Assessing Land Use/Land Cover Dynamics in Two Identified ‘Hot Spot’ Areas: Oudomxay Province of Lao P.D.R. and Makong Delta of Vietnam
Chandra P. Gir1, Eike kratzachmar2, Rey S. Oftren3, D. Pradhan1 and Surendra Shrshtha1
1UNEP Environement Assessment Programme for Asia and the pacific,
Asian Institute of Technology
P.O. Box 4, Klong Luong, Pathumathani 12120, Thailand
Tel: (66-2) 524-6236, Fax: (66-2) 516-2125,
E-mail: [email protected]
2Institute of cartography,
Drsden University of Technology, Dresden, Germany
3University of Auckland,
Auckland, New Zealand
The macro-scale time series analysis of AVHRR data for Lao P.D.R and Vietnam identified two hot “hot spot” areas, one in Oudomxay province of Lao PD.R. and the other in Mekong Delta of Vietnam. Detailed investigation of these areas using high resolution satellite data supplemented by field survey revealed some interesting observations. In this paper some of the pertinent issues such as driving forces responsible for the changes, policy implications and further sceneries have been discussed for both the cases.
UNEP Environment Assessment Programme for Asia and the Pacific (UNEP/EAP.AP) has been involving in the macro-scale assessment and monitoring ecologically important land cover types of selected countries in South and South East Asia. The principal goal of the land cover assessment and monitoring project is to prepare a wall-to-wall map of the major land cover types and monitor the changes across time. The time series analysis of coarse resolution satellite data such as NOAA AVHRR HRPT, identifies areas undergoing major land cover transformations, often termed as “hot spots” .Detailed investigation of these areas using high resolution satellite data such as SPOT, Landsat and IRS is needed for accurate and timely information pertaining the rate and phenomenon of change. It is also helpful in identifying driving forces responsible for the change (Giri & Shrestha , 1995).Such information can be useful for decision makers to formulate rational programs in land management and policy planning.
Multi-temporal analysis of AVHRR imagery consisting of 1985/86 and 1992/93 for the whole country of Iao P.DR. and Vietnam identified two “hot spot” areas, one in northern Laos and the other in Mekong Delta of Yitnam. Detailed investigation of these two areas were conducted using SPOT XS data. The approach, methodology and results have been discussed in this paper.
2.0 Study Area
A bried description of Oudomxay, Loss and Mekong Delta of Vietnam has been described below.
2.1 Oudomxay, Lao P.D.R.
The Study area encompasses considerable portion of Oudomxay province (Fig. 1). It is bounded between longitude 101o 14′ 15″ to 101o 56′ 10″ E and latitude 20o 12’38” to 20o 48′ 47″ N.
Figure 1 Approximate location of the study area
The study area is having a mountainous topography drained by two river systems, Nam Beng and nam. The greater part of the highland consists of an extensive rugged mountainous area which runs north to and is dissected with steep slopes and narrow valleys.
Oudomxay province has a population of about 291,000 persons in 1990 (Makong Secreatraiat, 1993). There major ethnic groups namely Lao Theung 55%), Lao Lum (31%) and Lao Sung (13%) are residing in the area. The main occupation of the population are farming and livestock raising. Shifting cultivatin remains the pre-dominant agriculture practice.
2.2 Mekong Delta, Vietnam
The study area is situated in the Southern part of Vietnam and bounded between latitude 9o 42′ 43.92″ and 10o 19′ 27.87 N and longitude 106o 10′ 1.35 E and 106o 51′ 12.71″ E. It is located about 25 km south-west of Ho Chi Minh City (Fig. 1).
Fig. 1 Approximate location of the study area
The mainlandform types in the area include sand dunes, alluvial planins, fluvio-marine pains and denundatin slopes. The area is strongly influence by changes of the water level mainly because of its altitude and flat terrain. During July to November, about 75-80% of the annual total amount of surface water flows into the Sea (Hung and Luong, 1989).However, during January to April soils dry out very quickly and part of the study area suffers from drought.
The population density in the Mekong delta is 800 persons/sq. k, highest in the country (natons average is 179 person/sq.km). Villages in the study area have linear or radial patterns distributed above riverbank road and canals.
3.0 Data Basis
3.1. Oudoxay, Lao P.D.R.
SPOT XS data acquired on March 26, 1992 was used s the principal source of information Topographic maps and published information regarding land use/land cover practices were also used. At intensive field visit of four days was conduced on December 1994, approximately three months earlier the month of the acquisition of the satellite data. During the field trip, formal and informal interviews were take
With the government staff and local people. A part of the study area was visitd by establishing number of sample plots. In each sample plot, information on shifting coultivation, forest types, topography, slope and land use/land cover types were collected.
Villge map was digitized from 1:100,000 scale topographic map. Other information layers such as river, roads, elevation and geology were also used as a GIS layer in the analysis. These information were extracted primarily from the Digital Chart of the World (DCW).
3.2 Mekong Delta, Vietnam
SPOT XS data acquired on March 04, 1995 was used as the principal source of information of derive present status of land use/land cover in the study area. Other secondary information such as topographic maps, soil map, district and provincial boundary map, geological map, land use map, transportation network and work and canal Network map were collected from various sources and utilized in the data analysis.
An intensive field visit of six days was conduced in November, 1995, approximately three months earlier than the month of the satellite data acquisition. A representative sample of the study area were visited by establishing a number of temporary sample plots. In each sample plot, information on agricultural crops, cropping patterns, management regimes, dominant vegetation types, topography and soil types were collected Global Positioning System ()GPS) was used duplicates ample plots in the satellite imagery.
River and canals as well as land use maps were digitized from 1:100,000 scale topography map. Other data layers mentioned earlier, were available from UNEP/EAAP.AP and Mekong River Commission (MRC).
A common methodology was used for both the studies, as described below.
The SPOT image was spatially geo-referenced to a Universal Transverse Mercator (UTM) map projection using first order polynomial and reasampled with nearest neighbor algorithm. Ground Control Points (GCPs) were selected from 1:50,000 topographic map. A Root Mean Square (RMS) error of 1 pixel (20m) was accepted for rectification.
A hybrid approach of supervised and unsupervised classification was deployed. Isodata clustering followed by iterative labeling was used for unsupervised classification. Tanning areas was selected based on the field observation for supervised classification. The information from unsupervised classification was incorporated in the outcome of supervised classification. Supervised classification using maximum likelihood classifier in ERSAS (an image processing software) was performed by selecting a number of training samples. Statistical analysis of these training areas were performed to find out their consistency. The classified image was converted to vector format for further GIS analysis in ARC/INFO environment.