application of gis for land-use/land-cover change analysis in a mountainous terrain

Photonirvachak Journal of the Indian Society of Remote Sensing, Vol. 24, No. 3, 1996

Application of GIS for Land-Use/Land-Cover Change Analysis in a Mountainous Terrain

S GHOSH*, K K SEN*, U RANA*, K S RAO* and K G SAXENA ° *G.B. Pant Institute of Himalayan Environment & Development, Kosi, Almora - 263643 (U.P.)

°School of Environment Sciences, Jawaharlal Nehru University, New Delhi - 110067

ABSTRACT

Integration of remote:Sensing data with other spatial/non-spatial data was carried out

Suitability assessment of:land where agricultural: extension occurred between~ I963 and 1993 was made using GtS .sOftware package. E~l:maasion..:6f?agrieutture land. ~as found.:..to be maximum in 2200-2400 m elevation~ zone and 20-30~ slope classes. When topographic

~as maximumon south eastand:west facing slopes. The aspects were considered expansion. ~ loss of vegetal cover is estirnated ~0 ~be 15 per centbetween t 963~ t 993: Howe~er rege!~eration o f forest was found to be m ~ m u m ..in elevati0n ranges of 1600~2000:metre and: mostly having 20~307 average slope. Land deterioration over the two:mapp!!!g periods was identified and strategies were suggested to mitigate the problem.

Introduction 1995). Information on existing land-use/ land-cover, its spatial distribution and

Land-use or land-cover change is change are essential pre-requisite for critically linked to the intersection of natural planning (Anonymous, 1992). Thus land- and human influences on environmental use planning and land management change. The changes in the state of the strategies hold key for development of any biosphere and bio-geochemical cycles are region. Geographic Information Systems driven by heterogeneous changes in land use were found to be effective in preparing, and continuation of those uses (Turner, maintaining and carrying out futuristic

(Recd. 24 June"96; in final form 8 Dec. '96)

194 S. Ghosh et al.

analysis on land-use planning and management. This is even more important in mountainous regions where the physical constraints makes it difficult to update the information very frequently and even availability of information is rather poor in comparison to adjoining plains. Thus, this attempt to build a micro-level database using GIS technology is a significant step towards digital land-use information management. The rural ecosystems in the Himalaya are so diverse that careful consideration of location specific attributes become a precondition for ensuring the success of development efforts (Saxena e t al., 1994).

Since rural ecosystems in the Himalaya are primarily dependent on surrounding forest ecosystems, management of forest resources must be dealt with urgently and sensibly. Environmental degradation in the Himalaya has caught the eye of environ- mentalists only for the last two decades or so. Difficult terrain and inaccessibility makes it almost impractical to obtain information required for efficient management of the natural resources with reason- able accuracy. Remote sensing has proved its potential for providing such information (Anonymous, 1983; Anonymous, 1989; Saxena et al., 1991; Singh, 1991; Dhinwa et al., 1992).

The Pranmati watershed, a represen- tative micro watershed, was chosen for the present study. This area has been experien- cing land-use changes as a consequence of degradation of natural resources during the past 20-30 years. There is still a possibility to control the deterioration process through

better land-use planning. The present study was undertaken with the objectives of analysing land-use/land-cover changes in the area using topographic maps, remote sensing data, census and revenue data and field observation data.

Study Area

Pranmati watershed (30°4'N and 30°lYN latitude and 79°28'E and 79°36'E) lies in the Pindar macro watershed. The area is part of the River Ganga catchment. Administratively the area comes under Tharali block of Chamoli district. There are 21 revenue villages within this watershed, of which four are partly within the watershed (Fig. 1) as they spread across the water divide. The important villages are Dungri, Gerur, Bunga, Ratgaon and Kurar. The watershed is a part of West Pindar Forest Range of Garhwal division. Physiographically it is a part of Garhwal Himalaya, located in the Central Himalaya. The planimetric area of the watershed is 94.05 km 2 whereas the actual surface area of the sloping mountainous terrain is about 106 km 2. The elevation range is 1120 to 4070 metre above mean sea level (msl ) .

The watershed is characterised by rich biodiversity, and its vulnerability to rapid land use changes. Its natural set up in mountains makes it ecologically fragile and promotes a system where there is greater dependence on common resources. Lack of motorable road and electrification in the watershed area is indicative of the level of inaccessibility and seclusion from urban centres. However, during the past 30 years the area has been undergoing rapid changes

Application of GIS for Land-Use/Land-Cover Change Analysis in a Mountainous Terrain 195

i n land-use and with the new motorab le road

unde rway the rate o f changes are likely to

be accelerated. The densi ty o f popula t ion is

a round 4 0 persons per square ki lometre ,

wh ich is modera te for the H ima layan

region.

i "--a~ /

i " \

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/ " i / ' . -x" ,, , , , , ,

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i I I I I II ' /# t l l ' " ' ~ \ z ' " 1 " , " " z ' / II

,' : ' - . ' . ~ ' , / s . - : " ,, , ~ " - - ' . - , , " .-" / . ; . ' , . ' 1 , ,.'. \- ,

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Olnaik K~',"=:"A'.. ''~" / ,' "," ;:-'~"~~-~, ;" ";", "".f-~'-. . . "-',"'-" " \>~ - _ , f . . . . ~ , , . ] ." , /+ ._ - - - ~ . - , . , ~ . -

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K I I , O M E ' [ ' R E S

Fig. 1. Location of Study Area.

196 S. Ghosh et al.

Materials and Methods

The basic methodology include:

1. The Survey of India topographic map (RF 1:50000) of 1963 was used as the base map for registration, and digitization of topography and land-use status of 1963;

2. IRS-1B image (RF 1:50000) of 1993 was visually interpreted to map the land use status during 1993. The map was finalized after ground verification;

3. Collection of Census of India Abstract figures for demographic criteria;

4. Procurement of data from different government authorities for defining administrative or jurisdiction bounda- ries, planned roads etc.;

5. Recording of climatic data for the year 1993-94 using weather station as the meteorological data for the area was not available;

6. Collection of field data for soil, crop, livestock, phyto-sociological status of vegetation;

7. Spatial data on altitude, aspect, slope, soil, vegetation, geomorphic features, settlements, paths, land-use, etc. was taken as attribute data.

8. SML programmes, mathematical and statistical operations in 'tables' and dbase were used to derive land acreage and extent of changes.

Use of spatial data from maps or remote sensing for mountainous terrain implies that the area is being represented by

a flat surface, thus the planimetric area is considered for most purposes. The actual surface area (of the sloping land, which is greater) was not considered. However the same was derived trigonometrically. There was also the problem of over estimation of vegetation density while interpreting from remote sensing image in case of sloping terrain. This problem was adjusted by considering the angle of each hill slope from topographic map and suitable methodo- logies.

Problems of Data Collection

Being in the Himalayan region, and within 40 kms from the Nation's border topographical data obtainable from Survey of India is restricted. There is lack of climatic and socio-economic data. The available data on land ownership is not always compatible, thus leading to doubt in its reliability. Data collection is also difficult due to lack of motorable road and many a times lack of any path, steep terrain, forest clad slopes and harsh winter climate in the upper reaches. Rivers in spate (when the discharge is ten times the normal) and landslides add to the problem of accessibility. Seasonal migration of members of the family to the alpine pastures in the summer months, results in multiple homes which could easily lead to duplication of data, and in some cases it may be difficult to contact any member of the family for socio-economic survey.

Results and Discussion

Some basic land-use and land-cover types only were discernible from the 1963 map, hence further subdivision to Level-I


and Level-2 categories was not possible, although for the year 1993 detailed classification was possible from remote sensing data, it did not allow change detection for each of its categories.

Area under major land-use or land- cover categories was calculated for the years 1963 and 1993 (Fig. 2A & 2B). Cultivated area includes all agricultural land and settlement area inclusive of community land, and cultivable waste. Forest area includes Village Panchayat forest as well forest under the jurisdiction of Forest Department. Alpine pastures occur generally above the elevation of 3200 metre above msl on the southerly aspects in this watershed. These are interspersed with large rocky surfaces and these have been grouped together as their details were not available from 1963 topographical map, however, these could be differentiated and mapped separately from 1993 IRS image.

The barren and uncultivable lands include bare rocky surfaces and alpine meadows, along with the minor categories, like ravine slashed land and landslides.

Land-Use/Land-Cover Change Analysis

Changes in areal coverage under major land-use and land-cover types were derived by spatial intersection of 1963 and 1993 data (Fig. 3, Table 1). This showed a significant increase in cultivated area as a result of conversion of previously forest or pasture land to agriculture. However, some areas also revealed an opposite trend where previously agricultural area was afforested.

Table 1. Land-use change (in km 2) from 1963 to 1993,

Categories

1 Agriculture

9 Forest

6 Pasture

3 Others*

1 9 9 3

Agric. Forest Pasture l Other

- 2.629 0.155 0.00005

9.053 - i.578 0.576

0.451 0.351 - 0.123

0.0 0.0 0.0 -

Changes in Agricultural Land

Details of changes in agricultural land and settlements could be analysed through comparison of their spatial distribution in 1963 and 1993. Changes were found to be greater in the proximity of settlements, considering 1 km buffer zone for each settlement area. Agricultural and settlement area increased from 12 percent in 1963 to almost 19 percent (17.63 km 2) of geographical area in 1993. Encroachment on marginal lands for cultivation is taking place due to increasing population pressure and need to generate more income. The magnitude of decrease in cultivable wasteland is an ideal index for reckoning the extent of its colonisation (Singh, 1990) as they are the areas of horizontal expansion of cultivated land. Increasing the yield with technological input would reduce the pressure on marginal land. But only increasing crop yield and introduction of means of generating more income is not enough to stop encroachment on marginal lands. Public awareness and decision at village level towards soil conservation and environmental protection must be firmly embedded.

198 S. Ghosh et al.

F o r e s t 7 5 %

C u l t i v a t e d C u l t i v a t e d 1 2 % 19%

1 2 % P a s t u r e s B

A 1%

F o r e s t 67%

Others Pastures 12% 2 Z

3500 1 300o f

3000 ~ 2500 b

ii { ~ zooo

~ 2000F ~.15oo 1500

tOOO [] ~ {ooo

C

3000

25°° I 2000

~ 1500

IO00{

500

500

Elevation range Averaje slope range

0 ~ - / o.." /" / / o." ,o* /

/ / / / Aspect

Fig. 2. Land use/Land cover in the watershed in 1963 (A); in 1993 (B) and Extension of agricultural land (1963-93) in different elevation zones (C); in different average slope classes (D);

in different topographic aspects (E).

' ' r ,

i o.5 0 I l

KIIDlm~'rzt~:~

I V " LEGEND :

Forest to Agriculture I n Pasture to Agriculture i Remaiu, ing .Agricultural

tana luncnangeaj s,~ Forest to Pasture mm Agriculture to Pasture me Remaining Pasture

land ~utnehanged] mm Pasture to Forest

Agriculture to Forest me R~maiuiug Forest

~uncnangeaj m Forest to major Landslide mm Alpine meadows, ha, re r~ok

~c other waste lane.

Fig. 3. Land cover and land use change in Pranmati watershed from 1963 to 1993.


The agricultural land of both 1963 and 1993 was separately intersected with physical parameters, such as altitudinal zones, average slope, aspect, soil factors, geomorphic features for various applications and detect spatial changes during the 30 year span. Extension of agricultural land in relation to elevation, slope, aspect and bio-climatic zone was derived by intersection and Simple Macro Language (SML) programme. The extension of agricultural land in the zone between 2400-2600 metre elevation above msl has enhanced soil erosion. This might be due to outward sloping terraces, cultivation on un-terraced slopes, sparse vegetal cover by potato plant which is the major crop in this zone.

Maximum agricultural extension was found in the ranges close to 2200-2400 metre elevation during the years 1963 and 1993 (Fig. 2C). This is due to the fact that all possible land at lower elevation had already been under agriculture and higher elevations restrict intensive agriculture. Moreover due to the shape of the basin the percentage of land available at lower elevation is less. Extension of agriculture in the 2200-2400 metre elevation range has been mainly in the form of potato cultivation as a cash crop. Similar reasons are inferred for the extension of agriculture in different slope classes and topographic aspects. Maximum extension occurred in 20-30 ° slope classes (Fig. 2D) as limited land was available in lower slope classes and greater slope classes are not conducive for agriculture, even with terracing. In respect to topographic aspect maximum extension was on south-east and west facing

slopes (Fig. 2E). Warmer aspects (southern slopes) are preferred for agriculture as the growing periods are longer here. In addition, east and west facing slopes having moderate temperature and moisture regimes are also preferred for agriculture.

Land where agricultural extension took place after 1963 was evaluated and grouped into three suitability classes. Those having slopes more than 30 ° and elevation above 2600 metre were considered least suitable for agriculture and conservative landuse is prescribed for these areas. Lands below 2200 metre elevation having less than 20 ° slope were considered suitable for agriculture, and those in having 20-30 ° average slope were classed as moderately suitable for agriculture.

Changes in Pasture Lands

Pastures or grazing lands in the proximity of cultivable lands are used throughout the year, but have relatively poor vegetative cover. The alpine pastures at elevations above 3000 metre are used during the summer months when the non- milch domestic animals (bovines and ovines population) are taken there. There has been increasing dependence on these alpine pastures as the other pastures are being brought under cultivation under pressing demands for more production. As a result there was net loss of pasture land during the period from 1963 to 1993 (Table 1).

Changes in Forest Cover

Since details of sub-classes of forest cover were not available for 1963, changes

200 s. Ghosh e t al.

in forest cover density or type could not be ascertained. However, it may be inferred that total forest cover has decreased from almost 75 per cent in 1963 to 65 per cent of total geographical area of watershed in 1993, regardless of changes in forest quality (density of crown cover, composition etc.). Vegetation crown cover density was classified and qualitatively defined as, dense forest with more than 60 per cent vegetative cover; open forest or degraded type with 30 to 60 per cent vegetative cover. Degraded forest bear a distinct relation to cleared land, including agricultural area. The degraded forests are on the periphery of agricultural lands indicating human interference. Loss of forest area to other land-uses (Fig. 3 & Table 1) was about 11 per cent of total area in the watershed, which implies that 15 per cent of total forest area of 1963 was deforested during the last 30 years i.e., 1963 to 1993 period.

Encroachments are common in the Panchayat forest land towards the upper reaches of the watershed, which is managed by an elected body of villagers and is accessible to all villagers on equitable basis. The gently sloping lands devoid of trees in this area are under potato cultivation as the climatic and soil conditions are favourable for potato cultivation.

It was found (from Boolean operations in ARC/INFO tables) that area where forest regeneration occurred (between 1963 and 1993) was maximum in elevation range of 1600-2000 metre and mostly having 20-30 ° average slope. Regeneration was found to be the highest (41.8 %) on the East facing slopes and West aspects and on the North

and South facing slopes. The regeneration has been less on southern slopes due to poor moisture conditions and pressing demand for agricultural use. Regenerated forest area is only 3 per cent of total watershed area and 4.8 per cent of forest area existing in 1963. Regeneration was concentrated in the southern parts of the watershed. This perhaps reflects greater vigilance of the Forest Department in the area closer to their office and having less hostile terrain. Another obvious factor is that the rate of success of afforestation is likely to be low in very high altitudes, moreover most of the high elevation area was already under 'protected forest' cover. Kimoti and Juyal (1996) while studying watersheds across the present one found that the impact of Chipko movement on the regeneration of degraded forests of 1972 was noticeable in the 1992 assessment. Thus they concluded that, if the . anthropogenic pressures are excluded, the natural regeneration will ensure forest cover to the desirable level.

Encroachment of forest area in the watershed is mainly done by the rich villagers or people from neighbouring areas. On the other hand new settlements on village wastelands, open forests within the village have been done mainly by the poorer and scheduled caste people. The government policy to support scheduled caste predominated villages have led them to combine and migrate to inhabited villages (as in the case of Darmola Chak Dungri) and bring the uncultivated village land under cultivation.

Forests seem to be better protected when the local people are given the


responsibility of managing them and not alienated. Good environmental management demands that each settlement has a clearly defined environment to protect, care and use. There is a long way to go to solve people-Government conflicts in issues for forest management (Saxena et al., 1994). Changes in land-use have also been positive in some cases as forest regeneration has taken place in some areas which although is far less than the area deforested. However small this signifies a positive role of peoples participation and disagrees to common belief that no regeneration is taking place.

The interplay between a dynamic human society and static land resources makes development of agricultural production both necessary and possible in the decades ahead in India. The area is under the pressure to generate more income for increasing population and better livelihood. Thus marginal lands on high elevation, greater slope and are with shallow soil cover also being brought under cultivation, as a result pasture lands and forest area is being exploited. All land viable to agricultural area extension is shown here and only those presently wasteland or low altitude pasture could be proposed for cropping after considering edaphic and other site factors. Other areas, those currently under forest having 'cultivable quality land' and high elevation grazing land must be safeguarded from agricultural encroachments. With the suitability classification of agricultural land and deduction of areas for possible agricultural extension some shifting of cultivated land is possible. Shifting is suggested only within the same elevation

zone to cause least disturbance to the cropping system. With agro-environmental management of the region, agricultural production could be improved without disturbing the ecological balance of the agro-environment.

Conclusions

Changes in land-use were inferred from the differences between 1963 and 1993 status. Cultivated land has increased significantly at the expense of forest land and partly of pasture land, and it is presumed that the density of vegetation has also decreased as we find large tracts of degraded forests, especially adjacent to the newly extended agricultural lands, but degradation cannot be specified spatially or quantified due to lack of such data for 1963. The extension of agriculture area at higher altitudes has been mainly brought about by bringing more area under potato cultivation for economic reasons.

Acknowledgements

The authors are grateful to Dr. A.N. Purohit, the then Director and Dr. L.M.S. Palni, the present Director In-charge of G.B. Pant Institute of Himalayan Environment & Development, for their encouragement. Support by NORAD, ICIMOD & TSBF and participation by NORAGR1C in the project activities enabled us to complete the task.

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application of gis for land-use/land-cover change analysis in a mountainous terrain

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