh is on the
coastline, the distance is 0 km from the sea; otherwise, the distance is calculated in
km by multiplying the number of meshes to the coastline by the length of the
diagonal line or side line.
10.3.5.2 Land Use
Current land use is important is assessing the coastal erosion risk due to human
factors as well as to natural factors. In this study, the authors used the land use data
by the Ministry of Agriculture and Rural Development in 1996. Five types of land
use are classified as follows: village, rice paddy, rush field, saltpan, and mangrove
forest. The village has been destroyed by coastal erosion; and houses, churches and
other buildings ceased to exist. The people living there had to move to another area.
Then, the importance of the villages is assigned as the highest, 4. The paddy fields
were also destroyed or contaminated by salty sea water. Because the produce of the
paddies is very valuable, damage to them entails serious economic loss. Therefore,
the importance of the paddy field is assigned as 3. The saltpan uses sea water, and
salt is not so expensive so the importance of a saltpan is assigned as 2. There are
rush forests in the deposition area because the rush is highly resistant to salt water;
and the produce of the rush forests is less valuable than that of the paddies. There
are mangrove forests in some areas, but the mangroves are not salable. The
importance of rush field and mangrove forest are assigned as 1, the lowest. The
land use mesh map is Fig. 10.8 below.
10.4 Results
10.4.1 Altitude Map
An altitude map of the southern Red River Delta was constructed (Fig. 10.1). The
delta is very flat and low with an altitude varying from 0–5 m. There are some
patchy areas of 0 m. The Red River and Day River are partly raised bed rivers.
Upstream of the Red River and Day River, the altitude of the rivers is higher than
that of the surrounding area.
There are some sand ridges which are perpendicular to the rivers. The sand
ridges show how the delta has been expanded. The Giao Thuy area has been formed
by the Red River and Hai Hau, The Nghia Hung and Kim Son areas have been
formed by the Day River and Ninh Co River. There are islands formed by
10 Mapping Coastal Erosion Risk in the Southern Red River Delta, Vietnam
207