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Objectives
The
objective is to perform the inventory of the coastal ecosystems covering
the full extent of the three sub-areas, in terms of mangrove vegetation,
soil types and salt intrusions. This mapping will include the
identification and positioning of aquaculture farms and land use in their
surroundings.
Data
acquisition will mainly concern :
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vegetation
types : mangrove and brackish water species, and their status
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land
use : paddy fields, orchards, plantations,
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aquaculture :
spatial data about farms
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salinity,
obtained through hydrodynamic models,
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soil
types.
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The
secondary objective is to design and implement a spatial data base
gathering all spatial data about the farms and their environment. Such an
asset will be essential to produce overlay maps and display an overview of
the activity, as well as to provide a basis for future monitoring.
Innovative
aspects
The
innovative aspect is to be found in a specific way of mapping, focused on
farms and their relations to their immediate environments. Unlike most
thematic mapping projects that tend to cover vast expanses using one data
source, the idea here is rather to use all available documents on relevant
scales to produce some kind of “ macro indicator of environmental
health” on limited perimeters around farms in activity. The stress will
also be placed on methods replicability.
Methods
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Land
use and ecological mapping
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As
preliminary investigations carried out in Vietnam in November 1988 have
shown, it seems reasonable to adopt 1/50000 as the mapping scale. This
level of scale is within the reach of current remote sensing imagery. It
is large enough to allow display of extensive farms (typically covering
a few hectares) as well as significant land cover units. Besides, it
allows the integration of data derived from existing Vietnamese maps, in
particular land cover maps on scale 1/100000 available in some provinces
(e.g. Ca Mau). Finally, considering the dimensions of the envisioned
study areas (20 km alongshore and 30 km upstream), 1/50000 will also
prove adequate for practical mapping outputs.
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Collection
of existing mapping data
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This
task will be performed in the various agencies that have been (or are)
concerned with the Mekong delta in the past. Some land cover maps,
soil maps and geological maps are available at the Institute of
Geography and in universities (Can Tho). An inventory and a selection
of documents fitting with the project scale will be made. For recent
undertakings, the corresponding digital files may also be available.
Administrative limits of provinces and districts will also be made
available to the project and digitised if not already in digital form.
Digitisation will be contracted to local firms.
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Acquisition
and processing of digital imagery
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Up
to three most recent satellite images will be acquired over the three
sub-areas. Their interpretation will be carried out in Vietnam under
the supervision of a mangrove mapping and remote sensing expert from
Université Paul Sabatier. The Spot 4 product line will be
contemplated for this work, as it features the following advantages :
an improved resolution (10 metres in the P+XI mode), an additional
channel in the middle infra-red region (specifically devoted to
vegetation), a programming mode allowing high probability of very
recent images.
This
task will be supported by extensive field work focused on the farms
selected as the sample network. An in-depth ground truthing will be
carried out, including soil ph measurements.
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Data
completion |
All
data resulting from digitization will have to be completed and checked.
This may imply ground truth missions. The process will be as follows :
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superimpose digitised maps with satellite imagery in order to locate
interpretation conflicts, recent changes and solve for geometric
distortions induced by digitisation, prepare work documents for
field checks,
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superimpose available low scale layers in order to refine
classification whenever possible (e.g. soil and land forms on 1/100
000).
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Hydrodynamic
modelling |
Previous
work has been performed over the Mekong delta within the EC-INCO Cuu
Long project (DG XII), the results of which are available in a
publication titled “Proceedings of the International Workshop on the
Mekong Delta ”. One scope of this project was the understanding
of the hydrodynamics in the outer reaches of the distributaries,
namely as far as 40 km upstream the main distributary of Dinh An (city
of Can Tho).
By
re-running the model, these results concerning salinity intrusions
could be extended a) to other distributaries included in the sub-areas,
b) to secondary branches (arroyos) stemming from the former that lead
to aquaculture farms. It will be attempted, on the ground of these
results, to infer salinity structures along secondary branches, with
the help of limited field work, i.e. conductivity measurements at
regular stations along the arroyos. Salinity data obtained from
networks or campaigns managed by IO Nha Trang will also be exploited.
The model part will be contracted to Université de Caen.
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Farm
positioning |
For
farms identified and selected as samples of the farm network, a number
of parameters will be stored: ecological, hydrobiological, technical
and socio-economical. The “ hydrological distance ” to
the sea will be computed and attempts will be made towards the
definition of a marine water renewal rate, combining this distance and
salinity outputs from the hydrodynamic modelling.
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Management
tools
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Spatial
data management will be performed using a GIS geared at storing and
retrieving all information layers relevant to farm sites. A conceptual
model will be designed after defining which queries should be regularly
addressed to the system during current monitoring phase. This model will
help define proper attributes qualifying farms and ecosystem units, as
results from activity 5 (statistical data
analysis).
Various
displays of graphs and pie charts will use a “ base map ”
as a geo-reference on which they will be overlain. The base map will
consist in classical layers such as the coastline, administrative
boundaries, place names, etc...
A
complete mapping set up will be implemented at the Institute in Nha Trang.
Duration
24
months
Expected
outputs
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1/50
000 digital data base for land cover, land use and contours of shrimp
farms;
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1/50
000 digital data base of administrative contours;
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various
paper prints on 1/50 000 illustrating data analysis;
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the
upgrade of the GIS lab at ION. This will include 2 complete high
quality PC setups with map digitising equipment, CD/ROM writer and
electrostatic A0 plotter, plus network, room installation and air
conditioning. Details are given in the financial plan.
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Training
of 2 persons to survey methodology, mapping and GIS.
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Participants
IFREMER/Brest,
IO Nha Trang , University of Toulouse (including likely support by
the French Embassy)
Bibliography
Blasco
F. et al., 1997 - Recent
advances in mangrove studies using remote sensing data. Australian
Journal of Marina and Fresh Water Research , vol. 49 (4) : 287-296.
Fuchs
J., Martin J.-L.M., Populus J., 1998. Assessment of tropical shrimp
aquaculture impact on the environment in tropical countries, using
hydrobiology, ecology and remote sensing as helping tools for diagnosis.
Final report of the E.U. contract RS3 - CT 94-00284. Rapport
interne de la Direction des Ressources vivantes de l’IFREMER, DRV/RA/RST/98-05,
262 pp.
Nguyen
K.D. et al., 1998. A
3-D Numerical Study of the Tidal Circulation in the Mekong Delta Coastal
Vietnam. Proceedings of the International Workshop on the Mekong Delta, EU
INCO-DC, Chiang Rai, February 23-27, 1998.
Populus
J. et al., 1995. Remote
sensing as a tool for diagnostic of water quality in Indonesian seas. Ocean
and Coastal Management, Vol.27, No.3, pp. 197-215.
Populus
J., Loubersac L., Prou J.,
Kerdreux M., Lemoine O.,
1998. Geomatics
for the management of oyster culture leases and production. Proceedings of
CoastGIS’97, Second International Symposium on GIS and Computer Mapping
for Coastal Zone Management, Kluwers editors (under press).
Rasolofoharinoro
et al., 1998. A
remote sensing based method for mangrove studies in Madagascar.
Int. J. of Remote Sensing . 19
(10) : 1873-1886.
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Project
