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Application of Remote Sensing
imagery for investigation in the Haiphong estuarine and costal zone
Pham Viet Cuong, Nguyen
Hong Cllau, Tran minh Hlen
Centre of Geography and natural resoutcon
NCSR of Vietnam
Centre of Geography and natural resoutcon
NCSR of Vietnam
Introduction:
The HAI PHONG coastal zone has a dense river and tidal breaks weiem it is directed by claws and currents of the rivers calling in to the sea. By breakers and tides. Under the influence of all these factors many beaches. Sandbars. Flow marshland and mangrove have been formed. Causing the seawards intent transgression process on the centrally. The willing covers breakers. Swells and tidal currents have been eroding the shoreline. Causing the landwards sea erosion process
HAI PHONG is an economical developed region with high I immolation density. Large sea harbor and in connection with main water road and airhostess. It closes to important industrial. Agricultural and fish centers of the country.
Following the traditions local inhabitants have been outinomsly using mangrove forest and dirking literal region to enlarge area for agriculture and fishery. . The to the lack of necessary knowledge on ecological and naturenvirenmental real touchup in outfall region. They usually spontaneously lead dicer leery transgression in many places. Thus cause environment hangs and direct damage of the life resource. Labor and money lost.
Therefore, it is now high time to conduct estuarine coastal region survey and assessment to carry out inventory and supervision works for coastal zone. To analyze the rate of sandbar acceptation and littoral ersion for proper utilisation and management.
Aim of study:
The purpose of this study is to investigate the estuarine and coastal zone aided remote sensing imagery with short-term observation dates specifically the following objectives were pursued:
- To inventory landuse patterns for the estuarine and covestal zone of
Hai phong by using remote sensing dates
- To evaluate the estuarine and coastal resources
- To detect change of shorline (coastal erosion and accretion)
tidalflats.
- To recommend proper utilization and management.
The estuarine and coastal zone of Hai phong is situated along a part of the north coast of Viet nam. This study aren falls within 106°35' to 106° 55' longtitude. 20° 36' to 20° 58' latitude
It was recored within:
A landsnt 2 frame 135/46 A landsat 4 frame 126/308 (see figure 1)
A spot 1 frame 271/308
This area is considered typical for the north estuarine and coastal zone of viet nam.
Figure 1: Map of North of Vietnam showing the study area
Methodology and Data
In present day the Remote Sensing method with satellite and aerial imagery is widely used in Viet name and gradually comes in to a stable technology. In combination with fieldwork. Remote sensing method has got a lot of advantages to the traditional one it includes in this study:
- Oplieal and chemical processing of satellite and aerial data: Black
and white enlarging and printing false color composition of satellite
images (see photo slide)
- Rectification: The purpose of this step is to correct distortions
existing in the data as accurately as possible bared on the control
points selected on both topographic maps and satellite images. The
reelifier SEG 5 rectified the images.
- Visual and stereoscopic identify and locate the position of
estuarine and coastal features.
- Ground truth: to check the result and correct map.
- Landsat image scenes of 29.Dec. 1975 May 1984 and 7 Jan 1986 Spot
image scene of 21 May 1988.
- Arial photographs during January 1976 and December 1986 at sealer of
1:250000 and 1:20000 these aerial photos were supplementary only used
for the must changeable region, such as pinch vu and Cat hai. Because
map was established at scale of 1:100000.
- Water level and tidal data of the study area collected by Department
for hydremetgrology.
- Topographic maps at nine of 1:00000 and 1:50000 Ground survey data.
- Hydrology: The HAI PHONG coastal area has a dense brook river system
with height sediment content, especially branches of the Red-Thai Binh
river system. Also six rivers fall within study area supplying with
water for agricultural irrigation on the year round.
They are Chanh. Bach Dang. Cam. Lach Tray. Van Uc and Thai Binh. These rivers have been running through the region of the Red-Thai Binh river system delta with soft alluvial soil bed. Bearring a great content of sediment to accrete their estuaries into large tidal flais.
The concavity areas located between 2 tidal flats have a negative relief. They formed weak place. On this distributions of breakers. Swells…. Are concentrated for scashore erosion (Dinh vu. Tien lang).
- Wave: The Hai pong coastal zone has been under influence of
alternating monsoons. The North - East monsoon and the south - East one
with an average speed of 6 - 8 m / sec. Especially typhoons gale storms
often occur in July, August. September. October with high speed. It is
the wind. That creates waves and provides them the same direction with
most part of energy to hit seashore, causing erosion. The stronger storm
is. The heavier wave. It causes .
However the pressure of wave depends on the angle between its direction and shoreline. It reaches the greatest value while this angle is a right one. that happens from May to October when the South - East monsoon occurs and creates coastal erosion. But under influence of the North - East monsoon (from November to April), the wave direction is cutting the shorline an acute angle. That is why the wave acts on the shoreline a weak dynamic not create or coastal erosion. Tide exists one times per day with average tidal range of 3.7m.
The Hai phong estuarine and coastal region is with river current, swells. Breakers and tidal influence by tropical monsoon wather. It is the specific action zone of vigorous continental and marine process. Therefore it is necessary to confine the shoreline between sea and continent.
- Shoreline:
In this training area. Using remote sensing data we consider the shoreline is the boundary between the dark grey color of the sea and the light tone with clear details of mainland objects on the infrared landsat image channel 7. In which seawater or wet tidal flats can be clearly distinguished from continent (dry land or mangrove. Dike….)
- Object in the sea
-Tidal flats:Processing satellite dates, using necessary references and field survey results, we classified tidal flats into 2 following types: intertidal (inner) and subtidal (outer) flats (see figure 2)
+Intertidal flats: The tidal flats adjacent to continent and not overflow by the lowest high water. This area in overflow only by higher high water and covered with bewared in rare mangrove in the further. Sediments drift and deposit accretetion and the result of continuos disking for agricultivation, shrimp and alga plantation. This area gradually become apart of continent.
+ Subtidal flats: the area of tidal flats being overflown with using tide and emerged with ebb-tide. This is the transitional area from intertidal flats to the sea. And mainly of sandbed of thick mud bed.
Inertial and sub tidal flats are distributing on estuaries of six rivers falling within the study area and can be easily identified on false color composite (see photo 3)
Seabar: There is the sediment for drifting into the offshore.
Figure 2: Coastal land forms.
A : The shoreline, according to the highest intertide
B: The line , according to the lowest intertide
C. Object in the continent:
The following objects were classified.
Swamps (or ponds), mangrove, rush trees, pine trees, shrubland. Farmland, resident areas.
They are characterized for the Hai phong estuarine and coastal zone and easy to distinguish each other by interpretation of remote sensing images at scale of 1:100000 (see photos) Results and discussion:
After photo interpretation and checking by ground truth survey, these classified objefts were mapped and their areas were measured with planimeter at scale 1/100.000 in (ha).
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By the about 50 km-long-shoreline of Haiphong the tidal clats areas of 6514 ha are thick to distribute on 7 estnaries.
That mind: The study area has dense rivers they are running through soft bed Red. Riverdelta and bringing a let of allnvial sediment to drift and accrete on the estuarles.
The map shows two parts of the study area: Region 1 : Cathai - Dongxa: Allmost areas of swamps (3675 ha) and mangrove (2500 ha) exist in this part (see table 1).
Table 1: Areas of mangrove and swamp in region 1
| Coastal region 1 | Area (ha) | Area of [ha] | Mangrove % | Area of swamp [ha] | Swamp % | Another [ha] % |
|
| Cathai | 3075 | 250 | 8.1 | 1350 | 43.9 | 1475 | 48.0 |
| Bai nha Mac | 2450 | 1000 | 40.8 | 1375 | 56.1 | 75 | 3.1 |
| Dinhvu | 700 | 325 | 46.4 | 275 | 39.3 | 100 | 14.3 |
| Vuyen | 750 | 525 | 70.0 | 225 | 30.0 | 0 | 0 |
| Dong xa | 850 | 400 | 42.1 | 450 | 57.9 | 0 | 0 |
| Sum area | 7825 | 2500 | 31.9 | 3675 | 46.9 | 1650 | 20.2 |
The coastal region 1 was new accreted and closed to the big city of Haiphong. Due to high density of Haiphong population inhabitants aggress into the new land to disorderly exploit mangrove and dike to cultivate for agriculture, alga, shrimp, fishery….while this area were not enough accreted with stable bed and influenced of wave dynamic . Thus conduct;
+decreasing of mangrove areas and ability to keep soil
+increasing of swamps areas and sinking of this coastal region. Inside of mainland, the map shows areas of shrubland, farmland and resident areas.
Region 2 : Doson-Tienlang This region is more stabil than another one. Almost areas are shrub land. Farmland and resident areas.
There is only 182 ha of pine tree in some hills of Doson . 161 ha of rush tree in Tienlang and a small area of mangrove in Tienlang, Changes detection
Comparing the shoreline in a interval of 10 years (from 29 Dec. 1975 to 7. Jan. 1986) through landsat images, it was found that major changes occurred at places:
Erosion in Cathai, Dinhvu, Van uc, Tien lang (see table 2).Accretion in estuarine areas of Bachdang, Cam, Lachtray, Lach huyen.
Table.2 Eroded areas
Table 3: Accreted areas
| Regions | Length [km] | Max width [m] | Area [ha] |
| Cathai | 5,2 | 320 | 115 |
| Dinhvu | 4,2 | 390 | 82 |
| Van uc | 5,6 | 450 | 162 |
| Tienlang | 6,8 | 460 | 182 |
| Total | 541 |
Table 3: Accreted areas
| Regions | Length [km] | Max width [m] | Area [ha] |
| Bachdang | 2,2 | 200 | 35 |
| 2,0 | 110 | 15 | |
| Cam | 3,2 | 370 | 71 |
| Lachtray | 1,0 | 180 | 12 |
| 4,6 | 580 | 152 | |
| Lachhuyen | 3,1 | 310 | 60 |
| Thaibinh | 2,5 | 310 | 55 |
| Total | 400 |
Grandtotal of areas changes : 141 ha -> 14,1 ha/year. Also grandtotal n the estuarine and coastal zone of Haiphong 14,1 ha per year was eroded.
Conclusion
Remote sensing dates provide a reliable and economical source of information for conducting in ventories and for evaluating and monitoring coastal zone resources.
From the remote sensing dates, it is found that the Haiphong estuarine and coastal zone is a region with much dynamic process
+Developing of tidal flats in estuaries
+Decreasing of mangrove areas
+Increasing of swamp areas and breaking up of Cathai, Dinhvu, Bai nha Mac, Vu yen
+Some areas were eroded and some another ones accreted, but in grandtotal the mainland of study area were eroded in last 10 years from the result of this study. It can be predicted that in the future, many parts of areas Cathai, Dinhvu, Bai nha Mac, …may be lost
In this study problems of inventory of farmland, new land, detailer investigation and arrangement of or rational using of coastal zone are not to resolve. It need mapping in larger scale in next phase.
The autor would give some recommendations:
+It s necessary to investigate and evaluate this area at larger scale (1/50.000-1/10.000) for rational using . Espectially : Areas of Cathai, Dinhvu, Bai nha Mac, Tienlang.
+conduct local inhabitants to realise arrangement form and structures of exploiting and planting of mangrove. Rational diking and using of coastal zone.
+ paying attention to disasters, typhools erosion, sinking.
Reference
- Barrett and L. F. Curtis. Introduction to environmental remote
sensing. Chapman and Hell Ltd. London 1978
- Vipada Apinan. Remote sensing application to coastal resources
manegement and Planning in Thailand.
- D. K. Barua and F.G. Koch.Field measurements and remote sensing in estuaries for engineering development *2 and 3 are belong to Proceeding of the Regional seminar on the applications of remote sensing techniques to coastal zone management and environmental monitoring. Dhaka, Bangladesh 18 - 26 November 1986