IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002 
TERRAIN MAPPING AND EVALUATION IN HIMALAYAS USING REMOTE SENSING 
AND GIS TECHNIQUES- A CASE STUDY FROM TEHRI DAM AND ITS ENVIRONS. 
Arvind.C.Pandey* and Chandra.S.Dubey^ 
"Haryana State Council for Science & Technology, Chandigarh. email: arvindchandrap Q yahoo.com 
"Department of Geology, University of Delhi, Delhi-110007 
KEYWORDS: Terrain Mapping, Tehri dam, Lithology, landuse, slope, Landslides, Remote Sensing, GIS. 
ABSTRACT: 
The area under investigation (579sq. km.) is located in the Tehri district of Uttaranchal State. In the present study the terrain 
parameters of the Tehri dam and its environs viz. geology, slope, landslide, elevation and landuse-landcover are mapped using 
satellite images of IRS-1C, LISS-3, FCC (1996) and ancillary data on 1:50,000 scale. This database is utilized for terrain evaluation 
with special reference to landslide inducing factors using Arc-Info GIS software. The area statistics of lithological units show that 
the maximum area around Tehri dam is occupied by Chandpur phyllites (57%) and Pratapnagar quartzites (26.4%). The various 
types of landuse-landcover around Tehri dam mainly pertains to agricultural land (47.2%), degraded forest (14.1%), open forest 
(21.2%) and dense forest (7.1%). About 42.4 % of the area that will be submerged in the Tehri dam reservoir (59sq. km.) is under 
25°-35° slopes indicating increase in landslide incidence after submergence. The spatial relationship between different terrain 
parameters indicate that agricultural lands occupy about 60-70% of the area of Chandpur phyllites whereas over Pratapnagar and 
Nagthat quartzites forests occupy 60%-70%. The Chandpur phyllites (54%) and Pratapnagar quartzites (5790) occurs mainly over 
slopes of 25°-35°. Landslides are maximum in frequency and aerial spread over agricultural lands. Majority of active (78) and old 
slide (65) are occurring over 15°- 45° slopes. About 79% of the active landslide area lie under elevation of 1200m. Terrain mapping 
and evaluation in Himalayas using remote sensing and GIS techniques is very useful as majority of area is inaccessible or forest 
covered making the conventional methods of terrain mapping an arduous task. 
1. INTRODUCTION 2. STUDY AREA 
Remotely sensed images provide a wealth of information of The area under investigation is located between 78° 20-78°40 
large areas of the earth's surface and permit evaluation of  E longitudes and 30°20'-30°40' N latitudes covering an area of 
regional geological structures, broad lithological about 579 square kilometers in the Tehri district of Garhwal, 
discrimination, spatial distribution of landforms and landuse- ~~ Uttaranchal State. The Tehri dam under construction is located 
landcover patterns. Geographical information system (GIS) on the Bhagirathi river near old Tehri town. The reservoir of the 
provides a scientific framework for storage, analysis and dam extends along the Bhagirathi and Bhilangna rivers 
retrieval of spatial (thematic) and non-spatial (attribute) data. encompassing about 59sq. km. area. The catchment of the dam 
The real strength of GIS and its applications lies in its covers about 6700 sq. km. area in the Tehri and Uttarkashi 
capability to depict spatial association of multi variables. districts. 
Coupled with Remote Sensing data base, it can serve as a test 
bed for understanding the environmental processes or for 3. OBJECTIVE 
anticipating the possible results of planning decision (B urrough, ; a 
1986). The present study was undertaken with the objective to carryout 
terrain mapping of Tehri dam and its environs with reference to 
The present GIS studies covers an area of approximately 579 lithology, landuse-landcover, slope, landslides and elevation 
square kilometer around the Tehri dam. This area being in the Using satellite images of IRS-IC, LISS-3, FCC (1996) and 
vicinity of the Tehri dam would be highly effected after the ancillary data on 1:50,000 scale. This database was utilized for 
filling up of the reservoir. There exist a marked variation in the terrain evaluation with special emphasis on landslide inducing 
geology, landuse and slope characteristics in area. The majority factors. To understand the control exerted by one terrain 
of the landslides and river terraces along the Bhagirathi and parameter on the other, Geographic Information System (GIS) 
Bhilangna valleys are concentrated in this area. Hence this area techniques using Arc-Info GIS software was utilized for spatial 
needs more attention in terms of geo-environmental monitoring. analysis of data. 
Keeping this in mind the GIS database pertaining to various 
terrain parameters viz. lithology, slope, landslides, elevation 4. METHODOLOGY 
and landuse-landcover of this area has been prepared using d : 
satellite images and ancillary data to evaluate the contro] In the present study, Arc-Info GIS software has been used as 
exerted by one parameter on the other with special emphasis on the core of the spatial and non-spatial database. A number of 
landslide inducing factors. thematic maps viz. lithology, lineaments, landuse-landcover, 
slope, major ridge lines, springs, river terraces, landslides, 
drainage, contour, roads and reservoir extent are prepared on 
1:50,000 scale using satellite images, topographical sheets and 
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