Estimating Riparian Forest in the Watershed Areas of Northeast Thailand: Application of SPOT Data

Charat Mongkolsawat

Geo-informatics Center for the Development of Northeast Thailand, Khon Kaen University

E-mail: charat@kku.ac.th

Abstract Riparian forest is an important ecosystem that protects the loss of water quality, habitat, recreation quality, natural filtering of sediment and connectivity with other landscapes. Intensive activities in riparian areas lead to the depletion of the riparian vegetation which in turn affects the overall ecosystem. The estimation of the riparian forest is needed with objective of analyzing its distribution with floristic composition in relation to locational setting. The study area, Northeastern Thailand, which comprises three main watersheds and covers an area of about 170,000 km2. These watersheds were drained by the three main rivers (Mekong, Mun and Chi) and its tributaries and were used to have abundant vegetation cover. The SPOT imageries acquired during the years 2005-2007, totaling 78 scenes covering the entire Northeast were used for identifying the riparian forest. The areas of 300-500 m from the river and stream banks were digitally performed to establish the masking areas for the subsequent processing. The methodology of image processing included geometric correction, image classification and result verification. The tree-decision method with Normalized Difference Vegetation Index (NDVI) was applied for the area under the masking to classify the vegetation. In addition, information on the vegetation composition was collected by ground investigation in the main riparian areas. The results obtained indicate that the riparian vegetation in the Northeast encompassed totally 4,530.20 km2 with an approximate area of 1,681.43, 1,261.06 and 1,578.43 km2 for the Mekong, the Chi and the Mun, respectively. The vegetation composition in the riparian area was identified in terms of its functionality or vegetation setting (aquatic, stream bank and terrestrial areas). The establishment of GIS database based on the results obtained was conducted together with watershed and province areas. Information established provides spatial distribution of vegetation forest along the rivers and its tributaries which can be queried and retrieved or visually displayed. Key words: Riparian Forest, SPOT Data, Northeast Thailand

1. Introduction Riparian forests are vegetated areas that locate immediately adjacent of streams lakes, swamps, or other surface waters. The areas differ from the uplands because of periodical flooding, stagnant water, high soil moisture condition and the unique assemblage of living organisms found there. Through the interaction of their soils, plant and animal communities and hydrology, riparian forests are importantly recognized as physical, biological and ecological as physical, biological and ecological functions on which social benefits are based. Ilhardt, B.L. (2000) defined the riparian areas based on the functional definition as an interdisplinary approach. The approach recognizes ecosystem functions developed and applied from many professional disciplines from many professional disciplines in a common landscape rather than the equal grouping of soil, water and plant variables. As a result, the areas are the three- dimensional ecotones of interaction that include terrestrial and aquatic ecosystems, that extend down into the ground water, up above the canopy, outward across the flood plain, up the near-slopes that drain to water, laterally into the terrestrial ecosystem, and along the water course at a variable width. Riparian areas are considered as environmentally sensitive areas where, if not protected, the depletion of the areas lead to the loss of water quality and quantity, habitats for plants and animals, native plant and animal species, recreation and aesthetic qualities, natural filtering of sediment and connectivity with other landscapes (Verry E.S 2000). From the viewpoint of demands, we need wood and wood products, opportunities for hydropower, grazing and cropland, water uses and access to mining and sand sucking. In Northeast Thailand, the riparian areas are critical as directly observed the encroachment of agriculture, aquaculture, services of resort and restaurant on the areas extends inward over the stream, laterally into the forest and along the river courses. Each of individuals or communities sees riparian areas differently. Individuals focus on opportunities for benefits, commerce, aquaculture, agriculture or sand sucking; communities require the land, vegetation and water functioning together, optimization of their functions and the management with shared decisions. To serve the communities, political strategies on these issues should be formulated by the authorities concerned. For the entire Northeast, the spatial information of riparian forest is needed in terms of catchment areas/administrative boundaries and the vegetation setting and functioning. The information to be obtained can be used for strategic planning to prioritize the management implementation. Satellite data is widely accepted for rapidly providing spatial information for the riparian areas in the Northeast particularly the moderate resolution of SPOT data. Estimating the riparian forest in the watershed areas could be performed to identify the present situation of the vegetation distribution and its setting. The study aims to analyze the distribution of vegetation along the water courses in the Northeast watershed areas and present the vegetation setting and composition 2. Study Area Northeast Thailand, one of the distinct main physiographic features of Thailand, covers about one third of the total area of the kingdom. It lies between the latitudes of 14° and 19° N and the longitudes of 101°and 106° E (Fig 1). Average rainfall varies from 1,000 m.m. in the southwest to 2,000 m.m. in the Northeast. The rainfall is unevenly distributed during the rainy season (May to October), with over 80% occuring during August and September. Physiographically, the main area of the Northeast is formed by the so-called Korat plateau and a part of the central highland. The Phu Phan range lies in a Northwest-Southeast direction, dividing the plateau into two basins, the larger Korat basin to the south Fig 1 Study Area

and the smaller Sakon Nakhorn basin to the North. The two basins are characterized by gently undulating alluvial plain with scattered tree and patches of forest remnants. Flood risk area in the Northeast is a result of large rainfalls, the increased frequency and volume of surface run-off, the rising levels of river bed and human modification of land. The main rivers overflow their banks frequently resulting in devastating floods. 3. Methods 3.1 Data sources Estimation of riparian forest in the Northeast was derived from the following sources. - Multitemporal SPOT data acquired during the years 2005-2007 were used in this study, the indices (path/ row), acquisition date and resolution were presented in Table 1 and Fig 2. - Topographic maps (1:50,000) covering the areas of the entire Northeast were applied for performing geometric correction and some geographic features.

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Fig 2 Imagery Index

Table 1 SPOT data acquired during the years 2005-2007

Index SPOT-5 SPOT-4 SPOT-2 Order K J Resolution

10 m Resolution

20 m Resolution

20 m 1 261 315 27 Mar 07 2 262 314 1 Apr 07 3 262 315 1 Apr 07 4 262 316 31 Mar 07 5 263 314 22 Dec 06 6 263 315 13 Jan 07 7 263 316 3 Feb 07 8 263 317 4 Feb 06 9 263 318 4 Feb 06 10 263 319 28 Dec 06 11 263 320 18 Feb 07 12 263 321 18 Feb 07 13 264 314 28 Dec 06 14 264 315 22 Apr 07 15 264 316 3 Jan 07 16 264 317 16 Mar 07 17 264 318 3 Jan 07 18 264 319 16 Mar 07 19 264 320 16 Mar 07 20 264 321 12 Mar 06 21 265 314 28 Apr 05 22 265 315 29 Jan. 07 23 265 316 12 Dec 06 24 265 317 29 Jan 07 25 265 318 26 Jan 05 26 265 319 7 Mar 07 27 265 320 3 Feb 07 28 265 321 27 Feb 07 29 265 322 13 Jan 06 30 266 313 12 Jan 07 31 266 314 7 Nov 06 32 266 315 7 Nov 06 33 266 316 9 Feb. 07 34 266 317 9 Feb 07 35 266 318 9 Feb 07 36 266 319 6 Nov 06 37 266 320 6 Nov 06 38 266 321 9 Dec 05 39 266 322 9 Dec 05 40 267 313 23 Dec 06 41 267 314 23 Dec 06 42 267 315 24 Jan 07 43 267 316 31 Jan 06 44 267 317 25 Dec 06 45 267 318 25 Dec 07 46 267 319 27 Jan 07 47 267 320 22 Nov 06 48 267 321 29 Dec 05 49 267 322 25 Jan 06 50 268 314 19 Jan 07 51 268 315 19 Dec 05

Table 1 (cont.) SPOT data acquired during the years 2005-2007

Index SPOT-5 SPOT-4 SPOT-2 Order K J Resolution

10 m Resolution

20 m Resolution

20 m 52 268 316 20 Nov 05 53 268 317 15 Jan 06 54 268 318 11 Mar 07 55 268 319 12 Mar 07 56 268 320 12 Mar 07 57 268 321 3 Jan 07 58 269 315 10 Feb 06 59 269 316 2 Jan 06 60 269 317 2 Jan 06 61 269 318 2 Jan 06 62 269 319 17 Jan 07 63 269 320 1 Apr 07 64 269 321 1 Apr 07 65 270 315 9 Feb 07 66 270 316 5 Feb 06 67 270 317 5 Feb 06 68 270 318 5 Feb 06 69 270 319 5 Feb 06 70 270 320 8 Dec 06 71 270 321 13 Mar 07 72 271 318 19 Dec 05 73 271 319 6 Jan 06 74 271 320 15 Jan 06 75 271 321 27 Dec 05 76 272 319 7 Dec 05 77 272 320 10 Jan 06 78 272 321 10 Jan 06

3.2 Study approach The approach of this study addresses the areas of riparian forest along the main rivers and their tributaries over the entire Northeast Thailand. The area of 300-500 m. from the stream banks were digitally performed to establish the masking areas for subsequent processing. We used the 300 m. and 500 m. buffering areas along the meandering streams for small and large streams respectively, based on visual observation of the imagery. The methodology procedure comprises preprocessing of satellite data, image analysis and field verification. 1) Proprocessing of satellite data The SPOT scenes as given here above were geometrically corrected, transforming the image coordinated to the ground control points selected from the topographic maps and performing resampling of the pixel values with nearest neighbor algorithm. There provided the rectified images for which were used for future image analysis.

2) Image analysis The tree-decision approach was used to classify the riparian vegetation (Fig 3). The process of image analysis was digitally preformed in the masking areas. Distinguishing between water body and non-water body was executed from on analysis of the threshold of the pixel values. The vegetation and non-vegetation classes were differentiated over the areas of non-water body, performing the normalized difference vegetation index (NDVI) analysis. The NDVI, widely used and accepted for vegetation study is defined as:

NDVI = (ρNIR - ρRED) / (ρNIR + ρRED)

Where ρNIR = reflectance values in the near infrared band ρRED = reflectance values in the red band We used the enhanced NDVI - [(NDVI * 128) + 127.5] for the differentiation of the vegetation, the values of exceeding 150 were classified as vegetation. 3) Field verification Ground investigation was conducted to validate the result of image analysis. Over 44 test areas (Fig 4) were inventories and studied, including ground cover type, land type and floristic composition of the covers. We used GPS, topographic map and false composite colour of satellite imagery for this investigation.

Fig 3 Procedure for tree-decision approach

Fig 4 Test Area for ground investigation

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4. Results and Discussions 4.1 Riparian forest areas The riparian forest in the watershed areas of the Northeast is presented in Fig 5. The riparian forest in the Northeast cover an area of about 4,530.20 sqkm. of which is 1,578.43, 1,681.43, 1,261.06 and 9.32 sqkm. for Mun, Mekong, Chi and Pasak respectively. Table 2 presents the riparian forest areas for each watershed/ sub-watershed in the Northeast. From the result studied, the sub-watershed of the Northeast having abundant and diverse riparian vegetations were listed. The sub-watershed of the Mun included upper part of Mun, second part of Mun, third part of Mun, Lam Chi, Lam Se, Lam Dom Yai, Lam Takhong and Lam Plai Mat. The sub-watershed of the Mekong are lower part of Mekong, seventh part of Mekong, eighth part of Mekong, ninth part of Mekong, Nam Phung, lower part of Loei, lower part of Songkhram, Huai Nam Kam, Huai Nam Un, Huai Bang Sai and Huai Luang. The sub-watershed of the Chi encompasses lower part of Chi, second part of Chi, third part of Chi, fourth part of Chi, upper part of Phong, lower part of Phong and Yang. We identified the lists of the sub-watershed based on the acreage, ecosystem function and locational setting. These include diverse vegetations and animals, pre histories resettlement, raw materials for industry, natural filtering of sediment and connectivity with other landscape.

Table 2 Riparian forest in main watershed/ sub watershed in the Northeast, Thailand

Watershed Area Main watershed / Sub-Watershed (Sq.km.)

Riparian Forest (Sq.km.)

Total Area of Mun Watershed

71,223.89 1,578.43

Upper part of Mun 2,870.35 98.06 Lower part of Mun 1,014.43 42.35 Second part of Mun 3,740.05 147.86 Third part of Mun 2,744.03 103.20 Lam Chakkarat 1,447.27 37.47 Lam Chi 4,933.01 73.46 Lam Choengkrai 2,973.76 24.71 Lam Se 3,632.74 104.65 Lam Se Bai 3,219.95 53.82 Lam Sae 1,672.17 59.48 Lam Dom Noi 2,165.67 70.06 Lam Dom Yai 4,838.36 223.93 Lam Takhong 3,935.11 91.51 Huai Ta Khong 1,770.84 20.08 Lam Tao 956.10 1.73

Table 2 (cont.) Riparian forest in main watershed/ sub watershed in the Northeast, Thailand

Watershed Area Main watershed / Sub-Watershed (Sq.km.)

Riparian Forest (Sq.km.)

Lam Nang Rong 1,372.03 17.25 Lam Plai Mat 3,974.50 104.45 Lam Pathai 692.20 5.68 Lam Phraphloeng 1,871.37 30.99 Lam Phlapphla 903.70 3.09 Lam Phang Su 1,343.81 3.26 Lam Sa Thaet 2,599.55 40.85 Lam Sieo Noi 700.33 0.16 Lam Sieo Yai 2,801.78 11.44 Huai Khayung 1,778.69 37.46 Huai Tung Lung 840.05 34.36 Huai Tup Than 3,643.53 45.50 Huai Tha 1,588.90 21.47 Huai Phong 665.16 4.14 Huai Samran 3,356.65 50.99 Huai Aek 1,177.80 14.98

Table 2 (cont.) Riparian forest in main watershed/ sub watershed in the Northeast, Thailand

Watershed Area Main watershed / Sub-Watershed (Sq.km.)

Riparian Forest (Sq.km.)

Total area of Chi watershed

48,267.60 1,261.06

Upper part of Chi 2,545.62 52.75 Lower part of Chi 2,770.98 101.84 Second part of Chi 3,803.82 162.23 Third part of Chi 3,228.94 191.54 Fourth part of Chi 5,245.15 112.25 Nam Phrom 2,076.88 37.87 Huai Phuai 914.65 15.30 Upper part of Phong 3,866.82 80.01 Lower part of Phong 2,423.61 75.94 Lam Krachuan 889.31 30.61 Lam Khan Chu 1,738.78 35.19 Choen 2,523.97 75.32 Yang 4,075.00 98.52 Upper part of Lam Pao 3,202.81 49.86 Lower part of Lam Pao 4,227.93 53.51 Lam Phaniang 1,839.92 39.42 Lam Phan Chart 687.62 5.57 Lam Saphung 762.87 4.42 Huai Sam Mo 771.27 34.43 Huai Sai Bat 671.64 4.50 Total area of Pasak watershed

844.06 9.32

Upper par of Pasak 324.81 4.09 Lam Sonthi 380.85 0.71 Huai Nam Phung 138.40 4.52 Total areas of the

Region 167,030.40 4,530.24

Table 2 (cont.) Riparian forest in main watershed/ sub watershed in the Northeast, Thailand

Watershed Area Main watershed / Sub-Watershed (Sq.km.)

Riparian Forest (Sq.km.)

Total Area of Mekong Watershed

46,694.49 1,681.43

Huai Hi 730.03 23.46 Lower part of Mekong 3,339.20 148.46 Third part of Mekong 604.85 25.94 Fourth part of Mekong 803.84 34.80 Fifth part of Mekong 1,748.72 67.62 Sixth part of Mekong 2,870.35 98.06 Seventh part of Mekong 643.66 15.22 Eighth part of Mekong 2,467.45 73.12 Ninth part of Mekong 1,893.07 70.03 Nam Phung 440.78 10.32 Nam Suai 940.03 73.78 Huai Nam Puan 1,271.46 20.22 Nam Mong 1,175.70 18.50 Lower part of Loei 2,714.46 48.40 Upper part of Songkhram 2,758.52 120.64 Lower part of Songkhram 3,292.37 75.77 Nam San 3,049.46 142.39 Huai Nam Som 876.66 30.81 Nam Man 1,049.52 42.23 Huai Khong 611.93 36.90 Huai Dan 703.38 7.37 Huai Nam Kam 2,608.32 111.79 Huai Nam Yam 1,738.42 31.31 Huai Nam Un 3,469.86 122.13 Huai Bang I 1,501.77 64.39 Huai Bang Sai 1,382.04 95.53 Huai Muk 796.16 31.31 Huai Luang 3,366.74 125.23

Fig 5 Riparian Forest in Northeast Thailand

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Riparian Forest in Northeast Thailand

Source Data

Geoinformatics Center for the Development of Norhteast Thailand

Spheroid.............................................................Everest

Grid...................................100,000 meter UTM Zone 48

Projection.......................................Transverse Mercator

Vertical Datum......................Mean Sea Level at Ko Lak

Horizontal Datum.......................................Indian Datum

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±0 25 50 7512.5

Kilometers

Legend

Main Watershed Boundary

Main River

Tributary

Water Body

Riparian Forest

Khong Watershed

Chi Watershed

Mun Watershed

Northeast Boundary

Sub Watershed Boundary

4.2 Vegetation Types Variation in water content affected by river stage is the most important factor sorting the group of vegetations. The vegetation in the riparian areas was therefore identified in terms of their setting: aquatic areas, stream bank and terrestrial area. The aquatic areas are divided into emergent and shallow water zones. The vegetation species in the emergent zone or zone below mean river level include Hydrilla verticillata, Ceratophyllum demersum Linn, Utricularia aurea, Potamogeton cripus, Najas graminea Del, Salvinia cucullata Roxb, Eichornia crassipes, Pterolobium macropterum Kurz, Nymphaea lotus var. pubescens, Nymphaea stellata Wild, Nelumbo nuclfera Gaerth, Pistia stratiotes L, Teminalia bellirica (Gaertn.) Roxb, Ipomcea aquatica Forsk, Jussiaea repens Linn. The species in shallow water are Eleocharis dulcis (Burm.f.) Henschel, Typha angustifolia L, Scirpus grossus L.f, Cyperus corymbosus Rottb, Eragrostis nutans Retz, Imperata cylindrica (L.)P. Beauv, Syn. Sclerostachya fusca A. Camus, Arundo donax Linn, Hemarthria compressa, Hymenachne pseudointerrupta C.Muell, Leersia hexandra Sw. The main species in the stream bank comprise Artabotrys spinosus Craib, Terminalia tripterordws Craib, Phyllanthus collinsae, Barringtonia acutangula (L.) Garetn, Combretum quadrangulare Kurz. Terrestrial areas can have two groups of vegetation according to their settings: flood plain vegetation and non-flood plain vegetation. The flood plain vegetations include shrub, bush bamboo and Thickets: Bambusa sp, Capparis micracanha DC, Capparis siamensis Kurz, Croton caudatus Geisler, Euryeoma longifolia Jack, Ficus heterophylla L.f, Gardenia hygrophila Kurz, Gomphia serrata (Gaertn.) Kanis, Homonoia riparia Lour, Lepisanthhes senegalansis, Melodorum siamensis (Scheff.) Ban, Oxyceros horridus Lour, Phyllanthus reticulates Poir, Hymenocardia wallichii Tul., Colocasia esculenta (L.)Schott.

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Fig 5 (cont.) Riparian Forest in Northeast Thailand

The non-flood plain vegetation are the remnants of evergreen and dry dipterocarp forests. The main species of the evergreen are Hopea odorata Roxb., Dipterocarpus alatus Roxb.ex G.Don., Parinari anamensis Hance., Lagerstroemia floribunda Jack., Dipterocarpus intricatus Dyer., Shorea talura Roxb., Syzygium cumini (L.) Skeels. The species of the dry dipterocarp are Dipterocarpus. obtusifolius Teijsmex Miq., Dipterocarpus intricatus Dyer., Shorea obtusa Wall. ex Blume., Shorea siamensis Miq. The result from the ground investigation indicates that encroachment of agriculture, restaurant and human activities on the riparian forest is increasing at the alarming rate. If these situations are not protected, the riparian forests will be depleted, leading to loss of water quality, habitats for plants and animal species, natural filtering of sediments and connectivity with other landscapes. The findings of ground investigation are a relation between image elements and vegetation cover, vegetation type, composition and setting, from which better understanding of riparian areas is achieved (Fig 6). We report the distribution of vegetation in each sub-watershed and provided information to prioritize the riparian areas at risk of depletion. The detailed information on the sub-watershed listed should be further investigated to make an appropriate management. In addition, fast growing trees which affect the ecosystem functions are normally found in the terrestrial areas i.e. eucalyptus which is tolerant to flooding, saline soil and drought.

5. Conclusions The results obtained indicate that the riparian vegetation in the Northeast encompassed totally 4,530.20 km2 with an approximate area of 1,681.43, 1,261.06 and 1,575.43 km2 for the Mekong, the Chi and the Mun, respectively. The vegetation composition in the riparian area was identified in terms of its functionality or vegetation setting (aquatic, stream bank and terrestrial areas). The establishment of GIS database, based on the results obtained was conducted together with watershed and province areas. Information established provides spatial distribution of vegetation forest along the rivers and its tributaries which can be queried and retrieved or visually displayed.

Chi Watershed X: 355824 m. E./ Y: 1853491 m. N.

Songkhram Watershed X: 370486 m. E./ Y: 1975392 m. N.

Mekong Watershed X: 393780 m. E./ Y: 1877360 m. N.

Mun Watershed X: 459401 m. E./ Y: 1673934 m. N.

Fig 6 Show some vegetation covers as related to the SPOT imagery in the selected areas

6. References Henderson, F.M., and Lewis, A.J. (1998). Principles & Applications of Imaging Radar, Manual of Remote Sensing. 3rd Edition. Vol 2, John Wiley & Sons, Inc. Ilhardt, B.L. (2000). Defining Riparian Areas. Proceeding of the Forestry and the Riparian Zone. Maine: Wells Conference Center, University of Maine. Mongkolsawat, C. & Sombutputorn. (1997). Wetlands in Northeast Thailand. Paper submitted to ONEP. Reich, R.M., & JOY, S.M. (2002). A Non- Parametric, Supervised Classification of Vegetation Types on The KAIBAB NATIONAL FOREST using Decision Trees. Retrieved February 10, 2006, from http://www.treesearch.fs.fed.us/pubs/24021 Schnabel, R.R., Cornish L.F., and Stout. (1994). Evaluating riparian Zone control on mitrogen entry into Northeast streams. P432-445 In Proceedings of Conference on Riparian Ecosystems in the Humid U.S. Functions, Values and Management. Verry, E.S. (2000). Forestry and the Riparian Zone: Why Do People Care?. Proceeding of the Forestry and the Riparian Zone. Maine: Wells Conference Center, University of Maine.