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Assessment of land use changes in Mukdaham and Nakhon Phanom provinces (NE Thailand) by means of Remote Sensing

©2002 Diplomarbeit 198 Seiten

Zusammenfassung

Inhaltsangabe:Abstract:
Tropical land use changes, predominantly the clearing of tropical rain and monsoon forests, have long been recognized as a trend with dramatic consequences. FAO estimated the global loss of rain forest area at 0.6 to 0.9 % per annum in 1993. Most of it can be attributed to the conversion of forest lands to agricultural areas. In Southeast Asia, two countries have suffered from this phenomenon more than any other nations: the Philippines and Thailand. Between 1961 and 1975, the forest reserves of Thailand have been reduced from 57 % to 37 % of the total area, while at the same time the area put to agricultural use has almost doubled. Only a small part of that process was due to organized resettlement programmes; to an overwhelming extent the deforestation has been performed 'illegally' by spontaneous activities of the rural population. The share of forests further declined to 28.9 % in 1998, at a current rate of -0.7 % per year, meaning that Thailand's forest cover has roughly halved since 1960.
The author of this thesis stayed as a visiting researcher at the Asian Institute of Technology (AIT), immediately north of Bangkok, for 6 months from November 2000 until April 2001. The AIT is a small international university for graduate studies with students and teachers from more than 40 countries. The core institution for this scientific cooperation was the Asian Center for Research on Remote Sensing (ACRoRS) of the AIT's School of Advanced Technologies (SAT). Field work in Northeast Thailand was carried out in two legs in February and April 2001.
As an underlying principle of this study, it was attempted to incorporate problems from the realms of social as well as physical geography, i.e. to maintain a balance between questions of applied geography (regional studies) and remote sensing. This also means that no special focus was put on advanced RS methodology such as the development of new image processing techniques; the study is rather based on a somewhat holistic approach, joining aspects from many different fields of science as diverse as geology, geomorphology, climatology, agriculture and agricultural economics, sociology, ethnology, politics, and spatial planning.
Accordingly, the basic objectives were:
- to give a geographical description/characterization of the Northeastern Region of Thailand in terms of its physical properties as well as its social and economical peculiarities.
- to try a quantification of forest […]

Leseprobe

Inhaltsverzeichnis


ID 6135
Rennenberg, Nils: Assessment of land use changes in Mukdaham and Nakhon Phanom
provinces (NE Thailand) by means of Remote Sensing
Hamburg: Diplomica GmbH, 2002
Zugl.: Göttingen, Universität, Diplomarbeit, 2002
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Printed in Germany

2
Contents
List of figures
4
List of tables
6
List of abbreviations
7
Remark on the quotation of Thai authors
7
Remarks on the spelling of Thai place names
7
Remark on Thai administrative units
9
Acknowledgements
10
References
147
Internet references
150
Map references
151
Glossary of Thai terms and map designations
152
Glossary of Thai measurements
154
Appendix
155
Photographs
184
1. Introduction
11
1.1. Statement of problem: tropical land use changes
11
1.2. Objectives, scope and limitation of the study
12
1.3. Cooperation with AIT
13
2. Theory/literature review
13
2.1. Deforestation and agro-colonization
13
2.2. Spontaneous versus planned colonization in Thailand
15
2.3. Remote sensing + the Landsat System
17
3. Overview: Northeast Thailand
20
3.1. Location, administration, population
20
3.2. Geology and geomorphology
22
3.2.1. General outline
23
3.2.2. The Khorat Plateau
29
3.2.3. Soils
36
3.3. Climate and hydrology
37
3.4. Vegetation
46
3.5. Economy and land utilization
51
3.5.1. The importance of the rural space and agriculture in Thailand
51
3.5.2. Per capita income and living conditions of the rural population
52
3.5.3. General conditions for crop growing and overview of cultivated plants
54
3.5.4. Farm size, farm income and land tenure
57
4. Study Area
59
4.1. Selection
59
4.1.1. JICA PLANET Project
59
4.1.2. Mukdahan and Nakhon Phanom Provinces
61
4.2. Location, size and population
62
4.3. Topography
67

3
4. Study Area (continued)
4.4. Geology and soils
69
4.5. Climate
72
4.6. Land use/land cover
74
4.7. Agriculture
77
4.7.1. Rice
81
4.7.2. Sugarcane
83
4.7.3. Cassava
85
5. Methodology
89
5.1. Data, materials and tools
89
5.2. Impressions from field work
90
5.2.1. First visit, February 2001
90
5.2.2. Second visit, April 2001
93
5.3. Image processing, part one (Thailand)
94
5.3.1. Data pre-processing
94
5.3.2. Rectification and geocoding
94
5.3.3. Mosaicking
94
5.3.4. Masking
94
5.3.5. Visual Interpretation
95
5.3.6. Unsupervised classification
97
5.3.7. Supervised classification
98
5.3.8. Accuracy assessment
105
5.4. Image processing, part two (Germany)
106
5.4.1. Resizing of year 1972 image
106
5.4.2. Data calibration test
106
5.4.3. Choice of area for case study and masking
107
5.4.4. Unsupervised classification
108
5.4.5. Band ratios and vegetation indices
108
5.4.6. Tasseled Cap Transformation
114
5.4.7. Supervised classification
116
5.4.8. Accuracy assessment
122
5.5. Elevation model
124
6. Results
126
6.1. Results from remote sensing, part one (Thailand)
126
6.2. Results from remote sensing, part two (Germany)
126
6.3. Reasons for land use changes
129
6.4. Current situation of forests in Thailand
130
7. Conclusion and outlook
131
7.1. Assessment of methodology
131
7.2. Development planning in Thailand
131
7.3. Regional development planning and future trends in the Mekong Region
133
7.4. Summary: problem structure and recommendations for the study area
140

4
List of figures
Figure 1: Forest destruction in Thailand 1965-1978 ... 11
Figure 2: Schematic overview of the image interpretation process in remote sensing... 17
Figure 3: Landsat-4 and ­5 observatory configuration / Sun-synchronous orbit of Landsat-4 and ­5. ... 19
Figure 4: The physical regions of Thailand... 22
Figure 5: Geotectonic structure of South-East Asia. ... 23
Figure 6: Tectonic overview of Asia... 24
Figure 7: The main rivers of South-East Asia. ... 24
Figure 8: Left: Physical orientation map of Thailand. Right: Elevation map of Thailand, highlighting the Khorat
Plateau... 25
Figure 9: Left: Land forms of Thailand. Right: Land capability map of Thailand... 28
Figure 10: Escarpment of the Khorat Plateau, seen from Khao Phra Wiharn Temple Complex (Si Sa Ket
province), looking westward. ... 29
Figure 11: View of the Khorat escarpment from roughly the same location as in fig. 10, this time looking
eastward over Cambodian jungle in Preah Vihear province. ... 30
Figure 12: Physical orientation map of North-East Thailand... 34
Figure 13: Idealized cross-section illustrating relationship between landforms and substrata material of a river
plain and adjoining area (the Mekong at Pa Mong). ... 35
Figure 14: Left: Winds influencing the climate of Thailand. ... 38
Figure 15: Main features of the low-level circulation over eastern and southern Asia in the cool (left) and in the
warm (right) season... 39
Figure 16: Annual normals of rainfall in Northeast Thailand, according to meteorological sub-regions (30 years'
average 1931-60)... 41
Figure 17: Monthly normals of rainfall in Northeast Thailand, according to meteorological sub-regions (30 years'
average 1931-60)... 41
Figure 18: Interaction of meteorological data in North-East Thailand, expressed in index figures. ... 43
Figure 19: Hydrological map of North-East Thailand. ... 44
Figure 20: Discharge regime of rivers in North-East Thailand. ... 45
Figure 21: Example for the extensive annual inundations along the Mekong River (Mae Nam Songkhram and
Nam Kam river mouth area)... 46
Figure 22: Forest map of North-East Thailand. ... 47
Figure 23: Single trees as remains of a former forest in a sugarcane field near Ban Sam Kha, A. Muang
Mukdahan... 56
Figure 24: Location of the JICA study area within the surrounding provinces of Northeast Thailand... 60
Figure 25: Location of the study are within Thailand (left) and the JICA study area (right). ... 62
Figure 26: Administrative divisions of the study area... 64
Figure 27: Overview of the main landscape units of the study area, superimposed onto band 7 of the Landsat TM
2000 image ... 67
Figure 28: Contour map of the study area with main rivers. ... 68
Figure 29: Main land forms in North-East Thailand. ... 69
Figure 30: Geological map of the JICA project area... 70
Figure 31: Climate diagrams for Mukdahan and Nakhon Phanom. ... 72
Figure 32: Monthly rainfall averages for the JICA study area in May and October. ... 73
Figure 33: Landsat ETM+ scene 127/48 during the dry season (23/11/2001) and the end of the rainy season
(17/09/2000), channel combination 542... 73
Figure 34: Extent of agriculturally utilized land in Northeast Thailand (Khorat Plateau) up to 1963. ... 75
Figure 35: Degraded monsoon forest in Northeast Thailand during the rainy season and the dry season. ... 76
Figure 36: Paddy fields burnt after harvest. Near Ban Pla Pak Noi, A. Pla Pak, Nakhon Phanom province. ... 76
Figure 37: Rice tractor. ... 79
Figure 38: A conceptual zoning system of local characteristics in the NBR. ... 81
Figure 39: Rice fields with impounded rainfall irrigation in Northeast Thailand during the rainy season ... 82
Figure 40: Thai farmers transplanting rice. Source: www.fao.org ... 83
Figure 41: Sugarcane ... 84
Figure 42: Cassava plant.. ... 85
Figure 43: Landsat WRS II tiles overview for Thailand. ... 89
Figure 44: Nong Samong ­ A Khorat Plateau wet-rice village with additional cassava cultivation on newly
cleared forest land (Sankamphaeng Range, Nakhon Ratchasima province). ... 91
Figure 45: 742 composite of the Landsat TM 2000, showing Huai Bang-I valley in the southern sub-scene. ... 92
Figure 46: Maximum likelihood classification ... 98

5
Figure 47: Left: Classification principle of a maximum likelihood classifier, showing equiprobability ellipses
around training classes A-F. Right: Probability density functions defined by a maximum likelihood
classifier. ... 99
Figure 48: Details of the 1972 MSS and the 1989/2000 TM images, showing areas in the surroundings of Huai
Kabao Reservoir that were probably subject to deforestation and then reforestation ... 103
Figure 49: Outline of the case study area. 742 composite of the year 2000 TM... 107
Figure 50: Left: Typical spectral reflectance from a living leaf. Right: Interaction of leaf structure with visible
and near infrared radiation. ... 109
Abbildung 51: Left: Differences between vegetation classes in the visible and near infrared spectrum. Right: DN
scattergram for band 4 versus band 3 of an agricultural scene, with superimposed isolines... 109
Figure 52: Comparison of a 7/5 ratio (left) and an NDVI (right) pseudocolor image of the area near to Huai
Chanot Reservoir (with 5 km grid lines). ... 110
Figure 53: Comparison of different colour composites, showing the area near to Huai Chanot Reservoir (with 5
km grid lines). a = 321; b = 432; c = 742; d = 7/5-NDVI-2 ... 111
Figure 54: Simplified cross-sectional view of behavior of energy interacting with a vegetation canopy. ... 112
Figure 55: Scattergram showing the relation between the 7/5 band ratio and the NDVI for the year 2000 TM
image... 112
Figure 56: Scattergram comparing the 7/5 band ratio and the NDVI for crop and forest pixels in the year 2000
TM image. ... 114
Figure 57: Seasonal variation of a field in data space defined by the greenness and brightness axes... 114
Figure 58: Band 3 versus band 2 Landsat MSS subspace showing trajectories of crop development (left). Crop
trajectories in Landsat MSS band 1,2,3 space, having the appearance of a tasseled cap (right). ... 115
Figure 59: Tasseled cap transformation for the area next to Huai Chanot Reservoir (with 5 km grid). Brightness-
Greenness-Yellowness (RGB) colour composite. ... 116
Figure 60: Rule classification result for the 1972 image with an NDVI threshold value of 0.4. ... 122
Figure 61: DEM of the study area, seen from the southeast... 124
Figure 62: Detail of the DEM from fig. 61, showing the Phu Phan Range with the narrow valley incised by Huai
Bang Sai river and the "Dong Luang East Basin" in the background (arrows). ... 125
Figure 63: Detail of the DEM from fig. 61, showing the steep slope of the Phu Phan Range, seen from the
northeast. Vertical exaggeration factor = 3...125
Figure 64: Areal changes of land cover classes in the study area, 1972-2000. ... 126
Figure 65: Areal changes of land cover classes in the case study area, 1972-2000. ... 127
Figure 66: Comparison between the shares of the different land cover classes in the 1972, 1989 and 2000
classification results. ... 128
Figure 67: Projected changes in the age structure of the population in Northeastern Thailand and Lao PDR... 129
Figure 68: The NBR in the east-west corridor of the GMS (Greater Mekong Sub-region). ... 135
Figure 69: Spatial structures of different development alternatives for the NBR. ... 138
Figure 70: Problem structure of the Northeastern Border Region (NBR) in a socio-economic context. ... 141
Figure 71: Degree of crop diversification in the provinces of Northeast Thailand, based on average rankings for
selected diversification criteria... 145

6
List of tables
Table 1: Forest statistics for Thailand, Asia and the world
12
Table 2: Spectral specifications of the Landsat scanner systems bands (wavelengths in µm)
18
Table 3: Hypsometric analysis of Thailand
25
Table 4: Stratigraphy of Thailand (1914-1951)
26
Table 5: Hypsometric analysis of Northeast Thailand
29
Table 6: Overview of stratigraphic units in the Khorat Plateau and bordering areas
30
Table 7: Stratigraphy of the Mesozoic Khorat Group (Upper Triassic to Cretaceous)
31
Table 8: Stratigraphy and facies of the Khorat Group and Huai Hin Lat Formation.
32
Table 9: Synopsis of the main watersheds of Thailand (km²)
43
Table 10: Forest types in Thailand by region (in %), 1999
50
Table 11: Plantation areas in Thailand by species groups and ownership, 2000
51
Table 12: Development of the shares of the economic sectors in Thailand and in the Northeastern
region, 1960-1998
52
Table 13: Per capita income and debt by region, 1994 and 1998
52
Table 14: Gross Provincial Product (GPP) at current market prices for selected provinces, 1994
53
Table 15: Land Utilization in Thailand by Region, 1965 (in percent)
55
Table 16: Land Utilization in Thailand by Region, 1995
55
Table 17: Number of holdings, area covered and average holdings in Thailand, according to
regions and sub-regions (1963).
58
Table 18: Baseline administration and population data for the study area
63
Table 19: Data of population changes in the study area, 1995-1999
64
Table 20: Occupations of the working population over the age of 13 in Mukdahan and Nakhon
Phanom provinces by economic sector, 1999
65
Table 21: Mukdahan: Gross Provincial Product (GPP) by economic sectors at current market
prices, 1993 and 1999, in millions of Baht.
65
Table 22: Nakhon Phanom: Gross Provincial Product (GPP) by economic sectors at current
market prices, 1993 and 1999, in millions of Baht.
66
Table 23: Average monthly household incomes in the study area (in Baht), 1998
67
Table 24: Major soil types in the study area
71
Table 25: Land utilization in the study area, 1985-1989-1995
74
Table 26: Utilization of farm holding land in the study area, 1995
77
Table 27: Main crops and their average yields in Mukdahan province by planted area, 1997/98
77
Table 28: Main crops and their average yields in Nakhon Phanom province by planted
area, 1997/98
78
Table 29: A conceptual zoning system of local characteristics in the NBR.
80
Table 30: Production of raw sugar from sugarbeets and sugarcane, 1999 and 1990
84
Table 31: Crop calendar for selected field crops in agricultural zone 3 of Northeast Thailand
(Khon Kaen, Maha Sarakham, Kalasin, Roi Et)
87
Table 32: Area of land cover classes in the year 2000 first classification round (Thailand)
99
Table 33: Area of land cover classes in final classification of the year 2000 image (Thailand)
101
Table 34: Some spectral characteristics of the final classes in the 2000 supervised classification
102
Table 35: Area of land cover classes in final classification of the year 1989 image (Thailand)
102
Table 36: Area of land cover classes in final classification of the year 1972 image (Thailand)
104
Table 37: Final classes used in the classification process in Thailand
104
Table 38: Confusion matrix for the year 2000 classification result (Thailand)
105
Table 39: Range of 7/5 band ratio and NDVI for some land use classes in the study area
113
Table 40: Area of land cover classes in the year 2000 first classification round (Germany)
117
Table 41: Area of land cover classes in the year 2000 second classification round (Germany)
117
Table 42: Area of land cover classes in the year 2000 third classification round (Germany)
118
Table 43: Area of land cover classes in the final classification of the year 2000 image (Germany)
119
Table 44: Area of land cover classes in the final classification of the year 1989 image (Germany)
119
Table 45: Area of land cover classes in the final classification of the year 1972 image (Germany)
121
Table 46: Farm income per area by product item, 1982-1998 (in Baht/rai)
134
Table 47: Number of industrial establishments in the NBR, 1998
134
Table 48: SWOT analysis for the NBR (summary)
136
Table 49: Projection of socio-economic framework in the NBR
139

7
List of abbreviations:
A. ­ Amphoe (=district
*
)
ACRoRS ­ Asian Center for Research on Remote Sensing
GAC ­ GIS Applications Center
AIT ­ Asian Institute of Technology, Bangkok
JICA ­ Japanese International Cooperation Agency
PLANET ­ Plan for Laos and Northeast Thailand
NBR ­ Northeastern Border Region [of Thailand]
Lao P.D.R. ­ Lao(tian) People's Democratic Republic
GMS ­ Greater Mekong Sub-region
PCI ­ Pacific Consultants International
RTG ­ Royal Thai Government
RTSD ­ Royal Thai Survey Department
NESDB ­ National Economic and Social Development Board
OAE ­ Office of Agricultural Economics
DMR ­ Department of Mineral Resources
FAO ­ Food and Agriculture Organization of the United Nations
NGO ­ non-governmental organization
GDP ­ Gross Domestic Product
MSL (m.s.l.) ­ Mean Sea Level
GIS ­ Geographic Information Systems
RS ­ Remote Sensing
BIL ­ Band Interleaved (Format)
BSQ ­ Band Sequential (Format)
IFOV ­ Instantaneous Field of View
IR ­ Infrared
NIR ­ Near Infrared
MIR ­ Middle Infrared
RGB ­ Red, Green, Blue
HSI ­ Hue, Saturation, Intensity
NDVI ­ Normalized Differential Vegetation Index
MSS ­ Multi Spectral Scanner
TM ­ Thematic Mapper
UTM ­ Universal Transverse Mercator (Projection)
Remark on the quotation of Thai authors
In Thailand, family names are seldom used, only for official purposes (documents etc.). People normally address
each other by their first names, which is by no means impolite, even in formal situations. This custom doesn't
depend on a person's social status, either. Therefore it is common to cite Thai authors by giving their first and
their last name (or abbreviated last name) and to arrange them according to their first name in the references list.
Remarks on the spelling of Thai place names
Transcribing words from Thai script into Roman script can lead to considerable confusion. That is not only due
to the fact that the Thai alphabet is rather voluminous with its 44 consonants, 28 vowels (not considering
additional complex vowel combinations) and 4 tone marks and not quite easy to read because of particularities
such as the distinction between three different consonant classes, complicated tone rules, the absence of
punctuation marks and gaps between the words and, finally, many exceptions in pronunciation. Notwithstanding
all these difficulties, Thai words could well be reproduced in a slightly modified Roman script (including only a
few special signs) without major problems.
The main problem is rather a lack of standardization and the predominance of insufficient or inconsequent
transcription systems. And it's exactly the transcriptions based on English writing/pronunciation that have to be
regarded as completely unsuitable, especially where the correct rendition of the vowels is concerned.
Besides that, any transcription that tries to manage without the use of tone marks should be disapproved. In this
context it has to be underlined that a Thai word can receive up to five different meanings due to different
intonation (normal, deep, falling, high or rising). As far as the Thai place names in this study are concerned, tone
marks are not really significant, however, and can thus be omitted.
*
see glossary, p. 152

8
The most important problems in the writing of place names and map designations will be explained below with
the help of some examples:
As there is no standardized transcription and virtually every publishing firm for maps, guidebooks, phrasebooks
etc. keeps on inventing new variants all the time, one important factor is whether the writing of the Thai words
was mainly intended for an English speaking public or for other people. Hence versions like neua ­ nüüa,
muang/maung ­ müüang, loei ­ lööi, yai ­ jai, djai ­ dschaai, eeg ­ iik, Esan ­ Issaan, Buri Rum ­ Buri Ram,
Ubon Rajthanee ­ Ubon Ratchathani, amphur ­ amphoe ("English" vs. "German" transcription) and endings like
-ern/-urn/-oen/-ön.
Unlike European languages, Thai has no capital letters or punctuation marks and in addition to that, single words
aren't separated from each other by empty spaces within a written sentence. Words are written in one long row
and gaps only made to finish phrases or paragraphs. So basically it doesn't matter if certain place names are
written separately or in a single word (Pathum Thani ­ Pathumthani, Samut Prakan ­ Samutprakan, Nakhon
Phanom ­ Nakhonphanom), though they do consist of two distinct units that carry their own meaning.
Often it is crucial whether a decision between aspirated and unaspirated consonants is made or not, for example
by contrasting gk ­ kh, dt ­ th, bp ­ ph. This leads to forms like khlong ­ klong, Phimai ­ Pimai.
Important remark: "ph" is always pronounced as an aspirated "p" in Thai transcriptions, never as "f"!
The same is true for the discrimination of long and short vowels (a-aa, e-ee, i-ii, o-oo, u-uu), a basic element of
the Thai language system. Most transcriptions don't highlight the long vowels.
The soft/unaspirated consonants -b, -bp, -d, -dt, -gk are always pronounced like their "hard" counterparts when
occurring at the end of a syllable and are therefore best transcribed as -p, -k, -t in such cases. Not all
transcriptions pay attention to this fact, though.
Finally there are certain particularities of Thai writing (or pronunciation, respectively). For example, mute letter
combinations (Nakhon Chaisri ­ Nakhon Chaisi, Surawongse ­ Surawong); or certain vowels (short "a" and "o")
which aren't written and have to be added when pronouncing the word (the Thai word for "street" is written
"thnn", but pronounced "thanon"; hence varieties like Ayodhya ­ Ayutthaya). In addition, there are also
consonants that change their pronunciation under certain circumstances. So the letter "l" becomes "n" when
ending a syllable (resulting forms: Mahidol ­ Mahidon, Cholburi ­ Chonburi), whereas "s", "ch" or "dj" becomes
"t" (Thewes ­ Thewet, Ratchaburi ­ Ratburi, Phetchaburi ­ Phetburi, Somdej ­ Somdet).
Some very special cases include: "-dr" = "-don", "-khr" = "-khon", "-rr" = "-on", "thr-" = "s-", "-aar" = "-aan",
"yy" = "nj". The sounds "ao", "iu", "eo", "äo" are written as "aw", "iw", "ew", "äw" because "w" is always
pronounced like in English (e.g. "water"), no matter if at the beginning or at the end of a syllable. Then there is
an abundance of quite confusing vowel combinations (e.g. ee+oo = öö, ee+aa = au, ee+ii+y = iia). Sometimes the
Thai version of writing is kept in the transcription of words with such particularities (e.g. Wat Phra Kaew),
meaning the word is transcribed letter by letter, which is not useful at all, sometimes an attempt is made to
imitate the corresponding sound (e.g. Wat Phra Kaeo/Keo), and sometimes there is even an inconsequent
mixture of both, which is maybe the worst of all possibilities: for example, the word "nakhon" (city) is written
like "nkhr" in Thai and accordingly rendered as "nakorn" sometimes, though the "r" is mute and produces an "-
on" sound in this special case.
In addition to all of this, some very strange spellings are to be found that don't make sense at all, like the
insertion of hyphens ("E-san") or the use of "v" ("Sukhumvit") instead of "w", disregarding the fact that there is
no such sound in Thai language. A similar case is the use of "-ie" ("Chieng Mai") where there's only an "-ia"
sound in Thai. Sounds like "bh" or "dh" ("Bhumibol") simply don't exist either.
So very often there will be an enormous number of possible spellings, as is the case with one of the main
boulevards in the centre of Bangkok: Ratchadamnoen / Ratdamnoen / Ratdamnöön / Ratjadamnern / Rajdamnern
/ Raachadamnoen / Ratchadamnurn, or any other thinkable combination. There is virtually no "correct" version
of this name (which translates as "Royal Route").

9
Some other random examples for varying spellings:
Ayutthaya, Ayudhya, Ayodhya
Isan, Isaan, Issaan, I-san, Esan, E-Sarn, Essarn
Phayathai, Phyathai
Phaholyothin, Phahonyothin, Phahon Yothin
Sathorn, Sathon
Nakhon Si Thammarat, Nakhonsithammarat, Nakorn Si Thammarat
Mukdaharn, Mukdahan
Pathum Thani, Pathumthani, Prathum Thani
Phetkasem, Petchakasem
Samut Prakhan, Samut Prakarn, Samutprakan
Pattunam, Pratunam
Ubon Ratchathani, Ubon Rajthanee, Ubol Ratchathanee
Chao Phraya, Chao Phya
Cholburi, Chonburi
Chatuchak, Jatujak
Nakhon Chaisri, Nakhon Chaisi
Bang Sue, Bangsu
Chiang Mai, Chiengmai
Amphoe, Amphur
Hat Yai, Haadyai
Muang, Mueang
Phang Nga, Phang-nga, Phangnga
Buri Ram, Burirum
Petchaburi, Phetburi
Roiet, Roi Et, Roi-Et
Bhumibol Adulyadej, Phumiphon Adunyadet
The abovementioned facts lead to the following important consequence: Should one find two more or less
similar names in different sources or on different maps (e.g. Srinagarind ­ Si Nakarin), chances are that exactly
the same thing is meant.
In this study it was attempted to use a wide-spread and at the same time linguistically plausible spelling for
Thai place names in each case and to provide for a certain overall homogeneity in writing. One notable
exception must be mentioned, though: While the form "Khorat" was preferred over "Korat", it was decided to
stick to the internationally common spelling "Mekong", rather than writing "Mekhong" (or "Mae Khong"),
which is more accurate, but a bit unfamiliar.
Remark on Thai administrative units
The expression changwat (djangwat) was generally translated as "province" in this study, as it is common
practice. The changwat (sing./pl.) are the 76 primary administrative units of Thailand with an area strongly
varying in size between only 500 km² (e.g. Phuket Island or Samut Songkhram) and as much as 20,000 km² (e.g.
Chiang Mai or Nakhon Ratchasima). The population may be between 130,000 (Ranong) and 2.5 million
(Nakhon Ratchasima), not considering the very special case of Bangkok. Thus they sometimes correspond to a
German "Landkreis" in size, sometimes to a small or even medium-sized "Bundesland", but in most cases to a
"Regierungsbezirk". On the other hand, it has to be considered that they only command a small amount of
autonomy and are ruled by a high-ranking professional civil servant (a governor) who is installed by the central
government in Bangkok, more precisely the Ministry of the Interior. He is assisted by the Provincial Board,
consisting of civil servants providing technical services on behalf of their respective ministries, such as
education, agriculture, health, etc. (cf. D
ONNER
1978:49). The following administrative unit is called an amphoe
(sometimes abbreviated as "A."), something like a district, or "Kreis" in Germany. They are headed by the
District Officer (nai amphoe, also appointed by the Ministry of the Interior) and again divided into tambon
(tambol) (sometimes abbreviated as "T."), i.e. sub-districts or rural communities/ municipalities/ groups of
villages. These are administrated by the kamnan (Chief of the Commune), elected by the village headmen. The
smallest units ­ and the keystone of local government in Thailand ­ are the muban, or villages. They consist of a
group of at least five households and are headed by the elected pu yai ban (village headman).
As a general rule, there are roughly about 10 amphoe in one province and again 10 tambon in one amphoe. The
terms for these smaller units weren't translated in this study because they are very common in everyday speech in
Thailand and because the possible English words wouldn't be very accurate.
A king amphoe is an administrative unit that is still under construction: a newly established district that has yet to
be recognized as an independent administrative unit, but will become a regular amphoe in the future.
(NONGLUCK SUPHANCHAIMAT
*
, oral comm.)
There has been a general trend in Thailand to split up big provinces and add new ones every 5 or 10 years over
the past decades and new districts are still created inside them in a similar way, so their numbers are growing all
the time and the presence of one or several king amphoe is likely in most of the larger provinces at any given
time. D
ONNER
(1978:49) describes them like this: "If the population grows beyond the administrative capacity of
one office, sub-districts (king amphoes) may be set up, headed by a Deputy District Officer."
*
(Dep. of Agriculture Economics, Khon Kaen University.)

10
Acknowledgements:
The author would like to thank the following persons who have made it possible to realize his idea of
writing a thesis based in Thailand, or who have contributed to this study to varying extents by giving
useful advice, help or simply the opportunity for interesting talks:
Prof. Ryosuke Shibasaki, University of Tokyo
­ for kindly providing me with the necessary satellite data from the 1970s and 1980s.
Dr. Sripen Durongdej, Kasetsart University
Associate Professor Nongluck Suphanchaimat, Khon Kaen University
Mrs. Amornrat Khanti and Mr. Chitti Chuenyong, NESDB
Mr. Nikorn Sunthornkomol, Thammasat University
Dr. Nitin Kumar Tripathi, SAT, AIT
Ms. Sri-saang Kaojarern, SAT, AIT
ACRoRS Staff:
Assoc. Prof. Dr. Kiyoshi Honda, Director
­ for accepting me at ACRoRS as a fellow researcher and generously funding my fieldwork in Isaan
Dr. Lal Samarakoon, chairman of GAC
Dr. Koki Iwao
Dr. Donald Ugsang
Mr. Abhijit Patil
Mr. Francis Canisius
Mr. Shanmugam Ganeshkumar (Ganesh)
Ms. Yumiko Saiki (Yumi)
Ms. Mona Lacoul
Ms. Sepalika Rajapakse
Ms. Jirathana Worawattanamateekul (Nonglek)
Ms. Sudchai Naikaset (Lek)
Ms. Kulapramote Prathumchai (Nah)
Ms. Phallapha Petison
Ms. Wandee Kijpoovadol
Ms. Supannika Potithep (Puk)
Department of Physical Geography/ Department for Cartography and Remote Sensing, Geographical
Institute, University of Göttingen:
Prof. Dr. Jürgen Hagedorn
Prof. Dr. Martin Kappas
Dr. Stefan Erasmi
Dipl.-Geogr. Michael Härtel
Dipl.-Geogr. Carsten Mönnig
My driver during fieldwork in Mukdahan:
Mr. Piyarat Sudsoowan (Lucky)
And finally, my parents, Wolfgang and Erika Rennenberg, for their love and unlimited support.
15 August 2002
N.R.

11
1. Introduction
1.1. Statement of problem: tropical land use changes
Unlike any other interference with the earth's ecosystem, the clearing of tropical rain and
monsoon forests has been stirring up the ecological conscience of the world-wide public for
about 30 years now. It was with the launching of the very first land observation satellites in
1972 that the actual extent of the tropical forest destruction became clearly visible and
measurable. But the devastating process has been advancing ever since; FAO estimated the
global loss of rain forest area at 0.6 to 0.9 % per annum in 1993. Half of the original stands
have vanished in the meantime. The highest loss has been recorded in West Africa, followed
by South East Asia, Amazonia and Central Africa. Without doubt, agriculture is the main
culprit for this development. Most of the loss can be attributed to the conversion of forest
lands to agricultural areas. (cf. S
CHOLZ
1998:141-42)
While the principles of deforestation will be further dealt with in chapter 2.1., it should be
noted here that in Southeast Asia, two countries have suffered from this phenomenon more
than any other nations: the Philippines and Thailand, whose Northeastern Region was chosen
as the general area of interest for this study.
Figure 1: Forest destruction in Thailand 1965-1978. (Legend: grey = forest 1978; black = deforestation
1965-78; white = cultivated land.) Source: SCHOLZ 1998:147

12
The consequences of this trend are dramatic:
"The devastation of huge forest reserves for agricultural purposes has been escalating dramatically within recent
years in Thailand.
Between 1961 and 1975 the forest reserves of the country have been reduced from 57 % to 37
% of the total area, while at the same time the area put to agricultural use has almost doubled. Only to a very
limited extent did the government participate in this process of land reclamation in terms of organized
resettlement programmes; to an overwhelming extent the deforestation has been performed 'illegally' by
spontaneous activities of the rural population." (S
CHOLZ
1980:131)
According to figures from FAO, the share of forests further declined to 28.9 % in 1998, at a
current rate of -112,000 ha (-0.7 %) per year (table 1); Thailand's forest cover has roughly
halved since 1960.
Table 1: Forest statistics for Thailand, Asia and the world
Forest Cover Change
1990-2000
Distribution of Land Cover/Use
in % (1998)
Land area
(1000 ha)
Forest Cover 2000
(1000 ha)
1000 ha/a
%/a
Forests
Other Wooded
Land
Other
Land
Thailand
51,089 14,762
-112
-0.73
*28.9
0.0
74.6
Asia
3,084,124 547,791
-287
-0.05
17.8 4.6
78.3
World
13,139,618 3,869,453
-9,319
-0.24
29.4
11.2
58.6
Source: www.fao.org * of which 19.7 % closed, 5.5 % open (dry dipterocarp forests, pine forests)
1.2. Objectives, scope and limitation of the study
It was attempted to incorporate problems from the realms of social as well as physical
geography, i.e. to maintain a balance between questions of applied geography (regional
studies) and remote sensing. This also means that no special focus was put on advanced RS
methodology such as the development of new image processing techniques; this study is
rather based on a somewhat holistic approach, joining aspects from many different fields of
science. The frame was deliberately widened and covers subjects as diverse as geology,
geomorphology, climatology, agriculture and agricultural economics, sociology, ethnology,
politics and spatial planning.
As a result, the basic objectives of the study were:
· to give a geographical description/characterization of Northeast Thailand in terms of its
physical properties as well as its social and economical peculiarities;
· to try a quantification of forest losses since 1972 for a limited area of this region;
· to attempt a change detection, investigating the land cover (and possibly land use) changes
within a timeframe of about 30 years;
· to name possible reasons for these changes;
· to find out if there are any connections between the development and socio-economic
factors in NE Thailand (e.g. extension of crop area because of poverty/sinking
incomes/population growth?);
· to tackle the question if the problem can be solved with the existing data and to make an
assessment of the RS methodology that was applied;
· and to address the issue of future prospects and suggest a regional development concept to
improve the living standards of the rural population.

13
When talking about the limitations of the study, it's obvious that the biggest restrictions are
associated with the remote sensing part, where the possible findings through the evaluation of
satellite images are limited by the characteristics of the available data: their spatial, spectral
and radiometric resolutions. Another difficulty arises from the fact that the older data stems
from a different sensor type, raising the question of comparability (see also 2.3. and 5.1.).
1.3. Cooperation with AIT
The author of this study stayed at the Asian Institute of Technology (AIT) in Pathum Thani
Province, immediately north of Bangkok, from November 2000 until April 2001. The AIT is a
small international university for graduate studies with students and teachers from more than
40 countries. It comprises 4 "schools" (i.e. faculties): the School of Management (SOM), the
School of Civil Engineering (SCE), the School of Environment, Resources and Development
(SERD) and the School of Advanced Technologies (SAT), which focuses on Computer
Science, Industrial Systems Engineering, Mechatronics-Microelectronics, Space Technology
and Telecommunications.
The author was invited as a special program student within the STAR (Space Technology
Applications and Research) Program of the School of Advanced Technologies and worked at
Asian Center for Research on Remote Sensing (ACRoRS) and GIS Applications Center
(GAC) for 6 months. Both these institutions are directed by Associate Professor Dr. Kiyoshi
Honda who kindly agreed upon receiving a fellow researcher at his center. The author was
also provided with the necessary satellite and GIS data by ACRoRS/GAC staff. Field work in
Northeast Thailand was carried out in February and in April 2001, with some helpful
assistance by a Thai colleague from ACRoRS in the first case.
2. Theory/literature review
2.1. Deforestation and agro-colonization
The term "forest destruction" can be interpreted in different ways, necessitating a
differentiation in at least two basic forms (S
CHOLZ
1998:142):
1. Forest degradation, i.e. the qualitative change and gradual reduction of an original timber
stand;
2. Deforestation, i.e. the quick and complete cutting down of a forest area in order to use it
for different purposes, mostly for agriculture.
What are the reasons for the development described in the introductory chapter?
As S
CHOLZ
(1998:126) states, there's a strong public notion that the quick population growth
in many tropical countries leads to a growing demand for new land around the existing
settlement areas, land that is only used to secure the food basis of the local population.
However, this simple explanation is only partly correct. Though population growth remains of
course an important point, the actual reasons for the advancement of agro-colonization are
much more complex than that and also involve some other important factors:
· National economies have to obtain foreign exchange to pay back foreign debts;
· There is a rising demand on the world market for certain agricultural products such as soy
beans, tapioca, beef, and others;
· National governments strive for economic integration and/or strategic control of
unaccessed/undeveloped peripheral areas of their countries;

14
· Forest clearing and cultivation of soils have been facilitated by ever-increasing
mechanization (chainsaw, tractor);
· Improved traffic infrastructures brought about an improved connection of peripheral areas
to the regional markets, thus permitting the cultivation of cash crops;
· Speculation with land titles.
While these are merely the underlying reasons, the most important processes of forest
destruction can be summarized as follows:
· Fuelwood and charcoal consumption;
· Commercial logging;
· Traditional shifting cultivation;
· Modern agricultural colonization;
· Other human interventions affecting only relatively small forest areas, such as open-cast
mining for metal ores, gold washing, rubber tapping, construction of dams, roads,
industrial complexes and human settlements and, finally, war actions.
Accordingly, the array of acting persons comprises many different groups such as small
farmers (peasants), land workers, owners of large estates, land speculators, entrepreneurs from
the timber and plantation business, ranch owners, mining companies and even adventurers or
fortune-hunters.
The effects of forest destruction can be very grave; it should suffice to mention a few
keywords here, for example:
· Extinction of animal and plant species;
· Influences on the global climate (green house effect);
· Influences on the regional climate (changes in the water balance, altered transpiration,
interception, insolation, evaporation, precipitation, run-off, soil moisture, temperature;
usually resulting in lower groundwater levels, more floods and longer droughts);
· Soil degradation and erosion, growing sediment load of rivers, silting up of reservoirs and
irrigation channels;
· Economic effects (economic profits, improvement of infrastructures, creation of new jobs,
as well as a loss of traditional forest-related occupations);
· Social effects (displacement of indigenous peoples, social conflicts).
Contrary to a widespread misconception, the main process responsible for deforestation is
without doubt that of modern agricultural colonization and not the traditional shifting
cultivation. In any case, the so-called "slash and burn" clearing practice should not be mixed
up with the term "shifting cultivation", as the former is mainly employed for the development
of permanent farmland, plantations or grazing land, whereas the latter is a form of subsistence
economy and usually doesn't lead to a complete destruction of the forests.
The process of agro-colonization doesn't only affect the largest areas, but also has a special
quality to it. It doesn't simply mean a degradation of the forest lands, but their complete
clearing with the aim of a permanent use for crop cultivation or other agricultural activities,
excluding the possibility of re-forestation in the long run.

15
As a matter of principle, three forms have to be distinguished, namely:
1. the state-controlled land development and transmigration programs;
2. the spontaneous colonization processes of unorganized, individual pioneer settlers;
3. colonization through large agricultural enterprises (plantations and ranches).
Within these three movements, the spontaneous clearing colonization by small farmers and
pioneer settlers definitely has the highest impact on natural environments; it is the single most
important factor for the destruction of tropical forests world-wide.
(Summary after S
CHOLZ
1998:126, 142-53.)
The corresponding conditions
in Thailand are very similar to the developments described
above (cf. S
CHOLZ
1998:136): As opposed to the common belief that spontaneous clearing
colonization in the tropics mainly serves to extend the food basis of a constantly growing and
impoverished rural population, this practice has predominantly commercial purposes in
Thailand. The newly cleared areas are almost exclusively used for the cultivation of cash
crops (cassava, maize, sugarcane, pineapple, rubber), not for the production of staple foods on
a subsistence principle.
2.2. Spontaneous versus planned colonization in Thailand
U
HLIG
(1980, 1984) described the (then) recent development of clearing-colonization in the
ASEAN countries of Southeast Asia and himself conducted interesting studies of this
phenomenon in areas of Southeast Thailand and on the Khorat escarpment. Citing F.W. Fuhs,
he states that "agricultural development in Thailand depended mainly upon area expansion in
the form of undirected spontaneous land settlement". Compared to neighbouring countries, a
different historical background and different landownership policies, including liberal
property laws, facilitated the step-by-step opening up of the agricultural land. People were
permitted to retain the land they had cleared of forest and taken into permanent cultivation.
This gradual expansion of the farming areas by continuous clearance can especially be seen
on the Khorat Plateau in Northeast Thailand, where the study area of this thesis is located.
There is a tradition of sons-in-law marrying into the farms of the bride's parents, then having
to clear new ground in the forest as soon as possible, in order to prevent the inheritance from
too rapid a fragmentation of property. Strong ties with the old village community offered
opportunities of reporting back about the chances in the newly opened up areas and to draw
more and more settlers, usually from the same closely defined area of origin, to the new
clearance zones. The traditional forms of agriculture largely focused on wet-rice cultivation.
Pioneer settlements were easily to be recognized by recently planted rice fields with numerous
burnt stumps and "carry-over" trees, remains of the cleared forests (cf. the photograph in
3.5.3). In more recent times, however, a new socio-economic development has led to the
wide-spread abandonment of traditional wet-rice cultivation in favour of marketable dry-field
crops, namely maize, cassava and sugarcane. They are solely commercial products, with
maize and cassava (as tapioca) being exported to Japan and Europe as feeding stuffs and
sugarcane going to the recently expanded sugar industry of the country itself. This rapidly
increasing permanent dry field cultivation has widely transformed the classical picture of
Thailand's agrarian landscape which was characterized by the juxtaposition of pure paddy
cultivation of the sedentary Thais in the basins and plains with the shifting cultivation of the
mountain tribes. Nowadays, it is also the rice cultivators who promote the expansion of land
under cultivation and the diversification of agriculture by dry-field cropping and tree
cultivation in fringe areas that were formerly used for additional shifting cultivation and
extensive forest pasture.

16
Migration is a critical factor in the rural economy of Thailand; poverty, a lack of employment
opportunities and landlessness being the main causes. Between 1960 and 1970, out of the
1,700,000 migrants all over Thailand, only 35 % were from urban, but 65 % from rural areas.
The movements occurred mostly within regions and between nearby provinces. Increasing
pressure from population growth and improving transportation and communication facilities
added to this trend in the 1970s and 1980s. Another factor is unwanted migration caused by
the construction of dams and reservoirs, especially in the North and Northeast.
It wasn't before 1940 that the Thai government recognized the necessity of a public settlement
policy and passed an initial law. But it became effective in the 1960s only, when the
continuing growth of the population and the corresponding demand for employment and land-
reserves, with four-fifths of the population still living in the countryside, finally led to the
establishment of a "Land Settlement Division" of the Public Welfare Department (Ministry of
Interior). Its "Self-Help Land Settlement Schemes" cover the majority of the state-directed
projects and are the most thoroughly organized ones. Besides this, the Ministry of Agriculture
and Cooperatives created its own "Cooperatives Settlement Scheme" and there are at least six
other departments engaging themselves in this field, partly assisted by international
organizations. The scope and extent of the programmes are not well-defined and clear-cut,
however. Some of them have been implemented independently, some in cooperation with
other agencies. Frequent government changes added to the inconsistency of the official
settlement policy. The schemes aim at economic, social and political objectives; common
means include the introduction of new crops and rotations as well as cattle breeding in mixed
farms, the development of agricultural purchasing and sales organizations and the agricultural
training of settlers and settlement officials. The average number of families in the settlement
schemes is about 3,000, but ranges from 150 to 18,000 in individual cases. Farmers are
usually allotted about 2 ½ to 4 hectares of land each. There are two types of settlements: the
village system and the line system. The form of ownership causes some problems. State-
owned land has been assigned to two broad classes: as suitable for cultivation and as forest
reserve. In the former, title deeds may be issued to the settlers, but in the latter case, when
farmers squat in forest reserves, land titles cannot be given to them and they become tenants
to the state. This is meant to discourage migration and to prevent further infringement upon
remaining forests; but it may as well have negative side-effects as landownership is the most
valuable asset to the farmers, implying both wealth and security. Own land is more likely to
provide for a feeling of responsibility, the willingness to invest etc., than rented land. Another
point of concern is that the growing number of landless farmers is often excluded from the
selection process for new settlers within the official schemes. Instead of them, authorities are
preoccupied with squatters or farmers who already live inside the settlement area.
(after U
HLIG
1984:27-35)
Summarizing, the success or effectivity of the government schemes has to be questioned and
the phenomenon of spontaneous land clearing and colonization remains an urgent issue:
"In view not only of pressure on the land, which continues to rise together with the growth of population, but
also in the face of indebtedness of farmers or the hardship of stringent rent conditions in many excessively small
farms, the relatively slow development of planned settlements, restricted to certain areas, state controlled by a
mechanism of selection which remains foreign to the Thai mentality, was bypassed by many spontaneous
clearings, the extent of which is probably unsurpassed anywhere in Southeast Asia." (U
HLIG
1984:32)

17
2.3. Remote sensing + the Landsat System
There are many definitions for "remote sensing", be it in a broad or more restricted sense of
the term. Basically, it means nothing more than the acquisition of physical data of an object
without touching it. According to the nature of the observed object, the desired data, the
employed sensor and the kind of energy it uses to make its measurements, this broad
definition can be refined very specifically; for the purposes of this study, however, an
explanation given by C
AMPBELL
(1996) appears to be most suitable:
"Remote sensing is the practice of deriving information about the earth's land and water surfaces using images
acquired from an overhead perspective, using electromagnetic radiation in one or more regions of the
electromagnetic spectrum, reflected or emitted from the earth's surface." (C
AMPBELL
1996:5)
Because of the unusual or abstract features of data acquired by earth observation satellites
(such as the unfamiliar overhead perspective, the unusual resolutions, and the use of spectral
regions outside the visible spectrum), a careful image interpretation process is made necessary
(see fig. 2).
Figure 2: Schematic overview of the image interpretation process in remote sensing. Source:
C
AMPBELL
1996:10.
It includes the extraction of information, i.e. the transformation of sensor data in order to
provide answers to specific questions in different scientific disciplines. The derived
information can then be combined with other data in applications, such as geographic
information systems (GIS).
The Landsat sensors are undoubtedly the most successful and best-known earth observation
satellite system to date. Therefore, a short reminder of their characteristics should suffice here
(see table 2 on the next page).

18
Table 2: Spectral specifications of the Landsat scanner systems bands (wavelengths in µm)
Landsat 1-3 (MSS)
1972-1978
1975-1982
1978-1983
Landsat 4 + 5 (TM)
1982-1987
1984- today
Landsat 7 (ETM+)
1999- today
1
0.45 ­ 0.52 (blue-green)
1
0.45 ­ 0.515 (blue-green)
1
0.5 ­ 0.6 (green)
2
0.52 ­ 0.60 (green)
2
0.525 ­ 0.605 (green)
2
0.6 ­ 0.7 (red)
3
0.63 ­ 0.69 (red)
3
0.63 ­ 0.69 (red)
3
0.7 ­ 0.8 (near IR)
4
0.76 ­ 0.90 (near IR)
4
0.75 ­ 0.90 (near IR)
4
0.8 ­ 1.1 (near IR)
5
1.55 ­ 1.75 (middle IR)
5
1.55 ­ 1.75 (middle IR)
6
10.4 ­ 12.5 (thermal IR)
6
10.4 ­ 12.5 (thermal IR)
7
2.08 ­ 2.35 (middle IR)
7
2.09 ­ 2.35 (middle IR)
(8)
0.52 ­ 0.90 (panchromatic)
Note: Landsat 6 (ETM) was lost at launch in October 1993.
While the Multispectral Scanner (MSS) had a spatial resolution or nominal IFOV
(instantaneous field of view) of 79m x 79m and a radiometric resolution of only 7 bit (128
grey values), these characteristics improved to 30m x 30m and 8 bit (256 values), respectively
for the Thematic Mapper (TM) sensor. In case of the thermal infrared detector (band 6), the
spatial resolution is reduced to 120 m (TM) and 60 m (ETM+), however. In addition, the TM
has 3 more bands and the spectral bands were tailored to record radiation of interest to
specific scientific investigations, as opposed to the arbitrary definitions used for the MSS.
Some of their possible applications are listed below:
Band 1 ­ penetration of clear water; bathymetry; mapping of coastal waters; chlorophyll
absorption; distinction between vegetated and unvegetated areas, between coniferous
and deciduous vegetation; also helps to recognize man-made forms
Band 2 ­ records green radiation reflected from healthy vegetation ("green peak" at 0.55 µm);
assesses plant vigour (or plant damage); reflectance from turbid water; also helps to
recognize man-made forms
Band 3 ­ measures in a range of chlorophyll absorption, important for plant-type
discrimination; also helps to recognize man-made forms
Band 4 ­ indicator of plant cell structure; assessment of biomass, plant types and plant vigour;
complete absorption by water facilitates delineation of shorelines and recognition of
soil moisture
Band 5 ­ indicative of vegetation moisture content; soil moisture soil mapping;
differentiating snow from clouds; penetration of thin clouds; suitable for geological
mapping (peak of reflectance for most rock types around 1.6 µm)
Band 6 ­ vegetation stress analysis; soil moisture discrimination; thermal mapping;
relative brightness temperature; plant heat stress
Band 7 ­ discrimination of rock types (covers absorption bands of carbonates and banded
silicates at 2.0-2.5 µm); alteration zones for hydrothermal mapping; hydroxyl ion
absorption; recognizes the water content of plants
(c.f.
C
AMPBELL
1996:174, K
RONBERG
1985:127+129, L
ILLESAND
+ K
IEFER
1987:566-67.)

19
Both the MSS and the TM are opto-mechanical "whisk-broom" scanners with a swath width
of 185 km, mounted on satellite platforms that circle(d) the earth on sun-synchronous, near
polar orbits with an inclination of 98°-99° and at an altitude of 907-915 km (Landsat 1-3) and
705 km (Landsat 4-7), respectively (fig. 3).
Figure 3: Landsat-4 and ­5 observatory configuration / Sun-synchronous orbit of Landsat-4 and ­5.
S
OURCE
: L
ILLESAND
+ K
IEFER
1987:562, 565.
The 16-day ground coverage cycle for Landsat 4-7 is accomplished in 233 orbits. At the
equator, the ground track separation is 172 km, with a 7.6 percent overlap. This overlap
gradually increases as the satellites approach the poles, reaching 54 percent at 60° latitude.
(c.f. http://landsat.gsfc.nasa.gov)
The advantages of the Landsat system can be summarized as follows:
"The civilian space-based remote sensing industry is characterized by the ground footprint, spatial resolution,
and the spectral channels of today's sensors. On one end of the scale are the low-resolution, large footprint,
multi-spectral sensors such as NOAA's polar orbiters that have one-kilometer resolution and a 2000-kilometer
swath or footprint. On the other end are high resolution, small footprint, panchromatic snapshot sensors such as
IKONOS which was recently launched by Space Imaging. Landsat occupies a unique niche between these two
extremes. No other sensor can match Landsat's uncommon characteristics which include repetitive, broad-area,
and global coverage at high spatial resolution in all four passive optical regions of the electromagnetic spectrum
(i.e. visible, near IR, short-wave IR, and thermal IR regions), and accurate radiometric calibration. In addition,
Landsat's retrospective archive stretches back 25 years." (www.bsrsi.msu.edu)
According to these characteristics, the Landsat satellites are ideally suitable for a wide array
of scientific disciplines, e.g. geology (structural geology, geophysics, mineral prospection),
geomorphology, botany, agriculture and forestry (land use and forest damages mapping, land
use change detection, soil moisture mapping), nature protection, climatology, hydrology,
spatial planning and cartography.

20
3. Overview: Northeast Thailand
3.1. Location, administration, population
The region of Northeast Thailand comprises about 169,000 km² (that is 33% of the total area
of Thailand) and 19 provinces (changwat) with a population of around 21,38 million people
(1999), equalling a density of 127 persons per km². This region basically consists of a low-
lying, gently sloping plain also known as the Khorat Plateau, forming a part of the Mekong
River catchment, right in the middle of the SE Asian mainland. (Compare maps in the
appendix, page 155 ff.) Contrary to the other three regions of Thailand (North, Centre and
South), the Northeast is also called by a special proper name (Isaan
*
) by the Thai people due
to historical reasons and ethnic and cultural particularities. In fact, the traditional language
spoken here is very much the same as in Laos, while differing a lot from the usual dialects in
all the other parts of the country. Nonetheless, everybody can understand and speak Standard
Thai, the official language originating from the Central Plains. The Northeast is the second
biggest region in size (immediately behind the North) and the biggest in terms of population,
but at the same time the poorest (see 3.4.). The vast majority of Isaan people adhere to
Buddhism, with some very small Christian, Muslim, Hindu and Sikh communities.
The 19 provinces are (in alphabetical order): Amnat Charoen, Buri Ram, Chaiyaphum,
Kalasin, Khon Kaen, Loei, Maha Sarakham, Mukdahan, Nakhon Phanom, Nakhon
Ratchasima, Nong Bua Lamphu, Nong Khai, Roi Et, Sakon Nakhon, Si Sa Ket, Surin, Ubon
Ratchathani, Udon Thani and Yasothon.
Changwat Amnat Charoen and Changwat Nong Bua Lamphu were created on 1
st
December
1993 only by separating them from the large provinces of Ubon Ratchathani and Udon Thani,
respectively. Changwat Mukdahan was formed from the southern part of Nakhon Phanom
Province in 1982.
The biggest province of the Northeast ­ in terms of area as well as population ­ is Nakhon
Ratchasima with 20,494 km² and 2,540,662 people (1999). (Actually it's the largest in the
whole of Thailand and also the most populated, apart from Bangkok, which represents a very
special case.) Its provincial city, also known as Khorat (from Nakhon Ratchasima) in short
form, is the biggest settlement in Isaan at a population of 173,000 and said to be the gateway
to the Northeast and the informal capital of this region ­ as the Thai regions are rather loose
administrative entities created for planning purposes and don't have any capitals. Other big
cities in the Northeast are Khon Kaen (127,000), Udon Thani (157,000) and Ubon
Ratchathani (105,000). In fact, only these four carry the title nakhon, city. The other
provincial towns all have less than 100,000 inhabitants (typically 30,000-40,000), Nong Bua
Lamphu being the smallest with only 21,700. The smallest province in size is Amnat Charoen
(3161 km²), the smallest in population is Mukdahan (333,035). (cf. S
TATISTICAL
R
EPORTS OF
R
EGION
2000:5-11.)
All provinces are divided into so-called amphoe
*
(districts) (between 6 and 26, typically
around 15 per province), which are again subdivided into so-called tambon
*
(sub-districts,
municipalities) (typically 9-10 per amphoe). The smallest administrative unit is the muban, or
village. One tambon normally comprises around 10 villages. Altogether there are 30,022
villages in Northeast Thailand, which gives an average population of 712 people. The 278
amphoe in the Northeast measure an average 607 km² and 76,900 inhabitants; the 2,678
tambon average 63 km² and 7983 inhabitants.
*
After Phra Isuan or Phra Siwa, i.e. Shiva, the Hindu god of destruction and redemption.
*
(Singular or plural.)

21
The shape of Isaan comes very close to a simple square with a size of approximately 400x400
km which is nevertheless completely marked off by natural borders (see 3.2.). The extreme
points are marked by 14°05' N (Sankamphaeng Range, Khorat) and 18°27' N (Mekong
riverbanks, Nong Khai) on one hand, 100°53' E (Phetchabun Range, Loei) and 105°38' E
(Mekong riverbanks, Ubon Ratchathani) on the other hand, meaning the region is entirely
situated in the semi-humid outer tropics.
Following a clockwise direction, the Northeastern Region of Thailand borders on: the Laotian
People's Democratic Republic in the North and East, the Kingdom of Cambodia in the South,
the Central Region of Thailand (Sa Kaeo, Prachin Buri, Nakhon Nayok, Saraburi and Lopburi
Provinces) in the South and West, and the Northern Region (Phetchabun and Phitsanulok
Provinces) in the West.
Finally it should once again be pointed at the fact that the population of Isaan actually hasn't
much to do with the Central Thai culture, arts, language etc., but entirely belongs to the Lao
culture area. In addition, there are some notable Khmer influences in the south, especially in
Surin and Buri Ram provinces. As everywhere in Thailand, a substantial share of the
population is of Chinese descent, and finally there are Isaan-born Vietnamese people.
"For 70% of the total population living within Isaan, Isaan is the primary heart language and Thai is the
secondary language. Among the remaining 30%, other languages are primary, Isaan is secondary and Thai is
third. Included in this 30% are the Khmer speakers, Chinese and Vietnamese born and raised in Thailand, and
the tribal groups such as the Phu Tai and others, each with their own distinct mother tongue."
(www.iserv.net/~thaicov)
The ethnic and cultural particularities are more developed here than in any other region of
Thailand (not taking into account the various hill tribes in the north and west because they are
virtually unimportant in terms of population figures), which is largely due to the isolated
situation on a plateau that is cut off from the rest of the country by steep mountain ranges.
Accordingly, people from the Northeast are marked off and called by special names like thai
isaan, laao isaan or even laao (Laotians) by the other Thais. They are often looked down
upon as poor, uneducated and somewhat strange people. The spoken language is not merely a
dialect form of Central Thai, but almost the same language as in Laos. (Thai and Lao are
closely related to each other.)
"The majority of the people inhabiting the Northeast of Thailand call themselves 'Lao people'. [...] They still
claim that Laos is the home country of their ancestors and that the Mekong river has never been a real border to
separate them from their relatives on the other side. [...] These people have a specific regional identity which is
neither Lao nor Thai but genuinely 'Northeastern', and they say that they have other customs, other food, wear
different clothes and speak another language compared with the people in Bangkok and in the Central Plains of
Thailand." (Luther 1978, cited in T
RAUB
1989:15)
The existence of an Isaan identity of its own is being denied by the central government,
however, and it is even tried to assimilate the population. For example, only the official
tongue is taught in schools and all written documents have been destroyed in the past. An
Isaan script doesn't exist anymore. So the passing on of language and customs is based on oral
tradition in the families, and the survival of independent Isaan culture is strongly endangered
today. The reason for direct repression of indigenous movements from Isaan is that these are
considered threats to national stability that have to be controlled at any rate.

22
3.2. Geology and geomorphology
Figure 4 gives an overview of the basic physical regions of Thailand.
Figure 4: The physical regions of Thailand. Source: F
RYER
1970:130.
Note: the Central Plain comprises the Bangkok and Upper Plains.

23
3.2.1. General outline
Southeast Asia is the continuation of the Alpine fold zone of Europe, superimposed upon
older blocks such as the Sunda Platform and the Sahul Shelf. Various ranges of this zone have
their centre in the Pamirs and meet again in another mountainous complex in the east,
between the Brahmaputra valley of Assam and the basin of Szechwan in China, with Minya
Konka at the centre (fig. 5).
Figure 5: Geotectonic structure of South-East Asia. Source: D
ONNER
1978:8.
From here the folded system bends into the Indo-Chinese peninsula, creating pronounced
mountain ranges and important river valleys. In the west, the continuation of the Himalayas
are the Western Burmese Highlands (Chin Hills, Arakam Yoma), parallel ranges of Tertiary
rocks. The second chain, older than the Himalayas and corresponding to the Karakoram,
forms the Central Cordillera, consisting of paleozoic sediments and huge granite intrusions. It
is cut into several divisions with different names such as Dawna Range, Bilauk Taung Range,
Tenasserim Mountains. The third main range is the Annam Cordillera in Laos and Vietnam,
again older and geologically related to the Kunlun Shan Mountains.
Thailand only has a share in the Central Cordillera, which builds up the mountainous north of
the country (culminating in Doi Inthanon, at 2565 m
*
) and the western part of the Central
Region and then stretches southeastwards as the spine of the Malay Peninsula. Whereas in the
northeast, the Annam Cordillera encloses the Khorat Plateau and Mekong Valley, but isn't
directly touched by the territory of Thailand. (Compare fig. 6, next page.)
*
Formerly known as Doi Angka. Information on height varies, most common values being 2565 m and 2590 m.

24
Figure 6: Tectonic overview of Asia. Source: H
ANLE
1973:10.
The third structural characteristics, apart from the old blocks and the Alpine fold belts, are the
tectonic depressions, filled with accumulated alluvium. While not as big as the Gangetic plain
in Northern India, for example, they gained importance as the most densely populated areas in
monsoon Asia: the valleys of the Irrawaddy and Sittang in Myanmar (Burma), the Mae Nam
Chao Phraya in Thailand and the Mekong and the Hong (Red) River in Cambodia and
Vietnam. Practically all these rivers follow a direction prescribed by the abovementioned
mountain chains, i.e. north to south (fig. 7).
Figure 7: The main rivers of South-East Asia. Source: D
ONNER
1978:10.

25
A hypsometric analysis shows that one quarter of the area of Thailand lies below 100 m, and
only 5% of the relief is higher than 1000 m (cf. table 3).
Table 3: Hypsometric analysis of Thailand
Altitude (metres above MSL)
Area (km²)
Area (%)
Sea level to 100
137,342
26.7
101-200 148,224
28.8
201-500 123,190
24.0
501-1000 79,865
15.5
Above 1000
25,379
5.0
TOTAL 514,000
100.0
Source: D
ONNER
1978:9
Altogether the relief of the kingdom is stamped by the folded mountain ranges, the flat
alluvial plains, often dotted with limestone outcrops, vast stretches of undulating land in the
Upper Central and Northeastern Region and finally, maritime features (sandy beaches,
mangrove swamps, islands). Geologically speaking, three structural areas can be
distinguished: the region of the folded mountains, the Chao Phraya depression and the Khorat
Plateau (figure 8). See also the big relief map in the appendix (page 156).
Figure 8: Left: Physical orientation map of Thailand. Source: D
ONNER
1978:13. Right: Elevation map of
Thailand, highlighting the Khorat Plateau. Source: www.maps.com

26
The following is a short summary of the structural development:
"In the earliest orogenic movements the Ratchaburi limestone and the old rocks were compressed in longitudinal
folds from the north down to the Peninsula of Thailand. This folding corresponds to the late Paleozoic
Appalachian orogeny of North America, and is followed by intrusion of elongated granite which appears in the
north as Khuntan Range. A late Mesozoic orogeny is suggested by the folding of the Korat series of sedimentary
rocks along the west side of the Korat Plateau and followed by intrusions of tin and tungsten-bearing granite.
The late Tertiary orogeny occurred by the elevation and gentle down-warping of the Korat Plateau, by the
depression of the Chao Phraya region, and by high angle faulting which is clearly shown by the Phnom Damrek
Range. In very recent time the Peninsular Thailand has been slightly tilted northwest, making the east coast
appear as a broad coastal plain and a smooth emergent shoreline. The west coast is marked by drowned valleys,
such as the V-shape Mae Nam Kra Buri and the very irregular shoreline."
(G
OVERNMENT OF
T
HAILAND
1968:10, cited in D
ONNER
1978:12)
An overview of the stratigraphy of Thailand, according to different authors, is given in the
following table.
Table 4: Stratigraphy of Thailand (1914-1951).
Source: K
OBAYASHI
1964:5.
Land forms of residual material (hills and mountains, limestone outcrops, dissected erosion
surfaces, structural plateaux, lava plateaux and volcanic remnants) constitute the north of the
country and the western mountainous spine down to the peninsula, as well as the Phetchabun
Range (the western margin of the Khorat Plateau) and parts of the Phnom Damrek Range.
Hills and mountains are sharply dissected and, though not very high in elevation, show a
remarkable degree of relief, with steep to very steep slopes, generally exceeding 20%.
Originally covered with dense forest vegetation, they are now subject to clearing for timber
and to shifting cultivation. Limestone outcrops, with slopes usually exceeding 30%, often in
the shape of impressive tropical tower karst formations, are present everywhere except for the
Northeast. Dissected erosion surfaces and structural plateaux occur over various rocks
throughout the country except in the plains. They are typically situated in front of hills and
mountains bordering the alluvial terrains of basins and valleys and have been formed by
denudation processes, involving slope retreat. They are more or less dissected and the relief
may be undulating to rolling with slopes ranging from about 4 to 20%.

27
Here, weathering and erosion develop those soils which are the economic basis for tree and
upland crops (see chapters 3.2.2. and 4.4.).
Land forms of transported material include beach and dune formations, active and former
tidal flats, flood plains of recent river alluvium, low alluvial terraces and high alluvial
terraces.
The former tidal flats of older brackish water deposits, such as the plain that stretches north of
Bangkok for 75 km, with a width of up to 160 km and an elevation of 1 to 4 m above MSL,
are the most important rice growing areas of the country (compare map in the appendix, page
157). The soils are poorly drained and flooded by water during 4 to 7 months of the year up to
a depth of about one metre.
Flood plains of recent river alluvium can be found along all main rivers and streams. The
wider forms show a distinct levee-basin landscape with all features of meandering river
plains. The soils are flooded by rivers and rain each year and receive additions of fresh
alluvium. They are moderately well drained, stratified, loamy brown alluvial soils. Low-lying
portions are used for rice planting. They are flooded during 4 to 8 months. When there are
irrigation facilities during the dry season, upland crops are grown. The levees are mainly used
for upland crops, orchards and garden crops, and villages are built on them. This type of
agricultural landscape is especially to be found in the Upper Central Region and the
Northeast.
Low alluvial terraces of semi-recent and old alluvium occur in all parts of the country, but are
especially common in the Upper Central region and the Northeast. Their soils are older and
more developed than those of the recent flood plains. Sometimes they are saline due to the
presence of rock salt deposits. Their lower levels are cultivated with rice which is transplanted
and irrigated with rain water, while the higher levels carry homesteads, orchards, garden and
upland crops.
Finally, high alluvial terraces form the link between the low terraces and the dissected
surfaces and structural plateaux. They comprise various landforms and consist of varied soils,
partly under forest, partly under tree cultivation or already abandoned and covered with shrub,
secondary forest and grass.
Figure 9 (next page) shows a simplified map of the land forms of Thailand and a simplified
land capability map.

28
Figure 9:
Left: Land forms of Thailand. Legend: 1 = beach and dune formations, active and former tidal flats, flood plains
of recent river alluvium; 2 = low and high alluvial terraces and fans of alluvium and colluvium; 3 = dissected
erosion surfaces, structural and lava plateaux and volcanic remnants; 4 = hills and mountains, including
limestone outcrops; 5 = depressions with peat and muck. Source: D
ONNER
1978:18.
Right: Land capability map of Thailand. Legend: 1 = areas suited for paddy; 2 = areas suited for paddy and
upland crops; 3 = areas suited for upland crops; 4 = areas not generally suited for the cultivation of crops.
Source: D
ONNER
1978:20-21.
The corresponding study by the Government of Thailand and FAO (1972) stated that 9.62
million hectares (18.7 % of the surface) are suited for paddy, 5.92 million hectares (11.5 %)
for paddy and upland crops, 14.2 million hectares (27.6 %) for upland crops, whereas 21.65
million hectares (42.2 %) are not generally suited for cultivated crops.
(After
D
ONNER
1978:6-19.)

29
3.2.2. The Khorat Plateau
As indicated in the preceding paragraph, the Northeast of Thailand is clearly cut off from the
Central Region by pronounced mountain chains and has its own characteristics as far as soils,
climate, vegetation etc. are concerned; its geological structure is simple. The general
appearance is very uniform, the landscape rather monotonous. According to the marked
plateau shape, the biggest part of the area is situated on a level between 100 m and 200 m
above MSL (table 5).
Table 5: Hypsometric analysis of Northeast Thailand
Altitude (metres above MSL)
Area (km²)
Area (%)
Sea level to 100
170
0.1
101-200 107,072
62.9
201-500 48,345
28.4
501-1000 11,575
6.8
Above 1000
3,064
1.8
TOTAL 170,226
100.0
Source: D
ONNER
1978:549
"Geomorphologically the Khorat plateau is strictly an almost equidimensional basin, but it has
a plateau-like aspect because of high escarpments [...] along its western and southern edges
and mesa topography [...] over parts of its area." (S
ANGAD
B
UNOPAS
1982:357)
Figure 10: Escarpment of the Khorat Plateau, seen from Khao Phra Wiharn Temple Complex (Si Sa Ket
province), looking westward. Thailand is on the right, Cambodia on the left. The Phnom Dangrek
Mountain Range reaches a height of approx. 670 m here, while the adjoining lowland jungle in Cambodia
is around 100 m above MSL. Photo: N. Rennenberg, 27 April 2001. (Position 14°23' N, 104°41' E)
The first sedimentary rocks which now form the basis of the Khorat Plateau were deposited in
an early Mesozoic era. Later these layers were folded up in the west and south to form the
bordering mountains chains; the plateau was lifted up as a whole, and gentle warping brought
the hill ranges in the centre into existence. Then shale, clay, gypsum, anhydrite and rock salt
were deposited in remaining marine sea basins. Finally, erosion shaped the landscapes and
still continues to do so.

30
Figure 11: View of the Khorat escarpment from roughly the same location as in fig. 10, this time looking
eastward over Cambodian jungle in Preah Vihear province. Thai territory lies left of the cuesta ridge.
Photo: N. Rennenberg, 27 April 2001.
The geological structure of Northeast Thailand is altogether rather simple and uniform, as can
be seen in table 6.
Table 6: Overview of stratigraphic units in the Khorat Plateau and bordering areas
Age
(in Ma)
West
(Phetchabun ­ Lam Narai)
Northwest
(Loei ­ Phitsanulok)
Khorat Plateau
Cenozoic
65 ­ 0
alluvium
Phetchabun shale
alluvium
­
alluvium & loess
­
Cretaceous
144 ­ 65
­
­
Maha Sarakham Form.
Khok Kruat Form.
Maha Sarakham Form.
Khok Kruat Form.
Jurassic
213 ­ 144
Phu Phan Form.
Sao Khua Form.
Phra Wihan Form.
Phu Kradung Form.
Phu Phan Form.
Sao Khua Form.
Phra Wihan Form.
Phu Kradung & Nam Phong
Form.
Phu Phan Form.
Sao Khua Form.
Phra Wihan Form.
Phu Kradung & Nam Phong
Form.
Triassic
248 ­ 213
= K
horat
G
r
oup
Lom Sak Tuff
­
Nam Pha & Huai Hin Lat
Form.
­
­
­
Permian
286 ­ 248
Saraburi Group
Saraburi Group
­
Source: S
ANGAD
B
UNOPAS
1982:358, modified
The Khorat Group of sediments consists mainly of continental red sandstones and shales, with
some paralic deposits near the base, the middle and the top, and the Maha Sarakham marine
salt deposits at the top. Strong consolidated sandstones in the Khorat Group are resistant to

31
erosion, form mesas and cuestas, and can be traced readily for great distances. The formations
have great lateral persistence and can be mapped over large areas. They were deposited in a
time span of about 170 Ma (Upper Triassic to Upper Cretaceous) and are altogether up to
4,500 m thick. (S
ANGAD
B
UNOPAS
1982:360.) The following table gives some more details.
Table 7: Stratigraphy of the Mesozoic Khorat Group (Upper Triassic to Cretaceous)
Sub-groups
(informal names)
Formations
Age
Maximum
thickness
Upper red-beds
Maha Sarakham ("salt formation")
Khok Kruat, Ban Na Yo
Cretaceous 300
m
700 m
Middle sandstones
Phu Phan
Sao Khua
Phra Wihan
Middle to Upper Jurassic
?
700 m
250 m
Lower red-beds
Phu Kradung
Nam Phong
Lower Jurassic ­ Rhaetian
1,000 m
1,500 m
Grey beds
Nam Pha, Huai Hin Lat, Lom Sak
Triassic (Rhaetian ­ Norian)
500 m
Source: S
ANGAD
B
UNOPAS
1982:359
A short description of the different formations within the Khorat Group (according to
S
ANGAD
B
UNOPAS
1982:360-369) is given as follows:
Huai Hin Lat Formation: basal polymictic conglomerate, overlain by interbedded grey
sandstone, grey shale and marly beds.
Nam Pha Formation: very similar to the Huai Hin Lat Formation.
Lom Sak Formation: basic to intermediate grey tuff and some carbonaceous shale.
Nam Phong Formation: soft, grey red to pale red siltstone and interbedded thick resistant
beds of brownish red sandstone and conglomerate.
Phu Kradung Formation: interbedded pink sandstones, red siltstone and red shale with
occasional thin fine conglomerates. Basal part is formed by hard calcareous siltstone and
pelletal, micritic limestone.
Phra Wihan Formation: predominantly white to pink thick bedded well sorted medium
quartz sandstone with some thin interbedded red siltstone. High resistancy, ridge forming.
Sao Khua Formation: interbedded red to pink quartz sandstone and red to purplish shales.
Less resistant to erosion.
Phu Phan Formation: mostly white to pink well sorted medium to coarse quartz sandstone,
with some conglomeratic sandstone horizons. High resistancy, ridge forming.
Khok Kruat Formation: interbedded moderately consolidated red siltstones and white to red
quartz sandstones and fine conglomerate.
Ban Na Yo Formation: probably identical with Khok Kruat Formation.
Maha Sarakham Formation: halite, carnellite and sylvite, with subordinate anhydrite and
gypsum, and with little terrigenous clastic detritus. Evidently precipitated from brine formed
by evaporation of sea-water. Topmost formation of the Khorat Group, only covered by a few
tens of metres of unconsolidated sediments over large areas of the Khorat Plateau.
Post ­ Khorat Group/Cenozoic: very thin (1 to 15 m) soft to moderately consolidated
conglomeratic sand, silt, clay and loam, forming low undulating topography.
As opposed to that, H
EGGEMANN
(1993:10-11) describes two additional members, the so-
called Phu Thok Formation of aeolian sandstones and claystones and an "Upper
Conglomerate Formation", and sets slightly different temporal borders (table 8).

32
Table 8: Stratigraphy and facies of the Khorat Group and Huai Hin Lat Formation.
Age
Formations
Depositional environment
Maastrichtian ­
Campanian
Upper
Conglomerate
Proximal braided river and alluvial fan deposits with pebble size up to 10 cm.
Campanian ­
Cenomanian
Phu Thok
Aeolian sandstones with interdune sedimentation, continental sabkha and
playa lake deposits with thick desiccation cracks.
Albian ­
Cenomanian
Maha
Sarakham
Three evaporite horizons with variable thickness, salt deposits poor in MgSO
4
and CaSO
4
, with thick layers of potash including trachyhydrite, intercalations
of continental playa lake and sabkha deposits.
Aptian ­
Albian
Khok Kruat Fluvial channel sandstones, siltstones, extensive fine overbank deposits with
calcrete bearing vertisols, some mudflows. Upper part with gypsum nodules
indicating the transition to the evaporitic environment of the salt formation.
Basal Early
Cretaceous
Phu Phan
Extended gravelly and sandy braided river system including petrified wood
fragments.
Late
Jurassic
Sao
Khua Extensive floodplain mudstones with calcretes intercalated by sandy
meandering streams, brackish and freshwater bivalves indicating estuarine
environments.
Middle to
Late Jurassic
Phra Wihan Semi-distal extended sandy gravel-bearing rivers. The decrease of gravel
content and the change of the river system from braided to meandering from
east to west coincides with the predominantly westward directed paleoflow.
Middle Jurassic
Phu Kradung Extensive red floodplain mudstones with partly intense calcrete soil formation
and intercalated sandy fluvial channels. Solitary meandering channels as well
as stacked channel systems. Deltaic environments to the west of the basin.
Early Jurassic
Nam Phong Local debris flows, alluvial fans, braided gravel stream beds, meandering
rivers with ox-bow lakes and thick mudflat and continental sabkha deposits in
the lower part.
Norian
Huai Hin Lat/
LAMPANG
GROUP
Syn-rift deposits, acid to intermediate and basic volcanic rocks, volcanoclastic
fanglomerates, prograding sandy deltaic environments, lake deposits rich in
organic matter. Coal seams in Northeast Thailand, marine Triassic of the
Lampang Group in North Thailand.
Source: H
EGGEMANN
1993:11,105
Most of the Khorat Group is considered to have been deposited on a wide alluvial floodplain
that had a warm seasonally wet and dry climate. It is assumed that deposition was not
continuous. Large scale tabular cross-bedding indicates a consistent northeastward paleoslope
in the formations up to the Sao Khua Formation, and a southwestward paleoslope in the Phu
Phan ­ Khok Kruat Formations. Bivalvian and reptilian fossils in the Sao Khua and Khok
Kruat Formations bear testimony to local marine transgression in middle or late Jurassic and
then again in the Cretaceous, this time leading to the development of the marine evaporitic
basin represented by the Maha Sarakham Formation. After that the Khorat Basin must have
remained close to base-level for most of the Cenozoic Era: if it had been uplifted soon, much
of the salt would have been eroded or leached away by ground water, and if it had subsided,
the Cenozoic sediments would have been thicker. (S
ANGAD
B
UNOPAS
1982:367-70.)
From a geomorphodynamic point of view, it is clear that Thailand has to be divided into three
distinct parts, but their denomination is far from being uniform.
K
OBAYASHI
(1964)
distinguishes the Burmese-Malayan folded mountains in the west, a "subgeosyncline" in the
area of the central plain and the Gulf of Thailand and the Indosinian massif in the east.
H
AHN
et al. (1986) also divide the continental crust of Thailand into three major tectonic
units, but with totally different names: the Shan Thai Paraplatform, the Yunnan Malay Mobile
Belt and the Khorat Kontum Platform.

33
Notwithstanding this ambiguity, the geodynamic evolution of the Khorat Basin is basically
determined by 6 tectonic events:
Precambrian Orogeny: affected the present-day basement of the Khorat Plateau, where it
produced high-grade metamorphic rocks, such as gneiss and crystalline schists.
Caledonian Orogeny: Paleozoic (Silurian to Devonian). The Shan Thai and Khorat Kontum
cratons were separated by a sea in which eugeosynclinal sedimentation was occurring. There
was a westward-dipping subduction zone, as well as folding and metamorphisation.
Variscan (Appalachian) Orogeny: middle/late Paleozoic (Devonian to Carboniferous). The
Caledonian ocean was closed. Uplift movements led to the formation of intramontane grabens
and basins in which clastic sediments with coal seams were deposited. In the southern part of
the block, marine shelf sediments prevailed.
"Indosinian Orogeny": before the deposition of the Khorat Group, late Paleozoic and early
Mesozoic (Permian to Triassic, with a climax in Noric stage). This event is somewhat
controversial. Plate collision supposedly led to the closing of the Paleotethys and the merging
of the South China Craton, the Indochina Craton and the Shan Thai Block along the Nan-
Uttaradit Suture Zone. Thus, the Khorat Group is often interpreted as molasse sediments
deposited in a "metaorogenic hinterbasin" by earlier authors. However, H
EGGEMANN
(1993)
denies an important orogeny in this era, stating that the unification process of the sub-
continents already took place in the Paleozoic. He interprets the Indosinian movements as
intracontinental events and describes the depositional area as a polyphase "intracontinental or
sag basin" which originated in two stages during a regime of tectonic extension in the
Triassic: an initial (rift) phase in which half-graben structures developed, and a long-lasting
"thermal subsidence" by lithospheric thinning. The drainage network was orientated to the W,
SW and S and the (Variscan) source rock areas located in the E, NE and N of the Khorat
Basin, accordingly. Uplifting of the whole complex was accompanied by a gradual retreat of
the sea from the entire Indochina Peninsula to the westernmost part of Thailand and the
change to a continental environment with a predominant deposition of red clastic sediments.
Alpine Orogeny: late Mesozoic and early Cenozoic (Cretaceous to early Tertiary). It caused
an upheaval and deformation of the Khorat Group sediments with decreasing intensity from
W to E and the formation of the Phu Phan anticline.
Post-orogenic uplift: Cenozoic (late Tertiary). Crustal movements finally caused the
subsidence of the median zone and elevation of the eastern part of Thailand, where it resulted
in erosion, the formation of grabens and basins and their filling with fluviatile-lacustrine
deposits. Miocene events led to updoming and new graben structures, associated with basaltic
volcanism that was increasing in intensity towards the east and continuing until the
Pleistocene. A subdivision into three uplift phases subsequent to the Alpine folding can be
made as follows: 1. Late Cretaceous to Early Miocene, 2. Late Miocene to
Pliocene/Pleistocene border and 3. Quaternary.
(After H
AHN
et al. 1986:29-34, H
EGGEMANN
1993:2-9 + 92-95, K
OBAYASHI
1964: 11-13)
"The summit level of the Phu Kradung and Phu Phan Ranges probably indicates the Tertiary peneplane.
Subsequent to the strong deformation, upheavals were repeated twice or more, as indicated by two steps of
planes on the Khorat Plateau at about 180 and 140 m in general surface elevation. The final uplift of about 75 m
is evidenced by the drop in the level of the Nam Mun at the entry into the Mekong River."
(K
OBAYASHI
1964:13)
Based on the above description of the geological history of the region, the principal
morphological units/landscapes of Northeast Thailand can be characterized as follows:

34
The western boundary of the region is mainly formed by the Phetchabun Range (fig. 12), a
densely forested mountainous area of mixed geological composition. The backbone of the
range belongs to the Ratburi formation and consists of massive Carboniferous and Permian
limestone with embedded shale, sandstone, conglomerate and volcanic tuff. These are
surrounded by Phu Kradung formations, Jurassic and Triassic micaceous shales with siltstone,
micaceous sandstone and conglomerate. Igneous rocks can be found in certain places, such as
porphyry, granite and basalt (in Changwat Loei), porphyry and tuff (between Phetchabun and
Lopburi) and extended basalts northeast of Lopburi.
Figure 12: Physical orientation map of North-East Thailand. Source: D
ONNER
1978:552. Legend: 1 =
national boundary; 2 = regional boundary; 3 = changwat administrative centre.
The Sankamphaeng (Sankambeng) Range could be regarded as an extension of the Phnom
Damrek Range, but its western part is quite different and made up of a huge porphyry massif,
up to 1351 m high. The Dong Phaya Yen Mountains, finally, designate a range of foothills
which geologically are a continuation of the Phnom Damrek Range.
The Phetchabun Range (also named Dong Phraya Range by some authors) runs nearly exactly
north-south from the Thai-Lao border in the north to the Sankamphaeng Range in the south,
where it allows road and railway to cross from the central plain to the Northeast by a
mountain pass of less than 500 m altitude near Pak Chong. The range is about 350 km long
and split lenghtwise by the valley of the Pa Sak River.
The highest elevation of the whole massif is situated northwest of Lom Sak (Phetchabun
province, Northern Region), where the Khao Paeng Ma Mountains reach 1746 m. The eastern
wing is slightly lower, with Phu Luang (1571 m), Phu Rua (1375 m) and Phu Kradung (1316
m) in Loei province as the highest summits. In the southern part, the range descends to an
elevation of less than 300 m above MSL.
The Dangrek or Phnom Damrek Range (also called Phanom Dongrak) forms the border
between Cambodia and Isaan. It measures 300 km from the east to the west and appears as a
stretch of flat hills consisting of Phu Phan and Phra Wihan formations of massive sandstone
and conglomerate, micaceous shale and siltstone, hidden by a dense forest cover. The range is
characterized by its gentle slope to the north in contrast to its steep declivity towards the
south. The highest point (Phu Khok Yai, 753 m) lies in the extreme east, near the so-called
"Emerald Triangle", where the boundaries of Thailand, Laos and Cambodia meet.

35
There are quite a number of mountain passes, but none of them is open for border traffic
between Thailand and Cambodia. North of the range, at least a dozen hills of basalt rocks can
be found between south of Khorat and south of Ubon Ratchathani. The highest of them is
Khao Phanom Rung (377 m).
The flat bowl of the Northeast which covers the area between the marginal mountains and the
Mekong River is split into a smaller and a larger portion by the Phu Phan Mountains, visibly
stretching between Mukdahan and the southeastern part of Udon Thani province. This is
where the study area is situated. In fact, this folded range originates in the centre of the
plateau and extends east into Laos, crossing the Mekong and causing narrow channels and
rapids in the river bed around Khemmarat. The mountains consist of the lower cretacious Phu
Phan formation (which derives its name from here), sandstone and conglomerate, shale and
siltstone. In certain central parts, Jurassic sediments of the Phu Kradung formation appear.
"The mountains, which are the dominant topographic feature of the northeastern plains, are generally flat-
topped, but numerous streams have cut deeply into the material. Therefore the appearance of the range is
mature to old-aged in the erosional cycle. Reliefs of 300-500 m appear especially rugged because they rise
immediately from a low-lying alluvial plain. [...] Some of the small streams which emerge from the range
developed, in their upper basins, intermontane valleys or bowls due to erosion." (D
ONNER
1978:553-554)
The highest peaks are Phu Lop Wai (695 m) and Phu San Pa Yang (666 m) on the border
between Sakon Nakhon and Udon Thani provinces.
Finally, the Khorat Plateau proper, i.e. the wide and shallow basin which lies between 100
and 200 m above MSL and which is interrupted by flat hills rising in only a few cases to more
than 300 m, should be divided into two sub-regions, the southern Khorat Basin which is
drained by the Mun/Chi system, and the northern Sakon Nakhon Basin which is drained by
the Songkhram river. The bedrock of the plateau consists of cretaceous rocks such as
sandstone, shale and siltstone. There are considerable layers of rock-salt, gypsum and other
salt-bearing strata, especially in geological depressions. Khorat group sediments (salt and
Khok Kruat formation, Phu Phan and Phra Wihan formation, Phu Kradung formation) were
deposited on an underlying erosion surface during Mesozoic time.
Figure 13: Idealized cross-section illustrating relationship between landforms and substrata material of a
river plain and adjoining area (the Mekong at Pa Mong). Source: D
ONNER
1978:555.

36
The northeastern plains are much influenced by the rivers. Typical landforms include the
actual flood plains, often dotted with natural levees which are 1-5 m higher, the alluvial and
bedrock terraces (fig. 13). The plains are subject to regular floods, but the levees are not
flooded except in extreme cases. The alluvial terraces have a width of 0.5 to 3 km, but
normally don't reach more than 3 m above the flood plain. The higher alluvial or bedrock
terraces reach up to higher altitudes, are free from floods, but only have a thin layer of good
soil. (Description after
D
ONNER
1978:549-554.)
3.2.3. Soils
The general conditions for soil development on residual surfaces in Thailand, dependent on
the parent material, are as follows (cf. D
ONNER
1978:15):
· Soils derived from granite and gneiss prevail in the folded mountains. They are deep, well
drained, fine clayey soils of reddish brown, yellowish or red colour. Occasionally they
include reddish brown lateritic soils. Formerly covered with forest, they are now often
used for field and tree crops.
· Soils derived from sandstone prevail in the Northeast and in the central highlands. They
are loamey or clayey red-yellow Podzolic soils, originally covered by Dipterocarp forest,
but often cleared for upland crops.
· Soils derived from shale and its metamorphic equivalents can be found in the Southeast,
North and South. They are usually well drained, fine clayey, partly gravelly and yellow-
red to red in colour.
· Soils formed from calcareous material are to be found in many places, but especially
around Lopburi and Ta Khli, in the Chao Phraya plain. They are well drained, fine clayey
soils with lime concretions, some with a thick humiferous surface horizon.
· Finally, there are mixtures of the above types.
The soils of the Northeast are known to be poor and not very suitable for growing crops
successfully, compared with other parts of the country. They are mostly sandy, often with a
sandy clay layer or lens present at some depth. Lateritic nodules or layers of compact laterite
are common in many soils. The typical soil, however, is a fine sandy loam on the surface with
some increase in clay content with depth. The content of organic matter seldom exceeds 1 %.
The surface soil tends to be only slightly acid, as opposed to the more clayey layers. These
soils are quite infertile in comparison to the silt loam soils of temperate regions. In addition to
the low level of nutrients, there is a relatively high ratio of magnesium to calcium and of
sodium to potassium. Furthermore, the soils have low water-holding capacities.
Although most of the Khorat Plateau is underlain by old sedimentary rocks, most of its soils
are formed from alluvium and colluvium deposited during several cycles of erosion. Present
day alluvial plains are most extensive along the Mun and the Chi rivers and their tributaries,
but rare along the Mekong. Textures of the soils here are loamy on the levees and clayey in
the basins. The low terraces are most common in the southern and southeastern part of the
region. Their topography is flat to slightly undulating with only minor stream incision. There
are heavy textured sediments in the lower sub-level and medium to light textured sediments in
a higher one. The middle terraces are widespread throughout the region, but most extensive in
its northern part. Their topography is undulating to rolling. They show a distinct lithological
break with a sandy upper part and a clayey lower part, often with interspersed laterite gravels.
The oldest or high terraces only exist in the form of small remnants or islands that are
scattered throughout the region.

37
Their sediments are generally sandy-clayey loams of a typical red colour. Finally, colluvial
fans skirting the hilly areas and the escarpments on the different terraces are also an important
feature of the northeastern landscape.
The major soil groups of the Northeast are the following:
Alluvial soils, occurring on the immediate riverplains, are characterized by generally poor
drainage in the lower levels and a moderate fertility for rice production with high contents of
calcium, magnesium and potassium, but low contents of phosphorus, organic matter and
nitrogen. Acidity is slight to moderate.
Low humic gleys, often with laterite concretions and sheets, form extensive areas of the
Khorat Plateau. They show poor drainage, low content of organic matter, nitrogen and
phosphorus, but high content of magnesium and calcium. Acidity is moderate to strong.
Saline soils may be associated with them, but usually don't obstruct the rice production
because each rainy season dilutes and washes away the salts. Where conditions do not permit
the cultivation of rice, upland crops may be grown.
Grey podzolic soils are typical for the foothills in the south and west as well as the Phu Phan
Range. They are poor in weatherable minerals, have a high content of quartz and more
organic matter than other soils, but their ingredients tend to separate so the clay content is
often washed out, leaving large areas of coarse sand-surfaced soils.
Red-yellow podzolic soils prevail in the Sakon Nakhon Basin, but they also form mountain
soils in the Phu Phan Range and in the western and southern border mountains. They contain
laterite concretions and are susceptible to erosion, so they are rarely cultivated. They are
moderately acid in the surface, but strongly acid in the subsoil. The organic matter content is
low and there is a lack of calcium and phosphorus.
Red-yellow lathosols are scattered throughout the region and don't form large coherent areas.
They are often used for upland crops, but low contents in calcium, magnesium, potassium,
phosphorus and organic matter together with water deficiency result in low yields.
(D
ONNER
1978:573-579)
3.3. Climate and hydrology
Globally, Thailand belongs to three tropical climatic types, according to the system of
Köppen: the Northeast, the North, the Upper and Lower Central Region (about 83.0 % of the
total area) show a savanna climate of the type "Aw" with low precipitation and distinct
dryness in winter. The eastern portion of the Southeast and the peninsula south of Hua Hin,
except of a part of the east coast (about 13.6 %), may be classified as tropical monsoon
climate of the type "Am" with heavy annual rainfall and a short dry season. Finally, the
peninsular east coast between Nakhon Si Thammarat and the Malaysian border (3.4 %) fulfil
the conditions of the tropical rainforest climate, type "Af", humid throughout the year and no
month with less than 61 mm of rainfall.
Generally speaking, Thailand is a monsoon land with a dry season from November to April
and a wet season from May to October. But actually the climatological conditions and their
background are more complicated. D
ONNER
(1978:26-29) explains that they are basically
affected by the direction of the wind and its force and humidity in combination with the relief
of the country, and distinguishes between 5 main kinds of rainfall regimes (orographic and
cyclonic ones): the winter monsoon, the summer monsoon, the pre-monsoon storms from the
Bay of Bengal, the typhoons from the Pacific Ocean, and the local thunderstorms (fig. 14).

38
Figure 14: Left: Winds influencing the climate of Thailand. SM = summer monsoon WM = winter
monsoon B = Bengal cyclone C = convection (local storm) T = typhoon The numbers indicate the months
in which the winds prevail. Source: D
ONNER
1978:28. Right: Diagrammatic representation of the three
principal air streams and their zones of confluence in Southeast Asia. Source: T
REWARTHA
1981:200.
Tropical Southeast Asia is dominated by three main air streams, as depicted in figure 14 in a
broadly generalized form. With some modifications, this system moves north and south with
the sun, resulting in seasonal weather changes.
Already
H
ANN
(1910:242) stated that the climate and yearly course of the weather in
Southeast Asia is very similar to that of India, with the exception of the strong winterly winds
resulting from the deep temperature of the Asian land mass in the north, the extensive, warm
tropical waters in the south and the lack of a mountainous barrier (such as the Himalayas in
the case of India). This leads to a significant cooling of the south coast of China and
remarkable differences in temperature between East Asia and areas of the same latitudes
further west on the continent.
In the dry season, the northeast tradewinds, also called the winter monsoon, reach Thailand,
but since these winds come mainly from the continental land masses of Asia, they are dry and
do not result in much rainfall. If they have been moistened above the Pacific Ocean, however,
they can cause pronounced winter rains especially along the east coast of the peninsula.
According to T
REWARTHA
(1981:174), "the vigorous northerly flow is derived from the
Siberian anticyclone and is relatively cold, although its temperature may vary considerably
depending on the length of its land or sea trajectory". As can be seen in figure 15, only the
northern and northeasternmost parts of Thailand are influenced by the continental northerly
air in winter, while the rest of the country is dominated by the zonal trades.

39
When in spring the sun proceeds northward and heats up the Indo-Chinese landmass, the
resulting differences in temperature and pressure between the land and the surrounding water
areas causes strong air movements from sea to land. So the winter monsoon is forced back
and replaced by the summer monsoon blowing from the southwest from May to September. It
is most intense from June to August, heavily contributing to the water regime of Thailand
with fairly large precipitations every four to five days. (cf. fig. 15.)
Figure 15: Main features of the low-level circulation over eastern and southern Asia in the cool (left) and
in the warm (right) season. Source: T
REWARTHA
1981:174, 176.
Besides these large-scale wind systems, there are developments of a more local character,
forming high and low pressure areas and thus leading to cyclonic centres forming on the
various seas: Between April and October, pre-monsoon storms, or small-scale cyclones, may
form in the Bay of Bengal, moving from south to north with the wind blowing in a northeast
direction. The centre of such a cyclone usually starts in the Andaman Sea near the Thai west
coast in April and reaches the top of the Bay in July; it then follows the Indian coast down and
dies out in October in the Indian Ocean.
A similar storm centre, the typhoon, develops at about the same time in the Pacific Ocean. It
has three routes, but only the southernmost one is of relevance for Thailand. Heavy rains
caused by typhoons reach the North, the Northeast and the Central Region in June every year,
causing the first sharp rise in river levels. When the typhoon moves farther north, Thailand
comes out of its reach, occasionally causing a short period of drought. On its way back south,
it brings rain to Thailand in August, but the heaviest rain occurs in September, when the
typhoon passes again through the country on a wide front. In October and November, the
centre moves farther south, brings some rain to the northern peninsula and usually dies out in
December.
Finally, there is a third type of cyclonic rain, the local storms, the centre of which develops in
the hot season between March and April in the Gulf of Siam. Due to the small area of water,
the rainfall is minor, and its path cannot usually get farther than the Central Plain.
According to the beforementioned facts, continental Thailand receives on average between
1,240 and 1,370 mm of precipitation (1,246 mm in the North, 1,255 mm in the Upper
Central Region, 1,277 mm in the Lower Central Region and 1,369 mm in the Northeast),
while peninsular Thailand averages 2,423 mm and the Southeast 2,321 mm. (Compare the
rainfall map in the appendix.) Cloudiness (expressed in an 0-8 scale) is closely related to
rainfall and proximity of the sea shore. It is 4.7 in the North, 4.8 in the Northeast, 4.9 in the
Upper and 5.4. in the Lower Central Region, 5.5 in the Southeast and 5.8 in the South. The
distribution of annual mean temperatures depends on various factors such as elevation
above sea level, humidity, etc. High elevation, dryness, and distance from the sea usually
cause lower temperatures and more pronounced differences between minima and maxima.

40
Thus, the lowest mean temperatures appear in the North (26.1° C) and Northeast (26.5° C),
while for the rest of the country, they differ only slightly between 27.3 and 27.9° C. The
difference between the mean minima and maxima shows very clearly whether an area is
continental or maritime; this variability is 12.4° C in the North and only 8.6° C in the South.
The average relative humidity has the highest values in the extreme North, in the Southeast
and the South, and the lowest in the upper central area from Tak to Chaiyaphum. It is closely
tied to the rainfall regime. In winter, the northeast monsoon season, the relative humidity is
sometimes high in the morning due to fog, and decreases rapidly in the afternoon. The annual
evaporation
generally varies inversely with the annual rainfall. Thus the South, the area with
the highest precipitation, shows an evaporation of 826 mm only, whereas the North, Northeast
and Centre record values between 811 and 1,040 mm. Usually, the maximum evaporation
occurs in April, the minimum in September. The average pressure throughout the year
ranges from 1,005 to 1,010 mb. It tends to rise sharply from August to the highest peak in
January, then gradually decreases to the minimum in June. (cf. D
ONNER
1978:25-32 and
D
ONNER
1989:26-31)
In Northeast Thailand, the basic climatic conditions are strongly modified by the topography,
as the Khorat Plateau is locked off by mountain ranges in the west and south and, beyond the
Mekong River, also in the northeast. It is far more continental than all other regions of
Thailand. The Phetchabun and Phnom Damrek Ranges form a barrier against the southwest
monsoon and consequently create a rain shadow area in the western and southwestern part of
the region. The Annamese Cordillera beyond the Mekong, on the contrary, causes heavy
precipitations which still influence the northern and northeastern part of the Khorat Plateau.
This is a general climatic rule for the continental part of Thailand: B
RAAK
(1931:39) mentions
that the amount of rainfall from the southwesterly winds quickly decreases within a short
distance behind the Burmese mountain chains in the west of the country and then again slowly
increases to the east. In the time of the northeastern (winter) monsoon this picture is reversed:
in Isaan, there is a rain shadow behind the Annamese Cordillera in the northeast, whereas the
southern and western border mountains force some additional rainfall out of the winds. In
addition, the centrally situated Phu Phan Range, if not very high in elevation, further destroys
the climatic equilibrium of the otherwise very homogeneous plateau.
The annual average rainfall in the Northeast amounts to 1,368.5 mm; according to the
climatic zone it belongs to, the precipitation is unevenly distributed over the year, but the
concentration within a few month is not as strong as it could be expected. The month with the
heaviest average rainfall is September with a value of 281.7 mm, that's only 21 % of the total.
July, August and September amount to 54 %, June-September to 68 % and May-September to
82 %. December is generally the driest month, with not more than 10 mm of rainfall
anywhere. On the other hand, September is generally the wettest month, with more than 200
mm in every area.
D
ONNER
(1978) identifies 4 meteorological sub-regions:
1) the western mountains and foothills (Loei, Chaiyaphum, Khorat) with an average rainfall
of 1,146.1 mm,
2) the southern mountains and foothills (Si Saket, Surin, Buri Ram) with an average rainfall
of 1,276.7 mm,
3) the Mekong valley (Nong Khai, Nakhon Phanom, Mukdahan, Ubon Ratchathani), the area
with the highest precipitation at 1,585.9 mm, and
4) a transitory zone in the centre of the region, comprising four changwat (Maha Sarakham,
Khon Kaen, Kalasin, Roi Et) which neither fit together nor fit clearly into the
neighbouring areas. Their average is 1,277.8 mm.

41
1146,1
1277
1277,8
1368,5
1585,9
800
1000
1200
1400
1600
1800
Western
mountains
Southern
mountains
Transitory NE Region
average
Mekong
valley
a
nnua
l r
a
in
fa
ll
(mm)
Figure 16: Annual normals of rainfall in Northeast Thailand, according to meteorological sub-regions (30
years' average 1931-60). Data source: Meteorological Department, cited in D
ONNER
1978:570.
According to what has been said above, the seasonal distribution of the precipitation has
distinct sub-regional characteristics. The northeastern sub-region from Nong Khai to
Mukdahan receives more than 200 mm by May, when the regional average is only 183 mm,
whereas the southern sub-region between Khorat and Ubon still has more than 125 mm in
October, when the regional average has already dropped to less than 100 mm (see figs. 16 and
17). So the extreme northeast (Mekong valley), where the study area is located, is altogether
marked by an early arrival of the rainy season, extreme summer precipitations with vast,
frequent or long-lasting inundations, and finally an extreme dryness in winter.
0
50
100
150
200
250
300
350
400
Western mountains
Southern mountains
Mekong valley
Transitory
NE Region average
Mukdahan (1998)
N. Phanom (1998)
Figure 17: Monthly normals of rainfall in Northeast Thailand, according to meteorological sub-regions
(30 years' average 1931-60). Data source: Meteorological Department, cited in D
ONNER
1978:570.

Details

Seiten
Erscheinungsform
Originalausgabe
Jahr
2002
ISBN (eBook)
9783832461355
ISBN (Paperback)
9783838661353
Dateigröße
37.1 MB
Sprache
Englisch
Institution / Hochschule
Georg-August-Universität Göttingen – Geographie, Geographisches Institut
Note
1,3
Schlagworte
change deforestation entwaldung geography geographie south east asia südostasien development entwicklungsplanung
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Titel: Assessment of land use changes in Mukdaham and Nakhon Phanom provinces (NE Thailand) by means of Remote Sensing
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